Document 65Bn9g7MymDXJNvNV72ak8MD9

wii the silica tlm: - Dial wre romjowd i,f with other elements iti ust cited the Tl) {k*iv*>m silica, plus 40 jicccttiit ,4 in certain dost r (miles 1. Hied (as quartz) pre-eni 3 by the silica that U it: -y to devise a method r*r dust in a given sample -t arising from cutting a -ercent of total silica the . TO, since only one-third rxnore, rocks and minerals _Ithougb they contain uo a reported in customary _nt of free silica. ~aht2) is socks 'ermine the percentage of method*, because it is easy ur and other minerals zr hie microscope, as ays: By examining a thin i approximately 0.03 mm ,<s slide, or by studying a by cru-sliing the material -out 0.00 rum in thickness, vriy itnmeraed in oils of died where in no position 'tween the grains and the .ictivc index f Die mineral rh it is immersed. In litis Jnxitd) orrefractive indices -.ogvUier with other optical wdvred rock and mineral :ho*L" serais depends upon the r *% 57 Ci) PlcochrnUm, in minerals that show selective nlisorplinn of ligliv. (::) Crystal fonn. * (I) Cleavage. (.*) Refractive indices and relief. (f) Birefringence. Numerical value. (7) Isotropy r anisotmpy. Extinction (complete, parallel, or inclined). (s) Optical cluHneler of the mineral. (0) Optical elongation of principal zones. (Iu) Optical urientation of mineral. (II) Value of optic axial angle. (12) Twinning. (13) Inclusions, (14) Alteration products. No ono of tho preceding criteria nlone is sufficient to determine a mineral, although ono criterion may be enough to distinguish it from sumo other mineral with which it is associated. Some minerals enu l*o identified by determining three or four optical properties, others require more for conclusive determination. The methods of determining the optical properties require a famil iarity with the difficult principles of optics and a special laboratory training in petrography. The reader who desires furtlier information about tho detailed technique of the petrograpliie identification of miucmls is referred to the standard works on optical mineralogy, such as Rosenhusch's MikroskopUeho PJiysiogmpliie der Pctrngnipiuscb Wiehtigen Miuendicn, volume 1, part 1, revised by Wolfing; Bock Minerals, by J. P. Iddings; Manual of Petrographic Methods, by A. Johaiinsen; or Sana's Textbook of Mineralogy, fourth edition, hr W. E. Ford. For a comprehensive description of the immersion method of studying minerals, Dio render is referred to The Micro scopic Determination of the Nonopaque Minerals, by E. 3. Larsen. Qvaslitatln determination An easy and satisfactory way to determine the percentage of any mineral in a ruck section is hy the Jtosiwal method. This method consists in measuring Die linear intercepts of a given mineral along numerous parallel lines. The ratio between the sum of all tho inter cepts of quarts to tho length of the measured traverso gives tho per centage of quartz, because, as can be shown mathematically, the linear intercepts are proportional to volumes. Tho measurement is carried out by Dio use of a screw tnirromefer ocular or n mechanical 'luge. The Rosiwal method can lie applied both to rock sections mid to rock powder* examined hy Die immersion method. . DID _S flriis f WAS NOT A HiCOi.D PPG INDUSTRIES, INC. DIO NO) COME FR IT'S FILES AND CANNOT BE AUTHENTIC^' BY PPG INDUSTRIES, INC. 710020024 25XB <53 DKTKIUlIN.Vnu.V OK Qt.AUTZ IN DUSTS It w mm| *(>' easy {nr tint petrographcr to apply the methods desrriiicti above iu making a quantitative determination of quart/, in thin sections uf rocks or in n*dc janvders, but iu dusta where the irnliriduni jvirtichv* a roof the order of magnitude of 0.f)fl5nun ( microns)in diameter petrographic examination of tliu material must l>c supple ment ed by other methods, because the minimum grain size that can bo conclusively identified under the petrographic microscope is about ' 0.010 mm (10 mienms) in Itameter. The results of quantitative dust analysis can only bo conclusive when severs! methods ore used m the same material, thereby checking one against the oilier; and the accuracy of the final result depends largely on the skill and experience of the analyst, because each sample to be analyzed presents an individual problem. The general method that has been found highly satisfactory is a combined chemical and petrographic procedure by which all the con stituents other than quartz are eliminated from tho material. The accuracy of any method of quantitative estimate is much greater .where the estimate is applied to two constituents than where many constituents are present. Therefore, by concentrating tho quartz a Irrge factor of error in quantitative d 'termination is eliminated. If the dust is.rhietiy composed of quartz, the elimination of foreign constituents is not difficult. If the quartz is in smaller amount than the other constituents, a clean concentration may be more difficult. But n satisfactory quantitative estimate can always bo made on a moderately clean quartz concentrate, because the mineral present in marked excess can be much more accurately determined than tho other constituents. For the fine dnU whose individual particles cannot be satisfactorily determined chemical methods ore accessary iu order to remove tho constituents other than quartz. Various methods arc used dependent upon the composition of tho dust, but the first step in the analysis is to examine a small portion of the material under the petrographic microscope. PreRaUtaur petrographic examination r the dust ' It is a common practice to eito the jereentnge of silica in the chemi cal analysis of a dust us a measure of the quartz present. Thu erro neous nature of this conclusion has 1h*cii already emphasized. The ; only value of the chemical analysis to tho dust analyst is based upon the fact that the amount of silica locked up in the various silirnto minerals iu the dust- ran he calculated from tho percentages of bases (K*0, Na-O, CnO, efc.) that are shown by tho analysis. The jmreentage of silica that remains after all the bases in the various silicate materials have been satisfied should represent the free silica present. Thi* i mtitpu-i example granite.-,, siluti. j feldspar, is emupti present. pota>simi muse, nit, satisfy th various in lock-form compositii As tho < to the pocmphusiz'-i sable prr dust sump! quniltitsln petrogrnph exantineti i dust by n suited to t! if the du-t i material, a again exami: proccthire. free iron ma; with hydnw, particles as ! works cental heated with residue slmul. The nmst di: mineral dust:or asbestos d in sueh mate, acid, Il-Sit*,. not at tack qm Chemical esaiuir After the p< Uic chemical: mcnT was NOT a record of S mC OID NOT COME FROM CANNOT BE AUTHENTICATED ruJSTRlES. INC. beTooESSS-' 75 >jily the mctlMnU . :<tiiin of quartz in ;s where t!o ir.di- nun (ii microns) __1 must he hi'jjj)!.-. -rain size that fsm Jerojcopc is about - nlv be conclusive .. thereby checking ^al result depends muso each sample -- satisfactory is a which all the etm...e material. Tlic is much greater than where many matins tbo quartz ion ts eliminated, Tii of foreign ,&l. mount than lifeoro diiSmlt. mode on a Tniiu-nd present in erroined than the 7t be satisfactorily. ;er to remove the re used dependent in the analysis L* the petrographic ilira in the chojnircscnl. The cm-mpliasizcd. The yst is based upon :0 various silieale Tentages of Iwses .alysis. Tbe jhm;i various silieale ree silica present. on This method of computation Is useless, however, unless the mineral rtiei|siti<-u of llio dust has l>een detennined ]K*t-n*grophictdly. For example, in potassium feldspar, which is a common constituent of all granite:*., every luoleculo of potash is combined with C molecules of M*liea. If the only minerals in tho dust are quarto and jiotnsaiuin feldspar, obviously the silica left over after the jailnsh in tho analysis is computed us feldspar will be mi accurate mcasuro of tho qunrto present. But if, ns is often true, the dust is made up of several jxitassium-beari:*^ minerals, such as potassium feldspar, biotile, and miiseovite, it is impossible to compute bow much siliea. is required to satisfy tbe potash, became neither the relative proportions of the various minerals arc known nor arc their eoinjimitions known. Most lock-forming silicate minerals have wide ranges in their chemical composition. As the chemical analysis of a dust can only serve as a rough guide to tho possible amount of quartz present, it cannot he too strongly emphasized that a careful petrographic. examination is an indispensalilo irerequisitc to the quantitative determination of quartz in a dust sample. For although it may be. impossible to mako au nmirntc quanrite.tive determination of extremely minute individual grains by petrographic methods, it has proved possible in nil the samples so far examined to obtain a clear idea, of tbo general composition of tho dust by a petrographic examination. The analytical method liest suited to tho individual samplo can then be selected. For exnmplo, if the dust shuns under the mic.-osropo a largo admixture of organic naiterial, a preliminary sample should lie ignited and tho residue again examined under the microscope in order to decide on the further procedure. If (ho dust shows a largo amount of metallic mineral, free iron may be ext meted by a magnet or the sample may bo heated with hydrochlorie acid to mnnvo the iron oxide and such metallic tKirticlpa ns brass shavings from brass-works dust. Dust from marble works containing chiefly particles of carbonate minerals should bo heated with hydrochloric acid to dissolve .the carbonate, and tho mddiro xhonld then bo examined with tho petrographic microscope. Tito most difficult problem is tho separation of quartz in rock or mineral dusts that contain silicate, minerals, sueli ns granite, slate, or asbestos dust. Tho procedure employed to separata tho quartz in such material depends u]>ou tho fact that cold hydroiluosilicie acid, U.SiKfi, wilt in time decompose tho silicate minerals but will not attack quartz. (Vmltsl examination of the dust After the preliminary petrographic examination tbe procedure in tiir chemical actuation of quartz is as follows: THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOf COME FROM IT'S FILES AND CANNOr BE AUTHENTICATED BY PPG INDUSTRIES, INC. | BB 0020026 T 2520 f 60 /7nWin.--In order lo facilitate the action of tlio hydro/luosilieic acid llic material is ground lo pass a J50-niesh sieve! thus insuring uniformity of size mid a largo surfaco for treatment. Weighing.--It is (lien weighed in a platinum crucible. About half u grain makes a convenient amount to work with. . - JgnUiun.--'H the preliminary microscopic examination indicates the presence of any organic material, tlto platinum cruciblo and its con- tents arc carefully heated to white heat for 30 minutes to bum oft the organic matter. It is tlien cooled. Dusts that are strongly con- taniinated with oil arc digested for 5 minutes with other, then filtered, and ignited for liulf an hour to an hour. micniir,,, I*e e-.i!.-ul; ^ risv volatMizii, ailim in the (t.-au, cmnlihisii fluurb-.n,* Hrdraehtnric odd treatment If the preliminary examination shows tho presence of carbonate minerals, hy-'uochloric acid ir. added to the contents of the platinum crucil.Io and (he crucible is gently heated. Tho contents of tho crucible arc filtered, washed, and the Alter paper and precipitate ore ignited in the same platinum crucible, which is then allowed to cool. I/jritrtiflttcsilicic arid treatment After these operations hydronnosiHcic acid in moderate excess is added to the material in the platinum crucible. If tho coni]>osiUon of the dust is such that the ignitiou and hydrochloric-acid treatment am unnecessary, tho hydroAuosilieie acid is added to the substance to be analyzed immediately after tho first weighing. The crucible is carefully covered and set away in a place where the temperature is reasonably constant and not above room temperature. Caro must be exercised not to raise the temperature during the bydrofluosiliric acid treatment, bccauso hydrufluosilicic acid (HSiF) dceomjKwes on heating into silicon tctrafluoride (SiFJ and hydrofluoric acid (III'), which will readily attack the free silica. It is left for a time that ranged in different specimens frem 24 to 4S or even 72 hours. It is then carefully decanted into an asldess Alter paper and the crucible is thoroughly washed onto the Alter paper. The precipitate is waslicd until the wash water gives no precipitate in a dear mixture of dilute KCl with 05 percent alcohol. The precipitate is dried, ig nited in tho platinum crucible, and weighed, mid the percentage loss in weighfc noted: Tho hydrofluosilicic arid treatment is repented until the weight of tlie residue remains unchanged. Microscopic examination sf residua A small portion of the residue, is then examined under the petro graphic microscope. If minerals other than quartz are present, the amount of quartz in tho residue* enu be estimated with a reasonable degree of accuracy. If quartz is tho only mineral indicated by the hath uf n As the. i different si determine longed tnn analyse.; of more to do The Ml,, quartz grot By using i end of an at originally prr ltisuppar, individual pr, analyzed, iir. etc. Thvrcfo be aeWted at dust have l*v ! ,, \aihc not a RECORD o? DOCUMENT WAS NOT coM fR0M authenticated __ _________ i U Ml,. \ l 2521 #.y<lrifln>.4!irl.* sieve, Jims insuring .cut. -ucible. About half Ai. mat ion indicates the -ruciblo ami it-* cim. min ulcs to bum off .at nro strongly con. ether, Uicu Alien'll, escuco of carbonate *nts of the platinum lie contents of the and inecipitatc are non allowed to coot moderate exress is If lho composition .ioric-nnd treatment .'d ' 'he substance uiji Tho cruciijlc rc^^ temperature rd^^. Caro must the hyilrot'uoiilicic decomposes on -oAuoric acid (HF), eft for a time thatven 72 hours, liter paper and the r. Tho precipitate o in a clear mixture eipilato is dried, igthe percentage loss until the weight of 'd iiufler the petrorlz an* present, the 1 wilh a reasonable al indieated by the Cl Hiii-rou-opie. e,\-;.iiiiu.-!(uui, the percentage of quartz in (ho sample can |m* ealeiilatetl ilircct.ly from the weight of the residue. YuhiiUizalfon of residue with hjrdraUuorie acid A check on the microscopic determination of quartz is given by v<*l;Uilizing the. residuo with hydrofluoric arid i n the pla tiniini crucible. Kn-o silica volatilizes completely with liydrolluopiu arid. Comblued silitii in silicate minerals volatilizes with hydrofluoric acid, hut after the treatment a residue remains made up of the liases that were in roiuhuuttiou in the silicates. If no residue is left after the hvdro:iu<rizatioa, tin', material was all quartz. HATH OK DECOMPOSITION* OP Ql'.Umt OX FUOI.OXCED TREATMXT WITH HYDKori.rosn.ictc acid As the rate of decomposition was found to difler considerably in different silicates, a control test was run on pure quartz in order to determine the error introduced into quantitative analyses by pro longed treatment of quartz with Il-SiF, at mom temperature during analyses of dusts tlial contain refractory' silicates requiring a week or mor i to deeom)HiaC. T*no following table shows the results of a test on 0.509 gm of pure quartz ground to pass a 150-mesh screen: Tawlv. \C>.--Quarto [Ortelnel *Jpfai llm uuuont *rlth Uitlfi-MU rmj Tiaw te* tLirwuiuSrasi (gruuu) hlu*nitni0ill I||ibnwT:lvreirstUrxpSifanuewrlatiMloliall f. M ...... ... -.................. ....... ....... . __ ----- .. .. tt...p4aoO3rU1rt .on 1zT*41...<.*71l >Ii>t..C.aaM7 1 AmiwJ inniiuptikir HittUUn U> willml iSjtlil. By using tbo alioro factor of error it is possible to compute at tho end of an analysis Uie maximum ]iossiblo loss in weight of quartz originally present, thus obtaining a maximum Agnro for quartz. It is apparent front the preceding discussion that each dust presents individual problems in regard to tho puriliention of the samplo to bo analyzed, the mribudsof eruuinating the various mineral constitueiiU, el**. Therefore, tho best procedure in analyzing a given dust must Is* selected after tbo minerals and other constituents muking up the dust have been iilentilU'd; euusequeully it is impossible .to set forth W K0NOV CoSm 3? SSSScMINOT BE AUTHENTIC* BY PPG INDUSTRIES, INC. beTqo2oo28_, any nuit torluiiqiw that will apply to all dusts wpirtlloss of tlioir <*oinjsitMMt. Jn flto following tablo a fnv m-wlts am prrs**nl<*d on (Jto determina tion of quartz in iiiihisirial ditsU: Tamlk J7.--uf ifHnrt! prcxcml in twin** imluntritU Jn*U IVrcMa** f qiHTU ilrar.;mila:......... ... ...... ihvr*'-r* jf'iuh*iia*t............................................................................................................ U*uami|*wMiJwtf^............................................... i*H- fc.ifl CTve4 ........................... Alifllii fUtUOS! dtfttltWWMH>4***a .! M.# S3. J . !. 4.4 It IT L* 1.3 s: S'M Xw i V. Ki. *** .i;iiuian : in.!* liv.u At V. liii'l I In: ci f*NT st quaW prrltn Kr (I Tinindnsl Kauilai Tiie*. iiMt n* fl**U study i the saui afTimln nmipat and tin' an anal.' . wltiHi *d |H)illt of of person (into dti\ All UtLt i r ' WAS NOT A RECO.iO OF , INC. DID NOT COME FROM ;annot be authenticat ed --1-0 imp ! 88 0020029 Ji -- dusts regardless ,0/ their scnled <m the determina- xrwtta imhuttrial T. TIIK AIMMJCATION OF DUST DliTEttMlNATIONS TO PRACTICAL PUOItl.KMS Dust determinations in industry serve & three-fold purjxjse. First, they enable oiio to evaluate the rxtuiit of the hazard; this is accomplished liy obtaining occupational dust exposure*, which disclose the dust-creating tasks. Second, if cliuiral studies nro made, dust counts may indicate the permissible amounts of dust wliirh may Ito breathed with impunity. Third, dust determinations nro used in an attempt to control the dust hazard; this is performed by testing the efficiency of any devices which may have been introduced fur the sup pression of dust in those processes which have been revealed by inves tigation to I>c hazardous. tmvBMtyjiTinv or THE EXTEXT OF THE DUST HASAHD Attention has already been called to tlie three properties ot a dust t which determine its capacity to produce injury, Having established * tbo composition and size of a dust the only important item remaining for study is tbo quantity of dust in the air. Prior to evaluating the : quantity of dust in tbo industrial atmosphere, however, certain preliminary stcjis, such ns those outlined in section 1, are essential. For the sake of emphasis thrsc stej are briefly reviewed. The investigator should first become thoroughly familiar with the ; industry being studied. This is best accomplished by conducting a * sanitary survey and occupational study of each workroom (4fi). \ Tho sanitary survey of workrooms in any plant yields definito in formn^ lion concerning the presenco and extent of various health hazards and * often serves as a.-guide in establishing which lwzArds require further study in the form of actual quantitative analyses. In other words, U10 sanitary survey may well be regarded os a listing of the facilities afforded the workers wldlo in tim industrial environment. The occupational study permits ono to learn of the activities'involved and tbo particular huznnls associated with each occupation. Such an analysis also shows the uumlier of persons in each occupation, . which gives an idea of tho inqiortancc of each hazard from the view point of tho numl>crs involve*!. In the case of a dusty industry, the occupational study shows (1) the dusty occupations, (2) tho numlier of persons in each occupation, and (3) the various activities and tho time devoted to each activity in any ono particular occupation. AU this information is essential in tho preventive program wliich r THIS DOCUMENT WAS NOT A RECORD Or PPG INDUSTRIES, INC. DID WOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. I BB 0020030 | r , y * u 04 should fopnw, nud experience has proved dial only by such a system* nltc and c-ndul study can (hist- dctenninaturns bo of any real vnluo in the control of the industrial dust- haxard. Perhaps a typical example of such a study may serve to clarify further the methodology involved. Tahls 1 --Occ*pvtiaHttl ein**ijUatioit of grnuilc qHarrten Omiuiifcin Drflira: OUXPI`T1oiu'il^iraTtnmtTni tJrsvrUhbii/.-.'.n..w^f. . 1Or1vkmrc":a-mmr tfi.i.*---rnmr.'tMlr.-r.,.r_.t.,__ Uav>:m4i\v r5twf UiwBvr... heimlMtil man.--TM Com opemor Xiualir la rmh ,i eUcubpba* " --------- i! OwNI-- 17 Other lyanr fmployia CaaUatW. UerrVfc m................ r Murker*. lUl^MWlll .. ------------------ Toni V.aicr lr______ Ctl 11 Marnini<tj----... AirAi.-ia M;airen, Itp* ItliOT ...... Tmi......... Ntoumeb*e*r cni|* 31 aasI1i. te Table IS shows the various occupations in a granite quarry and tho number of workers employed in each occupation, and that drillers are tho only persons using pneumatic tools, devices known to produce considerable quantities of dust. In other words, 3S percent of llio quarry personnel are shown to bo exposed to dust of a ]>oten> daily dangerous sizo and quality. The occupational analysis at onco indicates that tho dust investigation should especially concern itself with drillers in on effort to control the dust exposure of these workers. Tho next step in this study involves the determination of the occupational dust exposure. Table 19 shows tho results of such a study. Taau Iti.--Occupational dual erjiwim oj granite 7burner* OmpMba Pmm MBUI lit milMvtn at partteto Nnl#r IwranMebMolair In tart tta* WHrlunl Minimum Msiqpw| . .......... . -- n Mil * Li l.aa.1 Plus wot brt-taiMK driMns (tnaiTT Mb.......... 37 Ittl 4.1 3M.t 3& a.a 4.0 as Al 4.1 10- 7 It Is apparent from the results shown in this table that the drillers aro exposed to high dust concentrations, especially the Lcyner and jaek-liammcr drillers working in tho quarry hole. From a further analysis of the occupational dust cxjKisuro of drillers it is jMissibln to detenuiuo wliich activities are responsible for tho dust associated i with l the v.- p.-ilinr. this tv rach a sum fi results drill*T. Tam t; : Ibinfau... UItf'itiiatoUijlri;.*,k, TteiJ 1,1 It will dust exp table -*i) obtain a oecu|>ati( is 1-14.4 found didetennuK dust liaJU. blowing t hole is att it is on aiis one whi It is eviil may be at lastly, sue effort* to activity aa Leym-r < So far w rule, do iM who luivc 1 - - T-'y i i -- i-- /T' BB 00 20031 I ! _ 2525 +at niily by such a system- -nunations lie of any real value ; lutmrd. IVrhajK a typical vlorify further the metlwalnhigy *3Tmm mf gniqrnmm'm Ottuw* I<a*iet.*..._._.__._"~y'~ -*1"? *?>~**r-`-------- - __ cr.TtiuI'Ha*ii--re^t i*_yy--7 TMaL. If I I3Ii IS tions in a granite quarry an<l each occupation, and that lunatic tools, devices known to z. In oth.'r words, 3S percent be '0*cd to dust of a potenTf wcpational analysis at .'.u^motild esqtcctally ntneem rr^Pie dust exposure of these *res the determination of the j shows the results of such a pvfiir iJHarrirr, "W1 ua I" incc a*t W/irl-wttoW Wi>fctlWif 1 .... M j AltaiBoa Sfailnw IT K HU ite.1 a 3*. u at 41 43 41 U<n.a 330.3 440 . 147 in this table that the drillers as, *pcriUy the Levner and quarry hole. From a further uro of drillers it is powublo to -ilrie for the d9 ust associated 65 ntih this occupation. For example, experience has taught us tliat ilio various operations comprising the processes of most dusty occuIhliana are usually associated with dissimilar dust exjiosures. For this rcasou it is essential to estimate the uiuouut of time spent in ,-.ieh activity in any one occii{>atiou and to determine the dust expo.ure for each actinty in tliat occupation. Table 20 shows the ivsidfs of such a difrcreniial dust study in the ease of a Lcyner driller. Tahi.h 2a.--Summary of iluxt tiftuture of ` Leyiter drCLert in a granite quarry StaltUT Amn Out u> luur* In uUkHMOf (-irudr* |*r *tWo but at Xotalwr u/ bmin incurU ftctitity (1# ranW*. Imn io millmm iwr rob* im taxi) UM nofiiiwilrilli..----.................... Itawigt wll --.................................. T--l 30.4 U ... 40 40 4M40 4 313.3 44 * I4C 43 S43 3 4141.3 UiaLt ron^h^y.ig -mum*jrtyrt* tot. bum |WlWn It will be seen from table 20 that a Levner driller bos fire different dust exposures. A dilforcutinl analysis, such as the one presented in. tublu 20, yields several valuable finding*. First, it enables one to uhtaiii a truo average dust exposure for worker* engaged in the occupation of Lcynor drilling. (In this case the weighted average m 144.4 as contrasted with 213.4 million particles per cubic foot found during drilling operations only.) Second, it enables one to determine which activity, or activities, contribute the most to the dust hazard. In this instance it is quite evident tliat the .practice of blowing off holes by means of inserting a compressed air line into each ImIo is attended with an exceedingly great amount of dust; and though it is an activity lasting but 15'minutes of the S-hour working day, it is ono which is responsible for 22 percent of the total dust exposure. It is evident tliat 23 percent of the Ixwncr driller's dust exposure may bo at once eliminated by tbo proliibition of this practice. And lastly, such an analysis indicates the necessity for devoting all one's rlfurls to the removal of dust during lhe drilling process, since this activity accounts for 74 percent of the total dust eqjosurc, although a Lcynor driller spends hut one-half of tlio working day at bis drill. So far we have dealt with an industry in which Ilia workers, as a rule, do not change their occupation. Often one encounters workers THIS DOCUMENT WAS NOT A RECORD Of PPG INDUSTRIE^, INC. DID NOT COME FROM IT'S RUES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. . OS' PHILADELPHIA . ' ' \>T r t i- * , . fH T"bb"002OO32"T 2SZ6 CG several different lands of establishments. If the worker has been employed in various occupations in the industry under investigation, it is <i simple nuttier to determine his total dust exposure dutinghis entire trade life in that industry. Tliis is important from (he view* point of corrcln tins ft worker's dust exposure and his clinical condition. A typical example of such a. case will suffice to clarify this point. Tams 21.--Total occupational duel txponttri of an antkradla eoat mrkcr In tlio aboro tabic the worker's occupations are arranged in the order of employment, the lost one being bis present occupation. It is obvious that bad one considered this last occupation only the dust exposure for Ibis individual would not have yielded a true state of affairs, nor would it iuavo been possible to correlate this dust exposure with the man's clinical picture. In the above toclmie correct weight is given to the number of rears spent in each occupation and tiro dust exposure associated with each occupation. Only by such an analysis is it possible to arrive st a fair estimate of a worker's dust exposure and his proper designation. That one is justified in resorting to such on anulysis is evidenced by the fact that results obtained with tlus technic yield excellent correlations with the cUnica-ruentgcnological. ` ' ' studies conducted on antliracite coal miners. ......... ArmcATiox oy dust comers to cubical studies Earlier in this chapter it was pointed out that one of the purjioscs of dust investigations is tlio determination of the threshold dose for any one particular dust, so that permissible amounts of this dust may bo known and efforts to suppress the dust to this Hunt may be mado. Such evaluations are sometimes nuidc possible breludics in which in addition to the occupational dust exposure one also obtains clinical, niorbidtlv, and mortality data on a large group or workers over a period of time. One such study was made in connection with nu investigation of the health of granite cutters. Table 3, shown earlier r~ ^S0^J0t COME/ROM S CANNOV BE AUTHENTICATED 1 INDUSTRIES, INC. . . 1"bT00 20033_| f t 2527 j worker Ira* hern ^Bunder invesiigntion, oust exposure duringliis iportant from the view.nd brsclinical rendition. .'0 to clarify this point. 1* anthracite coal wirbr Nfywamrftthtnhf ir* pUnpJfltXtidiftmoiornaoittUlts1!t^fri^*i Minina* -f ruiw f|cWwt U333s3 4`te*7711a1 7 ---- Luia1n1un2 33 ana .* ace arranged in the reamt ocrupa tinn. It eupifctioii cidy the du*t vie*T t & true state of .-la. U dust exposure li*. .c correct weight r^Btion ami the dust djHysuch an analysis .vorisex's dust exposure icd la resorting to such :lts ebcainrd with this liaieo-rucntgcnological ZA&srtrens it one of tlio purposes :b threshold dose for iiudsqf this dust may Ls limit may ho made, in studies in which in also obtains clinical, ip of wurker# over a . connection with an 1`abUs 3, shown earlier in sertion I, is repealed at this time to show the occupational dust \\jwwtire of a group of these workers. T.WH.K V,.--lianli>iy the turtvH* accitptiiHw* in the gramte^utting indottrg according to duel t'S/Mwwrr . OmiuilM Xuitifcvr Jfambw dM* KMcr *>f**nl UuM IImm wit fat nUMnna ot imrtirtr* |vr mi--it *ai Mlnh Mum MmI- Av*n* Alt iwnmtk hatkMuS |ici:tua_u.u.,,,,. Burlvxt'iitttt: ii.ii.i---------- ...... -.......... iliivlr._________.......... .--........ ** * *>*a*,tm, to t.irni't-1 tiLiai nin--------------------------------, I 1jiio |*H|l*hlVl - . ...................................... _________- j ----ITTMIIflimH Smal^ilart cjKnun____________________________ lU*k*mith**t>iJ otfcm...... --. -- (Aliev *04~>*ni_______________________________ 303 ts JO 91 30 SI 4 43 4 10 tat 10 00 3.4 SOLO 31 .0 MS. 7 10 14.0 JOIS W 11.7 5.1 14 &3 CIO 43 il M.0 4 to 33.7 u L3 2/LH LO 1L4 4 4.0 4.1 3 .0 S3 4 1.3 14 413 44.0 43*0 37.6 ST.l 91*3 17.3 *0 1.1 10 S3 L0 It was found possible to divi te these grauito cutters into four groups, depending upon tlio nvciagc exposure in tenus of tho amount of dust in the air, when considering tho clinical picture associated with thero workers. Figure 21 shows the annual frequency of ab sences from tuberculosis and the annual death rate from tliis disease among tlio men in tho four groups. In group A, which included hund-puouinatic tool operators and in which the exposure averaged a'xjut 50 milliou particles per cubic foot of air, it was found that practically 100 percent developed an established silicons within 10 years from tlio time of beginning em ployment. A1*o in tliis group tho highest rate was found for cases diagnosed on physical examination ns having active tuberculosis. Furthermore, a definite relatiouwns established between length of service in tlio industry and tlio prevalence of tuberculosis. All of tlio statistical data obtained judicalrd definitely that hand-pneumatic tool operators in these plants suffered from an occupational hazard. In group B were included those workers other than hand-pneumatic' tool operators who were also exposed to more than tho overage plant dustiness. Taking llic group as a whole, tlio averago dust conccn(ration was nearly 4$ million jiarticlcs per cubic foot of air. This group showed the same rrlbrctinn of a dust hazard as group A. In group C, consisting of those occupational groups exposed to tho average plant dustiness (about 20 million jiurtirles per cubic foot of nir), silicosis developed much more slowly than ill the groups just discussed and (hero appeared to he very little excess in tlic rate for tuberculosis, with no tendency for an increase according to length of service. Analysis of occupational mortality over n period of 2a years, THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. L-JL 00 20 03 h" . 252S f GS however, indicated that some of (ho occupations in this group may MUST t have Imvii t'\|M*svil to u n*:il dust iutzard. 'Mm Group T) was made up of those occupations in which the dustiness prim-ip was less than that of the average plant atmosphere. Tho average ])est*ri| exposure for tho group was less than 10 million particles per cubic and o:! * method tvs|>irai such jr mu' (lit or not < meat in tletermi jug leve willi a i lion of criteria Menti cutters ( rngagnl hvs (!ia< from sili granite these *rr otbiT bn dust c\i cutting i nl its s>> foot, pres Hlieienev lust, del* lit table : rutting : opiip|Nt| Tasui gg. foot of air. Although a certain amount of silicosis was found even in tlrnt group, them was no judication of serious results, even wltett the workers had lecn employed for many years. From Uio results of this study it was found practicable lo suggest a tentative standard for the upjier limit of allowable dustiness between 10 sutl 20 million particles jier cubic foot of air for workers cxjwscd to dust resulting from granite cutting. 1.07 ~ Mi '*11* <im Ho ** i#i** * ' iu> lu. ` *'j - * llj-I M t 1^ THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM ITS FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES. INC. 7 B-B-0020035J ! *^ r 2529 /* up may Justines* average t*r cultic .38>. -cl even n when a .x..p..o. -ted. NOT C G9 > .O COUNTS AS CUITUUIA IN THU CONTROL Of TIIF. DUST HAZARD Tim lotions which will follow discuss in some detail the various fniiu-iplc.s anil inathod* involved in tlio control of industrial dust. I ).-**ripi inns arc presented on the correct design, air-flow requirements, and other pertinent dat* dealing will) tlio control of dust by wet litrlhods, merhuiiicul enclosure, exhaust ventilation, and personal respiratory protection. One of tlio important factors in the use of siieli protective equipment is the proper nmintenaure of thceo devices and tin* testiug of their enioiciicy in an effort to determine whether or not tho dust is actually being eliminated by tlio particular equip ment in use. Such efficiency tests resolve themselves in making dust dHmnmntions in order to determine the dust content at the breath ing level of tho worker operating a dust-creating machine equipped with a dust-removal device. A few examples of the practical a pplicaiion or efficiency studies may servo to indicate tho value of such criteria in tho present problem. Mention has olreudv b**en made of the study of the health of granito miters (2) Li which it was possible to demonstrate that those persons engaged for mauy years in tasks associated with a dust exposure of hss than 10 million ]irticles per cubic foot of air were not suffering Conn silicosis or tuberculosis, the diseases most prevalent among theso granite cotters. It was also possible to demonstrate that among these granito cutters tho inddcnco of silicosis and tuberculosis, all other factors being equal, was directly proportional to tho degree of dust exposure. Tlio solution of tbo dust problem in tho granitecutting industry therefore, resolved itself in the removal of the dust at its source, to an amount less than 10 million particles per cubie foot, preferably by cxliaust ventilation devices (47). Studies of tbe efficiency of such dust-removal devices have been made, using tho dust determination at the worker's breathing zone as a final criterion. In table 22 a comparison of air dustiness is presented between granitecutting plants using exhaust ventilation devices, and those not equipped with such protection. Tabu SS^-Cmptrum of .ctmoopherie dn*t eomiiHono bettmn tea gronp* of 0roMite*euttimff |iInnU AmWmtri--MmUdlfilmuMrmpoelururnluIMnnlckwiMIIuUwl ohf ' om^km wM1MlI1iHkmi-nlal*itt lynm IHfloftuiTmOrMfrtiliyraiMumit ItwlX Maui Y in 1--iim.u* fcu-4-t--l-feralinn*.---_-_--_-_------- ----_- _--_-_._-_--- -_-_--_- IWIIA-Jl*!, -- - ........................... " ----- ------------------------ ------------- K.5 sa. ti AO 33.0 A1AAA3O.043l ' A1 mIX0A..o191 j"*BB 0020036 1 THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. . 2530 70 It is apparent from the results presented in lablo 22 that iu plant X the exhaust devices in use with pneumatic tool operations nccdod attention, since the dust concentrations associated with these opera tions wore slightly higher than tiio proscribed standard. On tho other hainl, the ventilation system in plant Y was apparently func tionin'; satisfactorily at the time Ihcso studies were conducted. Iu studying the degree of exhaust ventilation necessary to keep tho dust at tho worker's breathing level to an amount less than JO million particles ]mt cubic foot, tho dust determination method again proved ***** frmhmwse i M itw 1A* KM HM Atm Krxoc/rv *r jc**trtr Jitter-a str // rvtetr/ttvre Tokmx tli BOitlorSilp hawtes t*a drov* of air tcineity ai r\)sml iliwti aod CM awemt f dtad tataMbr Wtcomitmutef pBnaaaifatoinfc. very useful, figure 25 presents the results of a study of the relation between the degree of air velocity at exhaust ducts and the amount of dust iulmicd by granite cutters using various pneumatic tools. It is apparent from this figure tliat by maintaining an exhaust velocity of 1,500 linear feet per minute at tho face of the dust-removal hood of tho typv investigated in the present study, the dust concent ration t tho worker's breathing ioao will l>o less than JO million particles per cubic foot. Again, in studying tho efficiency of sand-blast helmets used in tho protection of men working inside sand-hlust rooms, it was found Unit a rmntS^ such pro* inside th> maintain! the hclim 2531 r 22 that iit plant z 1* jH-ruliuH* needl'd iviih tJie^i'npera- :lmr standard. On thn Y was apparently funcs wi'w r*mbicli-J. on nrcwsar-y In kt**p tin* omit less lltiiu 10 million on method ijain provi'.J 71 rel;,k*n**hip existed lwhve.ii the amount of air supplied to the helmet end iho ruiieentrulion of dm-t inside thn helmet during blasting (4$). In an attempt to determine! the optimum nir volume to be supplied to 4* I l1 t iI r^C/rfvrr atutiimuaml Um wncc&t at daft .ic f a study of the relation ducts and tint amount of pneumatic took. It is ng an exhaust velocity llto dust-removal Imod tlm dust conceitl nit ion ,:an 10 luilUtm particles nst helmets used in the oho, it was found that A Tkoi 3&--Gcas&dwwiarfttaiiuohis l.*orwn U rvtam* fair snM'Br't tn btiatuawl it* aoiBhr SAM jmtidM ImIt liintM If mlM. Fitch protective devices, it was necessary to obtain dust samples from iusido tho helmet while varying the air volume, at the satno time maintaining the dust concentration in the sand-blast room (outside the helmet) constant. Figure 26 shows the results of such a study f THIS DOCUMENT WAS NOT A RECORD OF' PPG INDUSTRIES, INC, DID NOf COME FROM IT'S FILES ANO CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC.' * TlTMY003l 1 2532 72. and H*arly indicates thuL the positive supply at 0 cubic feet of dust* free air per minute will protect a worker under the operatin'; con dition* now' in practice )>t sand-blast rooms. The ultimata criterion of protection, however, is the result of dust determinations of the air witidu the helmet; that is, the air actually breathed by the worker ami not tlic volume of air supplied. Figures 27 and 28 show the arrangement of the dust sampling devices used in determining tho clegreo of protection alfonled a worker by such protective equipment. It is apparent from the few praetieul applications sliown in this discussion that the dust determination method offers a mil criterion for determining the effectiveness of the various dust-control measures which are treated in the sections to follow. PIOUSC ZB.--AS JMEiST WAS NOT A RECORD OF 5TR.ES, INC. DID NOT COME FROM AND CANNOf BE AUTHENTICATED NDUSTR1ES, INC. 1 BB 0020039 1 l 2533 feet or lw-u ;<ld c operating m#* T ;umto criterion ?t^HmatiuU-S of the uir rSwed )>>* the workrr a 27 and 23 show ll,.. :sl in detenuiuius tU protective equipment, iv'ati U5 shown in tlU i ffers a real criterion dust-control measures ^r- i - -1 '' ! < ' * `J r THIS LU.ui. c. .I vYA'i ilUf . ;<oO..D Ur PPG INDUSTRIES, INC. DID NOf COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. ^b"oo^1 YL GENKRAI. DUST-CONTROL METHODS The prevention of occupational disease hazards is clucfiy an cngiproblem. Until recently, very little definite information was ninl scarcely any attempt was made to develop control ! ..-i!hh|a. In an age of progress, during which production and .-Linizutioti were uppermost considerations in industry, comparu- lively little thought was given to the health hazards associated with i!.r*u. The serious consequences of the neglect to provide adequate i: iliiifs for prevention have grown, until at the present time, their rt*i has become a vital concern to industry- There is, moreover, a iv.-iliznLion that compensation for the occupational diseases is ouly a iiiaiter of time, end that, as in the ease of accidents, a preventive )>Mrnm must he worked out. Just as tho cost of insurance under workmen's compensation acts are in a large measure based upon .tr-i.h-nt experience, so also will tho cost >f caring for these suffering fruiii the diseases of occupation be determined by their relative frequency. TJic formation and development of a preventive program bt this time is of utmost importance. It must he realized that the benefits of even tho most extensive prirgraiii of controlling dusts are not always immediately realized. This is particularly true of tho fibrosis-producing dusts, whose effects n? not evidenced except after e long period of time. Thus, occasional iliyahilitics are likely to occur amongst workers exposed prior to initiating a preventive program. On the other hand, tho control of toxic dusts containing lead or cadmium may produce beneficial ri-Milu in a comjwrativoly short time. Nut aU the methods in use for controlling dusts are successful. TJiii choice of any method depends chiefly upon its efficiency in rnltirhig a given hazard and uj>oa its adaptability. A largo perrmistgo of reduction in dust concentration achieved by a certain li*vro docs not necessarily imply tlmt it is efficient, since the measure **f Mirerss attained depends upon tlio ability of tlu dcvico to reduce roiirentrations below the threshold or safe limit. A method of con trol also cannot lie said to bo cinnidctely successful which interferes with tho process or which lundem the worker in the performance of hot hi ties. The chief methods of controlling industrial dust hazards are (1) iiiliKtiliition of noudust-producing or harmless substances, (2) > olutiou of dusty processes, (3) wetting dust at source, ami (-1) local (73) | BB 74 f.' V exhaust ventilation applied at point of dust generation. All Uinta method* have bivn used mui huve ncluoved considerable success in iiumy instil uees. With regard to the first method of controlling dust--namely, substitution of nondust-producing or harmless sulistances--there is only limited application. In ccrtuiu eases substances hare been replaced by others known to bo less harmful, such as in the cose of polling compounds applied on foundry molds. Pure silica was for merly widdy used; butrceently this has given way to other compounds which arc noninjurions to health. Considering that the chief dust exposure of foundry molders is from the application of parting com pounds (49), the substitution of s. nnndlien-eoutaiuing compound lias eliminated a serious occupational disease hazard. Again, in Uio caso of abrasive denning, sand has to a large measure given way to metal shot. Tho improvement obtain'd by such substitution is dearly shown by tho dust counts given in the following data, taken from a report on abrasive cleaning (4S):' Dut concentration !u and-blut room using saad abrasive, 960 inOUoaparticles per cubic foot. Dust concentration in euuhblaat room uniu- metal abrasive, 1X5 million particles per cubic foot. 1 co improvement as shown by these figures is remarkable, end it is possible that with the cleaning of costings preliminary to blasting with metal shot, the dust concentration might lie further reduced. The second method of controlling an industrial dust hazard consists of isolating the dusty process. This method possesses many possi bilities, but unfortunately is not widely used. The theory under lying isolation is to conecntrijlc.the dust sources to one locality or to a single dosed spaco. In this way, a minimum number of employees are exposed to dust. At the present time, many foundries, during shake-out, expose workers who normally ore engaged in occupations with low dust concentrations. Thus, molders in a particular foundry may be exposed to & dust concentration of 3 million particles per cnbie foot under normal occupational conditions, but when shako-out operations are carried on dose by their exposure may ho increased to more than 50 million. The sumo condition* exists when annealing flasks containing ground slag are emptied in malleable iron foundries, frequently exposing grinders and tumbling barrel attendants at work dose by. Perhaps tho best example of_ isolation of a dusty process is the * nhra.sivo cleaning room. Tills completely encloses a very* hazardous process and expose* only the blaster who is generally equipped with a protective helmet. The room is also exhausted wlurh further assists in reducing the dust concentration. Processes which nro isolated require good vemilutioiu Other examples of isolation are - l Lu.0 the auti Inibt'.lMU A pn< limiting imnimut may be t implies t with pm The II smirrt-- i about llu getting h wetting, Th follm roek-drilii Dust com Dust com \Th3o tl several dri content, tl, rive. In v drilling^wh wet mctlux That wet 1 by a study show** an a. | brought on TulmwuliwL TubmruUwr Recently wet method.* consists of a! fresh casting Water under an perator i washed away times placed & suitnbl lm fortmrati'ly, i cahility of tin eastings foumi eontnil is far.' method at prr vplnpiin'iit, i h DOCUMENT WAS NOT A. RECORD OF ,NC. DID NOT COME FROM FILES AND CANNOT BE AUTHENTICATED PG INDUSTRIES, INC. | BB 0020042 l 2E3S generation. All thr-<, 2 <t T 'idoruhlc surges* in a. ng dibit--namely, .^nulntanccs--tlioro in -^Rbstances have hern U, surlt as in tho case u( 2s. Pure silica was for. way to other compound* ring that the chief dma beation of parting com.intainiug comjiouud lu* .zrd. Again, in the ca*.sure given way to meLri substitution is dearly ring data, lak.cn from a rraiirc, 9GW mHiion particle* _etal abnjuve, 155 million is remarkable, end it is *ireliuanary to blasting 1 be furtiier reduced, -ini dust hazard consists possesses many posrii, Tho theory under*cs me locality or to .a i jor of employees foundries, during r^^vd in occupations in a particular foundry i million particles per us, but when shake-out .re may bo increased to exists when annealing ullcablc iron foundries, rel attendants at work dusty process is tho oses a very hazardous nerallv equipped with austed which further I'rocerwcs which am -uples of isolation am 75 miloiimUc turntable Tor abrasive cleaning, tumbling barrels, and l, li, lt.i!ii\iug room.'', that arn found in some pottery establishment*. A (iractiro which has lately gained wide use in foundries cuiisisU in limiting tho shake-out oimra lions to ft single night idlift when a minimum number of workers arc employed. While r.uch methods may Itn thv.rrihetl us isolation, they are uot exactly so, sinco isolation implies that dusty operations shall ho corned on in sepiuwtc quarters i(!t provision for exhaust ventilation. The third dust control method--namely, wetting at the dust mint--is gcncndly employed in rock drilling. Water is spmycd nlmiil tlm hole being drilled, thus preventing the dust generated from f*-itlog into the air. Considerable success lias been achieved by ueiling, which is perhaps tho oldest dust-control method known. Tlie following dust couuts exhibit tho success attained in an actual riM-t-drilling 0|>cnitiou (50). JVixl nHtccntrullon ilh water spray 11.2 million jartlrta jx?r cubic foot. Dust rxiiicuiitratinn without water spray G14.5 million particles per cable foot. While tho reduction lias been considerable, it is still possible when several drills are working simultaneously on rock lugli in free silica rmilrut, that the concentration of dust produced may become execsidv\ In view of a inure positive method of controlling dust in rock drilling, which will Ire described later, it is sufficient to point out tluit wrt methods actually reduce tho concentration of dust. 'Dint wet methods are not positive methods of eoutrol Is borne out by a study of wet grinding in a Connecticut ax factory (51), uluch shows an abnormally high death rate from tuberculosis presumably brought on by dust exposure. The data follow: TiiIhtcuIimui death rate (male), State of Connecticut, 1.7 per 100,000. Tulxarultmia death rale (grinders), ox factory employees, 10.0 }er 100,000. Itcrently there bos been developed a combination of isolation and wet methods for controlling foundry shake-out dusts. This method nmsists of a largo room similar to a sand-blast room in which the hvsli castings (generally wiih copo and drag removed) ore placed. Water under high pressure is then directed against these eastings by ait |ierator outside tho room until tho molding sand and cores are wtudicd away. In order to fucQitato cleaning, tlie castings are some thin** placed on a slowly revolving table. Tlie sludge is collected in a mutable hup|>cr and ilio water drained o/T and recirculated. Un fortunately, there is a lack of published data relative to tho nppliraiiHUv of this type of hydraulic cleaning to all the various forms of nuttings found in industry, but it is obvious that this method of dust control is far superior to many other methods now in use. While tho method at present lias only limited uso and is In the process of de velopment, there can lie no question that tlie problem of controlling 1 iA""' _ ' DOCUMENT WAS NOT A RECORD OF NDUSTRIES, INC. DID NOT COME FROM ILES AND CANNOT BE AUTHENTICATED PG INDUSTRIES, INC. -TS'*' -'-l Ti- |~B8~0020043*'7 -"mm? tl>' dust funned at- foundry shuko-onts, wlilr.li has nlways been ex tremely diflieull In attain, will gradually lie lin accomplished fuel. With regard to the fourth method of controlling dusts, it may be said that of the various mccltmiicutl methods devised, none has such wide application as exhaust vetililaliim. Exhaust systems are de signed to utilize the directional forces of uir currents at tlie dust source and to convey tlie dust captured to a suituhlo collecting place. An exhaust system iwy briefly bo divided into four distinct parts: (1) The hoods used to capture tho dust, (2) the duct system to convey the nir ilo\v and dust collected hy the hood, (3) tho dust-collecting equipment, and (4) tho fan and luulivc power. Hoods assume a wide variety of shapes depending on. tlie manner of dust production. Iu some cases they completely enclose the dusty process, as in ruck drilling, while iu others they utilize the directional effects of a dust producing source, being placed so that tlie issuing dust is thrown into it Upon hoods which arc correctly designed depends a great deul of the success of exhaust methods in controlling dust sources. The duct system consists of an outlay of duet work so proportioned that its various branches band e tlie necessary volume of air rvquircd by the hoods. Tho system conveys the dust collected and lienee cveiy part of it must maintain velocities wliich will transport the largest particles which enter it. Dust-collecting equipment, where used, is designed to capture and to restrain the du-l collected by the hoods. Cyclones and doth fillers am frequently used and, in rases wliere high cflirienfie* of sejwiration are obtained, recirculation may bo practiced. The fan and motor serve to maintain tho air Hows through tlio hoods and duct system. Their size is dependent lqion tlie volume of air handled and tlie total resistance of tho system. Tito ty]*c of material to he conveyed often determines tlie type of fan blade and housing which must bo usnd. In the subsequent sections, the chief applications of exhaust venti lation are described, giving the results of researches in granite cutting and rock drilling and tho status of exhaust ventilation with respect to grinding, polishing and buffing wheels, foundry slwkc-outs, and abmsivD cleaning. Becouso methods of exhaust ventilation vary widely even in identical industries, and because pertinent data per* tabling to titem are meager, the following sections will be devoted to discussing tbo underlying principles of this method of control. r- iT A RECORD OF NOT COME FROM AUTHENTICATED | BB 0020044^1 2533 f- rumts always lieri :t accoatplidu-d rolling ihwts, it may U devised, Done lias ;.Uaust systems am r ennruts at the tiu*i :;ilahlti collecting |.luiv. _ilo Tour distinct paiN: . duet system to c-i.-.v-v (3) the dusUcoltccriii;; .rending on the msim-r leleJy enclose the dusty y utilize the dirvriioiud _Cvl so that the issuing are correctly desigiMiI ujflhotl.s >u Controlling i work so proportions! volume of atr required ~t collected and hems* _icl' Mill transport the ysv ,J to rupture and and cloth Clt'-rs ^fflcjiciea of sepurutiou air flows through tlie .nt upon the volume of system. Tho ty|c -of type of fhn blade and tions of exhaust venti-ches in granite cutting mtihiliou with respect ^ndry shake-outs, and just \ enrilation van' so pertim-nt data perins will lw> devoted to .bud of control. r vn. DESK.'N 0? HOODS No field in indiistn' has received so little attention ns the design of vlmirst IhkwIs. Wltlt the exception of two or three instances where nine research work has been done, there is a surprising lack of data attaining to their requirements and design.. Hoods have been con tracted and installed without any certainty that they will perform hTehxpeedcetesdig.n of local exhaust hoods is complicated chiefly by the fact ihat tlic conditions vary tremendously, ranging from possible com* [ilcto enclosure of the point of dust gencRition to the need for on iwhnust hood operated iudcpendcetly of a. moving cutting tool, inter fering in tho least jiossiblo wnv with the manufacturing process. This h well illustrated by comparing the conditions associated with rock drdling where tho point of dust generation may bo completely en closed with tlioso involved in the operation of the band-pneumatte granite carving tool to whirh no attachment can be made, winch is moved about over the stone at will and which is hi the hands of a highly skilled and often temperamental individual. The function of & hood is to create a velocity at the dust source which will direct the particles into tho opening and thence through (he duet work to a suitable collecting point. Obviously, therefore, if the velocity characteristics of hoods are available, an approximate idea of tho performance of tho hood could be gained. For it is from Mich data that the designing engineer can foretell what to expect of a particular hood with a given flow of air. This procedure would be far better than merely staring that so many "inches of suction" are required; the term is perhaps convenient, but it does not express the miching-out qualities of a hood winch are to important. This chap ter, there/orr, is concerned with the velocity characteristics of hoods and presents many important principles pertaining to them which Itave practical application. xsmiATiox of VELoem'-msrrxxcE ksm.txoksiuf It is well known that tho air velocities-in the region in front of an >|icning under suction change rapidly. To obtain an approximate Murion lictweeu air speed and distance, consider a small opening miler suction surrounded by an imaginary sphere of radius r, figure Ilia clear that all I ho air entering tho opening must pass through ttm surface of tho sphere, except at tho region cutting the opening 07) __ ___ NC" ~ NOT THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. * l_BB_002005 | 2539 78 which may he considered small iit comparison. Xf tlio amount of nir flowing ba represented by Q, tlicn the velocity along the surface of tlio sphere trill bo giveu by the equation V**QfA whore A w tho surface of the sphere, Tho value of A is, however, front elementary geometry equal to 4s-/4. Hence, V-4*7* (1) Tho relation indicates, therefore, that tho velocity ntany point on tho snrfuco of the sphere is proportional to the volumo flowing anti invero-dy projtorlionul to the square of tlte distance from the opening. VELOCXTT CONTOURS AND STREAM UNIS OP HOODS If the nutuni distribution of velocities lie ascertained and drawn for a circular opening in a diametrical piano they would bo of the idtape indicated in figure SO.1 Tbo curves marked A, Jl, C, etc., are known as equal velocity curves, that is, every point on tbo curve represents a constant velocity. Tlio curves 1,2,3, etc., drawn so ns to lie perpendicular at tbo points of intersection with tho velocity contours, are called stream lines, or lines whoso tangent at any point indicates tho direction of air flow. Obviously, tho total flow between two such curves is constant, the convergence of tho rtocuc 39-iw hi dwt curves indicating an increased velocity toward uihtdnKtwrtiirtt<mut t krwp^moruttrr tuo opening. .-From-tho symmetry' of a circular opening rt is easily seen that tho velocity conditions shown in figure 30 arc tlio aaroo in ouy other diametrical plane. Consequently, tlio rotation or tho piano about tho axis will generate surfaces of equal velocity and tubular sheets of flow. Thus tho velocity and simim-lino distribu tions in a single radial piano of a circulur opening represent the veloc ity conditions existing throughoutthespberc ofinfluencooftlioopeulng. The determination of velocity conditions in cases of perfect sym metry, as in tho ease of tho circular opening described, is simple. For rectangular openings, however, the procedure would bo intricato and practically tuqiossibio of representation in two-dimensional figures. A fair approximation of conditions is, however, dcduciblo if tho contours ho niapjurd in two radial pianos jH-rpendicular to tho sides as site .to in figure 31. Jn tho caso of square openings tho con tours in each of tho planes are identical. ntzvciPi.D or stanuAiurr or vxtocrrr contours It can be shown fur a circular opening that whatever its size or volume of flow, tho velocity contoiini and stream lines are always of * Tfe* MM rt ihidinW IS Vr!artr (taMtffUn rt M Ir firm In Mia* IX. NO Tf I bo rlH<*r hv l any. l t&r l' m ituu rut ' nthtrrd / 4 inrliistt snctitui iwnm vtih: uf ti iurU* Tlial l!: twifiuiitn-. (lane Ihn. ttf I Wit !>{ . ggss ww .KM les and cannot be authenticated G INDUSTRIES, INC. --,-^V'Vi. yrgg "j BB 0020046 l 2540 -isoiL* If tlio amount of air ritf ng the surface uf ( 1m*. 2^ .oro - l i* tbo tuirtmv . > elementary geometry 1 3 (i) velocity at .any point on the th volume flowing mid distance from tho opening. : LINES OF H00U3 ascertained .and druwu for iier would he of the shape i A, IS, C, etc., aro known ?s, that is, every point on i constant velocity. The -a so as to he perpendicular -section with the velocity ream lines, or lines whu*o dicates the direction of air total flow between two t, the convergence of the increased velocity toward of r :*-cuhir opening it is iow figure 30 am the s|^kntly, the rotation of laKtat equal velocity and and stream-line distribuicning represent tho-vdoeofinfluenreof tboopening. i in eases of pcrfcot*&yinling described, is simple, rednre would bo intricate don in two-dimensional is is, J wcver, deduciblo mes perpendicular to the* _ square openings tho con- errr coxTOtnts :hat wliatever its size or uream lines am always of : i* stem to cUn* IX. 79 tj,,. sium- general fonu (fl?), These facts have been experimentally .MeriuUM ii and may be extended to alt bonds (33); they nro covered l,v the following theorem: The position* uj the relncity contour* for any homl when the contour* ore expressed tn term* of the Telocity at Its h<**l opening arc purely Junction* oj the shape. oj the hood; the funhtur* are identical Jor simitar hiuxl shajies when ouch hood* are ! to the some base of comparison. For example, if the velocity1 r*Ie*iditneu*cciuietmed**isoouu2ttdwwuparerrdrtcaaellnootnnoggftuhtihoeouavx.\eislowocf.itayunaS--t--it-nb-e-'o---h----p--d1i-ai--a--n---m--o---eo-ftef rthdoumcoutpreennnindinogu. ,ntidtlllei)or xuiio value must occur for a 12-inch diameter opening at a distauca rTfilimr.rtbtrhso. above principle holds for rectangular hoods mar appear rHtftwitig, since tbo velocity distributions will vary in every axial phtm* through a whole quadrant. However, in corresponding phmes *f two ojwnings the principle does hold (33). NOT"'....... 1'; k THIS DOCUMENT WAS NOT A RECORD Of PPG INDUSTRIES. INC. DIO NOT COME FROM ITS FILES AND CANNOT BE AUTHENTICATED ay PPG INDUSTRIES, INC. | Bfi 0020047 { 2541 Keclangulur Iiu'hU on desiguntwl n* nimilar if tho ratio f their sides Li the same. Two rceluugular hoods, therefore, will havo similar velocity characteristics provided the radial planes arc mapped in corresponding units ami if the velocities ure expressed as per centages of (he velocity at the opening. Tho principle of similarity oilers a powerful tool for research, for forgo hoods may W tested in model form and their characteristics deduced. It is a basic principle applying to all hoods, reducing them to their simplest terms. VKLOCJTY CUABACTEniSTICS OF COUUOX OPENINGS Tlie velocitycontours and stream lines for the usual openings found rtm ji.--.uui piB i wswi Trtociir *u* jn practice are shown in figures iMtttasvebanSvMflntoaateNetaasubrboaS*. . , . ,. 32-3G. Thus, provided tho re gion of influence for all round openings is mapficd in the coordinate units corresponding to figure 32 the velocity contours will all be identical and will be c.vpresed in percent of the average velocity in tho plane of tho opening. The saine is true fur the various sbajiod rectangular hoods where the short side ofeach is divided into eight units, and the long side in the same units in proportion to its length. An open ing, therefore, with a ratio of sides of 3 to 4 will have lOX unitson the long side. An examplo will illustrate the appli cation of tho contour fines of figures 32-36. tacu SS.--VatorUr Mtwn ami Mm Itow to radial trim M SupjMMO it is desired M #tMfltog, Cmhmm m mml m m*m S Um to find tho 8]>ocd and wkrttyat u ,paging. direction of tlio air movement at a point Amelias outward and 5 inches upward in tho radial plane perpendicular to tho short side of a 4- by S-inch hood lumdling 6-10 cubic feet per minute, Tho ratio of sides is one-half and expressing the coordinates of tho ]H>int on tho Imsis that tltoro oro S units of length on the short side the .coordinates of tho point in question are 8 units outward of the axis and 4 units upward, as shown by the circle in figure 33. Tho velocity at this |MUII 1 Ivjh uiinti * loinn iu'Iiii n>ut<> in ph sif'era nmlui nor** a- tlm figure is remove Effect of t> It tuny flaring of I Yrhmity r of flow tlm veha'ii of flare in which an* surface **r eoiitiiur ili the slut|H' OCUMEnT WAS NO" n RECORD Or DUSTRIES, INC. DID NOf COME fROM .ES AND CANNOT BE AUTHENTICATED 3 INDUSTRIES, INC. CTi v . _ T Ba*0020048 i 2542 the nil!.. *,! -, therefore, t.ii: . .tlinl plain** arv |. are esimuMti u , J tool lor rr-u vu ad their elianuM.i. it is a basin |.rit<o oil bunds, n-b. rir simplest term*. ckaractkkiktu > ... UitOK Ol'Uiv'lXiiS ritycantoursamUli. Sr usual Opening ; are shown in fi*,,*mius, provided llw t.' pped in the coordii.-* y contours will all Ithe average velorin for the various shut* I SI nt. Li approximately 12^ percent or the velocity at tho opening. 040X144 .:iv, Ihn velocity at the ojtctiing bring ----*~2,SS0 feet per nlet the velocity at the point must he 0.12oX2SS0*3G0 feet per These calculations assume that the flow in the- region of ' unco is not grossly impeded hy an ol>s(.ruction. 011101*11050 the ..t.mra arc altered and must be redeicnnined with the obstruction j.bn\ It may be said, however, that if the obstruction is eon'.rjhly smaller in cross-sectional area thnn the surfaco area of tbo iioiirs po&diig through it, the velocity distributions ns shown in i lion. la 9 nObl {.Imp. w J OIWMil a* mt tv s outward and 5 nu*lu-< ic short .lido of a 4- by tc. Thu ratio of sid*-- the point on the liadside the cmmluialrs of f the it.ti* and 4 imii* The vclueiiy at thi Imps a.--VSnciiroaolaun lota Itiuaat opsnloc- CoflU*giinC9ilri>w*T|ea"*<**r|lcftr ttlwoncaias. dm figure* are not suhstnnthdly altered. The farther the obstruction h removed from an opening the less is tho error involved.. mt aiwpe on tho distribution of velocity contours It may reasonably Ire supposed that the amount and the degree of daring of a hood has considerable effect on the distribution of the v.Udty contours. If, however, it is assumed that tho distribution ** *h*w across two openings of the sa mo rizo and slut pc. are similar, il*r velocity contours arc substantially the same, although the degree 4 Hare in each differs. The main portions of tho sphere of influence * bh*h nro affected lie behind the. edge of the ojiening, tho boundary uifart* tf (lie flnml jkHion Ivlng the. chief variable. Tho velocity nlour distribution, therefore, may l>c said to l>e drj>cndent upon be shiipo of fhc ojH'uing only, 'provided tho distribution of How THIS DOCUMENT WAS NOT a UZOO::Q Or PPG INDUSTRIES, INC. DID NOT COME FROM ITS FILES. AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. . I BB 82 f> L ' ; IM i i nereis It does nut vary greedy with the. di-grcc of flare. As a mutter of experiment it has 1h*oii found (hut over n very wide mngo tho degree of flare tilt era the distribution of flow items* an ojaming only slightly (52). lienee a 5- by 10-iuch opening with a 12-inch flare to a 3-inch diameter duct gives the same contour distribution forward of an ojtcnutg as one with an S-inch flnro (say) to a 5-inch diameter duet. In fact, were the opening but the end of a 5- by 10-iuch duct, tho velocity contour distribution would differ only slightly. Since, os a rule, most hoods arc gradually flared in order to reduce entrance losses, it is practical when dealing with contour distributions, to 4 5 i Vmvu a--Wei. Nn* IO-VMir coalman tar ft reti**uJr opentaj: *bar* ruta of Mr* b * to 4. Cwtiin aro wptwoni m lomuba* ut is* vtledir M Um apMlng. express the overall shape of the hood in terms of tlm *hajK> or form of its opening--that Is, in terms of the side ratio. A matter of considerable importance Is tho velocity distribution over tho hood opening. For tho purpose of simplifying calculations, it has born assumed in developing tho contours in figures 32-35, that tho velocity distribution over tho opening is uniform. Such an assumption is not correct, as may be judged from an examination of tho figures themselves, which show tlic 100 percent contour to l>e somewhat displaced from the opening. In other words, tho figures al>otr a higher velocity than the average over the central portions of tho opening. The situation is somewhat like the phenomenon oc curring when a fluid flows through a pi]x> which, because of viscosity, gives a liigher velocity at tlio axis than inward the edges. The ciTect iu tho caso of itoods docs not however, arise from similar considers- f I KtWftf *T * ( IS DOCUMENT COME from |^fc*?BEAUTHEWlCATE0 *ppa Industries, wo. 7~BB 0020050 \ 2544 * lore. As a . :v very ui.lc ran-*- : across an optmiir'.. .ig with n J2-iii*'!< j' 'ur distribution f.-,. y) to a S-inrh flLu:>"! of a 5- by 10-iiif!i tj:,. r lily slightly. Sirdcr to mince ciurai. nlour distributions, i. NOfC-v. Js ml Mn iillai CaatMt* m a Traiti is of tho shape or form ratio. lie velocity distribution diuplifyinp cm Iculalions, tours in figun* 32-Sti, ninp h uniform. Sndi etl from an examination >0 Jierreiit contour to !** other wonIs, the figures r the cent ml ms of kc the phcnoim-mm ** ch, lai-aiise of vim-unity, (1 t ho mini's. The eirtvt * frinn similar consider.-!- ( THIS c.miv i . PPG INDUSTRIES, INC. DID NOi CG./ni rKOM IT'S FILES. AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. i j~BB 0020051_| I 2545 "'0 84 4 tions. In hood ojiemngs it is necessary to contend with nn edgo effect. Air enterin'; fmm behind the hood ix forced to turn abruptly into it, thus cmi liny a stationary "vortex which restricts the effective area to a value less thim the actunL At the corner of a rectangular hood, the effect may be considered as intensified. Experimental data lend to show that the effective area is reduced in proportion to tlie perimeter of the opening. TJio edge effect may be considerably reduced by the use of a flange placed around the edge and lying in the plane of tho opening. A flange approximately 5 Inches in width is sufficient for hoods up to over, veil wimly.d*. . A simp) without << velocities ordinarily gov cn.ing which )n series of c: / s f o i A I' r $>JC TMexzS.--Vriorttr racismoml >Urua llmin araUfci] * Oanrnl ciira2arart8S. Caetaun wmw--rj a pmm.-i (U> tkicUrt laaorr'ans. 3 square feet in area. The flange tends to;cut off tbo floor from the region bcliind the opening which is frequently useless and is advan tageous in two respects: First, it increases the effectiveness of tho hood in the forward regions, and second, it reduces tho energy con sumption. of tlie hood. In figure 37 the velocity contours and stream lines of a flanged circular opening are shown and may be contrasted for the safco of clearness with the clioructcristies for tho some opening in figure 32. AXIAL VELOCITIES Tlie representation of aerodynamic rliamrtrrixtirs of exhaust hoods by means of velocity contours offers a fuirlv simple means of com paring graphically various typos of hoods. Tho determination of contour lines, however, involves considerable time and labor. More- Tlie point \t the opening, in no diivcii An analyst by tho CqUu! wlieto I'is tl velocity at tic *ro constants. DO=uBT cwR" ipQ INDUSTRIES, INC. |~bT00200^J 3546 r-x with nn cdg** ^Pb turn abrupt lr i'slricts (he effective *ncr of a rfct.un511l.1r Experimental data in prujwrtion lo thu v the nyc of a flange of the peniug. A .cut for hoods up to W over, velocity (umlours do not lend themselves to mathematical analysis. A simpler and more, direct means of comparison of elementary hoods ttiilwjut distinction to the opening may Im had by lho analysis of vrlncilic* along (he projected axis of openings. Since exhaust hoods ordinarily draw dust from tho area directly in front, tho chief factor governing the cflideiiries is.tlic distribution of air flow in this region -hieh may he cxpr<**xed it) terms of tho axial-velocity curves. A M*ries of curves for several circular openings are shown in figure 3S. s ^-rty*a&aicanz,isr pla& Couiwoiy off t3io flow from tiio useless and is advan* effectiveness of the aces tho energy concontours and stream d may ho contrasted for the same petting -tics of exhaust hood* unpin means of comlie determination of no ami lulmr. More norma.--Atioi wtadt? ww* far *w*lrtnubrumiac* Tlic point velocities are expressed os percentages of the velocity at tho opening. As may be seen, the axial-velocity curves arc limited* in ono direction and arc almost hypcriiolic in shape. An analysis of i ho data has shown that tlto curves may be defined hy the equation (32). n j(X) m where 1'is tho po'tit vclority expressed as a percentage of tho average vehieity at tho opening, x tho dislanco from the opening, and m and n are constants. When Lite function/()*) has (he form w-m=? <*>> THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM rrs FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. | BB 0020053 ! ss M Sulutlituting the value of b given in this equation m Tile*general rquati<ti (3), we obtain finally for square and rectangular o|H!uiugs uRfrr"l>-"! b+o-KA) J where (S'* j^rrthe distance outward along tlie axis measured in inches. .l*=the area of the openingin square inches, rolls' ratio of aide* (loss than unity). percent velocity at the opening found at the point t. Thus, tlie eenter line velocity curves may be defined completely in terms of the goomet ric shape atul size of the suction openings." Tho exponents of .-1 aud x in the general equation tiro close to 1 and 2, respectively. This suggests that the true form of the general equation may be /(O-bA'Jjt*. Tbe following simple formula is suitable for quick and approximate computations for openings usually found in practice: Y 0.L.4 too-)'-- (0) Equation (C) may also bo written so as to give the velocity at a ]X>int along tho axis directly in terms of the air flow Q, since J*-T7rrtX100 where F0 is tho average velocity at the opening and Q->A F0, A being the area of the opening. Thus r* 0.10. y+o.i^ (7) )l is interesting to note that this equation for values of Xs wliich are vwy large in comparison with O.lvl gives tho relation V- (8) wliich is identical to equation (1) deduced from elementary considers* tions, with tho exception of a larger constant in the presentinstance. The nomograph of figure 41 lias been preparcil and gives tho value of Y when z and A are known. To uso this noinogrnph a ruler is connected between tlie values of x and ^1 given, aud tlie valuo of 1* mid off at tlie intersection with tho- middle scale. Tho lino drawn in tho figure connects a value of x of 10 units with tin area of 150 square units, giving at the intersection with tho middle srule a value of }'equal to 15 percent. In other words, the velocity at a distance of 10 units from ini opening 150 units square is 15 percent of tlie velocity at the ojiciiiiig. Taiu.k 2t.-- /w Afn 4 qni. W Iwnl.i . . HI .|iof, fr~tu-:rr *-v ,, . Betelion Ule In table Z tlie lmod ax f this table fu vwy little raent in clli< be gained h tug the ope Die Wn1, the aven:" t at the ojM>n inversely as and cou>c({i crease* ns ti the pening Howover, t two advant. largo JxkmI: en Iranceli*** by reducing itira at the and second, of im'lm'icn increased in gions forwm peniug. 1 contours h; valuo of app ly 14 feet ]x for square q vnriniis shuv. convs|H>ndiii larger ana f. the cniiiiiur i is cun*tullt. (f THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, NC. DID NOT COME FROM irS FILES. AND CANNOT BE AUTHENTICArED BY PPG INDUSTRIES, INC. T BB 002005 2548 ie gcnrrul _ * opMlillJM (5^ d in incite*. the point 7. d completely in ripenings, re close to 1 anti of tlio general nple fonnuk is openings usually (6) tlio velocity at ir jl'"** Q, since ho dug ami (7) f Xs which are (8) itnrv considerssent instance, gives tlio value ;raplx a ruler is tlio valuo of The line drawn an area of lot) lo scale a value .y at a diitaiira percent of tlio M0TE: THi:- S9 n ^ -- . '' !Vi C i , \ _. TtnU! 24.--Vrlncil't ehnnga along am nf hmht of fw5 titan trilk eanMont air fiomnf 1,01*1 tahie/trl per nin><la--~h,tarmiiii,il Jrom Jormttla (7) Kclalion between opening area and velocity gradient In table 24 arc given tho velocities of various sized openings along the hood axis wlicu the volume of flow is held constant. Tlio data of (hu table suggest that very littlo unprovement in efficiency cun Ik* gained by increas ao-t /s AOmOGWfPtf too - K wr to-n ing the open errs of (lie hood, although the average velocity at the opening varies 5* Cinversely as the urea mid consequently de- (Teimes ns tbe area of tho opening increases. However, there are two ndvantages of a i;.- L: Imgo hood: First, tbe mlnuicclossislowcred X m rby reducing tbe veloc ities at tbe oponing, - mul second, the zone *4 influence is greatly 7" increased in tho re gions forward of tho jieniug. liolutive - r/ \ 5 rs -to to-- x>- 1i -JO 1 x -JO -09 S JO 30 \ \ -90 \ 1 roiitmirs having a tslno of npprnxiniatclv 14 foot jH*r niiuiito b*r w|iiaro openings of /- tool fStUIL -?!--il'h It IIi><SwIwIIwWmW wlciHla.. i minus sixes orusliowu in figuro 42. It will be noted tiiat.tho contour ctwrrajjonding to tho ri*f*niiig 20 square feet in area envelopes a iimeh lstri*r area forward of tho ojiening. Tho total surface developed by In* contour is tlio whim in each case, however, since tho total flow, Q, ** constaut (Qaa V*d). THIS DOCUMENT cOM^FRONl 55 Snd c'annot be authenticated by PPG INDUSTRIES, INC. pBB 0020055J :o TT0TErT^~~ " r-0iVri: rKui.i 90 Tho chief dirmTvuntngn of a large opening for dust collection lies in the Imt rati? of elmngiMif uirspM*d from tho jioint nt which (ho hood is desired to fundion lo iu opening. In tlio collection of dusts, it is highly desirable to luivc a high rate of change inasmuch as a dust must not only Ini arrested nt its origin but ulso conveyed into the hood and to n collecting system. On the other hand, largo hoods work success* rv >_) i may 1ms drsig each of whirl ratio.' f 1 tor connected hi wderablo>a\i t tho comnui It is not jk> ship between hood opening practice tho n length of flare g of Hoot/# font a-Hittib Hii: *t II brt t*t luJnan* ntaiir MMMn b* > wwss tM af air Iw pt tmanbirbri |*r senate {>esi<a>4,a, aad a|iiMatoaUa MBk fully in the collection of fumes which require low velocities for tlieir control and may therefore he handled with a lower consumption of power. It will bo shown later that in practice tlio zones of influence for most hoods are impeded by obstructions, and that it then becomes necessary to alter t> treatment of tlio problem of velocity distribu tion. However,-the lactora-tv b>ld in mind in any hood installation are the size of iho opening and its location with respect to tho region }i at ** expected to operate; "A ltK1-tTlOX betwjjkn set or noons ax coKsncimo nnets Tho distribution of air flow over tlio hood opening should be as uni- BCTiUOUNATJt >=*? wu *onu M l*blc. This cannot be secured when tho ratio of tho area of tho hood opening to the connecting duct area is large, unless tho length of tho transit ion piece is increased to accommodate the chango in air speed from revtion to section. Otherwise, the movement of tho air will all ho concentrated nt tho center of the hood opening, mid the JmkkI will fail to function pmfieriy. Unless there is an even distribu tion of air flow across the opening, there is little sense m maintaining tlio fuQ-sizo hood. There are many instances wlipre a high ratio between the size of tho o|ieiiiitg and Mm connecting duct is mvreMary, and yet a long flare cannot ho used because of luck of space. In such cases, tho hood When hoods velocity distrib tlio wngl large hoods pLuttl cd sections as slm directions of t'u contours may 1** solid lines indh*;i combimilitm an< single opening v H|io>iding ronton hood into iitdcpr r original velocity DOCUMENT WAS NOT* A RECORD" t)F NDUSTRlES, INC. DID NOT COME FROM ILES AND CANNOT BE AUTHENTICATED PG INDUSTRIES, INC. .... |_BB 002005b 1 2550 /<\ ; t^B^oIWliius lies in at which (he hood is -ctiou of dusts, it is much us a dust must d into the hood and hoods work success* 91 i t V . may I*o designed so that it is divided into several hoods, edge to edge, each of which i independent of (he other. A large hood with a side nitio of 1 to 3, for example, may be divided into (Urea square openings rwimreted in the manner indicated in figure 43, thus effecting a conalembic wiving in headroom over that occupied by a transition piece f (ho common tyjw. It is pot possildu (o formulate a deflnito rule to govern the relation ship helweou the ratio of tho areas of tho connecting duct and tho hood opening and the degree and length of tho flare. In modem pniefiVo the nitio is generally taken as 1 to 1C at a maximum, and tho length of flare as three times tlie diameter of the connecting duct. of Hoacts r mamiK trtl* pf rlf Jb* *t <v velocities for Jheir vvrer consumption of lie zones of influence thatit then becomes of icily distribu.nj ;l installation t^^Koning and its cs^RR to the region expected to pcratc. TTEX SB OS- HOODS xvxrnsa ducts tion f air flow ver ng should be as unide. This cann t bo lie ratio f tho arca a is large, nolens tho mmodato tho cluingo the movement of tho iOod opening, and the o is an even diatrihuseusc in maintaining etween the size f the and .vet a lung flam , such cases, tho lwod taMirliMla itoNtunuipMaa DETDMI1NS.TIOX OP YKLOCITr COXTOUSS FOB COUFOUND HOODS When hoods are subdivided in tho manner indicated abovo, the velocity distribution is not changed materially from that given by tho single largo opening. Tlio contour distributions for two square Imods placed edge to edge may bo combined vcctorially at their inter sections as shown in figure 44. Prom tho resultant velocities and dircrtiniLi of tho air movement thus obtained,* a new set of velocity contours may bo drawn. This lias been dono in figure 42, where tlio solid Hues indicate tlio contours obtained by tho principle of velocity romlunnlion and tho dotted lines represent tho distribution for a single .ojK'ning whoso side ratio is 1 to 2. Tho proximity of corrcK|ioudtug contour values indicate* (bat tlio sulxlivision of a largo hood into independent units of Kiuntler dimensions docs not altar tlio original velocity distribution of a hood. _r , HIS UO.WAS NOT A RSCOiiD Or PPG INDUSTRIES, INC. DID NOT.COME FROM ITS FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 7 BB 0020057 ^ 2551 This method cf combining squariTfOdUsi'Odgd-to edge, mny 1 employed in establishing the velocity contours f r any side ratio although lho method is laborious. It may also be applied to Lho -re/rrzxs^s ntfeoueu opmimt ones- corrrou^s ros$ opm/no Mvwj/otJtmo rroz runt tfv-Cflapwbm f rriodtr hr ilmbl*aimfe* *Ub miw bU*r*fc* f tfettnw stop* sad rtt*. CdMoonflfdMbtoopuinsalnilntrS^laecaRM, study of arrangements in which tlie velocity distribution is not uniform, such os tbo double hoods recommended for the control of fumes by somo State codes. In figure 46 are shown lho velocity contours for two square openings, edge to edge, one of wilicU is Turns^-\>fcfcyamtmmats>faoSh*^aturioa nnwwulVrrr dMrihoU-- mlB-r. |. mill ! lilt Jur rlnrtt f--"*----------* ~l------------- --* handling twico n* much oir as the other. As may bo scon, there is considerable distortion although it is not diflictijl to slum* that there is a slight reinforcement. Studies of this sort suggest that double hoods do not possess marked advantages over tbo well-designed ainglo hood. t/** *THIS document was not a record of PPG INDUSTRIES, INC. DID NOT COME FROM irs FILES.AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. | Bfi 0020053 1 S, edge to edge, may Jours for tiny side mis. y aUrt bo applied in |l,,. socr jJtJjST/WTO fTOJl rbh lg m<t>w l Matabnj-tr^i m In item 11. reloeity distribution is not mmcndcd for the control of 4G arc shown this velocity c to edge, one of vriiieh is ' hocos MUir li^ifhaiiniiif iUc, fimin " iirh 1 -(inrr UK in -Ural, icr. As may bo mm. then* is tot to show that, (Im*o* this sort suggest that double rs r' 't lio w*ll-d-i;'n'*d single a ..H lTY rO.VTOUJW OF UOOHS WITH SrKCIAI. IIOUKDART coxnmoxs Tlo* method of comjioumling velocity contours can bo adapted so - .t llio resultant contours hold for openings with special l*omidaries i;-. Hoods aro rarely used without sonto form of obstruction, .r..: lftinilct! pit her by extended planes or devices placed close to the of the opening. Consequently, if contours for special conditions . ,.n Is* developed from (hose known for simple openings, considerable ,.formation may l> "abed of much practical value. Four special aro discussed below which iudieato the general procedure for tie(doping contours for any shapo of hood under simitar conditions. Ttin method, wliilo approximate, nevertheless ns indicated above, ;*ivrs results wliich are surprisingly accurate. Tlio procedure in determining boundaries under certain conditions i; iiased on tho principle that a solid boundary may bo substituted W any free stream surfaco or for at.y stream plane of symmetry. In this respect, tho problem is analogous to tho method of images *! in capacitance calculations in electrical theory. In fact, the lMindary eases discuss'd Ik'Iow aro distinctly "image" problems. i\t*e J.--Infinite plane pirj*ndicv!ur to art* oj hood at a girt* j;*lttnrefrom the opening. This condition is obtained in the manner shown in figure 47. The idority charartcristics'of two square openings lying along the same avis have been combined in the manner described and tho velocity distribution traced. Since no flow can take place across the stream plane of symmetry, this plane may be replaced by a solid boundary, c'imscquently, tho hood drawn in dash liues may be removed without altering tins flow* into tho hood. (The hood and contours removed war, as shown nltove, bo regarded as images.) Tito velocity contours are tho samo for all similarly shaped hoods Iwaled above an infinite plane so long as their relative distance above th* (duiio remains the same. In the particular ease shown in figure 47, the iufitiitc piano is located at a. distance equal to one-fourth the length of one of tho hood edges. Thus, for an opening 4 feet square, tho distance is l foot. At other distances, now contours must bo hous'd. t'n*c JI.--Infinite- plaue 'at a giren angle to the plane of the hood -toning. . - . This condition is encountered in practice when a hood is placed at an angle to a largo surfaco. An extreme case is given in figure 43 shrro the edge of a square hood is shown touching n plane at an single *f If.*. The resultant contours aro develojwd from the distributions *f two square oiKMiings tilled at 00 to csseh other with corresponding 'dgrs touching. As in the previous case, since no liow takes place aentss tho stream plaon of symmetry, a solid bound;try may lie THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOr COME FROM ITS FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. n5*i i-4' inserted without all win" the conditions of flow. The rcmovnl of tho "image-hood " shown by tln> bruhen liucs consequently will not change tho velocity elmraetcristirs of tho other. The method may Iks duplicated fur hoods at any angle to a piano (except small angles) and for conditions where tho edge of tho hood docs nut touch tho plane.. For tho ease given in figure 4S one may draw conclusions similar to those given for tho previous en*c, namely, that tho contours aro <*s| . an * h< pc Stem j--Xriodiy mlwn br>wtkMdlMl*l a team t n Mirth th tongth tt n* *t tb* iUh abort u laflaOa ptua. CanMwa an en**N*la* wnraiasit at Uttvlocitrattht tho ruuo for all square hoods at an anglo of 45 to an infinite piano, ono of whoso edges meets the plane. Tho length of tho hood edgo ,1- may bo used to determine tlio relative locations of tho contours. I-. Case III.--Infinite plane parallel to the axis of a hood and touching one of its edges. Since the flow in an upper quadrant of a symmetrical hood is tho same ns that of tlolnwer,itfollowathaththlialvcsiiiay be separated by n solid boundary witItout affecting tho conPair distribution in either. Tliis implies, fur example, that tho contours for a square i- opening drawn in a quadrant piano may represent the velocity dis tribution of an opening with a ratio of sides equal to one-half with ' an infinite plane attached to tho longer ride and parallel to tho ImkhI HIS DOCUMENT VAS NOT A RECORD OF PQ INDUSTRIES, INC. DID NOT COME FROM HS Flt.ES AND CANNOT BE AUTHENTICATED !Y PPG INDUSTRIES, INC. BB 0020060 | 2554 f flow. The removal <>f thr lines consequently will n,,t o other. The method mny piano (except small i>"hvi) _:i0 ltood does not touch tin* my draw conclusions similar ..aiely, that the contours m<- 1S'i- j t*iy ivt i i i! .Co l|MMls included in enso III have a vory practical application, iii exha list ins fumes from tanks (iiruuslt lateral openins* ,,IMj dust generated by granite-cutting machines (55). Figure 40 the velocity distribution obtained in a quadrant ]ilnnc per- IM iidiciilar to Hie long edges of a rectangular aliening with a side at m dLmrf fqcal ta <mi fmothlhe IrarthW ijhimiI m pninn-n rfitn tt>m*`t ,L* .glo of 45" t an infinite plane. Tho len"fh of the hood edge locations of the contour#. the exit nj a hand and toueh>u -- t f a symmetrical hood is the t both halves mn v* lc separate! >j tho contour distribution in bat tho contours for a ju:ue :toy represent tho velocity di of sides equal to oue-iialf with r side and parallel to the Iwmh! lum.L--Vkah)r*00(00111 |nr*intiMapniiirktnuaie*atBOni>*elan. CMMinofnoS spMnnioSiti>iMiir>uiHrMkc rstio eqpal to one-half. However, since we are concerned with the iMrilmtiou of contours above an inflnite plane as shown in tho wire, tho opening must bo regarded as having a side ratio equal tie-fourth. t W JV.--Hood with injinilt plane eurrovndjng it and with a plane ,-"11:11)1 to its axis. This ease is a combination of tho simple-flunged hoo<l and enso III w represented for a circular opening by tho region marked "A" " Ihmru 50. This com, however, has only a limited application in ouhtfttry and need not bo discussed in detail. IS document comTfrom imeflSo cannot be authenticated r PPG INDUSTRIES, INC. 7 `I BB 0020061 WV w - ___ 2555 r ( OG U.i i-LCv) DOCUMENT WAS NOT A RECORD OF MDUSTRiES, INC. DID NO.* COME FROM HS AND CANNOT BE AUTHENTICATED PG INDUSTRIES, JNC. - * - * * .p 7 BB 002QQ62~~7 i r< Vo tHFirure wa/y'ySj?r *****iwfclinftInflotrpbispamiM tth, y"u'1 j*fec?ga W it* niJ.;r at is > : P\ i v - s _.>' ^ * SCMUAUV OF F.VCTOK.S ASSOCIATED WITH TIIK DKMIGJf OF tOCAX. EXHAUST UOOD* The important fnctoni diseu*sjd in the foregoing may bo summnrixotl in the following rules uf design: 1. Cmwistcnt with the miuircd efficiency of dust collection and operation of the machine, the hood should be so shaped sud located as to open*to with a minimum air velocity requirement. From a study of tho characteristics of ojK*mtion and dust production of the process, the proper location of tho hood opening, its shape, and the placing of bailies to interrupt a discharge of the dust sitould be determined. 2. Locate the hood as closely as possible to tlie point of dust generation. 3. Choose a hood having a uniform velocity contour-over the area of dust production. 4. Choose u hood having a maximum ratio of flow from effective to mcllectivo areas. smnsratf *ilh an SuwMnw<lir It awl wMk m * |nmlv>SMwnrlwiiy hi l!-ntiraliij. z''' HIS trOwUiWE T VMS NO f. * RECO.nD OF PPG INDUSTRIES, INC. DID NOi COME FROM IT'S FILES ANO CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. j.BB 0020063 4 2SS7 I \ 'U NO I Coiv 1 i-- i < >u:ii j j o i -o YITL DESIGN OP LOCAL EXHAUST SYSTEMS General rtmarks.--A knowledge of the factors governing the design of exhaust systems is important. Installations for controlling dust have failed in tlic past, bccauso fundamental principles were not considcred in their design. In many plants it was customary to regard exhaust systems as necessary evils, prescribed by "blower laws" and because such systems yielded no visible return, but rather added to the cost of operation and maintenance, no attention was juiid to them. Winslow cud Grccuhurg (5G) have aptly stated the situati n in the following words: The engineering journals cany elaborate accounts of the design of ventilating apparatus; but, once installed, we hear nothing about them if they work v*U; whereas if they fail, the result is usually a sweeping condemnation of the vrluJo practice of fan ventilation, without any serious attempt to discover the c*. source of tlio dilMeulty. Tlio following paragraphs arc intended to point out tho general considerations which enter into the design of exhaust systems. They attempt to lllustrato tho few simple principles of design which are within the grasp of most engineers and the methods of their applica tion. For the sake of clearness, it will be necessary to begin with a - - discussion-of-simple facts and gradually to show how these ore utilized in actual problems. STATIC AKA VELOOTT PRESSURES It is first necessary to begin with the laws governing tho movement of air in ducts. Those laws are similar to those pertaining to tiie flow of other fluids and are, in fact, borrowed directly from hydrody namics. The primary difference between gaseous and liquid flow * that one is a compressible fluid, markedly affected by temperature, while the other is considered practically incompressible with a fairly constant specific volume over a wide range of temperatures. In actual air-flow computations tho factor of compressibility is dis regarded, and except for temperature corrections, tlio laws governing tho flow of air are identical to titrate for wator. In a duct system tho flow of air is maintained by virtue of a pres sure supplied by tho fan. This pressure may he positivo or negntivi* depending on wheLher tho duct Lj connected to the exhaust or suet ion sides of tho fan. The total pressure* at any point in a duet has two eoiujMincnts which ore designated os velocity head and static hem!. Tin* funner is tho pressure required to produce tho velocity, and the (OS) ------------------------ - J-JJW2006r7 I?pS.k?^UtMENT WAS N0T A RECORD OF Jr?in FSATwnES',NC> DID N0T C0ME FR0M ITS FILES AND CANNOT BE AUTHENTICATED BY PPQ INDUSTRIES, INC. tUnST SYSTEMS factors* governing tl:allatiorsM for controlling <: .ontnl principles were )>> i.... _s it was customary to rescribed l>y "blower ism. riblc return, but rather ;*! !. ; nee, no attention was paid >, ive aptly stated tbe sitimti.i, unt* of the design of vcatilati:n* about Uimu if tber work n.; repine con<lcuuta.tioef '.iso * ;S attemiit tu dixunr the wsi< t iwl ir> point out tbe genera! ign xhaust systems, TUy ri^ vs of design whirls orr b^eccstbsuairlsy otof ibbecgirinapwpitlihesaally to show boa' these an* r rKESstmEs aws governing tho moveinenl ar t those pertaining to tin* rowed directly fromliydmd\Nm gaseous and liquid flow iedly affected by temperature, Really incompressible with u . wide range f temperatmvs. ictor f compressibility in di* orrections, the laws governing water. laiutainod by virtue of a pres* :v. may le positive or negative vied to tlm exhaust or suetinu t any ]>oint. in a duct ha** two .cloetly h'fid and static lend, produrft llm velocity, and the 4 99 Inter, a pressure supplied to overcome 'ihe frictional resistance of lie* moving air in tho duct. riitiro tho velocity jiressuro depends entirely upon the velocity of Ilia*, iiv change in veloeity cither from an enlargement or conlnusiitn of tho duet, causes a corresponding jnmnao or decrease of static linnl. Theoretically, the static ami velocity beads aro interchangeable ht practice, however, a change of velocity is not exactly compensated by an equivalent change of static head, inasmuch as nn enlargement or reduction of a duct is accompanied by certain energy looses. The movement of air in a duct entails a loss of static pressure. This loss is primarily due to the friction of the fluid to resist motion. A rhauge lu tho motion as a bending of the air through an elbow or a change in duet size also causes a loss of static pressure through eddy HTitIh set up. Tho pressure difference between any two points in a duct indicates the looses sustaiued in moving the nir over tho distance Iwtwivn them. nelation hetweex vstoriTT axo vixocrrr head It is obvious that between velocity and pressure somo relation must exUl. It is shown in textbooks of physics, that if water emerges fr..iu an orifice near the bottom of a tank, that the water velocity at ihr twitit of issue can be determined from the following relationship W where t is tho velocity in feet per second, V, tbe height of the water level aliovo the orifice, and Q is tlio constant of gravitation, equal to W.2. The relation between the velocity of nir flow and velocity head is *U given by equation (9). In tho case of water, tho equation merely e\pre**n tho fact that a water column of height equal to A',represents * pnurtiins which is proportional.to tho square of the velocity. The juno interpretation applies to air, where now, however, the pressure Treted by an nir column of height//, is proportional to tlio sqttoro of hi* air velocity. Imrconvenience in air-flow measurements, the term A, of the above is generally expressed in inches of water. Thu* to convert h` * i*vt uf air to A, in inches of water,-we lmve Unit h t 9 density of water.,, density of nir * * i= *!.. density of nir is taken as 0.0749 pounds jier whir foot and water 1 '*`1 {Niuiuls pereubir. foot at "O'* l1'., tlien k/ 02.4 0.0740 XA,-JK/. 20065*7 If It, is MjJiTiwiI in inches 'not* NO i '.-CO.-I/i, Thus, the bright uf ttn nir column at 70 K. equivalent tu otto inch of w ter is 09.4 feet. Substitutin'; in equation (9) we then obtain 09.4/i,"gy-j Therefore, if the velocity is expressed in feet ]er minute V-4009y5f. (10) ETTECT Or TEXLTElUTtnUR It was mentioned in a previous paragraph that air is afFeeted by termporaturc changes, contracting in volume when cooled and expanding when heated. If it is nssmued that expansion or contrac tion is jmportionul to tlie absuluie temperature/ T\ then tho following precaution is true .H or if A, is desired, Tu Tj, and Aj being knows rify Thus, given the height-of air column /* corresponding to an absolute temperature T}, the height of air column for any other temperature is at once determined. Equation (10) may be written Y-EJZ where K is a constant varying with temperature. This constant, following tho method outlined in this and the preceding paragntjdi has been calculated in table 25. * * Tmu JSr*VUw> / > ittmuitg, height af air talaam, e*d K im famain, mriMM air Irtnperalart* Ornkrui C+mmat Twniamtti** air u-tttmk waintfi* I-rruU* 1 lark tint 11,0 lint) to \-K*X l Tmimmijn Dimity * r*haMS 4r(|ua>k sjrrniul lu MOIW, 1 lark VahirafK m fceu TltOiM) W* r... ac y__--. - ______ ... . aaav ,C*I .DM LW All 0*71 Mai 1 *a 7* T-----... x*n >*** r----------- s*i K--____ 3WI u* r_......... aor .cs LSI Htn> 71. ' to** 4ua AWmm lnu|*aiii k it* tcmiwiaiuia at ata-hita am, | WWU, wkw <U Uunktrvid l*mr*raiuc itjf i'. i iiitillift MW|latia*; IW k THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DIO NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. | BB 0020066 J SS60 'I uivalent to mi#* miuute ( .At air is affectm! l.\ - when cooled .! expansion r cumra. Tx then the follow in * ending to an al*4ir other temperaintv U uro. Tills coitsfani. preceding paragraph nn, amJ K in fnrmuU. ;ra Tnium* W :nusib irriualw nibic J tarii U Did Itcrt) Vh t* *v- .oru *lC.T AMrnl y.w 717* 1* * 4 '* NOT 101 NO) Problem: Calculate the height of air column and tlio air density : W" F., give:: tho corresponding data at 70. Sdution: A 4M.(I+(H G9.39TM459.G+7Q A-72.5 To enleulnte the density, wo have, since h is inversely proportional the density D: D 459,0+70 0.0749*"45U.0+94 D-0.0717 EQnanox or rt.ow Tlio volume of air flow* may be directly obtained in terms of tho cross -rtinnal area of tho duet. If Q represents tho volume of atr flowing in cubic feet per minuto at on overage velocity equal to T'and a is tho area of the duct in square feet Q-aV-40QQoi/ht (11) If tho diameter of the duct is expressed in inches, a0.0055d* slid C-22.9 (Fjn, (121 In tho enso of a duct of varying sections of ureas equal to c, a', a"> He., with constant flow, Q-eI*-a'r'-c"r"-etc. (13) lw*m the T's correspond to the velocities in the various sections. If tho velocity is known in ono section, it can then bo determined for nv section provided that tho areas of both sections arc known. Thus, d 1*, and ' are known, the velocity in the latter section is simply r-J>For r |M*m 4 and df are corresponding dinmctcra in indies or feet. When ' ** exprraoed in inches, tho corresjtomling areas in either square inches r Mjuaro feet may bo obtained from tablo 29. - - ' T ^ p. | BB 0020067 l THIS 0Q-:.Uk:E .T VMS NOT A RECORD PPG INDUSTRIES, INC. DIO i-iOT COME FR IT'S FILES AND CANNOT BE AUTHENTICA' BY PPG INDUSTRIES, INC. 2561 NO; NOTHU \j \ 103 Tamuk 2(3.--Ircu* of ciedra in m/nttrc fret amt equate incite*, diameter* in iatkea JtaKlIlMMW liurtm JWfWKf >imw Mil ** DiMlilfalMW iMrtaim l*ai tr Mm 3Imehm Tl. .,r. Min'.**_____________________ 3 IncMyii_______,,__ ___________ UUnriw............... .. 1A i!(**... lln.-h*s_n,r ,.rj am* mu i a w* . .AA 1 "--* -- _ niiwitN --.. U) InriiwL....-- 10 *rt It ................. XU .* T.er Uir ut" In. mi SI 74 2*. 27 At* 4L1* U.77 auu CL 3 niM 7AAJ cartel ,n*H ,nt - tIKTT till . IX .MO .WH SSI ,35? .wr .Srt .41) .4W .AU 4ou I1S3 A!*-------- ---,,r.. me. trt |IU,M uim ma US. 71 CAW IiIImKh. ... MiAU hirr1^ i, r , T -- ns. n _IVA IncMl______ w*. nj M hfhm _________________ an. in 1W?Ut1s*ia4>4isml--__r_-_-_-_TTi.^ia^i.Ti.h^-Ti r-- 3IXK5 S*.W IS liHM._wnwW. 1*4tsmoi^s--,--- - SU.4T, MM M. 13 S9L( MM _?21 .M MNI 1.117 L22? L3M LXW UN l.4* LtCtl IW LM9 LM SC4 1W TBAXSCOKT YtLOClTIKS The design of an cxlmiu t system depends upon the magnitude of tho air velocities roquinil for transporting t!ic dust collected by the hood, end U]>on on estimation of tho buses incurred by fluid friction and eddy effects. If tho velocities chosen arc too low*, there Is danger of dogging tho system with settled dust, while if too high, tho friction losses may l>o so prolubilivo os to bring the cost of operation to au unreasonable figure. Grrnt care should therefore bo exercised in the choice of velocities to be maintained. Taslx 27,--Air peed* in duct* accentry to caattp wi*n material* * "Ittm I*/*,;. Us* Mr, mSrt***m* hr. : i w.* UXm Ian tan mil IStW na a iw.n iiw.ia in.ru . 3H.SJ OK. Jut sn St* 9W.*q raw 311. W \ L t.v. t, *,; IIV 103 ./ iv ]:irtirln to lio omvcyed is known, the following forinulns /wr 1oi-- .-.ntui iiml vertical transport aro useful (57). 1`or horizontal ducts ' ,:nl /or vcrtieul ducts ri3;;oo'* CM) (Ms) ii<*ro V is the nir velocity in feet per lninute, * is the specific gravity ,d the. particles and S is the diameter in inches of the largest particle JUiignil title ,t( `Heeled I.y {!,,. r ' fl irf Hf* tjA . d.tn:T dWno frirtimt ">pentim ( an -xerviscd in tin* * -uticriala CMMNb|-|f -----------Hr-^i,imBi|1l,i1lmH,i.__ Jen Sf1t.*3--** I."" /or iwunn tl*N 27, but whet Ini j data regardi*: (Vuibtblr, andin in accord uiili *izn nail d*nM * ftovmtsi,--JUrvriadtiMnqaUMl tIUi tnttfctoi*quart* (NMctttcmltrlUQ. le conveyed. The velocities determined ly Iho nliovo equations minimum and should ho increased approximately 10 percent to f `k caro of sett ling which is likely to occur at d hows or enlargements. `or fine parliefes of dust--that is, those which oley Stokes' law-- !m1h bt known of tho vrlocilies required to convey them. Tito curve figure fil taken from data given hy Martin (5S) gives the velocities - jiuist Im exceeded in transporting particles of quartz (2.G5) nceif--v, , & SB 0020069 J THIS DOCUMENT WAS NOT A* RECORr ivl ,NC- D,D N0T n s FILES AND CANNOT BE AUTHENTIC/ BY PPG INDUSTRIES. INC. * 2563 from 10 microtis (in the range of Stokes' law) to 10 incites in diam eter. The values in the extremis ranges uro extrapolated. Determination of duct diameter THicu the volume of air required by a hood to control dust at a given source is known, and when the velocity of transport has Ixtu fixed, the size of duet required is at once determined from tiio equa tion of flow (equation (12)) Q-aV-22J *V where d is the diameter of tlto duet expressed in incites, relationship, wo obtain UO&iffy d-0. prom litis (lfl) tlte sizo of duet required to-maintain a velocity of T7 feet l>cr minute when a volume of Q cubic feet per minute of air flows. EXCUGT LOSSES zx A PCCT ststeu The esleulntions involved in the design of na exhaust system depend upon tho energy losses incurred at t-ho hood, and various portions of the system, tlto latter including tho losses due to fluid resistance, elbows, transitions (enlargements or reductions of the duct) and collecting devices. For each duct of tho system, tho loss's must be carefully estimated in order that a fan which will maintain tho air flows required may be chosen. It is well known tiiat when water flows in a pipe, the pressure diminishes in the direction of the opening. This loss of "head" indicates a loss of energy. The sumo is true for air flowing in a duet. There is a decrease in static head toward tho opening (tiiat is, if ilu* flow is toward the opening) and litis decrease is due to loss in friction. The nature of these losses are discussed in tho following paragraph Seed entrance leases The entrance losses depend almost entirely upon tho structure id tho hood. It has Iicm found * tiiat flared hoods without serii*** obstruction close to the opening have losses equal to about 50 penvni of tho velocity head in tho connecting duct. In the easo of pli" duet ends, however, without any flaring, tho losses are greatly *' creased duo to the cxccsaivo spin of tlto incoming air from regi"'*behind Use edge of tho opening. The losses for duct ends nm*: therefore bo taken as equal to tlte velocity head. Lorn in straight darts Tlto movement of a fluid in a duct gives rise to friction clbi-1 These Insure nre made up by the static head so tiutl in a duet of gtvi* * Vhj-iMMwiI Sola: J. M. U. DOCmZ.iT WAS NOT A RECOftO-eF * NDUSTRiES, INC. DID iiOl COME FROM rll$. AND CANNOT BE AUTHENTICATED PG INDUSTRIES, INC. T'bB 0020070 2584 4 "Tf", t**' t ?'" 'i kJ ! ; fM\ i ' " s j -v i~ r ^ THIS DOCUMENT WAS NOf A RcCOnD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES. AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. Bb"002007IT 2565 *. w) t 10 indies ill iHimh cxtruj*>hiti*d. hood to control dint a! a rity of transport 1ms I*-,!, etcnuincd from the wp*:,. hI j- -- i 103 i. n!fjJ, and uniform diameter, the loss is represented by the difference ,t( Static pressure between the ends of the section. In tho chart of ?sed in inches. From f li ft*.! .ocity of V feet per mimti>of air Honrs. T BtSTOI m of an relumst Rv*ir,,; at the liood, and vari*- the losses (Iite to Fui.: reductions of (!* r^K.ie system, the It*>**' a fan which will liuiiK-::. ts in a pipe, the jinssm. Hg. This loss of u head ** jc for air flowing in a di.-t ilie opening (that is, if jc is <](i<> to loss in fiirti*** . the following parajjrni*1-. Vriyr^ry^lX'-.Cy r,^.j|saca 3 jdy upon the structure red hoods without sen** s equal to about SO ]trrr>" ucL la t he ease of pL" , the losses are prrally bincoming air from nr-' losses for duet ends m head. vr* rise to frirthm nf*-* ` d so that in a duel 'f *5*t?s *# Frktia* kt Iabnf WUOf l#0FU Tmmt SL--Frink* in *4r UueW. *- 52, the frirlion josses per 100 feet of duet may l ohtaiueil 1 tl* <liii't diameter mid either tlic air velocity or volumo of klNIWII. - ' THIS DOCUME -T WAS NOT A PFCOSt> T)F PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES, AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 38*002022^-1 - w 256S K'ioo TJi Jiwwre* given in the tiltovn figure flro for *leovo-fiUed duct* ki.j naturally iuoimlo tho lenses at the connection* duo to eddy effect. An accurate formula fur Jengtlts of duct of lea* titan 10 feet is jpvni by Lee*' equation (5S) liascd on conditions at 70 F.* i'/-&0%(o.OOQtl+-i(1C; where kf represents the loss per foot of duet. .Example: Air is flowing in a smooth G-iiich diamoter duct at a mi., of 4,500 feet per miauic. Calculate by Lees' formula. tho loss in feel of duet atul eonijiaru with tho result obtained frurn tlio chart. Solution: (V)9M^ (4,500XO)*-3* 0.35 Gog *t,500-}-Jog 0-0.35 (3.G532+0.77S2) --1A3J0 antilog 1.5510-35.57 Hence, per foot of length, we bare HT x 4*500 X4^00X (o.0000+X 10~* -0.04" TTrO For a length of S feet, therefore, tho loss is SX0.04--0.32" HjO From tlio chart the rejdstanco is found to bo G.3" per 100 feet, or 0.50" UaQ for a lengtu of S feet. Loss at elbows The loss of head at elbows may be expressed in terms of tho velocity head. Tlio following data, taken from A. S. IT. V. E. Guido (59) ma\ be used in determining tlio Ion for elbows of various center line radii. TaIUI 2S.--.tow of head dm* tm Mi BmBHosohw--Hon ainmw imwh>iiiliMiMnnnllBioau..oili40t4.>--tiooitwla Lowtaf**ttjrtonl - p*1m1 THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC, DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED * BY PPG INDUSTRIES, INC. T"BB**0020073 I o,cr*? r sleeve-fitled dnrts m*! ns duo to eddy eirecN TMss Uum 10 foot is given -t 70 F. )X10"* (ir.) - diameter duct at ft rain ?*' formula tlio Inst in X ..tamed from the chart. G)-" .5532+0.77S2) --* aij w 3 > bo G.3" per 100 feet, or -1 in terms-of the velocity . H. V. E. Guide (59) may f various center lino radii. - lm 6cW ........ MInbu*y Itbatu'nsS***1 391* II Ip 107 Ui duo to uucldcn transition Tho loss duo to r-udden enlargement- or contraction in a duct may tat computed from St. Venant's formula (U0) (w)' (,7) where V' is the velocity in the smaller duct and T3 tlwt in tlio larger. Values of the loss A. in inches of water for various differences Tr,--Vj are given in figure 53. "When the enlargement or contraction is gradual, the losses are greatly reduced and mar be taken as approximately 10 percent of Uio loss obtained by the above equation. HOHSKTOWETt 1IEQVIKKD Tlio work done by a fan is equivula t to raising the weight of tho air handled per minute to a height equal to the resistance against f wliicii it must bo delivered, expressed in feet of air. If, therefore, tbo resistance is expressed in inches of water, it must bo midtipHod by 09.4 which represents the equivalent of 1 inch of water expressed m feet of air at 70 F. For other temperatures Urn equivalent may be obtained from table 25. If A represents I ho total resistance against which 1 he airmust flow in inches of water atul V represents tho density of the air, the work done H' is W'--QDzh. 7 BB 0020074 1 THIS DOCUMENT WAS NOT A-RSCOaD-OF....................... ... ... ------------PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES. AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 2568 ...... where ffw the height of a column of nir equal to 1 inch of water. At 70, lJ*=tf)A)7~i unit Zw*U0.*J, hence ir=0.."2 Qh. The iiorsejiuwer is immediately determined l>y dividing by 22,000 Horsejiowcr**0.000138 Qh (18) duct computations When the volume of air (low and the sizrs of the ducts have been determined, and when tho general plan of layout lias been drawn, it then becomes )<*:iy to calculate the or tho total resistance against which tho fan must work. Without such information, there can bo no assurance that a fan will supply an adequate air flow or any lucthocl of determinin'; tho horsepower that the fun will require. Tho total resutuuce, os has been pointed out in tlio previous para- I I C- I.. .1 ' i.. : j. . .. It. gmplts, consists of lire lueses incurred ut entrance, elbow* and transi tions, and those duo to lluid friction in straight ducts. The resistance of collectors (see see. X), if they form port of tho system, am also additive. The total losses, therefore, expressed in inches of water (aoruotimes oencus per square incJi) are for tho whole system from tlw point of air entrance furthest removed from the fan to the point of discharge. In rating a fan it is then only necessary to stato the volume of air it must handle ami tho total resistance against which it must deliver. Tho horsepower required may bo calculated by the metliud outlined above. It is possible, however, to ohtuin tho horse power ami sjwcd required for a given, type of fun from the manufac turers' catalogs. application or loss data l-- . n; U V. In-t.- n * I . III*. III*. : 1.* liulnl1!' -- In : I. ... . .!.. i: : i ii i The following problem demonstrates (he application of the nlaive data ami formula:: Given a single duct mnini*tcd to ntt cxluiust fan as slimvu in figure 4, determine the resist a mre a liieh the fan must overcomo when 1,000 * fSTo0200ZS-i UMENT LNcVoNor SSSM 2569  1 lurli of water, A: Tiio ltor.M [*i>uiV (L\> * tiic ducts have rvts .it lias boon tiniun, ;>r the total rcsislaifv jeh ironna;ion, '. adequate air Him' IH -t tlio fan will rtijiii.-f. ; in the previous ptir.i- auce, elbows and tranii-it ducts. The nwislam-i* . of the sysi tin, tire-aho .'ssedin inches of walrr the whole system fr* .com tii fun to the (mint y necessary to slate I In stance against which it ay bo calculated by il.* ?ver, to obtain-the hor-*o[ fan from tlm niaiiufac* UATA application of the abm*>wt fan as slum'll in (i**in'' nwt ovemimn when I ilGT> 109 : fH-: per minute of air is hnitdictl by the ftli.Ufttkc iho.loss.at as At) jiervcnt of the velocity head. The r-olniimi may be arrangin' ns follow*: Tlse rr'K-oscrlioiiul area of tbo S-inch diameter duct in square feet . fi-.nii table 2i, 0.340, hence tlio velocity in the duct must ho j- |,iH ti.n:n2^C5 feet per minute (equation (13)). For the .. inch diameter duct, the cross-soctionnl area is 0.7S5 square feet, in-; n velocity of J,27-i feet per minute. Tbo velocity head in, r* fnrc, suitstitiiting for V in equation AtVs/4009*2$05X si;:, i0i>!)X-tU09~0.51 inch 11,0. We are now in position to . ..-.quite the lns.-scfl in the duct system as follows: I. The loss at entrance is 0.*>0X0.51 *0.20 iitrh Tl-0. :\ 'Hie Joss in an S-inclt diameter duct with nn air velocity equal to feet per minute obtained from figure 52 is found to be 2.1 nH-hnt lli<) jH-r 100 feet of duct, approximately. For a length of 40 lhen*forc, the duet friction loss is 0.4X2.1--0.S4 inch H-0. :t. Tlie. loss at tlio elbow with radius of curvature equal to the lin t diameter is given in tabic 28 and is 20 percent of tlie velocity b.ad-0.20X0.51 *0.13 inch IIA 4. The bos at the enlargement can he obtained from the curve of I* 53 when* (F,-1 s)*/l,000-2^05-1^74/1,000-1JO. I loner, the loss at enlargement is 0.10 inch 11,0. 5. Finally, we must estimate the loss in 10 feet of 10-inch diameter .lir-i having a velocity of air flow of 1,274 feet per minute. This is bund m l>c approximately 0.33 inch H,0 per 100 feet of 'duct, or a tea inch 11,0 for a length of 10 feet. a. Tim resistance which the fan must overcome is the sum of the b in the duct system from the point of entrance to the point Ikw (be duct connects the feu, or 0.2G inch II-O, loss fit entrance; M iiii'h 11,0, loss in 40 feet of 8-incli diameter duct; 0.13 inch U.O, Iota at elbow; 0.10-iiicli H,0 loss at enlargement; 0.03 inch HO, hi** in ]0 feet of 10-inch diameter duct; total, 1.42 inches 11,0 t* -1 in tlie whole system and resistance which fan must overcome in I jinlling 1,000 cubic feet of air. reputation* la a branch -erstem In a multiplo branch system tlie duets must bo proportioned to i-.iiidi,* adequately the air flows required for each hood. Tbo problem . In*uever, slightly complicated when the velocities are fixed in order d*f tlm materials collected by tlio hoods may bo transported. Wbilo *i i. iHw^iblo to have velocities-greater than the loner limit required, > i. nt good practice to exceed tlieiu by a vety largo amount in view * dm increased losses which are incurred. Tho following problem ; <rairs the procedure involvctl for a fixed lay-out. 1`i\i`n a duct lay-out as shown in figure 55 with air flows nt each ' -d indicated. Calculate (lui wwm of the ducts and Uie horsepower THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES. AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. *| BB 00200^6 I # 2570 i !. 1X0 required, iii?t!iinnjr that a velocity of 110k less than 3,COO f*ct per minute in list l*o inninlnitiod in each duct and that the entrance 1**-* V are equal tu one-half of the velocity ltcnd in tlio rrspcclivo ducts. A-suinc a collector loss beyond tlio fan of 2 inches H-O. u Following the genend procedure given hi the provi iw problem, ami Ix-ginning with the hood A, we may arrange the computation* ns follow*: Step i.--Since the duct velocities ore fixed at 3,000 feet per minute, we have tlmt (lie urenof tho duct All is Area -d/f--<2a/V*300/3,000--O.OS-l square feet From table 20, the duct which approximates this area has a diameter of 4 inches. The velocity head is from equation (10). A,--3,C00X ! r/vt 3,000/4,009X4,009--0.51 inch 1I.O. This value of tho velocity head applies to all parts of the system. Considering now the looses in tho duct AB, we have-- 1* Lems at entrance--0.50X0.S1--0.41 ineli 11*0. 2. Loss in 4-inch diameter duct ut air velocity of 3,000 feet |wr minute is G-S inches 11-0 (figure 02), per 100 feet, or 0.4'X0^i<3.l inches 11.0 fur 4."* feet. 3. Tt-- ibow loss is, from table 2$, 0.2G A,--0-2GX0.N1 --0.21 inch data i Given W.dctcmu. tnl resistance in the dud AS for a flow of 300 cubic hvl is, therefore, the sum of tho looses 0.41+3.1+0.21 3.1 BB 002007"? I, THIS DOCUMENT WAS N01 A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 2571 3! > 3t low than 3,6no f.-d ]xT ind Ui.il (lie entrance h-*.* ;ul iti the respective ducts. 2 inches II/). :i the previous problem, titul range the compulations ns e! nt 3,6CO feet per minute. 0S4 square feet :cs this arm has a diameter quatiou (10). A,--3,000X 111 This value represents the static at U and hence the resistance of the brunch A'B must also bo equal to tho losses calculated, in the. hRiiirh AH. Otherwise the static head at If trill liave two values, which is iiujiOKsiblc. St,p 5.--The urea of the duet A'B is found as in the previous step. .Ami A'B^QA'I3,600* 650/3,000*0.1$ square foot which eorres|onds to a duct diameter of approximately 5.5 inches. Tlic losses may now lie computed as before. 1. The entrance loss at A' is 0.50X0.S1 --0.41 iucli U.O. 2. The friction loss in a 5.5-inch diameter duet with an air velocity nt 3,600 feet per minute b found to ho 4.5 inches II/) per 100 feet at duct, or 0.55X4.5*2.5 inches TI-0 fur n. length of 55 feet. 3. The olbour loss for a bend equal to 200 percent of the dud diameter is 0.14 A, or 0.14 X0-Sl*0.1l inch H-O. 4. lire total resistance A' to Jl is, therefore, ------5T+*-------------- c *x/r td 'Zd ralue of Uc velocity bend B, we have-- eh 11,0. velocity of. 3,000 fret jer 00 feet, or 0.45XGJ?x-3.1 /i,-052i;XO.SJ*.{)^| i,,di >r a flow of 200 cubic f*ct 0.41 +3.1 +0.21 3.7 0.41+2-5+0.1l*2.S inrlies IT/). The resistance of tho branch A'B is seen to be less tlion tlie resist once of the branch AJS. Since the fan must maintain tlic some static at tho point Ji for l>oth branches, it is obvious that if tlie larger value is to be kept, tlie air.flow, in tho branch A'B will be increased. The alternative is to cut down the diameter of A'B so-that tho resistance is equal to tho branch zltS, or to increase tlie diameter of AB. Tlie latter, however, is not dcairublo since it tends to cut down the nir velocity which is fixed at a lower limit of 3,000 feel per minute. In tho present case, although tho resistance is Jess than in AB, tlie in crease in flow in A'B can be shown to be only slightly greater than tlie 050 cubic feet required by tho hood. Tho approximation to tlie actual amount of air lutndlcd at A' with a static of 3.7 inches IT-0 at B can bo nuulo as follows: Assume that the braneh A'B handled 700 cubic feet per minute. The air velocity m the 55-inch diameter duct will I then be 70(1/0.18*3,800 feet per minute, wliich corrraqxjnds to a velocity head of 0,04 inch 1 IjO. * Proceeding as nliu.o in determining the various losses, wo find loss at entrance*0.47 inch 11/); friction loss*2.92 inches; elliow Jobs*0.13 inch; total lass A'-b'*3.52 inches, wliirli Corresponds ch/scly to the loss in tho duct ^17>. Tlius a volume of air flow corresponding to nstntichciid at B is approximate^'700 cubic, feet-permimite. More accurately tho flow >a found to be 710 cubic fret )mt minute, hut f r prartirn) calculations 700 cubic feet jn*r minute is sufficiently accurate. , Blfjt S.--At tho point B, there must he a transition to u duet which will tteeomiiuulnto a flow* of 3004*700*1,000 cubic feet ier minute' at a velocity of 3,600 feel jwr minute. The area of tho new duct will __ THIS DOCUM'-NT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED-....... ...... BY PPG INDUSTRIES, INC. *j BB 0020078 1 I*c, therefore, I,000/3,GQ0--0.27S square foot, or a. duct wliidi U 7 inches in diameter. The loss in friction in such a duct is 3.5 inch** 11-0 per 100 feet or 0.15X3.5--0.53 inch 11,0 for a length of 15 feet. The loss ut enlargement is, of course, nil hy St. Venant's equation. l>uo to the angle at which the flow from A'13 enters, the loss is usuully taken ns 10 jiereeut of the velocity head, or O.OS inch II-O. Tito total loss Blf is consequently 0.53+0.0S--0.G1 inch 11-0. Tills must Ito ndilcd to tlic value of tlie static at B and lienee gives tlte static to be maintained at if'; that is 3.7+0.G1--4.31 inches 11,0. Step 4'--As in the ease of tlio branch A'13, the losses sustained in the duct A"J>' must equal the static calculated at 2f, or 4.31 inches 11*0. - The procedure is identical to the preceding steps. The duct area is 700/3,500**0.19 square foot which corresponds to a duct diameter of G indies. Tlte loss calculations ore then: 1. The entrance lo3--0.S1X0.50--0.41 inch U*0. 2. The loss due to duct resistance for a 0-inch diameter duct with air vclodty of 3,500 feet per minute is found to be 4.5 indies 11*0 per 100 feet of duct or 0.S5 X4.5--3.6 inches for n duct $5 feet in length. 3. The elbow loss--0.14 X0.S1 --0.11 inches H-O. 4. Hence the total loss in A"If is 0.414-3.6+0.11--4.1 inches H^J. Since this is practically equal to tho static calculated at tlio point B', no corrections need be applied. SUp 6.--There remains now to calculate the loss from Bf to Jf* and the static at tlte point 13" which will indicate the total resistance f the system and the suction which tho fan must maintain in order tliat tho air flows and relodtics in tlio various parts. Since we must have an enlargement at B', we may at once calculate the area of tho duct " B'B*' to accommodate an air vclodty of 3,600 feet per minute. The total volume of flow in this duct is obviously the sum of tho flours of the various branches, or 1,700 cubic feet per minute. Hence area 1,700/3,GOO--0.47 square feet, equivalent to a duct diameter of 9.5 indies (approximately). Tho losses in BtB" are-- 1. Tho duct resistance loss-which is found from figure 52 to be 2.7 inches per 100 feet or 0.15X2.7--0.41 inch H-0 for a length of 15 feet. 2. Tho loss at transition is again taken, because of the branch duct A'B*, as 3 0 percent of tho vdocity head, or 0.03 inch H*0. 3. .Tho resistance B'B" is, therefore, 0.41 +0.QS-0.40 inch IT*0. Tho total resistance to the point B" is tho sum of the icristanco to If plus tho loss in IfB" or 4.1+0.49--4.59 indies H*0. This Is also tho static at B" and the suction wliich the fan must maintain to handle the air flows and vdodtios in tho system. Siuco tho fun must also overcome-a collector resistance of 2 inches IT-O, tho total resistance of iho system including tho collector is 4.51) incIics+2.0 inches or 6.59 inches Jl-0. Tho horsepower required by e UMENT WAS NOT A RECORD OF STR1ES, INC. DID NOT COME FROM i AND CANNOT BE AUTHENTICATED INDUSTRIES. INC. 1 68 0020079^*7 3573 or & duet whirl, , -h a duct 3J iiw|a a length fl*, U-i, 4. Venanth ere, the loss L> u>ii;,J., inch HjO, ).0S**Q.Gl inch" M ti. li ami henro givi',4t}., *4.31 inches 114). he looses sustained i:, at U*, or 4.31 Iff Step*. .iiicli corrcspoiiils in 3 are tlico: HA li diameter duct with be 4-5 inches U..O j-t ct SO feet In length. A o.u> 4.1 inches II.A 'W tiio point I!'. v* from It* t 1?* ami Iiim total tbiitMh e t*f naimam in order that Since we must hair s the area of the duet feet per minute. Tim ic sum of the Hows of. minute. Henee an-a it to a duct diameter '2?" are-- >m figure 32 to hr 2.7 for a leufftli of 13 f**t. iso of tlto branch duct inch IIA 0.05-0.49 inch HA of the resistance to l* os 11.0. This is a!-** *an must maintain 1" resistance of 2 inejir :g the cnUiTliir is l.;'*:! reejwwer required by t .'s 1 i, 'j 113 :l<, fan is, tl*ref,n', from equation (IS), O.nnoi.VXlTCKlXG.GJ)--1.77 h*rs**jswer. Wo may Twapitiihiti" in the following table: TaIsIiK g1*.- - Sm aamnrt)./ rraatU, hrnnrh ryalrM Hum Valimw airOaat 1,1--a ltnurtnan *> .* **--** * pt HUH mH M tiff Tu I.M lad*t 4 It. 5 M Jartf, 11.0 XT XT &U XI 0.0 Noml--TMllnt--vwairhba --SHIorsjpurt.XOiik.'iHalLQ. 11--pwswidini) byt% Kalsrsoneats at breach mimuIms The above problem illustrates the need cf rather extended com putations in pro|H>riiomn" a system. It U also quite clear that the sizes of ducts must l*c carefully determined if proper velocities and air flows are to l>c maintained in the system. In tbo calculations given, no allowance was made for future connection or disturbances in air flow which might occur in Cft-o one duet or more was cut out of use. Under such circumstances the system should be hiyetl out with all probable connections to he made, anti tins duet sires computed on this lands, rpmenibcrirff at all tunes that velocities in tho ducts sliould with one or more hoods out never get below the iiniiting trans port velocities. H is necessary to point out that some States require that when a brunch duct enters a main, the area of the main duet shall bo increased from 10 to 25 percent of tlto combined areas of lioth. This rule must ho followed, although it is actually not required in a well-designed system. Excess enlargements naturally call for larger air volumes through tho hoods in order that ndequalo velocities may exist. GCfSBAt. RUI.T3 TOK C0X3TTUJCTDC0 EXHAUST STSTEilS The following general rules should bo oliscrved in tho construction of an exhaust system: 1. Tho main trunks and brunch pities idiould lie straight, strongly supported, and with the dead ends cupped to permit Ins)lection and denning witch necessary. All lira licit pipes Aouhl join tlio main nt an neulo tingle, I be junction King at tho side or top and never at the Ktl-loni of the main. 2. Oran-out |*>rM having suitable covers should be placed ill tlio wain ami branch pqiosao that every part of the system e:ui le easily reached in ease the system clogs. BBJ3020030 (, THIS DOCUMENT WAS NOT-A- RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM ITS FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 2574 \ - pi|) of the same diameter to rim Mo Ilian to withstand tlm additional wear caused by changing tlm direction of flow*. They should prefer ably )i:ivon throat radius of nt Must ]Ji lintm the diameter of tlmpipe. 4. Evriy jmjhs should bo kept open nd unl>structrd throughout its enliru length, and no fixed screen should ho placed in it. 5. The passing of pipes through firo walls should bo avoided where* ever possiMo. G. All permanent circular joints should be lap-jointed, riveted, and soldered, and all longitudinal joints either grooved and locked or riveted and soldered. Every chango in pipe size should ho made with an eccentric taper flat on the bottom, the (taper to bo at least 5 incites long for each inch change in diameter. yjAS NOT t^C0R0 OF | BB 00 2008J__l 2575 .w heavier titan ml. ritiistand tlu* Tliey should ji*. Ji diamcterni th<*: 'stnieted thnatgli** .r. ;aectl in it. -ould be avoid'd *!. iap-joiutcd, rivet.-l. , grooved anil Im*hi ? s size should l* ;. die taper to be at ! ~JX. IS. EXHAUST VENTILATION* IN PKACTJCK Tho methods of dust prevention. vary widely even when identical .iprRitions tiro involved. Each plant in controlling its dust hazards wrnlly applies suH> methods as it finds best fitted to its particular by-out. Economic and mechanical factors are also. imjmrtnnt con.nlrratious which result in a diversity of typo and constructionj>( (revetuivo equipment. Thus, with few exceptions, infonnation with icganl to tbo pcrformauco of various equipment is confusing and traders a comprehensive treatment of preventive methods difficult to ncromplisli. At the same time, it must be stressed that extensive rfliriency data are lacking. This lack may. bo partially attributed i the reasons stated above, but it especially is duo to the fact tltat methods of testing control equipment as described in section V liave mil been generally used. The present section, therefore, attempts aly to supply information regarding tbo control of dust in operations illicit are widely used and for which somo data are available. EXHAUST VENTILATION IN THE CHANITE IN0U3THY The introduction of pneumatic cutting tools has done much to iwnw the severity of dust exposure in tbo industries using tltem. This has been the ease in the granite industry where band pneumatic Is and pneumatic surfacing machines contribute tho maximum limt concentrations. Ucfcreneo to table 3 shows that the pneumatic tools create the `u>\iiuuni amount of dust. I'tunimatic hand tools in tlio granite industry are used for practi * illy all detail work. Tho tools employed vary in size depending on hr type of work done. They are guided by hand over the stone sup* tit* end usually demand dose attention of tits operator whoso brrath" 1 level ranges from G to 15 inches above tho tool. Under surh con? it is diifirult to control dust without causing some interference - dm work performed. The surfacing iimehino is used only for bringing the rough stnno to - riane. surface. Tin.* tools used lit this machine are larger than the ' !"l pneumatic typo. They ore graded in size so as to bring tbo :* surface to any degree of smoothness. The tools are driven by ' '! T pneumatic hammer attached to a horizontal beam which swings '>t a vertical column which may bo mi/ed or lowered to amine * kiln Mtonca of various sizes. The machine is heavily built and llrd. <na) THIS DOCUMENT WAS NOT A RECORD OF . PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. In operation the hnnunor and tool of Ihc surfacing machine tinguhh-d over ll*o stonn by n ojK-mtor. The amount of dust general..i varies witli the lypo of hammer aud tool employed; the concent m. tion being a maximum for a four-point tool, decreasing with tlifuicness of cut. Jt is obvious from tho foregoing discussion that tho control of dti*; genenilcnl hy tho hand pneumatic tool and surfacing macliincs mit-t bo flexible. In tho former, because the worker must cut on stones in vertical and angular positions, it is extremely difficult to secure mlc quale control at nil tunes. Tlio general method used consists of cmi. nccting a llexible hose to the exhaust system and placing (he IkkhI in a jiosition offering tho least encumbrance to tho worker. As may Ujudged, however, the success of tho mcliusl depends upon the can* with which the worker places the hood; if it is too far from the wort being done, it clearly cannot function properly. With surfacing macliincs, on tho other hand, tho hoods were formerly placed on .tin stone and because of the inconvouicnco incurred, frequently were in* moved although tho tool would be of>or&ting at a considerable <fi.taneo from lliem. Tho exhaust system consequently failed to func tion efficiently because it was not properly utilized. The manner of testing pneumatic cutting tools has been indicated in section V. Tho results obtained by Bloomfield (47) in coraporiir.the dust concentrations in plants with and without local exhaurf systems have hown tliat, for ordinary operations, effective control of the dust generated can bo adiicved when the cxliaust velocities at the hood a ere kept above 1,300 feet per minute. The basic fundamentals of hood design presented in part VII Ho useful in assisting the engineer to estimate n priori tho probable jior- formnUce "of an exhaust system. Tliis has been done to a certain extent in tho easo of grauito cutting. Thus, Hatch, Drinker, ami Ornate (55) applying the methods given in tho above chapter wenenabled to deduce the fact that, regardless of hood shape, approxi mately 200 feet per minute are required about the surfacing tool in order to reduce tho dust concentration at the worker's breathing lrv.l to an estimated safe limit-of 10 million particles per cubic foot. Tinsame investigators analyzed the characteristics of a large variety wt hoods connected near tho pneumatic surfacing tool until one wo* devised wliirh adequately controlled tho dust generated with a mini mum amount of hind ranee to tho work and with low cost of opera ( hhi. Tlio hood firmlly designed by Ihcso investigators is shown in figure .V*It comprises a rectangular opening with a semicircular barrier t liiui- -- tho scattering of particles, With the tool in position within tl* . harrier, a minimum flow of about 520 cubic feet of air jxt minute i required lo keep the dust concentration below 10 million particles cubic foot under normal conditions of operation. The hood is mount**'-' NOT a record of DIO NOT COME FROM BE AUTHENTICATED P^T0020083_i 2577 :* the surfacin' machine .tri. ho amount. of duxt gmrrm***| .->1 employed; I he rmiriMitn,. t tool, decreasing 'with !! j-rion that the control of du-.t ml surfacing machine* iiiiim, worker must cut on stow** in etnely difiicull to wiirc :k|.method inl eoiti*l3 of siem and placing (he liood in e to (lie worker. As may lw .(hod depends upon (ho raro . ifit is too far from the work n properly. With surfacing - teens formerly placed on the incurred, frequently were not crating at a considerable <ILi consequently failed to four* jriy utilized. :tmg tools lias been indicated Bloomfield (47) hi comparing without local exhaust .mu.*, effective control of `hm the exhaust velocities nt :r minute. :gn presented in port VII ore jntc a priori the probable per-S has been done to a certain . Thus, Hatch, Drinker, and -en in the above chapter were rdlus of hood shape, appmxicd about tlio surfacing tool in at the worker's breathing level i particles per cubic foot. Tim .ctcristics of a largo variety of surfacing tool until one was lie dust generated with a mini* and with low cnt of operation, estimators is slmwn in figure atf. ii aseiuieimilar harrier to limit ic tool in ]M>sition within Ilia* i cubic feet of air per minute is lielnw JO miilion particles per iteration. The hood is mounted t -- -- IVV 1 117 an a carriago holding the cutting tool and connected by means of a flexible duet to on exhaust system. In this way, the hood constantly riofiravn the cutting tool as it movesover the stone surface. it is interesting to point out tluit the study of various hoods used In granite cutting made by Hatch of ah, shows tluit a velocity at tlio (tjiening which will roniml tlio dust generated is approximately J.50G feet ]H*r minute, or the amount specified by Bloomfield in his study aUive referred to. coxrr.of. of host in jiock dtullixo Tn order to cope wit h the dust produced in rock drilling, particularly m foundation mid tunnel work, special dust traps have been devised. ^4 IM*v, "\ :----) lawtSfCtawtHriithot 1--J a*il tor tmJtowrtatlns ci*li. f form these traps tiro similar to the Hay (Gl) trap with tlio exception that; whereas the latter utilizes the suction formed by an ejector eon* nwted to the drill cxlutist, tlio new devices aro connected to powerful 'limist fans. `Hir essential requirements of a dust trap liavc been described by Itwleh mnl itiseoworkers in a series or articles pertaining to tlio control f diul in lurk drilling (G2, G3, and 50), Figure 57 show's the type f trap investigated by the alaive workers in connection with down* Irilfitig operation* in foundation work. , The drill is inserted *a * hob* nt tlio top and the exhaust is applied nt the 2-inch cou'`lioii indicated. Alaiut GO cubic, feet of air per minute are required 'ainlain e low dust concentration, the air passing along the uneven THIS OOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DIO NOT COME FROM ITS FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. i~BT0020084^ 2578 r "'i r-' 11s surface of the rock and through the drill liolo, thus making m, trap* The dust collected passes through the exhaust dials i,, scjtaralnr and bay filler of high efficiency. In actual* operatic:,. convenient pij*.. POS/T/O/Y Juiust system is i stalled with a i;;: her of manifold. trap conncctiuns The air II*a . CO cubic feet . Mosecorr/r^cr/orf minute ncces.,.. represents a suction at the u .foc/r<su*rs)cs of only 0.S in.-], Fienw &/--K*Ucj trap Hr rack drUUns. water. Hoveu- tlierc is consider:/ i loss of pressure in |bo liosc connect ing tlic trap witli the cxlmust in.-:: fold. Tito suction required At tlic manifolds for hoses of vnri. Icngtlis liavc been determined and arc presented in the table I*-!.. TaM 30.--Static cudtan at tnanifcLl requirrtlfar rariout length* aj S-iurk /. kata with airfiaw aj VO cubic fer^yer minute LoneUtafluM Mali* WWI'W mnlitilit (toehttA UtOl LmtSStn xs T1M4........ .......................... 1.0 P*'! **r \ f^fir* IN... li * i 1 In any design, therefore, it is necessary to provide adequate stn-:.' at tlic manifold to take care of the longest length f hose to lx* t;- It is further important to allocate the manifolds at the most togcous ^Hiints to take care of tho progress of drilling operations. i'or vertical or horizontal drilling, Hatch lias described adapters for placing tho trap in any jxtsition (50), (tig. 5S). li such circumstances air flows of tho order of 200 cubic feet jut min: hnvo been recommended to keep the dust concentration lx*l.a million particles per cuhio foot. Tito proper disposal of collected dust is also important. TV particularly true in tunneling ainl consequently provision uni t made to collect tho dust efficiently in order to render the tmm- safe to breathe. It is further necessary that any collecting d. used should he easily moved and compact. In eollrrtiug the dust conveyed by tho exhaust system, a roll was employed which consisted of two stages (>) -a |n*iii**- TH1S DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 1 BB 0020085 1 2579 I. . 110 , thus makiii" an atr _& the exhaust darts (,, a ~y. In ariual operathiii, ., convenient pi|M-^-,. itniisb system Lt in* stalled with a iunn ber or nuiniTul.!.t Air trap connections. -- The air flmv of * CO cubic fret |>i-r --/ow miniito necessary represents A MtmV suction at tlic trap sedimentation vtiumlwr and eloth screen filters. In the fnnttcr, ihc dust uus blown tutu a belksluiped cntruiice where part of tho dust was thrown out by inertial hint*. Tlio air then passed through a Imille arrangement nt low velocity causing furtlier sej>;irutio> and thence to the cloth screens. Tito filtering was conducted at a rate of 2 cubic feet per wpmru foot of illter surface. Tho total filter area was 1,0O0 swptaro feet and the complete collector unit was capable of handling the dust from n> maximum of 00 drills. Tlio amount of dust yarn'd from 2.5 to 4 tons jcr day, giving an overall collecting efficiency of 00.7 jterrenf. The use of the trap was shown by Hutch arid Ills associates to increase tlio speed of drilling from 11 to 21 percent, while the cost of operation was estimated at $2.21 ]>cr day or 1.05 jicrcsnt of Uto cost of only 0.S inch .f water. However, ! there is considerable ! -rap with tho exhuiist maitt- j .folds for hoses of various ren*ted in the tahlo behm. 'WyimMr <mIiunvjlettl of $~i*ck Jterilir LrtCthhflw Miria*, alnliJvM.-t 0 jirovide adcfjua tc suetimi : length of how to lie'used, nifuhls at tho most advnuof drilling operations. ;rh has dcserilied Kftreiul .on (30), (ilg. 3S). I'mlrr ' 200 cubic fret per minute 1 concentration bdw in also important. Tliis is uoutly provision must !* rr to mulrr the tunnel air .hat any collecting device "IwiL-st avalam, a cmleeiur sgra --a preliminary xf}c-J3L Sf'jtr/n. rantltr-iMlM EdkfiaptBrSWiiRAWiMlitn. uf removing a cubic yard of stone (63). In view of the increased rate at witich drilling'cun Iks dona with a trap for only a slightly greater J cost per cubic yard removed, it may bo sccu tintl not only are hygienic conditions improved, but the speed of drilling has been increased at ? wnly'tt slight addittouul cost. COXTBOl. or DUST TOOit CHZXDZXQ, raUSntN'C, A2tt> BtTFFIKC WHEELS Exhaust systems for grinding, polishing, and buffing wheels vary widely in design. In the enso of grinding, tho hoods used serve not only to provide a means for capturing tho dust, but also act to protect tlio worherin case the wheel bursts. Fur tlio prevention of nceident* dim to the burating of htgh-sjmed grinding wheels a special rode cover ing tho requirements of hood construction has been written (C4). With regard to polishing and buffing wheels, which must bo adapted in handling intricate parts, the hoods used assume a wide variety of dinpm. C.7 r THIS DOCUMENT WAS NOT A RECORD ' PPG INDUSTRIES. INC. DID NOT COME FRC IT'S FILES AND CANNOT BE AUTHENTICATI BY PPG INDUSTRIES, INC. | 5B~0020086 7' 2580 120 Tim cltlff tliflicully to bo overcome in grinding winds is the otiiwartl sutt)* of iiir,-n fun notion, due to I!io revolving wlut-l. This iiffir-1, is von- marked with high sinfd nml rough whorls, ami is so r-lrvng that in many instance* it Is sunicieiit to counteract the normal inwartl ilow of air. Tho same effect exists with polishing anti bulling wheels, but to a less marked degree. l`rafticsv!!y all industrial Stales have coties reprinting the construe* tioti nml duet eonneclions for grinding, polisliing, and lndling wheels. They also regulate the air required for wheels of various sixes in terms of statin suetimt in the connecting duct. These codes, however, possess no uniformity as may bo won from citations taken from lb existing coties fur Wisconsin and Xcw York, ns follows: Tho Wisconsin code roriuires that-- Ott alt criiuiint;. bulling, and pnlulting vhcvU, the ituclhui at tho cuunectitni to tho huud must bu sullicient to di|dacu a column of watts- iu a U*tubo, fi iucho. The Now York code reads: Sutlicicnt static suction sitall lie maintained hi every branch pijw trilldn 1 loot of tho hooti to produce a ditTcrcnco of level of at bawl 2 inches of water between the two aides of a Unhajicd tube. The requirements designated by Stato codes must bo followed. Typical sixe connections for grinding and bulling wheels required in many States arc given in lablc 31. T*UX Zl.--SLxt of evtmcciiwt* fur grinding and buffing trhtdt diaamtr ml|kSt|aan*Si Oft**lias: e-urrfi nr k**, ant nvrr 1 inrh IhW:_________ 7- in Mneib itriiuivn. not mxrt IJ> Jtwfir* lhk_ PVtIMiiKa.fetBtiiiiiw.f*f.ertr;.'ln>-i<Mtl:in(. , IT-1 l>iadu inrtmiv*. But evers ijw-S*** Sb In Cl tartu iixrltc. ant owe 4 th< 3J- lo aMurft, iadiwitt. aat over A iueUm ibiik`-- SaSus: , .. Ouurhnrlr**, nntover I InehihWt,, 7- to tMnrh, U.UMW. Mbt **vrr I'jinriin Uii-t. IS- lo iModb hn-iiwire. am over 3 ii.r.-i iUHe. IT- WMiirh. io.4'*-!vr, M nter 3 iariiri llirt.. 31- (o S.'-tnrh. imHu-ivr, iwtmwUarlimlAiHi,, 37-toXHadb ioduurs, awi.t>vvr . uk!mUucO_ Jadni Table 33 shows tho amount of air handled by grinding wheel hood* with connections of various sixes. The effect of suction is dearly indicated. Thus, a duct connection 3 inches in diameter with 2-inrb static-suction bandit's only 0.G3 tho amount of air as when supplied with 5*inch suction. In other words, the volume is proporti mil tu tho ratio of thu square roots of the static suction ^-^^"0.03^- At tho same time, the increased static implies a higher velocity and a THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 1 Bb"002Q087 l 2581 _z wheels i the oniolving wheel. Tint ~ll wheels, and is M* untemet the normal L>olihing and liuJIjn.* bating the coastrn**. and buffing wlni>|... "arious sizes in term* CSO coded, however, lions taken from tint -jllovrs: .ztiow at the cwuMclimi zsx in a U-tulic, kwi** ranch |ti|M within 1 fut niche* o> water butwrm i must bo followed. 5 wheels required in Ithtil* VffujChgmUEft MedfiMmtmwhmwnTbm PHTM ____ ___ ___._. __... Irvw * * >IsCni*l KS9ft - la Ml41Vi i . Vv>t4 i grinding wheel 1m"1* of suction u clear!' diameter with 2-m*h air as when suppiatl me is pr>>]M>riioiuil ! n " O.tW^ At igher velocity ami - sii!**equcnlly proa ter resistance iu tho duct connection. With 2*incli uielion on n 3-inch tliumetcr connection, the nir velocity is 4,012 feet per minute while with o-itirh suction it is G,354 feet icr minute; if the resistance ia assumed to vary as the square of tho velocity, tho resistance in tho case of the higher velocity is approximately 2'A times that at the lower. Obviously, good design would call for ft larger dact connection in the latter instance in order to offset tho increased Ins-tea. On tho other hand, since n 5-inch suction must be maintained in accordance with somo Stato codes, tho volume is increased with ft larger duct connection and any gain thus obtained is nullified. For example, a suction of 5 inches in a 3-inch diameter duct connection is equivalent to 107 cubic feet per minute; in a 4-itich diameter duct, the voluuto of flow would be equivalent to ft suction of 2% inches. It is clear, therefore, that tho ventilation performance of hoods (at least for tho purpose of efficient design) should bo based on tho air volumes handled and not upon a rigid suction standard. These volumes, of course, should bo established by cx]>criiucnt as tho most effective for controlling the dust generated. Theso in turn should take into aceount the quality, size and speed of the wheel used, tho typo of hood with which it is fitted and the cliaracterof the work done. Tut k 32.--Cubic feet ej air handled per minute through artrage grinding vked phwj *p HMfliilM wflkfrnt Wft111 liSaaMrfcraoMtisc dad r-.--4_ t- ------------- --------Soil-- mi tluml I IK eM w IU mno tm m S3 111 Ml SO 471 MS *** 3 3H MM 14* U3 m MM Ml 411 " 20 4M IM M '*MUl S43 m 134 m m ns su !C S3 313 a 49* 4MU7l 431 Ml in Cl C7 n* ---* PO MS MM tm U3 * At tho present time, little data are available with regard to tho mount of dust generated with and without ventilation. In table 33 . are given a number of results taken from ft recent Russian publicatiotL* No data regarding tho speed of tho wheels are available; how ever, tho effect of ventilation is clearly in evidence. In passing, it ia interesting to noto tluit although codes regulating tho design and construction of grinding wheel hoods are perhaps the hirst siiecifie legislation relating to tho control of industrial dust in tliis country, no basic data pertaining to their uctusl requirements have ever lieen obtained. f A, Qv al Otfiritirih B. Lf TW \VaflUtimi of Imtmirfcil KfetablbUoraU, voL V.ifct, fl" VinttbMLm Enukimtm* lotl-i trial owl iu KlZvrtlr* (Work* Of Uao LcttlrtgrotJ 1 lQiTUf Uu iWvtrwtiwyj ami i'rvtwtU** at LalmtJ ' . r' ' THIS DOCUMENT WAS NOT A RFrnon bSv5pfrieSEm52ofT5siISNf0t ,NDIcDENA0UTTHENT,CATED Taklk &i.--liutl nlluling cffieicncifn of grilling and palitking iakaU. TnSM TnaafwwkdMNt H Mem* AlrlWnr IiuMi m ftrinla- mtmj CMtn* tkm wit tall liod on TM. ctniri. liMn wHh t 111 itkm iwmtmn (nm Kiovry. Merit dbatrtcr Urt****- Iki lld tfunkvl h4 flabh* ini Askhlsf ... llnury nil wtaL to Xmi>', "Sari* ilLuitOct ||kUia(). .M irrur ___ Knwry iiil tin. 0 so at fro JU4 |7 115 ie* ea: LU 1| 15 It A3 FOUNDRY 5HAKE-OUT EXHAUSTS Ono of the serious occupational disease hazards encountered in industry is the dust arising frotu foundry shako-outs. Few installations have been generally successful. The problem in this caso is to have available means for eliminating the dust daring shakoout of molds containing fresh castings. The usual process employed is to knock tlio flasks containing the mold and eastings with sledge hammers to pry them loose. In some instances, this is douo in places known as slutkc-out dumps, but more often it is done wherever the easting happens to be. Large castings eoutaiaiug considerable hard .HIS DOCUMENT WAS NOT A RECORD OF. PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES* INC. I BB 0020089 7 --------------- -- 2583 pothkntf ichctJ* hazard* encountered diy shake-outs. Few 123 nro work, present serious difficulties nurl frequently cannot be brought tinder the control of an exhaust system. The worker is in such dose rentact with the dusty atmosphere ns to catiso serious exposure. |u Addition, this type of work is not generally isolated, and gives rise lo a very general exposure which nmy involve all workers employed in the foundry. Two systems of exhaust have been employed to copo with the problem. These may be roughly described as the lateral and the combined lateral ami down-draft system. In the first typo of system, air is drawn through a grill near which tho eastings are placed (fig. fiO). The hulk of the molding sand passes into a hopper wltieh is generally equipped with a conveyor, but es way bo expected, con- fi < 3*fcT The problem in this the dust during shnke-suai process employed J castings with sledge s this is done in {dares li dniHi wlirrover the aing considerable hard i * I ndcrable sand as well as dust enters tho ventilating duels which seriously burdens the collecting devices.and cause considerable wear on all parts. Tho method is, hmvover, desirable where small castings are to be slutken out and when no largo accumulation of molding sand is permitted. The second method, shown in figure GO consists of a similar grating and hopper for placing the casting but utilizes down ward as well as lateral exhaust. Thera arc no set air UoV* which have been determined, for either type of control. A determination made of one typo of lateral exiwust 5 by 7 feet in area which rania lltish with the edge of the grating had n velocity or approximately 3fit) feet per minute in the piano of its opening. This was in a brass foundry whero the eastings were small. Tho control, however, was excellent. I BB 0020090__l THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOr COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. m , :i -! ;: j 1 i :; j ; * f?C\T~, THin f"''.!nir *r' * IT n! Q Ur 124 A fault of all such large exhaust systems, particularly 5n lomuhy pnmtico, is (lio exposure of llio workers to detrimental drafts. Till; is partieulariy 1 ntc in winter when the men arc first subjected to i|M. lieat from their eastings which cause sweating and then arc suhjee!ti| to a cold nir movement at the shake-out. As a rule, foundries an* seldom heated in winter, and tlus consideration is one of cxtivn** importance. On tlio other hand, the advantages are beneficial; an ~ exhausted shake-out tends to localize a dangerous operation and at (1* samo time gives protection to all those exposed to the dust wiiicli U generated. Another difficulty which is common to the grate system of shake, outs is the rapid accumulation of molding sand. Jlard cores ami chunks often fail to pass through the grating or the rate f dumpiu" exceeds tlio capacity of tho hopper and conveyor to remove the snmL TJiis is a strong argument against the use of a downward-draft system in many foundries which is not easily overcome. It is extremely doubtful that any method of local exhaust ventila tion can be used for castings of extremely largo size. Tho core work frequently cncounterei in such castings is so closely bound with rodthat it is accessary to resort to jack hammers to remove them. Moreover, the difficulties of removing the castings and placing thiu on the grate aro proliibitivc. Id such cases oilier mothods must 1* used for tho protection of tlio worker. DUST CONTHOL, FOB ABBASTVE CLEjLXIXG EQUIPMENT* Abrasive blasting equipment may be roughly divided into four types--namely, rooms, barrels, tables, and cabinets. These four different types of equipment may bo classified more simply by stating tliat rooms aro used for tlio cleaning of large castings, whereas tlio otlicr tltreo tyjies of apparatus are used to handle material of small size in largo quauLities. Blast cleaning rooms Blast denning zooms, are as a rule, constructed of heavy metal plato and tho most commonly used size is 10 by 10 by 8 feet. In tl*-more modern typo of rooms air is allowed to enter through tlio cmlio* and is exhausted through metal ducts on tlio sides of the room at tlr ' floor level. Tho material to be cleaned is brought into tlio mow. - either on a revolving table or hv cars or monorail. When tho door* of tho workroom are closed, tho operator in order to protect liittwli from tho impact of the abrasive and also to prevent inhalation <: excessive dust, places a respirator or cloth over liis noao and motifl ami some form of a canvas helmet over his head. In some raw., potdtivc-air prwairo helmet* are used. Theso are provided with THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. BB 0020091 I 2585 particularly in foundry ,'trimental draft*. TIiU .re first subjected to tlw : and thm are subjt<ei,-,| As a rule, foundri-i an* .tion is ne of ext rvm* rages arc beneficial; uu jus operation and at Uu* :cd to the dust wliirlt i- grate system of sleil;eymd. Bard cores and or the rate of dumpin'; or to remove tiio sand, of a downward-draft overcome. f local exhaust venrilae size. The core work loscly bound with rods ]crs to remove them, ings and placing tlrni tlicr methods must lie C TCQCirMEifT jly divided into four :abiuels. These four led more simply l*y argo eastings, whereas jo handle material of * 1 i { i i / 1 i icted of heavy metal 10 ly S feet. Jn the jt through the ceiling ca f tho room at tlio night into the room, il. * When tho doors rr to protect himself irevent inhalation of his nose siml mouth ad. In sonic rases, am provided with a ViV 125 supply of fresh air obtained outside the blast cleaning room and delivered under pressure to tho helmet. It is also necessary for tho worker to wear heavy gloves to protect his lutnds from the impact of the abrasive, and at times he wears canvas leggings and slices pro vided with metal toe caps os protection fur his legs and feet. With the blast hose iu hand, ho directs the abrasive stream against tlic surfaco of tlio work, tho hofo being of sufficient length to allow him freedom of movement so that ho may direct tho blast ogaiust any part of tlte work. To provide tlio abrasive jet a pressure tank, known as tlio "hoso machine", is used. This, or a similar piece of apparatus, is the fundamental unit of all room blast cleaning equipment. In this machine the compressed air and the abrasive arc combined and dis charged together from a .single nozzle or a group of nozzles in tlio form of tho abrasivo blast. Alter tho abrasivo has onco served its purpose il is returned through a proper separator to tho hoso macliino for re-use. Tltis abrasivo handling is accomplished by ono of several systems, depending on tlio typo of installation. With the mechanical lift system, tlie abrasivo falls through openings in the iloor to a hopper below, where itis picked up by a spiral conveyor and carried to tho l>oot of a bclt-and-buckot elevator, wiiich in turn raises it to tlio separator. Tho separators are a combination.of screeus and air exhaust, by means of which tlio heavier particles arc separated and tho lighter material is drawn oil by suction. The cleans sharp abrasivo for re-use is delivered to a storage bin, from which tho hose machine is automatically refilled. Tho rejected material and refuse is accumulated in a separate bin provided with a spout for unloadings. In some installations it is necessary to have a solid room floor, in which case tho operator at intervals, shovels tlio used abrasive into a hopper from which it is raised by a bdt-and-bucket elevator to an overhead separator. This system is known as tho "scmimanual" typo. Where it is practicable and desirable to locate the hose macliino in a bin beneath tho room no abrasivo handling system is necessary since tlio spent abrasivo is allowed to fall by gravity through a hopper to tlio hoso macliino below it. This typo is known os Ibo "gravity system." In tlio pneumatic lift system, tho abrasive, after passing through the floor perforations, fulls into tlio air current of a pneumatic lift, which raises it hy suction to tho separator. Practically all blast cleaning rooms now in use linvo' provisions for ventilation. In sonio of tlio inoro modern installations, tlio exhaust air, after passing through dust arrestors where it Is cleaned, is 0. i *7Ati NO i . iitCQ.\D Or DUSTthEu, INC. DID NO l. COME FROM LES. AND CANNOT BE AUTHENTICATED G INDUSTRIES, INC. ** 1 BB 00 20092^1 2586 120 \ delivered back into I he workroom in order to wive its licet content and to provide veiltU:i( ion. The correct nnioimt of ventilation minimi in abrasive cleaning room'; has not been delennined. Older types utilize from 2 to 5 nir dtaugc* per minute, while tho luotv meat types use from S to 12 and sometimes as high as 20 air changes per minute. From a number of observations made in recent tvpo3 of nbrusivo cleaning rooms it appears (hut uir movements at the breathing level beer no relation* ship to the dust concentrations found. For example, a. high dust count of 251 million particles per cubic foot was obtained with a velocity of 74 feet per minute at the breathing level, whereas a velocity of 75 feet per minulo was associated with 171 million particles per cubic foot, and a velociry of 77 feet per minulo with a dust count of 4S-S million particles. In all tie*oe cases metallic grit was used as tho nbmsive. The variation in counts with practically the*amc air movements in tho nhmsieo cleaning rooms may bo ascribed to differences in nozzlo pressure, to tho cleanliness of tho castings, and to tho mlo at which the work is being done. The above results may bo contrasted with a velocity of OS feet per minulo in an abrasive cleaning room using sand, and yielding a high dust count of G20 milium particles per cubic foot. From such data, it would naturally appear that when moro than eight air changes per minute nro provided, tbo abrasivo used plays an important part in the dust concentration to be expected, and is apparently much moro important than the amount of ventilation provided. Tho low value of 4S.8 million particles per cubic foot cited in a previous paragraph, was found for an abrasive room of modem con struction witli 12 air changes per minute. It is clear, therefore, that in *i>ite of tho best equipment available, it is essential that other method* (personal respiratory protection devices) bo used to prevent exposure of the blaster to rather high dust concentrations. Tim roodnet of work in abrasivo cleaning rooms may contribute a considerable quota of dust to the general nmnsphero of tho plant in whirh the room is situated. Naturally tho dust introduced-by this meins* may have an important tanning on the health of workers not specifically engaged in abrasive Masting occupations. Tho need fur maintaining nlmtsno room* in good condition is evinced from an analysis of data which show that with average equipment, workers in llm general air of a plant in which abrasive cleaning is done may In' existed to concent rat ion* which may run ms high ns 2i> million particles per cubic ftmt during blasting, while when no blasting is done, I Is* average concentration j* normally lwtaw 4 million particles. Tin* modem typo of abrasive denning mom is, ml tho other hand, so eon* stii*-(el that unlr:-* it is |H.riv lunintnineil to dust can jmssihly csc:i|h\ Obviously, dust-tight unit wdl-inninlained abrasive di-- 7 BB 0020 093 | THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT-COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. ------------------ 2587 .sheet cuntrul und abrasive rlnnitiK -zc from 2 to 5 air - use from S to 12 From a number cleaning rooms it i bear no relation* mplu, a high dust s obtained with a ' level, whereas a 71 inillion particles * with a dust count allie grit was used nctirally the soma iay -bo ascribed to f the eastings, and ocitr of GS feet per zn|^ Uingahiy-h . ^V.n such data, glit air changes per i important part in >arrntly much more ?d. jbic f ot cited in a win of m dem conlear, therefore, that essential that other ) bo used to prevent ntralions. ns may contribute a `here of Uio plant in l introduced by this ealth of workers not lion*. Tlio need fur is cvinccil frmn an equipment, worker* :ning in done may In' :is 20 million pari irlo* blasting is done, (be Mioti particles. Tbe not Iter band, so emt io dust run jtos*i!ily itr> vc 1`kiitin;! room* are utvl Imds of oliiuiiinthig a cniMiJcruhTo jHirlieiT of the dust which is found in many plan U. Bloat elesalnc barrels Blast cleaning lwirrcls nre often confused with tlio 'Humbling m31M or barrel as a method of cleaning. The principles on which Ihoso methods depend aro entirely different. In tho "tumbling barrel" cleaning accomplished by 1 lie nbrasiun of the objects to be cleaned against each other or against a given abrasive wluch is dumped into tho barrel, whereas in the blast cleaning barrel tlio cleaning is accom plished by the abrasive blast, the rotation of the barrel serving merely to bring tin: metal ohjt'rls under tbe abrasive blast streams. Various types of blast clemuug barrels are ia use. In general, a blast cleaning barrel consists of a drum matin of heavy sheet plate, mounted as a rule on trunnions and capable of rotating. A rather common type now in nso consists of a properly fashioned, movablo scries of plates driven by a chain drive, and so arranged that the work is constantly corriod on this endless belt. Them aro various type* of blast cleaning barrels, all of them differ ing in the method of abrasive handling and reclamation. Tlio threo most common abrasive lia udliug methods in blast cleaning barrel installations aro the suction, pressure, ami gravity types. Somo blast cleaning barrels are provided with a eomplcto outer housing winch encloses the barrel while in o{>crution. During loading tho door of such a housing is opened, the barrel door is then opened and the material to bo cleaned is placed in tho barrel. Bot h doors are then closed and the air jets set into operation. Such a housing may bo, and often is, provided with exhaust ventilation. In many coses the barrel is not provided with n complete outer housing. As n rulo tlio use of abnndvo hlat cleaning barrels constitutes a small portion of the cliain of processes in the course of tho manufac ture of certain articles. Fur tins reason barrels aro usually located in ono portion of tho plant or foundry whom tho material to bo blasted is made. In other words, barrels aro not generally segregated from other dusty processes. Tims, it is necessary to bear in mind that adjoining processes may possibly contribute a certain amount of dust to Uio atmosphere in which tlio attendant works. The advantage of housing is clearly demonstrated in tho following data obtained from a series of dust counts, ruado on various equip. ntunt in use; Jjpmntmf+pkajmtkht * Hand Inin# metal nlmwlvtt am! |HHMnL....w..... It 2 IlnnH uidir- wl aIirumiv ami ImhimiI----------------------------------------- 2. 2 lUm4 uniiitf metal l<nMvti ami wit hi>iwn|........... 24.0 Uanvl uxing *aa*l al>raxivr amt nut SS. 0 --j t BB 0020094 | THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOTCOfflE-FRGM ----------IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 25SS 12S Tho dbcrupain'y in counts for metal and sand abrasives In Imrni. which arc housed is duo to design factors in the equipment sUidiiil, However, it is evident from the data presented (fiat unhoused ItnrivU nrc productive of ratlier high concentrations of dust. In Uiohundung of fresh castings, especially while loading the harn*li, considerable dust is evolved. Tho dust, thus formed may bo ivditml somewhat by (ho use of chain-hoist loading skips and a certain d<~n-r of care on the part-of tlio barrel attendant. During tlio uuinuilh*? operation, similar care should bo exercised so as to prevent the di>~ semination of dust from tho abrasive admixed with the costings. Tj*. most important source of atmospheric pollution however, in coiuht. tion with blast cleaning barrels is that dust which emerges from (hr openings in the barrel structure. Such openings are provided (<> n small extent by poor design and to a greater extent by poor niuiute. nance of equipment. Blast deaniac rvtarr tables For certain types of work, it lias been found efficacious to use Hie rotating blast cleaning table inctlmd. Tbeso tables are of a heavy metal, substantial type of construction; ore circular in sbapo and >f * an averago diameter of 6 or 7 feet, mounted usuully about 3 IWl above tlio floor level and rotating at a speed of 1.5 revolutions |n? minute. The tablo is divided into two halves by means of a series of flexible, split rubber curtains. Ono sido of tho tablo is completely enclosed, and is provided with threo or more traveling nozzles ftr directing the abrasive onto the work lung on the surface of the table below. At tho other balf of tho tablo is stationed a worker, wlm*e function is to remove tho finished objects, to replenish tho supply of work to bo done, and to turn over the objects on the table so that the under surface may bo blasted. The abrasive is, as a rule, deliv ered against tlio objects at on air pressure of 60 or more pounds to the square inch. With sueh tables the abrasive reclamation i* accomplished by either suction, gravity, or pressure method*. With reference to abrasive cleaning tables, tho remarks mado in * connection with abrasive cleaning rooms apply to a large extent. Well constructed and maintained tables permit littlo dust to escape. For example, a poorly maintained tatdc, using metal abrasive, gave dust counts of approximately 42 million particles per eubie foot of air hi tbo general air close by, whereas another table of good construc tion, using sand, gave dust concentrations below 3 million partirlrs. Tlieso results so clearly emphasize the imjtortanco of proper earn and construction of abrasive cleaning equipment that they should by carefully noted. N ,.i i i .$ > * 9 .* ` - * i - V* f. l/i. \* * **ea t. j: f ` .1 record of _ 2589 r.i abrasives in barrels s in tho equipment studied, .'tiled that uidfnnscd laurcLi >IIS of dust. fly while hauling the laurels, bus formed may lie reduced g skips and a cerium thvn*e nt. During the unloading d s ua to prevent (lie dis ced with the castings. The dii lion however, in connrc3i which emerges from tins pcniii3 are provided to a ter extent by poor luainto- otmd efficacious to use the -irsc tables are of a heavy re circular in shape and of ntrd usually alxiut 3 feet >ccd f 1.5 revolutions per -lives by means of a series - of tlic table is completely no* -aveling norrJrs for .airfare of the (able staWned a worker, w hose -S t rcplcnisli the supply ejects on the table so that jrasive is, as a nilc/deliv of CO or more pounds to abrasive reclamation is pressure methods, ics, tho remarks made in apply to a large extent, emit little dust to escape. ;ing metal abrasive, gave articles per cubic foot of er table of good construclielow 3 millinn particles, rtaiiro of jiroper care and .`lit that they should be 12D Rtast cleaning ratlineIs For special kinds of work, where it is necessary to clean small objects using air pressures of CO pounds or more, the blast cleaning mbinct finds much use. Blast cleaning cubinets nro of steel ]>lale mnstrurllou usually approximately 5 by 3 and 7 feet in height. They are, as a rule, provided with a single noxsdo through winch the abrasive material is forced by means of air pressure. In tho front or the cabinet, there is usual!)' provided a window of heavy pluto glass, tlirough which the operator may view tho work in progress. Also in front of the cabinet there are hand holes through which the worker places his bauds and arms in order to manipulate the work. The material to be cleaned is placed inside the cabinet through n lunged door, located nt the front or side of the cabinet. The operator then turns on tho abrasive jet by means of a foot treadle. Tho worker exposes oil surfaces of tho object to be cleaned to tho action of'the jet and removes the piece on completion of this task. As a rule, most cabinets of this type arc provided with an exhaust system for tho removal of tlio fine dust created in the blasting process. The abrasive reclamation employed with cabinets is either of tho suction or pressure typo. It is possible to conduct abrasive cleaning in properly designed and wcli-maintained cabinets with a low dust exposure. It is neces sary, however, to point out tho important part played in dust control by proper operation of equipment. In many cabinet installations, the hand holes aro provided with gauntlets and a separata opening is furnished by wiiich work may be introduced aud removed. Such an installation would bo considered excellent from the point of view of preventing the pollution of tho almospbr.ro by dust. On tho other lutnd, where gauntlets or curtains aro not provided for the restriction of the hand hole openings, it becomes possible for dust to bo deflected from the insido of tho cabinet through these holes, and contaminate the workroom air. Hand holes, therefore, should bo os small in sixo as compatible with tho tasks to bo performed, and suitable exhaust ventilation (5-10 air ciutngcs per minute) should bo provided, in order to minimize the possibility of dust being forced outward through the Land holes. Aatomaltc bloat cleaning equipment In tho Mast droning of certain largo objects ordinarily conducted in rooms, it has been found convenient and desirable to eouduct the cleaning o|K*rntions without the intervention of a worker for the manipulation of tho object to l>o droned. Usually this is neeonil*UsheU by whnt is known ns automatic Mast cleaning equipment, Tho work is placed on a licit conveyor liy a "loader'*, the work pass ing through the blasting chamber or room where it is cleaned by tho-, . i\!i L ; * 1 ^ 1 ii-c$ . DOCUMENT WAS NOT A S^C^MAUTHSNTiCATEO PG INDUSTRIES, INC. 'b**002009^1 --^ ^ 1 2590 130 tihrnnivc stream. The liuiti'.rinl emerges in the cleaned stain on t|,,. cndhtM Mt ul lh exit side of llo room where it is removed by ,, worker. Automatic abrasive denning equipment obviously provides an excellent menus for denning certain articles too Inigo ( bo banditti by table or barrel equipment. Hero again, however, tho importune*, of proper design and upkeep of this typo of equipment must. |K. stressed in order to prevent excessive dust exposure of tbo opentloiv. . Housings should bo of sufGdcnt length and batllrd so as to prevent (lie egress of dust. Thus, it has been found that old autumn tie equipment without prn|>er euro may exposo tho operator to <?,ecnlrutious of approximately 90 nullion particles per cubic foot air, while newer types of equipment reduce tlio dust conccnlmuuu to about 5 million particles. Tumblinc barrels Tumbling barrels are frequently tho source of high dust conceotra lions. As a general rule, State codes provide tliat such apparatus duill ho exhausted and tliat a stated suction sliall bo maintained at the duet connection. Most of tho modern equipment is now mi constructed that there is little opportunity for tho dust to canti*. Thus in comparing tho new with the old typo barrels, tho former gavo rise to a dust concentration in tlio general plant air of 2.7 mil* lion )Kiriiclcs per cubic foot, wliilo tlio latter averaged 24 million particles. As may bo expected, however, tho care given the equip* incut is an important factor in its performance. HOUSEKSSFIKG Good housekeeping is an important aid in reducing dust concen trations. Tho dust collected on floors, benches, rafters, etc., sltouM be removed at frequent intervals. Either wot sweeping or vacuum denning should bo used. Good housekeeping not only serves xemovo sources which contribute to tho general dustiness t a plant, but also adds an important psychological factor. A dean workplan* not only tends to keep dean, but frequently comjicU somo method of control to bo applied to tlioso sources which are dustiest. am vsLocrrr nsQUtuiarares roit noons Tlio required atr velocity at a dust source is determined by the characteristics of dust production and operation or tho pmn**>. The frictiuii on the surfaces of tlio jutrtirics creutctl by tho moving air must bo sufficient to overcome tho force witlv which tlio pnr- tides aro thrown oik Hits force is a function of tho size, nlia|\ and weight of ihe partidvs and thdr. sjiccd of travel. Heavy par- (T * . '' " *' ft ^ \ "!0 DOCUMENT WAS NOT A RECORD - OF~ NDUSTRlES, INC. DID NOT COME FROM ILES AND CANNOT BE AUTHENTICATED PG INDUSTRIES, INC. T BB_0020097*7 2531 =^i n lie chained statu on tiic 13ft tcro it is removed by a tides require a higher nir velocity than light ones, and tho air speed obviously prondos nn too large to bo handled lowevcr, tho importance of equipment must !* rposurc f the operators, baffled so us to prevent md that old automatic o the operator to con'tides per cubic foot of tho dust concentration increases with tiio velocity of the dust particles. in many instances, the machine throws off tho dust in n well- ilclincd direction. This fact should 1>o utilized in shaping and locat ing the hood, since it has an important tieariug on tho strength of tho air stream required. It is well illustrated in tho application of exhaust hoods to high-speed grinding wheels. Tho uso of partial or complete enclosure of the point of dust gen eration offers on effective means of reducing the air velocity require ment. The speed of travel of the dust particles may be reduced and their direction changed by tho proper location of hollies or housing. Tlus phase of hood design is limited chicily to processes tiiat do not require close attention of the operator or delicate ma nipulation. The trap for uso with rock-drills is an example of co of high dust conccnidc that such apparatus 1 shall bo maintained at i equipment is now so for tho dust t escape, ypo barrels, the former irnJ * nt air of 2.7 mil- .uged 34 million >MRe given the equip- cotnpioto enclosure and tho application of partial enclosure is illus trated by tho hood used on gnuiito surfacing machines. Many examples of partial and coraploto enclosure are found in tho wood working industry. The characteristics of operation of the dusty process must be carefully studied and ever}' jiossiblc step taken to reduce the air velocity required to capture Ute du$L In general no other pliaso of liood design will give as great a saving in operating cost as re duction in the required air speed. co. t or>i batk ajutlow required { The air velocity at a given point in (lie zone of influence of a suc a reducing dust eoncenlies, ntfters, etc., should it j tion opening is a function of the rate of airflow through the opening, but also of tho direction nnd distance from the opening, and tlio 'et sweeping or vacuum shape and size of tho exhaust hood. Hence, the rate of airflow Jig not only serves to through the hood, necessary to produce tlio required air velocity ml dustiness of a plant, at the point of dust generation, depends upon the size, shape, and tor. A clean workplace location of the liood, as well os tho eliarncteristics of dust produc * compels soiiio method tion. It follows, therefore, that some knowledges of the aerodynamic ich aro dustiest. characteristics of suction openings is necessary to tho proper choice of hoods if economic design is to be obtained. Tlio airflow character on itoods o is determined by the :ration of the process, created by the moving vi with wliirli the per* tion of the size, ntuipo, of travel. Heavy pur- istics discussed in section VII are important in this connection. The rapidly decreasing center-line .velocity curves presented in figure 3$ show clearly the need for locating tho hood as closely ns possible to tlio point of dust generation. This is a general rule, aud is applicable to all conditions. It is im]iortant to note, however, that the rate of decrease of velocity with distance from the hood decreases with an increase in urea of the opening. Moreover, the contour lines become more flattened as indicated in ligurn 42. These facts jaunt to the desirability.of using as large an opening .is.pog^iUo (wlycif10|3 ` ILL COLIEGS 07 PHYSICIANS* r r? TW: fT .ADI*.! .T'fH *__ __ JI _BB^02098 | THIS PPG IT'S eNs"Jotc^ ^CANNOT BE AUTHENTICATED *,TRtES. INC. -- I. _ 2532 132 the further udvantngn of reducing the power consumption by lowering llio entrance pressure loss. Tho area of dust production must also be considered in choosing tho si74} of tlic hood opening. For o concentrated point of dust . generation, n Hut velocity contour is not as necessary ns for more exlcnsiva uresis of dust generation. In all eases, the object is to obtain a uniform air velocity over the region of dust production, nnd tho lowest jMMsible flow from areas of no dustiness, tho so-called ineffective areas. In other words, the ratio of effective to ineffective flow should lw rondo as high' ns possible. Since the distribution of flow in the stone of influence of suction openings is intimately asso ciated with the si/x> and shape of tho opening, great care must bo exercised iu choosing a hood to give a high ratio of distribution in effective to ineffective areas. In tliis connection, tho use of flanged openings is often -advantageous. Tho use of flanged exhaust hoods on hand pneumutie granite carving tools (55), in place of unflanged openings, demonstrates the saving in power consumption possible. For tliis process nn air velocity of 200 feet per minute at the tool is mptirod. Operating conditions demand that tin: hood be at least fi incites from tho tool. At tliis distance, tlio required air velocity is obtained by a flow of 300 cubic feet per minute through a rec tangular ojxming 3 by G inches in dimension. The addition of a 3-inch flange around the opening reduces the rate of eir flow to 200 cubic feet per minute, a saving of 33J* percent. Since tlio pressure loss at entrance is also reduced, the power consumption is lowered by more than a third. Wherever conditions permit their use, the installation of flanges is recommended. -1V. = / M/yf f |W i bv; .iV- , ,i \ i vj Y1LES. rl t. dh Ira sdj I tin Hit* |mrt ritu `A a o of ih> and *1 Wt w.the th r 2593 irapLiou by l,,w.. isideml ati *L--. atrd point >f rcssary ns fur i. the object L> i*.. tist production.. jness, the - 'ective to r - the (Jistrihnii..:. . i k intimately u great cere inu-.i ] io of duttrihntioii, v, the use of (Ini:..; ngcd exhaust I.-. 1 place f unflair. . nsumption jk- il.: niautc at the i*4 . .to hood be nt V ;uir* J air veWiu < ongh n We addition .4 .. 3 f air flow to Since the jmv-u: nption k lowered nuit tlieir use, it- t\ . X. DOST COLLECTION AND DISPOSAL iNTr.ouucnoN As a general.rule, the material collected and transported hr an .\liaiwt system yields no economic return. Nevertheless, its proper ,!ip;Kal is an item of eon.-idrra'do isujxirtnnec for three reasons: (I) To prevent reentrunee of dust-laden air into a budding thus-con taminating working places, (2) to avoid public, 'nuisances, and (3) tu conserve, especially in winter, warm indoor air for recirculation. The methods in use for tlio collection and disposal of dusts are by direct discharge to the atmosphere through suitable ports or stacks, Kv separators or cy-eloncs, by cloth filters or sc. ecus, and by electrical precipitation. Of those methods the first threo are most commonly used. Electrical precipitation is usually employed where the material io lie collected lias some value, such as the recovery of potash dust in a mucut plant. It k ako used in the abatement of nuisances caused ly large power plants burning powdered coal, tlio ash of which must lie discharged through the stack. Because of their limited uso as ndleetora of du-sU found in most industries, uo further description of tlicm will hero he given. Hired cKminalian of dust to atmosphere Unless the dust-laden air collected by the exhaust system can be eliminated through a stack of considerable height, it is undesirable In exhaust directly to the atmosphere. In some States, codes prevent direct discharge. Such methods, if practiced, may with strong con trary winds cause the dust to I>e swept back.into the plant or to adjoining buildings and causo a general nuisance. - Disposal through stacks, if sufficiently tall, lias been found adequate and k resorted to in many establishments. The success achieved by .this method k due to the dilution attained by the scattering of particles over a wide area. Cjrrloae separators A cyclone consists of two concentric, cylinders, the outer fitted to conical hopper and connrctrd tangentially to the exhaust duct **f the fan (fig. Cl). Tlo inner cylinder fits |inrtinlly into thn hopjier ; and discharge upward to the atmosphere. Thn air form'd tangentially "'tween lho cylinder is roused to rotate at a high speed and form* !be dust particles toward the outer shell by crnlrifugal action. Thn ' . i . THIS DOCUMENT WAS, NOT, A JtECQSD. GE-----PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. '* -- ii k : r\ nltfJI dust rraHiing the outer cylinder emiiiniirs to spin mid to drop grad ually into (he hopper, ilio clean nir passing through Uio opening pro vided by tin! inner cylinder. IWrmi'tt of their simplicity and freedom from care, cyclones nrc very widely used. Unfortunately, however, ninny cyclones have been installed without duo attention to their capacities. As a result they frequently do not function effectively and are discarded. The ellieiency of a cyclone depends ujion its size and llio volume f air luimllcd. Whit on (tin) has obtained n number of interestin'; curves relalivo to the collection ouricr cilieiencies and resistances of vari ous cyclones using precipitated ffy ash as a dust. These curves aro shown in figure C2 and as will be noticed, low resistance indicates a eompnmtively low collection effi ciency. Whiten 1ms also shown that dust concentration docs not materially affect percentage re covery. It will be noticed in figure 02 tluit the smaller the cyclone the more.efficient a separator it be nami^-tno tthwa mw*. comes. In recent years, tliis fact lias been used in tho design of small qyeloucs eonnecred in parallel. Them multicyelones Itaro (ho advan tage of being flexible. They cun be ojieraled at their muxiiiium efficiencies regardless of varying air flows since units are cosily added or shut off us required. Various manufacturers have designed special cyclones which Jtnvo relatively high efficiencies. In choosing a cyclone, for a particular operation, therefore, efficiency and cost of operation should receive careful consideration. When tlie air velocity in the fan discharge duct is known, t he follow ing equation is useful in computing the. resistance loss through the cyclone: **"0.0I3(l,(X)Q) (10) where V is the velocity in fw*t per minute in the fan disciuirgo duct and A, b tlic pressure drop through the cyclone in inches of water. The above formula is an average u hidi applies to the cotnmon cyclones in toe. 'Whenever possible, it is best to secure the manufacturers' figures for various flow's. Frequently the nir exhausted from n ryelone is reeirrnluUti without further cleaning, This is jHiesible under certain roiiduioiis, 1ml for i r i. w i; f r> I i; a n h jo UMt- r WAS NOT A RECORD OF INDUSTRIES, INC. DID NOT COME FROM files and cannot be authenticated RG INDUSTRIES* INC. , J.fB^02oToT"J I 2595 . and to drop gnuldh tbo pcning pn>- care, cyclones nany eye! nos hv<* idties. As a result r discarded. ' and tlio volume of uber of interesting to tbo collection resistances of vuri:ng precipitated fly Tbeso curves are * 62 and as will be astance indicates a lour collection offian has also shown entratUm docs not yet percentage rtv 135 toxic dtwis or such dusts with small particle-size, for which the effi ciencyof a cyclone is low, tbo uir leaving i t should be carefully analyzed by methods described iu chapters 2 ami 3 before recirculation. cloth narnss Cloth filters arc used where the product collected is ralnalde, or where clean air is desired for recirculation. Tho materials used for filtering mediums vary considerably. IJigh efficiencies are claimed for bulb muslin and wool. Each manufacturer of filter equipment recommends that which is best adapted for the collection of a par ticular product. Jt is, however, important to remember that cloth filters do not withstand tein|ieraturcs over 200* ]<'. and aro easily acted upon by caustic and arid sulistanres. Wet materials also arc not easily collected without overloading the system and it should be oticod in figure C2 .raga cyclone the a^f n(r it br ent years, this fact a tbo design f small tics have the advanat their maximum lit* ora easily added' yclones which have oc, for a particular *tion should receive is known, the followice loss through the (13) n discliarge duct and ches of water. Tho jo cumiuun cyclones tlio manufacturers' rmrriilafrd without i conditions, hut for held in mind that ir filter units arc subjected to places where tlio air temperature is low, tho warm air collected may be chilled, to tho dew point and cause tho filter to become wetted. A filter unit cousists of a closed compartment with either clotli screens or bags so placed that tho dust-laden air must pass through them, niters may bo operated either on tlio positive or negativo trfdo of a fan. Cloth screens whether under suction or pressure must bo housed whilo bags need only bo housed when placed under suction. Hog filters operated under positive pressure, such as aro used for rinc oxido and flour dust collection must lo well collared at'tlio duct con nection in order to reduce leakages and to supiKirt tho weight of the bag and tlio dost-collected upon it. ISag filters of this typo are aus. |*nded vertically, ranging iu size from 4 to 40 inches in diameter and inun 5 to 20 feet in lengtlu Jlcruitso tlio process of filtration gradually inrrrnses tlio resistance >f tIm system due to the accumulation of nuilerinl on tho filler surface, cs-----10 3....... TPHPGISINDDOUCSUTMREIENST.INWCA.SDNIOONTOAT CROECMOERFDROOMF ' -~, ^RLr2---2---2--0--102*7 IT*S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES. INC. ^. 13C . ' it is necessary to shake or tup the unite at definite intervals. This is nrcomplitdied mcciut ideally by dork arrangement, or by hetut Terry (() lias jvromincndcd the use of e manometer device whereby filters may automatically bo siiekcu when the limiting resistance set by (he manufacturer is reached. Tsirgo filter bags of the typo do wrilutl above are mounted bi batteries in sjiccial buildings and are shaken down mununlly by lapping with long sticks. Tn order to prevent overloading, a cyclone or separator is used to cfimimi t e. the coarser and heavier dusts. Some filters operating under negative pressure nro so constructed ns to produce a cycloning effect Wore the dust laden air enters tlio filter. Preliminary separators reduce the load on the filter surface. Tho dust collected by filter units is removed from the hoppers jwrindically or continuously by means of screw conveyors. Tho amount of filtering surface necessary varies with tho type of material collected and the typo of filter surface used. Wool has A very low resistance whilo some muslins, depending on their weave, may offer considerable obstruction to tbo flow. Table 34 gives tho rrfcMlMict! of some clotlis hi common use. Tamls 3-1.--RetimOutec oj furious flier materials I* tla flm of air IUmU RmWiinr* UhvoMl coUc t-H or TiJanwrer mmMluvt * Milter ratios Oeefcum. UmmW t flaw Ml nfcfelmtaf if )*T Mount*? MfUttwtuat MSUar (hrinn* nr meat `^hiit^k, . i, r. _. - JO.0DMLM1 fi amm .MO .eot-.dat A high concentration of dust naturally requires more filter surface in order to keep the resistance of the system low end to avoid frequent Miuking of llu> units. Sinubuiy, materials wlucli pack easily require t-in:** >urhrra. Tlio usual filter rates employed in practice range from half to in cubic feet per square foot per minute. Higgler rates -a 1 used where filler* arc sltaken at frequent intervals and where '^'dn-r is not enbesive in ebanictcr. *"* i,*,*s*1 Uuie-rrsistanco curves for ilyosh ore shown in figure C3 1:*t operated under suction. Tlio filtration rate for each i at 10 cubic feet per minute per square foot of filter effect of various dust concentrations is clearly indicated, ary condition* found in prarttce, fans operate at con-* b*tMM* an increase in filter resistance is comjmnsttled (he volume of air flow. Tbo curves shown in figure . \ ! G4 il ` tyjiM then r * I1 {I I t* f t t JTsetac velecit longer Tlie musts preduv 1 it i i o IkRtct- under w Utan fly give d;H snry in 1 Tim rale bmp* me. tlm t-vsii *? 'SSSSwmS BE AUTHENTICATED INDUSTRIES* INC. | BB 0020103 | 2597 definite interval*. T1* * angement, nr hv huml .manner device wh**rel\ to limiting jrvsistanre *,.{ .er hay* of the type d.*. jMH'ial buildings mid n sticks. a or separator is tired t> :jc filters ojkt;) ring im*W -ociurc n cyrluning efiWt Preliminary scpaialiuvt loved from the hopper* ;w conveyors. varies with the typo of face used. Wool has a lending on their weave, iw. Tabic 34 gives tJw wb to tko fiom of air lif-T- tif 11 Haw 1 *ui.>li*t<a te|*r wb* f*r WUi-r MBis* ftattav --v *wr> lUMM .tM*SN uircs more filter surface iv and to avoid frequent (rich pack easily require dinpruetic range from minute. Higher rates eut intervals and whore are shown in figure 63 ' i filtration rate for earh er square foot f filter ions is dearly indicated, e, fans operate at ctm-' istunrn is eulii|M*iHal('d curves shown in injure G4 illustrate the relation between resistance and filtration xato in a typical installation duo to a dropping fan characteristic. It is obvious, therefore, that filter cloths should be rapped or shaken before llio --i--i--rr 7 / 7&&s$*3tns/ft Ct'g.9 - - J AV ACj*C4 -- c/#r * * ^ I' TU A A7 / /nrosH / c* q 7 / y, r6- _-2 I' so 77/7T`- />f/swrS 7mU (St--'nolMwoto(swtea tUUr t vartuiik nMMstr^Uaa* t M foot per latent*). to *rt tnte(air Owr toeaHe<Mtr velocities in the various ducts are reduced to a point where tlicy no longer can convey the dust particles. (Seo see. VIXL) The curves of figure 65 servo to illustrato the relation between resistance and filtration rates at various rimes. The curves are produced from data obtained from on experimental unit using a constant rate of feed (435 grains flyash per minute).* Thus, wlicn the rate of air flow is 10 cubic feet per min ute per square foot of filter surface, the dust concentra tion is approximately 5.4 grains per cnbie foot. At intervals at 5, 20, 25, 20, and 25 minutes, therefore, rite corresponding resistances are 0.0,1.45,2.15,2.85, and M> *0 SO 3.55 incites of water gage, respectively. Theso values, it must be remembered, >w*uc(^-KaKtrew!atcfM)MatiMUwnu. apply only to the-conditions under which the curves were determined. Obviously, dusts other than flyash or the typo used in obtaining rite above figures would give different results. Much preliminary experimentation is neces sary in handling materials whoso filtering properties ore unknown. Tbo rale of resUtunce build-up, as has been stated, determines in a large measure the type of fan necessary to meet tlto requirements of the system. HpnlJi.b>u am*j. M. n. THIS DOCUMENT WAS NOT A RECOi, PPG INDUSTRIES, INC. DID NOT COME I IT'S FILES AND CANNOT BE AUTHENTIC BY PPG INDUSTRIES, INC. j_BB0020104 | i 2598 Noy, - Filters, when not overloaded, are very efficient, and it is possible U recirculate the filtered air. In Lid* way, the wiulcr heat josses in a building normally duo to exluuisting air outdoors may ho lowered, frequent]}' to a point where the operation costs may balance thoso <lue to heat losses. ]Tore Hgaiu, however, it is necessary to check upon the efficiency of filtration by means of dust counts. 1LUXTEX4XCE OF DUST COLLECTING BTSTEMS I >ust collecting systems should lie inspected at definite intervals. Abrasive materials cause considerable wear in elbows and duets con* neeted to the collector and these should bo repaired os soon as detected. Cloth filters often become wetted and mold with non-use, or else break with continued shaking- Tears in the filter medium should he re paired as soon as possible in order to provent the air from bypassing oilier units connected to it, or as in- tho cose of soino systems, overleading the unimpaired filters. Compartments containing fillers should also be inspected for leaks. Due to the vortex formed in cyclones the cone-shaped hoppers are continually under negative pressure. Consequently, if they are opened, the dust collected in tlieni will bo drawn upward and ettlter pass through the cxlmust or else circulule continuously, thus reducing tho efficiency of Iho'systein. It is therefore important to avoid leak ages. The usual method of collection for somo tyi>os of single units is to connect the eyrltwo hopper with a duct ieadiiigto an air-tight :U"E iTcImTfROM ' fS^EAUTHENTCATED INDUSTRIES, INC. r I^BB 0020105 | 1 and it is possible! lu ter host Iojws in a -s may be lowered, y balance tlioso due y to clicck u]ton tlic 'TSTEUS z definite interval!, ows end duets con es soon os detected. ........................ c\! r> NOT 0 0; ? i t~i iv; 11 i i O i i L L. 139 compartment. Tu such d device tbo suction will lte low of tbo dust collected wlulo tho and will not cyclouo is in interfere with tlio rcntovul opWerhaetionnh. ot substances nro convoyed to a filter collector there is danger of setting it on fire. As a method of avoiding such an occur rence, a preliminary coarse screen should bo used. Otherwise, it is necessary to remember in case of fire to first shut ofF tho fan or blast gate. Tho use of a sprinkler system in the filter comportment in plants where potential fire hazards caused by hot substances exist, is wood Practice, \ ~r r/i7# Jt ttvwtaw tfw Infwh. on-usc, r else break dium should bo rcntr from bypassing iomo systems, over- containing filters -shaped hoppers are ently, if they are upward and cither msly, thus reducing rtaut to avoid lcakyjies of single units Jin; to nu air-light i i THIS OOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME PROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 1_BB~002Q106~7 I 2600 V NOTE:Ti" :-io NOT COME FROvi rVG FILES THIS DOwUMEnT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. -3 XI. MEASUREMENT OP AIK FLOW In T\irt V it was pointed out tlml tlio efficiently of dust curiip.) liext measured with (lust counts. Tho methods of air-flqw iucumo. . meat, on the other hand, assist tho engineer in checkins; upon tin* r. Jiaust system fruni the ncrodynumic viewpoint. It assists him gaging the velocities which may bo required for tho transport of r, T tain substances and it gives him a powerful method in estimating it., meehauical efficiency of a system. In tlio present section, it will I. shown how tho air velocities and volumes, necessary to effect onir.4 may bo mensuryd. Not all tlio methods for measuring air flow iu e rawiai-nisMM. included but only those which arc most widely used and an therefor* most practical. THE STAXDAXD WTOT TUBS Air velocity is measured by means of a pitot tubo shown sehcmaii' colly in figure 00. This instrument consists of two independent roe* centric tubes bent into an L In use, tlio iubo is inserted into a dun and directed along tho axis so that it points upstream. Tlio tw* terminals A' and 11' are connected to a suitable gago and tho dclfo-tion observed is a measure of tlio speed with which tho air is moving. (U0) S DOCUMENT WAS NOT A RECORD OF l INDUSTRIES. INC. DID NOT COME FROM i FILES AND CANNOT BE AUTHENTICATED PPG INDUSTRIES, INC. MBB~ 00 20107" | 3601 of dust control ;,i air-flow iiicu uin;. -ki" upon the pv. It a-*si*ts him in transport of cer- in estimating Ut* section, it will |R. *' to effect control `.iriug nir flow are X~ 1/? -Jid arc therefore -hotni schematiMlcpciiilcnt coiirtnl into ft duct enm. TJio two ami dm delict*air is moving. 141 The tlicory of measurement of this supple device is briefly ns fol lows; Tito point A measures Uio total pressure within tlio duct which rtinsists of a. dytunniu or impulsive pressure trml a static pressure (m-e. VllJ). The former is nccuralcly inctisun*d only when the tube is pointed upstream, but the latter is n prrssurc which at a given point is (he sumo rognnliiw of direction, if therefore, the total pressure be ilrunlcd by IJ, the velocity pressure by A, and the static pressure by i,, then the pressure mcasureil at A is U*A, A, depending on wlmtli'T (ho duct is under positive or negative pressure. Obviously, since too velocity piessure can only bo measured in a direction upstream, it cannot possibly exert any effect at IS wlicrc tlio Imlcs arc pirpcadi.-uhtr to tlio bow. Hence, at B only tlio static pressure A, can have any influence. Since also, the two concculric tubes are independent and are connected by means of a U-tubo con taining fluid, it follows lliat tlio deflection observed is equal to AtA,7A, or amply Af, the velocity pressure. By using equation (10), A. may be directly converted in terms of velocity. V*400f>VE (X0) Information regarding the design of pitot tubes lias been given by Owcr,(G7),wlio lias shown that the static holes should bo at least 10 diameters removal from the dynamic opening. Ower lias also shown tlio effect of yuwing and turning of the tube in making measurements. When tlie volume of air flow is desired from tlio pitot reading, a correction factor must bo applied to obtain tlie average velocity of flow. Tiie movement of air in a duct is not uniform, but is highest at tlie aas. Tlio averngo velocity is generally taken as 0.S tlio axial velocity measured by tlio pitot. Consequently, multiplying through the right hand side of equation (12) by this factor, we obtain C-lSJd>VK . (20) wlicro d, of course, is expressed in iucltes. For simplifying calculations, the nomograph given in figure 67 lias been prepared. To find Q, it is merely necessary to lay tlio ruler on lli'o valuo of d and connect it to tbs observed pitot reading A*. The pouit where tlio line drawn lictwccn tlio values of d and A. taken and (ho intersection of tlio Qdino indicates tlio volume of air flowing. Tim lino drawn in the fijpiro connects thn point representing a diameter uf 5 indies with (be observed pitot reading of 1.4 inches. The inter section with Q shows that a volume of 640 cubic feet per minute flows ^ in iiirMT WAS NOT A RECORD OF lOT COME FROM HUS AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. ) BB~0Q201G3J^ 2602 142 iu the duel.. Actual compulation bj* equation (20) above gives a value of 539.S cubic feet per minute. Simple pilot ]n event a pilot tube cannot be secured, tho velocity brad may be measured by drilling a small hole iu tbe duct, say Uirce-sixlecnili* inch in diiitncier, aud inserting into it an L-shaped one-cigbtb iudi "*3 M/me&APff 20 *n OH fecc H Ot ( Ml. at an JH4 a tub la* u.-> r\ find lliSSM' lilt*n Is tl.lfi! it sect itmi open e itinem ihntogi tiijr* mi 9A /0-i mthwwsasiliMWrwilpiiswHiil^ *f1`J***r tolling, figure GS, tlio outer end of trlucb nuty bo connected to a ' Tliis gives tbo total pressure. Tlie tubo-mny then bo * <* ' tiiii a nipple with a rubber bushing almost fiusli with one ilm bole as sitown in If of tho figure. If no leaks occur iug tiro pressure recorded by tho manometer will Ik* <hn *I*1n* fllisolulo dilTercnoo observed between tbu readings tho velocity licud. O larger tliai l.Ji Iti 1,7*1 h\r jura ummitiag. desired tin: eali!*nii:.*tt VAS NOT A RECORD OF MC. DID NOT COME FROM WOf BE AUTHENTICATED >-o INC. j^BB 0020109*7 2603  MtVp give* ,, head JJIU V 'ee-sixtecntl^ -WidUi iad, '3 m bpkciai, titot For. uKAsrnixn i*oist vr.ixicmrs One of the diilimltics of the onlinaty pitot is tho fart that the and static pressures are not measured at identical {mints, t MiHequently in regions whore tho air movement change* rapidly as , i mi o|eiimg under suction, the ordinary j.ilut cannot bn used. For such condition*, TAPsro /xnn&nrfTV? a tile of the tyjxi shown in figure 09 may U* used. That tuho consists of a tlun brass . \ finder nppnixhmitely one-eighth incli in diameter with two independent compart- i.n-iits closed at one end. Two small holes iurj inch in diameter are drilled at its mid- iM*|Hv*tnionenad.nid.n.at.hpo.od.inirteecr.t.iio*nfaos,ftethnoedhonl,ee.ar Fthoer r,UlCm5sarl-m.-siwhawi*ti*rfieKiitataffrltwor.w measurement of duct velocities the tube is inserted diametrically through the duet witli the pointer directed along the axis. Tito read ings so taken are a measure of the velocity head. They on* much aJ ptlAl onneetcd (ti a May tlnm !xt iwh with one >o leaks nmir t will Ik* U,. tho readings Anglo of Turning (Degrees) !>>00K^aiitt4iSwlQgBieuirtaeiiUiawhdifaA larger than those obtained for an ordinary pitot, ranging from about hi* to 1.75 times as great depending ujam tho velocity measured. For measuring velocities near n liood, tho tuho m|iiin*s a sjieriul tiioiiitting. Tho tulo is turned at the jaiinL where the velocity i* desired until a maximum reading is obtained on a manometer. If & calibration with ail ordinary pitot has Ihmm made, this reading may lid THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES. INC. DID NOT COME FROn* rrs FILES AND CANNOr BE AUTHENTICATED BY PPG INDUSTRIES, INC. 1J3B 0020110* 2604 NOT v 144 ,rlnl directly and the velocity determined by equalinn (n. r,,<*' in!*' ** vvry sensitive t* the direction of flow* and can 1h? iws! ; *1 K w ithin 15 of arc os may he seen from lltecharartcrh,: h" "" j,, (Uo figure 09- Ticeatisc of the comparative anudlncss *l* t!.. " h|Mj the fact t hut it does not obstruct t he flow of air, the hue r-,. d'*' * \ |>rlptibie of giving accurate readings at a point. ii**n* it velocity ceatoan jirlrt " ^^vutl tube described in the above paragraph may be use I ** " velocity contours (52). The tubo requires a spv**i vrhicit nay be moved vertically and horizontally *-- t ,1,-liuito points with respect to the axis f tho hood. Tih'''' .-*-*,** at which readings arc made is iiulicatcd in figure 70 t.-l) noma of d--otopfoc < ^ taken with tlie tube horizontally outward from <!** j{rt*li,,5^tV!tt.tilivcl above the ccntcriiue. Tho data so btained at** openiiV'** j jyuthown iu if of tho figure, the otdinatesrepresenting tin* then I*'*;', vriixuly at tho opening and tho al>seissae tho distann* ptnyatst-t from thcao curves tho velocity contours may from d>,% * j*ttr example, to detemuno tho contours of velocities j,, CO and 70 percent of the average velocity at tho faco of ftpiivel^ ** vaiues of tho abscissae corresponding to tho inter* tin* .. -.si for tlie various velocity curves, as in if and plotted ecr><5;',;'r:.';cT0. as iu1 ' mm amuomrtsk .^-.cuwneter js a direct reading instrument. When it is TV 'an* ..-vat, tlio vanes turn and nctun to a calibrated IucIhuiiret in ** ..... IS DOCUMENT WAS NOT A RECORD OF 3 INDUSTRIES, INC. DID NOT COME FRO!# 5 FILES ANO CANNOT BE AUTHENTIC*! ED PPG INDUSTRIES, INC. I~BB~0020lit | 2605 ;nl fcfii. v-.I. id DKitlti'J r- ennmrd l>y equation (10). j of flow amt ran be u-e{ n. seen from I lie charrrtefisl it.uujinrativo smallness of the :*t tlo How of air, the iioitmj* at a point. ? paragraph may lie used in no tube requires n Fpeeial ally and horizontally nml ~.he axis of the hood. Tin* i indicated in figmi! 70 (.1) D Baton. ntaily ntwnrd from the The data so obtained are a ordinates representing the . the abscissae the distance ; velocity contours may be tho contours of velocities roga velocity at the face oforrespondmg to the inter* curves, as in H and plutt-d .n g instrument. When it a* tiiate a calibrated tachom eter. A stop watch must Ite used in connection with tliia instrument, since the reading of the tachometer dial merely indicates the linear feet of air travel. Ancuummtcts require calibration at frequent intervals. They aro not reliable at low air velocities, although special forms (G7) lutve been devclofied which are very sensitive. Vane anemomoters cannot be used in duct work, but arc useful in mak ing quick velocity traverses over largo hood openings. Ain vnLocm* uuasuremunts nv mkaxs op Tin: KATA TttEMMOMETEK Tim kata tlicnuomctcr was originally devised for Ute inrasurement of body comfort (GS). It is, however, highly sensitive to air movements and can be used fur velocity determinations. The instrument is essentially a thermometer with a largo bulb filled with ml-colored alcohol and two graduation Hues on the stem marked 05 end 100, figure 71. When used to measure veloci ties in eir below 95 l'\, the thermometer is inserted in warm water (about ISO0 F.) end the fluid allowed to rise half way up the safety bulb at tho top. The huge luilb is then quickly dried and held at the point uiiero the air vdocity is to bo measured. The time, in seconds, taken for tho alcohol to drop between tlio markings is observed; Ute average of 2 or 5 such readings is conMdi-ml sufficient to insure accuracy. Tho tiino 8 is then divided into Uto factor F marked near the top of tho kata by the manufacturer, that is, II--Fje, where B is called Ute cooling or warming power. For temperatures below 95, II is positive. Vlicn the temperature is abovo 100 F., the kata tiiermomctcr is immersed in cold water and Ute timo for the liquid to rise from 95 to 100 hr'notcd, first Inking rare of course that the bulb is carefully dried. B is then obtained in the same manner as previously, with tho exception lliat it is now regarded as negative. Yegloti and DokofF (GO) were unable to devdop reliable formulae for determining velocities with the kata thermometer which would ladil over n wide range of air conditions. Tito kata is inaccurate when used betwren 85 and 110*tF^ because theso temperatures re near its cooling rango and air movements have little effect. Tho *U*vn investigators therefore have prepared a chart (fig. 72) from wliirh the air velocities can lie determined. In order to determine vrWily, follow tlio curve eorrespuuding to tho given dry bulb tem- THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IBTY'SPFPILGESINADNUDSTCRAINESN,OITNCBE. AUTHENTICATED f BB 0020112 J ----------------------------- SoUO V `* 14G pcnitnrt' lo the value of Ft (equal to FJO), ami rend off tlie velocity vertically on ihn horizontal scale. The following problem illustrate* the line of thn chart: PrMum.---The time taken by the in a rod kata thermometer to fall from the 100 to tiiu Ov marking* on the atom is $3 second*. Tlie air temperature while taking the reading b$ CG* F,, ami the factor engraved on Uw atem ia 477. Calculate the air velocity. Swui/aa.--Tins cuoling power U i*. following tlie procedure outlined above, 477/53*0. If now the temperature curve corresponding to 0G* is followed uatil St Jnlcrocet* Uie /Wine corresponding lo ft, we find that the velocity read off on the alwcfasoe ia approximately 340 foot per minute. Tho principle of fiio instrument is based on temperature difference and air motion. Except in the temperature range above noted,-the kata is very neettrate; for obtaining readings from $5 lo 110 F., a special high temperature kata (blue kata) lias been developed. Kata thermometers are very sensitive to radiant energy sources. To nvtmi personal errors tho observer should hold the kata at some distance [rum himself while making observations. *i *3 c I t Vi u v In A rt>* iff (ho vi-l.. \H problem il!u,ir^)< .eruttmcicr In fall The rd OB the ftUllt it , ttlim nuiliiiwl ,,!..Vi PC* W filllriutil in,. ; 1-17 i i j.itki:mikatiox or aiu ixo'.v by tnuAsuitEiiKXT or static at u ou Fur simple nnd Approximate computation of air flow, the static .rrrtatre nt tho (brunt of a hood or opening obtained as described for , duct above can be used. The funnula fur determining Urn air iuiumo is then Q4000rf/V (21) Iwniy U a factor called a restriction cocflicient and A, tho static at iltn throat. This factor varies considerably (50) from 0.03 for pIkIructcd or small o|K>nings to as high os 0.94 for shaped openings. A good value fur nmst hoods encountered in pruclica is 0.71 although values of 0.S3 arc not too high. If it is assumed llmt the static A, at the throat is proportional to (ho velocity head h,, an assumption which is closely in accord with experiment, then/ can be obtained from tho fonnulu (59) *i/Z . * vumifti and oniric*) atKASunotons Tk venturi meter For continuous measurement of large volumes of sir flow, the venturi meter shown in figure 73 is useful. Tho meter consists of a IT tdeeitjr real uff -u icntfuro fliffrrtw'' * above notctl, il*- $5* to 110* K.p t. ;n dpvi'lojMil. it energy *urr*. (lie kata at omverging and diverging duct connected by a narrow collar. Tho usual dimensions followed are given in tho figure. The converging lithe is coned to one-third of a pipe diameter in a total distnneo of 2Jj pipo diameters. The diverging tube lias a length of 7% duct diameters in order to minimize the losses due to a reduction in air . velocity and at tho same time to prevent eddying. Tito principle of the device is based on the fact that, neglecting Ii*9c*s, tho velocity head and the static bends at A and U are mutually invertible. In other vrorils, the total heed JI is preserved. Thus, wo have EfA^--A.^+A ,M A manometer connected to A nnd U will, therefore, register tho differnwoA, --A, . lienee AU-/SA.,-A^ (23) 5 document was not a record of i INDUSTRIES, INC. DID NOT COME FROM FILES AND CANNOT BE AUTHENTICATED PPG INDUSTRIES, INC. i'bb 0020222--A 2608 .J equation of How, V'4 d.*** V,, A where Ax and .-t are the duct ureas at -1 and B, respectively, so that r#-44 VA. Substituting in equatio (22) ami calling A,-- where <h is tho duct diameter at *! and </* tho diameter at B. Hence p, _ 4009-//* C24) The volume of air handled is, therefore Thus Q1* determined in term* of tho manometer difference observed and known constants of the instrument. Somo lo^s, however, does take place between A and B; n more accurate relationship is where a factor 0.07 has been multiplied into tho right side of the equation to compensate for tho loss of head due to velocity change. Orifices * Sharp-edged and bell-shaped orifices are often used for measuring air flows. Orifice measurements depend on a principle similar to the venturi (5$). The pressure diffcrcnco between tho upstream and downstream sides of tho orifice are observed and a formula, identical to equation (24) above is used. Because, however, energy losses are large when an orifice is used, tho multiplying factor is approximately 0.G0, which is much smaller then tlic value used for tho venturi. Orifice measurements are not generally used in dust-collecting sys tems because they net as obstructions and as a result frequently give inaccurate readings. Water manometer* MAXOUETtBS Water manometers are used in connection with pitot tain's and `ntic readings. The simplest form consists of a vertical U-Uilus par- * filled'with water, figure 74. When tho tubo is connected to a. j-BB*0020115^1 AIao ly Ux; - oro the duel un*s . Iwthuting in oquu- jwvmiijt rotirce, the water column will lo displaced to an nmount Miilicienl to hutance the forge acting upon it. Thus, tlio distance be tween the water levels indicates the amount of pressure exerted by the fluid. Wien tino end of the U-tube is connected to a nipple flush with the inner surface of a duct, tho pressure indicated by the ditferrnco in water levels is the static head. When both ends nro con- meter at B. 1 ie'iru (24) difierence observed '.uss, however, does ationsbip is (23) right side of tbo t velocity change. used for measuring ciple similar to the tho, upstream and a formula, identical .*r, energy losses are or is approximately or tho venturi dust-collecting sya-ult frequently give itli pitot tidies and vertical U-lube parfO is connected to a 1> I Heeled to a pitot, tho displacement indicates tlio velocity head. A displacement of 1 inch of water corresponds to a column of air equal to U'J.-i feet, or to OAS ounces (0.030 pounds) per square inch. To increase tho sensitivity, tho U-tubo may be inclined. A on* nneter which is mounted on a right-engTed wodgo-sliapcd block with a riso of 1 inch for every )0 inches of tube length (figure 73) has u xenxitirity ten times as great as a vertical manometer. In other words, a displacement of 10 inches in a sloping U-tube corresponds lu a displacement of 1 inch in a-vertical manometer. U-tubes may 0 HIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES. INC. '* - 1 ^1 f 250 * t. also l*c tn givo sensitivities twenty times ;is prat as vertical tubes, but surh n'ti.utivitti's do not, guarantee ureunite muling. Ju :.*, a sloping manometer should always he carefully leveled. tlirwvpoint mounting slioultl l>e provided with at Joust one point adjustable for leveling purposes. The Walden face This instrument is extremely sensitive and is used for the measure* ment of vehieiues ranging fnun 100 tn 4,000 feet per minute (70). The gage h* shown seltenmticnlly in figure 7(1 and consists of two brr btillw filled with colored alenhol connected by an inverted U-t-ulie containing kerosene. Tlie bull) II is so connected to tho U-tul*c that it can U moved in a vertical direction by means of a vernier cnlqier* mounted to a framework. A stopcock is provided near the bottom of - . -- ' nmmH--SbpteEmMtmwr. .. ,, the stem conneeiion the of bulb II so that when pressures uro applied to tho bullis the liquids will not bo violently disturbed. When ready to use an initial reading is taken with both bulbs ojwMo the atmosphere-by briuging .tiie-mcnisrus at Z7 to the lutiiiinc.^`Connections oro then- made and the stopcock opened slightly to ascertain tlu? direction in winch the liquids move, and tho calipers turned until tlie meniscus at D is again on tho hairline. Tlie difference between this reading and initial rending of the vernier is tho actual displacement In terms of tho heavier liquid. Hie reading may be converted to inches of water by multiplying tho difference by the specific gravity of the alcohol. Jk'inga null method, tho Walden gage lias a distinct advantage over other forms of manometers. Aerumto readings, however, depend iqxm a kmmletlge-tif tho specific gravities of the . aicoliol over tlie range of tcnijierutinrs the instrument is to bo used and upon maintaining the instrument level at all times. Zen readings should )>e taken frequently during experiments since Hid meniscus at D lends to vaiy somewhat. aDOCUMENT WAS not RECOrD OF uni rcTRlES INC. DID NOT CO.-5: FROM S AND cannot be AUTHENTICATED >G INDUSTRIES. INC. BB 002023,1*1 2611 as gmit a< venita! -urate mtdiug*. arofully levcbd. ^ at least no jM,u,( *cd for tlic iiioasur*". *t per jniniiiu (7n) conskts of two lt> an inverted U-tuUI to ihe U-lul*o Mi.-it of a vender cali|t-i^ i near the bottom of 151 The factors contributing to tho sensitivity of the instrument arc easily derived by observing tbo do,'lections of the liquids when tlio pressure applied' nt A is greater than that at B. Obviously, tho liquid columns to tho left of the axis of symmetry must balance those on llic right. If j>a nud p* represent tlio pressures at A and It, respectively, and if ft denotes the specific gravity of the nlcoliol and $t that of tho kerosene, then the deflection in tho U-tul>e, d3, is deter* ircssurcs aro applied " jrbed. When ready i open to tho ntim**irline. Connections Jy to ascertain tin* tors turned until the rermce between tills actual displacement .ay bo converti*d In * tho sjierilic gntvii.v :i gage lias n distinct U Accurate readings rifle gravities f tin* iimeiit is to Ik* used at ail times, Zero perimenU since Uu* /f/coAo/. nm fttrosttsr* ^//Z/per/(f/kr*/s t+rte/r /2rVtz/9 * _____ /?rea C* ^ Tmm* 7i--W*hfcn pm mined by equating tho not pressures to the left with those on the right, thusly " . ....... * If we write &bi~S3 end p-- (p,--p) for convenience and colleet terms e-!rfi i--<fj b *" I, "" But constant, so that substituting for dt and dt (28) From this relationship, wo nolo that the sensitivity of tho gngo de pends chiefly on n low specific gravity difference between the liquids. 102311*- 7"bB 002011 I 00 I THIS DOCUMENT WAS NOT A RECORD -OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 2812 in2l t, and on tlio ratio of the arras of tho largo bullis to lltc area of the P-liihe. Tim cnhirpemmt lit Ct tvliich Arts os a reservoir for tlic kerosene, docs not materially affect tlic sensitivity. Tho liquids used in tlio Walden pups should he allowed to stand in the presence of ouch other in a stoppered hottlo for snmo time. This permits the Hquiils to reach a stable condition and reduce tlic varia tion of tlio meniscus at D duo to tlic solubility of kerosenu in alcohol. comtakisox or devices ron measckxxo am FLOW In table 35 are piven tho principle characteristics of tho devices used for the measurement of air flow. It will be seen from tlic arrangement presented tliut both the standard pitot and special pitot hove accuracies dependent on the sensitivity of tho manometer used. The pitot is the most practical device vilicit has been developed for measuring uir velocities in ducts and requires only moderate skill in use. The anemometer, wliile being the simplest device to use, has limited application to air-flow* measurements and frequently gives erroneous rcudiugs. $ THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DlU'NOf COME FROM IT'S FILES AND CANNOJ BE AUTHEIMTICAIEO BY PPG INDUSTRIES, INC. | BB 0020119 | 2S13 .5*< 3 JTHT aS? O ~ wm r2cf 2o>; D i h C 2 33 wmrn rn 2 2 < ^> 2- P-* O` w f^seg .-4 " > J Oa 5O m 1^8 S?3>3 mh D O* 2 On g *2. P.E *c _*5 (i- *= ti 2.1. S* S` 5 s Ss s* 3. o1 55 8.3 a~ 33 *a* sSS=> 3Cg .M7a, ~cn* " Un- tS * ^3 O'B*,. iisr g a I. fp A f* rPs s-C; .3p D 7* W* p r* 33 S5 s3 p it* a +i >sB. ioiiaouoa *-23 3fiS* b*; g- c sL ub3I . fcj sV*u* r ?--s* p AH. ,*%* < T*t 35.--Com|orf* e/rffrirt* *l * "^*HreMrH` /,r Mn nt iai.......... . trecfatfOletA......-..- Kit>HmMowettr...l t* VittvH******< CM6c*.. Hht4e(a*t Ranee l ale wteHIt* jj I vvtumr* wl*h tun h* I rdnAitiowitMpilM- MMNnil Atcieiejf *M!iiulile WIltilllNlI afOt% KTt W M Ini prr mlmrfe. I> jwr Hmh wet ttowntlneil. Pwnnitn V-W (*wi PP Vkmibe nnwlm *J*V" Ik* an* vrt"Cr * * ,*1 IW krt |-r mlniH., I'p prtUntil tea* ikletnrfiiM pH MeiRilfc* *I"*b* ____ lxk* *- t|iMrr* wllli*!** hut l.nibif<1 |4lii. Mi'jrtlM. A TlM wiaijrw"w*'l."* 311 ta ABB. l Ilr.pth'n Nii* welch tlblM. Itcrkvl* it-.-i ic!l:.4. *1*' |n( llitmr krt f e*t IPt Bull, mttri k *W. awl * BBuwMrli)ti*iRriarltkhlecWWHt^.i*r** an> i*T(Ulr1 llh nkllf. Fl*t*l bmtrnl **l tnl* fenutot loti * the *** Iftlct*. lit* wo......i CeabebalHIetMwIkeii* Miumeaelr Hew. Itt^piuc. Hielt............. FM'iuuk. ji i pi-/_r "-rPT^r. jowlt *i< KiwtilvUy J lb* etuwairlcr u*r<!. (Mne. tortile at Wl>* |j baiwrtinl. (WOrtetae. Tl *{v.if b m*hle 1" tvriVm <i r* awl re- cjiHuI nrteibl- tlnniUn a tfr>!i'<|iKt new , Ke .till mwiwi. lt>r *ilji awl tv* !r vth*4- tint* Wits nliiul u. llw OrvW* U nif ervuriiie, ttlwlil eartr* Welter* utni lw evuMnl. UrrW b <ty WJlt be rvluiii ilalaiinitiallout nj --I |Kfnl ttrut). KaPOttcphea. >!* Maitiait.iitla*>toi pMi*wwTM* rfimllr. tmriVr4. iH efmiln (Intheil. 4,--llnniritr *1 threat (liK'eer Orifice plete b Ihttl " twe Rem** 6 *tt ***** CmtmfhveowhmlwMHdlrbww*.e Feniun,,a. iwfiiT Peeheli r#trcrtrl'r,-" nrHull* eelihraltiL Da. w tJlj ..lkmcfif<4 mala Oechrrt illameiir *1 *rllU< O1 Tbo hula, thermometer w pcrhiijw one of Uio moat sensitive instru ments develujied for iticswirin'' low air velocities. It. {rives nverngt* midin^s deluding on tint period of time required by tiie liquid to pav< lietween the marking* on itsstem. The device, however, cannot $ bo conveniently used for duct work and must bo kept free from radiation eUccU. Tbo venturi und orifico tire widely used for measurement of air volumes. Since they fonn a part of tbo duct system, they givo con tinuous readings. Their dmrarlerutica have been determined and arc well known, so that when they have been carefully constructed, no extensive calibration is required. n-` 1 *' *..f. and rn. i:. Ldn Tl 20'ii.i' Bltrr rtuin-- idinjH-' and i* diskdii device, tbo nil wlvn mil,-,! f face. I fortlib is DOCUMENT WAS NOT A RECORD^OF S INDUSTRIES. INC. 010 t'ior COMfrFROM s FILES AND .CAN NOV BE AUTHENTiCAi 0 PPG INDUSTRIES, INC.' 2S15 sensitive instra. It pivcs ovcrajv by tbo IirjuifJ i,, however, rmia..i kopt free from asurcnicnt of ir a, they Rive c.odctcmiineti ami ally coiistructtii. f' i XL PERSONAL RESPIRATORY PROTECTIO*N " * In some dusty occupations tho methods of controlling dust have not been developed. In fnct, industrial operations, such ns removing i Im cores from very large foundry cnsiiugs, sand-blasting, lmndling of used storage batter}' plates, paint cltipping, and cadmium oxide manufacture appear to offer no practical means of adequately con- in;!ling the dust generated. In such cases, it is therefore necessary to furnish tho worker with personal respiratory' protection devices in order to prevent his exposure to tho harmful effects of tho dusts present. These devices consist of various types of respirators, masks, and helmets. It is important first of all to hold in mind tho limited use of personal protection devices. Because a worker cannot with comfort wear a mask or 1 chnet continuously, such devices must be employed inter mittently. - As a consequence, their uso is generally extended to those (Iterations where all other methods have fulled or supplementary to litem, as in storage battery repair where the exposure to small amounts of lead breathed is known to be detrimental to health. Respirators and Helmets are in a sense tho last resort in dust protection. TVTES or nESriRATOUT FBOTSenOX A.PP.UU.TUS FOB IXl>rSTHXAl, OUST Respiratory protection devices may bo divided into two general groups: (1) Respirators or facepieces using filters, and (2) masks or helmets using positive pressure. The first group consists of many types, the simplest being perhaps a cheesecloth packing covering the nose and mouth and tied to the bnefe of tho neck. Ollier forms vary from what is generally called a pig-snout typo to those consisting of facepieces connected to largo filter surfaces strapped about the waist. The pig-snout respirator runouts of a metal body, usually aluminum, with a rubber-lined edge, .draped to fit tho contour of tbo face. It covers tbo nose and mouth nd is strapped tightly to the buck of tho neck. A small cylindrical disk-like filter and a flutter valvo form the essential parts of tho 1-vicft. The valvo is so arranged that it cloaca on inspiration forcing the air to pass through the filter piece. On expiration, tho flutter 'lvo oj>cns, tints affording the expired air an easy exit. The sorailed 1'olger or Burn'll filler is essentially a mask rovering tho wliolo hire. It is xnado of a pliable composition with goggles and is com fortably but lightly strapped to the faco to prevent leakage. Tho OSS) THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM ITS FILES AND CANNOT BE AUTHENTICATED BY PPG |NDUSTRIES14NC.'' 4f4#JU* iiiusk is connected with a corrugated flexible tubo to a felt filler strapped (o l ho waist. In this way, a largo surfaeo is provided for tt-during the breathing resistance. Tho filter mediums used in respirators of tho first group consist of peiier, paper filler, gjwnge, wool cloth, oud felt. Manufacturers of various respirators provido tho typo of material behoved best suited to their desi-pia. Kispirntois uro so constructed that tho filter medium may 1h> easily replaced. In use, because of the small surfaeo given for filtration. Urn medium must be changed frequently; other wise the resistance builds up, ond hreatiling becomes difficult. The fiat Folgcr or JJurrcl! typo, which has been described, has a longer period of usefulness than the ordinary pig-snout respirator aud is cap-able of being cleaned. It is ouo of the most efficient of tho types so far employed in industry for retaining vory fine suspeusoids (71) efficiencies or filter iiEpitms used ix SEsruuToas Itespirators may be tested by several different methods, of whieh two are most commonly used. Tito first consists of testing the filtering medium independently of the respirator wliilc tho second consists of tests mado with the facepiece imbedded in clay or some similar pliable substance. aptaiutus you DETEuanKiNQ Ernarxcixs or tiltes mediums -Tho usual methods of determining efficiencies ore based upon methods described in section V, that is, by use of tl<o impinger or electrical precipitator. A considerable number of publislicd tests, however, ere based upon tho now obsolete Palmer apparatus (11) whose efficiency in tcmi3 of the present impinger is approximately 20 percent ($). A method which is frequently used with tobacco smoke and .dust suspensions is tho so-called "tyndall" meter. This consists of an arrangement (72), whereby the suspension to be estimated is passed through a beam oflight. The absorption and reflection or the beam on the particles of dust weakens it almost in direct proportion to the cot*, cenlration of particles present. Tho readings may be observed with a photometer or plioto-drctric cell arrangement. In actual tests, the suspension from a dust c'wmbcr which is to bo used in testing tho respiratoris passed through the beam elutmber and a reading obtained. A second reading is obtained with tho filtered air in the snnie manner and Um efficiency determined by tho usual relation 100 minus tyndnll reading of filtered nir divided by the tyndail reading of the original suspension. As a laboratory procedure the method is simple and convenient. |W i vw NAS N0Tnr 00J-S<fR0M -c;. INC- B0 t. tl U 1.1 lir 1-V Svl h-L. in ; eir-.' fihe. The ref}i sna>i cent, ter is Ag-Jj ciesa ease tests from C experh ker, r: rnngia-. The hi latter e: due to particifc mist :U table SS thuae f-T This inn rise end; demmirir below In; appear tc larger. \Yilh nDut inerra hand, ir.v-r dogging p and clot ty SSI7 tube to a felt nit<T .rfaee is provided f,v first group consist *.{ Manufacturer* bcliovctl best Mil!ml ctcd timt the CUit o of the small surfam ed frequently; oth*rcomes difficult. Tlw scribed, has a longer jut respirator anil U efficient of the types fine suspensoids (71) 2T XESmtATOHS :it methods, of which of testing the filtering he second consists of r some similar pliable or * tit uxnnais J^^aro bused upon ;o of tl>e iinpingw or r f published tests, diner apparatus (11) *r is approximately 20 * aeco smoke and dust Hits consists of an o estimated is passed lection of tiie beamon proportion to tbe conmy bo observed with . In actual tests, the c usr*l in testiug tho ul a reading obtained, ir in the (mine manner ion 100 minus tyndaii coding of the original ictbod is simple mid RI ^ 157 Tito procedure in testing respirators consists in setting up a dust or lobaccti smoke cloud in a dust dinntlicr and iiassing it at a fixed rate tlirough a definite urea of filter medium. Tho urrangenicnt used for liolding tho filler is also provided with a means of determining the reliance which is important in estimating tho lifo of tho respirator filter. Rcnalli f filter tests llosults of tests of various filter media have been published chiefly by the United States Bureau of Mines (71) and by the Harvard School of Public Health (73). The data obtained from these research laboratories ore given in tables 3G, 37, and 3S. It will be seen that in practically every ease tho. cinciencics are low for sponge filters and high for wool cloths. Tho efficiencies of industrial respirators against tobacco smoke range from 3 to 33 per cent. The Folgrr fiat typo fil ter is most efficient, f>7 percent. 5 /0 $20 30 Against silica dust, the cfiicicn- - dcs are slightly higher. In the caso of the Bureau of Mines tests tbe efficiencies ranged from 0 to 70 percent and in the experiments of Barreto, Drin ker, Finn, and Thomson (73) ranging from 49 to 97 percent. The higher effidencics in the latter experiments are probably due to the larger size of dust Z 34 6 portidc* used. In filtering lead in Hicrono mist tlie effidencics given in table 3$ are much higher than Funic iii* frtTet>* olJuit parUiHettn ropfc*- ll>irapSaiMMMiwlll|.m a* iwintilltf i ' iIiimo for silica, tbe spouga respirator giving an efficiency of S-l percent. Tliis increase is undoubtedly due to the fact that lead mist is large in size and tends to settle rapidly. Barreto and Ids associates have also demonstrated that respirators do not favor any particular size range below ten microns, os may be seen in figure 77. The finer particles p|iear to be filtered with practically the same efficiencies as the huger. With regard to resistance, it is to bo noted that tobacco smoke docs m>t inerraao the resistance of the filters. Silica dust, on tho other band, increases the resistance to air flow, but sonic materials have clogging properties more marked than others. Dense jinjier filters ami closely woven muslin clog rapidly, while loose textures dog slowly. - , ^ THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DSD NOT COME FROM IT'S FILES AND CANuOV BE AUTHENTICATED BY PPG INDUSTRIES, INC. . * J BB 0020l24_r 2S18 Tasui 30.--Filtering eficienaUs* end retUUnaet of meek* ond Ttrpimiort uhen MV * Tjpbaeafc t. KttrcUv* Allvrinf im It. Alrfla* m. Iruinuacs Ty0*D rffitkaey csaiMt IV. Tdam V. ftOrs llomll. blwlMUl nUa*. ltCM8PiaMdWtlKHki: v__ Drr- Ht yaw na. a: Wt^_ nr- Wc >hradM:U aw. 1: Vt. Dry. HlwwuHi 4 9U|NH. ttf. tm tm XMtfptt MtMM ID to IS ID 0 m1 m m c S S 8 8 l `to V 11 M*0 4 13 m is u to U u xt xt Lt r u a xt xo Xt xt H St to 1* xt xt AS xt xt xt >*r *>W *r nu 37 >w a tuM3r3 TakminniaLtaaf Humo. Jirittfcw. Ftna. aM TbanuM (73). in imm If ttm ini|Tiw lhl m irrmin rlrrt t ""* --r1*'` HKm tuts dji<c mss'* napDrad* *~ -- Tauljc 37.--Eficieneie* a} industrial du*i rmpiralor* filtering tHica duel, determined wiik Tended apparatus {JUteafair hue, a Bun paruisanl JKnptotitfF KOiWiND TllMMMCk Br af ir St 33 bllUdbMT wthMtua. UMMptraimiM 1 OHMS siaasy Kn- U< -wn. -m AIMf tab Mr of lasts MuL stsu^ bur rtoSSSM Ml* MS (am- MMB UNO >M<m) If * Mb /aUn **lwi.............. ... fftt................. bKOflT if (| 1.1 L* ,1 9 .a to. J Jl9 LI a.* la* 3 LI Cmim Oaaab............... <*1----Alkl .... ___ . ..f4fitt Lf0ffltt ftftna* nmol 19 99 t 1 39 9 IT IS 3 4 3 IDt 3 31 9 3D 4 CS 3D m 9 D ttoo 1 43 m t 33 3 ID ID HD 1 33 1 37 109 3 0 1 a **** too 3. U 9 3D to NO 3 33 3 M HO 1 M .. Mb 3 0 D 1 S3 33 tOpMoastliY. KiiiMfac Mamy I* ibun frwo tM<dlauWliiliio|wuMi>u. wTaMWraawtnwnA. lniilmi MmM1tIa* &u*m miMte; Wnuum wwlwiim aiunmt Uttowry Owrtiu W aatf >(1UCNT was not a record op ISTRIES INC. DID NOT COMtTFKOM 5Sand cannot be autnentioaied T/ahnwncfewy ttCHAtMI erattml i" ' || TitwowrtiuwtnHatfo Mto. Mm* mm we fWt s 4 5* to > 9 Ui 1 ) 0 c 1 9 s V 3 AI 3 s 13 # 13 re M SI SI m U s HtWHIlWtW Ml >1 Iww tmimntj. !^ 359 T n ibi.i: 3*vTMJ?0Weiwii i of tcriiintf*-* ig hint fn jwt*l unit /rom rprajf gun. IX!-' / air flow, JW liter* u minute. Time of l,-tiling. J/} miMuir* firing 1 CubU n,;.f of filmed air. Aecu of filer ntttlitun, 100 cm 1 pp.f s ' j.jMwr nteawrU ItokUM In Mf lhl*r BL .t lum i ciia. Ola,lif-twiof nur Annua arnoMiat Filmta; uf kl in nlritoT air mtUi* rffWIBmuti ru>ir |MT- (I 1 mife Start End sur itwrere. S3 S3 w CiMiiic |p*r_______ __ da _______________ ll-l ,.ref ..........I,,, to LO tl 9.3 fM LS S97 2.0 417 the ,M, llll>*<l|l............... .13 id !W (id. ____alii____m mJ ---------------- .9 .3 of* 374 .0 33 Gwuy ttouu ute__ .1 . 4ft* 1*.,--.. Cixuia Uani........ SMk nail ul rivfr .9 .03 4 4M 4*0 eiih. tl*....... Cmimi ved____ _-- .1 .9 m Gwnr tlwu* jMprr,, It i**.-- Cftitm waft________ 3.0 4.4 n 2.0 ret IM______ ____#W_.................................. 9.0 3.4 XO 10 r7e1.a3 3.4 13 <a 1.0 10 a; 4 5panC ww wt UM ImL 3*7 l-pty psprr to aiMr. 07.3 Do. 03.3 Do. 06 Da 14 Du, to. 3 3 Itliw rotor to BU*r. tt 4 iftui tutor in Oiur, tbliw nun UdmI in (he. 74 1-yly eili, ipbwctorwftiwh. 4 Ciuun bttwwre ttonretath. 100 iqwiM on*loanm* at flkrr wiueTrwaL 00,7 CartrtiiM wun naiMl'u* 9 OUavrerh at hi *3.7 Tie army n* r-u mwk wniurr reataia* s retina Okm. lo(Mwnfe.*mi C00 ratoftccaUnftMn dwtreftL 019 fU,t DDoa. 3ft. 1 lto. 19.7 Da T- V: With regard to the resistance of filters the following quotation taken fnou a Bureau of Mines publication (71) gives several important `delusions based on a large munber of tests: The resfotaneeof tlio filters to the flow of air through them is a highly important far!nr hr tho design of du*t respirator*, hccaueo rccpirslure lurring & reiiitanc* rater than 4 inches of water when tlio mto of air flow is S3 liters per minute at* otfeaelieaL They wilt not be worn, cveTt for short periods, because they nccos-*!ai too touch cwrtiou in breathing. Respirators witlt resistances of 3 to 4 uwirs may be worn, but after about half an hour the wearer must rest or exert *- , LuMa<if less.. Tho resistance of filters In dust respirators intended for continuous 'wurkfug-use should, not exceed 3 inches df water, and preferably should bo less thin l inch. TImso limitations on the resistance of fitters restrict filtering 'Uranieics, so in a pmeiieabto respirator it is necessary to strike a balance between IV ft'trr resistance and tho filtering eflieiency that may bo obtained. Tho area of respirator filters should bo made as largo at is practicable, boeause bwreasod area reduces tho rate of air flow per unit of area and thereby tends increase the filtering efficiency and decreases tb* resistance. POSITIVE TSXSSTntK MASKS Olt HELMETS * Tlio second group of respiratory protection apparatus consists of titstki or helmet? with fmdi air supply. In these types, compressed *ir from a dust-freo soureo is supplied to tho worker. Fositivo pressure ".-f&jiaitarulo arc roustructed of light metal, shaped to tho contour "f tlio face by special cushion*, and supplied with a small valve to "i'"It the vitiuled air to escajxx. Tho air is bled into tho mask near I J~ST 0020126_ THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME.FR.OM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 262 the lop mul diverted across ilit* isnrglc* to prevent fogging and sensa tions produced by air jeU. Jt i.s'neci*ssiiy in using jxwitivo prrssuro mailed lo fallen (lie air supply hose lo tbo worker so as not to induce a drag on the mask. Various types of |>osiUve pressure musics are available. Some have been designed will* li; ht ptiuqu and motors with cloth filters which nay lw strapped ulamt the waist. In this way tho worker need only cany almut with bun an electric extension cord. Such devices are csperially adapted for o[Ti-utions requiring freedom of movement, which ennnuot be attained with a stiff heavy compressed air hose. Positive pressure helmets nrc made of rubber, leather, or canvas. They fit over the head and rest on the shoulders of the worker. They are provided with lanru protected windows wliich may be replaced. Sufficient air Is supplied to these helmets to keep a constant flow of air leaking outward at tho sltouldcr contacts, thus proventing any dust from entering. Positive pressure huhnets are used almost entirely in abrasive clean* iug rooms und serve a twofold purpose: (1) To furnish the worker . with a clean supply of fresh air, aud (2) to protect Ids head and neck from tho force of rebounding sand or metal particles. 1 j : j j j j EmctExciEs ov rosmrt rnnsstmc devices . Bloomfield and Crcenhurg have investigated tho air requirements of helmets used in sand-blasting under normal working conditions (4S). Their studies were planned with the purpose of obtaining samples of air from inside a helmet, when: (1) Tho quantity of air supplied to the helmet was varied wlule. tho dust concentration in the room was maintained at as constant a level a* possible, and (2) the dust con centration in the room was varied while tbo quantity of air supplied to the helmut was kept constant, this quantity being the optimum as determined in (1) above.- Tho studies were conducted in an abrasivo blasting room in which fairiy clean castings were blasted with sand at a pressure of ranging from 55 to CO pounds. A modern room, equipped with down-draft ventilation, was used. An ordinary cloth-covered, fiber helmet was employed connected in the mannershown in figure 27, section V. This helmet was provided with a rectangular double screen about 4 by 2 inches in size, located at a point directly in front of the worker's eyes. Tho outer screen was a coarse mesh wlule the inner oiy> was of a 32-mcsb size. The dust concentrations were determined with tho . imptngor apparatus. Tho general air of the blast cleaning room (the air in tlie room, but outside Uto helmet), was sampled at a time corresponding with the midpoint of & pair of helmet samples by means of a second impiuger t I . \ j , : 1 j mcUME.MT WAS NOT A RECORD OF D^SmES INC. DID NOT CO!^FROM So CANwor be authenticated G INDUSTRIES, INC. 1 BB 0020127 t fogging aiJ sen$ains' positive pressure T so as not to induce -ailablc. Some iiave .h doth niters winch :be worker need only i. Such devices are -odom f movement, expressed air hose. lentber, or cuuvas. .if tbo worker. They eh may be replaced, -p a constant flow of ibus proventins any dy in abrasive dean furnish the worker ?ct bis head aud neck icles. . DEVICES tbf requirements mdidons (4S). o^reming samples of :y f air supplied to ion in tlio room was ad (2) the dust con* -ntity f air supplied being .the optimum isting mom in which >. pressure of ranging ">ed with down-draft ed, fiber helmet was i 27, section V. Tb screen about 4 by 2 of the worker's eyes, inner ne was of a letcrmincd with the air in the room, but rrsiHimling with the jt a second implnger flask suspended in the blasting zone. (Soo fig. 2S for assembly details.) Tlie operator was instructed to conduct blasting m a unifonn maimer so tluit operating conditions throughout the experi ments would be as constant ns possible. In the first series of samples, the helmet was tested with the double screens in place, while in a second series, a glass eyeshidd was used. Table 20 show* the. results of tlio two series of tests. Table 30.--Duti concentration.1 beneath helmet with air eupjdg of different calumet (MlEwai at pwtfcfat IwreuWe luat] matin VoImm at iir wpplr (e. t mj * 99 4 4 0- tt'tth tioultic r tarn-.--------.----------. tt 1.7 11 11 L* 10 HI M il 4.0 12 LU Efaran3*lMMaaa3mplM. *DutlaOrwppIr UbOUm. Bloomfield and Qrccnburg have assumed the inconsistencies of the first scries as being duo to the fact tluit the dust deflected from the casting at a considerable velocity gained access to the licliuet through the screens. It is dear from the table, however, under the test con ditions of the second series, that when 0 cubic feet of nir per minuto are supplied to the helmet, the worker breathes an atmosphere con taining but 0.3 million particles per cubic foot of air. In other words under such conditions, practically no blasting-room dust filters into tire helmet. This represents ideal protection for the worker. In order to determine whether 6 cubic feet of air was suffident under, all conditions of work, another series of samples were taken keeping a constant flow of air of 6 cubic feet per minute through the helmet while tho dust concentration in the room was varied by dump ing the amount of room ventilation. With 4,000 milliou particles per cubic foot in tho general air, there were 3.1 million particles within the helmet; with 3,000 there was 1.0 within tho helmet; with 1,000 there wus 0J. In other words, tho dust concentration of the air beneath tho lidinet during blasting remains low when tlio air in tho room contains as much as 1,000 million partides per cubic foot and more. It is only when tho dust concentration in tho room readies tlio enormously iugli figure of 4,000 million par ticles j>er cubic foot, that tho air benealii tlio helmet was found to contain as much os 3.1 million particles per cubic foot. Such con ditions in pEuedeo aro rare and in fact impossible to work under becauso of obscured visibility. _ It uuiy therefore lw concluded tluit a jmsitive nir supply of C cubic feet of dust-free nir per minute will protect a worker under the operas ting conditions iiojv in practice in abrasive elcaniug rooms if tho worker THIS DOCUMENT WAS NOT A RECORD OE PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOr BE AUtHENTICA l ED BY PPG INDUSTRIES, INC. 1C2 is supplied with a helmet similar to that described above. TIio final criterion, Jiowtn er, is tlio result of dust determinations of tlio dir within the hchntl, that is, (ho air actually breathed by the worker, and not the volume of air supplied. CmulEXCT STANDARDS IN' TESTING PERSONAL PROTECTION ATI'AIUTUS It is necessary to point out that tests of personal protection appara tus should ulwsys be carried out against the dust to which lhrsc de vices are to be used in practice under the most severe conditions which are likely to l>o encountered,w Furthermore, in connection with ratings given in percent, great care should be exercised that corrert iutorprctatiniw be made. For example, a device which is 90 percent efficieut, docs not necessarily mean that-it is sufficient protection against dusts with high quartz content when tlio concentration is of the order of between 50 and 100 million particles per cubic lout. Under such circumstances, with continued exposure, tlio worker is lilcely' to breathe dangerous amounts of dust, listings, should there fore, be obtained with regard to the quantity of dust which actually passes the respirator or helmet under the conditions employed. * 1UBTTEXAXCE Of* SESPIUATOKT T80TXCHVE DEVICES - * Devices used to protect the worker should always be maintained in good order. Frequently, in many industries they are not properij* cared for or maintained in good condition, with a result that they no longer function efficiently. It is important that periodic checks he made of all respiratory protective devices, observing any physical defects which they may have, and to retest them whenever any doubt arises ns to lltoir effectiveness. A necessary precaution in connection with positive pressure mask* and helmets is to make certain that the air supply is always from a clean or filtered source. ; . CHOOSING RESPIILVTOBT PROTECTIVE EVICTS Tbo choice of respiratory protective devices depends upon a num ber of factors. As 1ms been pointed out, their efficiencies must bo rated in terms of the dust actually passing the respirator or helmet under tlio conditions against which they will bo used; there are, how ever, oilier considerations, equally important, which in a large measure ere determined by tlio typo of operation under which they must Is' employed. These factors ore-- 1. fjghtiUM.--Fcspuatory protection apparatus should bo light and dun*hie. Heavy devices are cumbersome and tlio worker is prone to avoid using them. asMiw>iMMiiiiiUwiateWiiiiiaiaaiiaasai tr.s. Wiw--wm-- NOT --wc? THIS . DOCUMENT WAS NOT A RECORD OF '?(* INDUSTRiES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. ' 2623 bed above. The fin rminutioiu of tliu uir rallied by the wurti-i, nOTECTIOX ATPAUAT! nal protection apfwnjust to vrhit'li thes** !. svero conditions whii-i, , in connection wiiii exercised that com-: ce which is SO pen-mi 3 sufficient protectim ie concentration is of -tides per cubic fool, posurc, tho worker i* listings, should then-if dust which actually :ioos employed. Tims UrriCES s' i maintained in twy are not properly i result that they ;n iat periodic checks la* '.serving arty physical them whenever any ositivo pressure masks pply is always from, a x nrncEs depends upon & imiutr cfficicnrics must lie e respirator or helmet used; then* are, Iwliieh in a la rgc measure r which they must la* tu* should lie light and the worker is prone to - St, f. a. Jiwr-u M Man. 1C3 2. Ft.--Tle. fit of a respirator or mask in important. They should in every ease )>e fitted to the wearer. Otlicrwiso leaks will interfere with tho effective use of tho doviec. 3. Vhtihilittj,--Masks or helmets should attempt to give dear and tty visibility to tho worker. Tho air supply sliould attempt to keep die glass from fogging. Glasses should he easily replaced in case of tinmlcugo or pitting and should fit well. | J3B~ 00 20130*7 THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME'FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. 2G24 soil mnuoGiurHr L Window, C.-E. A., and Groenborg, Leonard; A useful factory inspection form. Public Health Report*, voL 37, no. 1, January C, 1032. 3. BntNlI, A. E., Britten, R. It, Thompson, L. R., and Bloomfield, J. J.: The health of worker* in du*ty trade*. II. Exposure to siliceotts dust (granite industry). Public Health Bulletin No. 1S7, July 1020. 3. Brutidage, D. 1C, and Bloomfield, J, J.: The pneumonia problem in the steel Industry. Jour. Znd. Hyg., vol. 14, no. 10, December 1032. 4. Blooraiieid, J. J., and Knowles, Fred L.: Hualtli aspects of radium dial paint. ing. If. Occnpatioual environment. Jour. Jnd. Hyg, voi. 15, no. S, September 1933. 6.Ruast.nl. A. K, Jones. R. IL, Bloomfield, J. J, Britten, 2. H., and Thompson, L. 1L: Lead poisoning in a storage battery plant. Public Health Bulletin No. 205, June 1033: 6. Drinker, P., and Thomson, R. M.: Dptenninalion of su*i>ensoid* by altrrnetb>g<enrrcnt precipitators. Jour. Ind. Hyg., voL 7, no. 6, Juno 1825. 7. Snowies, K. IL: Dust determinations in air and gases. Trans. Aroer. Soc. Beat, and Vent. Eng., voi. 25,1010. 8. Grecnintrg, Leonard; Studk-s on the industrial dust problem. II. A review of the methods used far satnpiiug aerial dust. Public Health Reports^ voL 40, no. 1G, April 17, 1025. 8. General report of the Miner*' Phthisis Prevention Committee of South Africa, Pretoria, 101G, p. 20, appendix O. 66. 10. Biggins, &, Lanxa, A. J., Lancy, F. B., and Rice, G. S.; Siliceous dust in relation to pulmonary disease among miners in the Joplin district, Missouri V. S. Bureau of Mines JIulL 132,1817. 11. Palmer, G. T.: A new sampling apparatus for tbo determination of aerial dost. Amor. Jour. Pub. Health, voL 6, no. 1, January 181C. 12. Final report of the Miners* Phthisis Prevention Committee; Union of Sooth Africa, March 10,1919. 13. Trostd, L. J., and Frevert, B. W,,- Collection and examination of explosive dust in air. lad. and Eng. Chcrn., rob 15, no. 3, ilarch. 1023. 14. Anderson, F. P., and Anuspoch, O. W.: A now method of making ~ir dust dotenuiuations. Jour. Amcr. Soc. Beat, ami Vent. Eng., rol. 2$, July 1022. 15. -Owens, J. &: Jet dust couutlng apparatus.. Jour. 2nd. Hyg* voL 4, no, 12; April 1023. 16* Drinker, P~ Alternating current precipitators for sanitary air analysis. X. An inexpensive precipitator unit. Jour. Ind. Hyg.* vol. 14, p. 364,1832. 17. Greeaburg, Leonard, sod Bloomfield, J. J- The impinger dust sampling appnmtus as used by the United States Pnblio Health Service. Public Health Reports, vol. 47, no. 12, March IS, 1032. IS. Hatch, T., Warren, B.r aud Drinker, P~ Modified form of the Greenburg. Smith impinger for field use, with a study of its operating characteristics. Jour. Itub Hyg., voi. H, no. S, October 1032. 10. Badham, Charics, Raynor, H. . O., and Broose, II. D-: Dust sampling in Sydney sandstone industries. Report of the Director-General of Public Health, New South Wales, for the year 1927. Serial no. 12. a> THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. mt. A awful factory inspect i.-n January G, 1922. and Bloomfield, J. J.: Th-ire to siliceous dust (arami.:ily J929. inmutia ftrohlcnt in the kIiv| I'Ccnil'cr 1932. aspect* of radituu dial ]iaiM. Ind. Hyg., voL 13, no. -ttcn, H. H*. and Thomjisuu, ant. Public Xlcalth ituUHin ion of suspensoids by nib*, i voL 7, no. G, June 1923. 1 gases. Tram. Arncr. Mir. lust prulitcm. II. A review - Public Health Rcimris, Committer of .South Africa, Siliceous dual in plin district, Missouri. the determination of aerial January 1910. Committee; Union of South `id resmiration of rejihwivr 3, March 1923. nmttiod of making air M nt_ Eng, voL 2S, July 1922. *. Ind. Hyg, n>L 4, tin. 12. for sanitary air analysis. Ilys* voL 14, p. 304, 1952. >o impinjtcr dust smpliK ie Health Service. l'uIJi*' cd.form of (lie Grvculsm: .1 operating ch.-iractorUli'"' . II. D.: Dust sanipliue *. Dirt-vtur-Gcncml *4 I'iiW* Serial no. 12. m ;>L Myew, 'V. M- Soiniulily of finely divided rock dusts in water, kermcne, ami alewlwL Human of Uims Heps, of Invest., aerial no. 2548, Novem ber 1923. ;l. Simon, Stahl u. Eum, vuL 25, p. 10G9, 1905. ,`i Mariner and Iloskirm, Rctort to Chicago Anoddion of Commerce Com mittee on Smoke Abatement and Electrification of Railway Terminal*. Laboratory Krind on Air Analysis, 1915. ^ Katz, S. 11., Smith, G. W., Myers, IV. U., Trostel, L. J, Inaeht, M., and GrcmbtirK, L.: Coinporativo teat* of instruments for determining atmos pheric dusts. Pub. Health Bulletin 144, January 1923. ;t. Grvenburg, Leonard.: Studies on the industrial dust problem. Public Health lirpotl*, VoL 40, no. 40, 1925. jS. Smith, 11. H., and Friis, lL & T.: l'ortahlo motor-driven impinger nnit for , determination of tulpliur dioxide. Jour. Iod. Hyg., vol. 13, no. 10, Docetobcr 1931. ;tb Bloomfield, J. J., and Blum, IV.; Health luumrds In chromium plating. Pub lic Health Reports, vol. 43, uo. Sti, Septcinhcr 7, 192S. 27. Moir, Jj Report on a Sjieeimen of Dust from Silicotic Lungs. General Report of the Minor*' Phthisis Prevention Committee, Pretoria, 1910, * appendix 9. I yt Watkins-Pitcliford, IV.: Tho Sitimtion, Outline, and Dimensions of Mineral j Particles VisilUc by l*olarued Light in Sections of Silicotic Lung*. Mounted In Canada Balsam. General Report of tho Miners' Phthisis Prevention { Committee, 1910, et*pcudix & 29. Mavrogonlato, A.: The Value of tho Konimcter. Publications of tba i South African Institute ofMedical Research, no. 17. : 3UL Schckt, C. F.: The Presentation and Determination of the Dust Deposited in PneunMutbconioiie Tissues. Bdtr. I'ath. Aoat. u. x. AHg. Path., voL j 89, 1032. j 31. Drinker, Philip: The Sixe-Frcquency and Identification of Certain Phagt^ * cytosed Dusts. Jour. Ind. Hyg., vol. 7, no. 7, July 1925. : 31 King, Ear] J., and Dolan, Marri-ry: Silicnris and tho Metabolism of Silica, j The Canadian Medical Association Jour., vol. 31, July 1934, pp. 21-28. | 33. Drinker, P., Thomson, R. M, and Finn, J. L-: Quantitative Measurements of the Iniudation, Retention, and Exhalation of Dusts and Fumes by ' ' Man. I. .Concentrations of 50 to 450 tniDigrams per cubic moter. Jour. Ind. Hyg, vol. 10, no. 1, January 192$. J M. Brown, CL E.: Quantitative Measurements of the Inhalation, Retention, and Exhalation of Dusts and Fumes by Man. IL Concentrations below 50 milligrams pur cubic meter. Jour. Ind. Hyg, voL 13, no. $, fymXer 193L * Brown, C. Er Studies In Dust Retention. HL Factors Involved in the Retention of Inhaled Dusts and Fumes by Man. Jour. Ind. Hyg-* voL 12, nu. 9, November 193L 33. Experimental studies on the effect of ethyl gasoline and Its combustion products. United States Bureau of Mines Monograph, no. 2. ;* Shaw, N., and Owens, J. S.: The smoke problem of great cities. Constable _ A Co, Ltd., Ismdnn, England, 1925. Bloomfield, J. J.: Tho Sizc-Kre<|icney of Industrial Dusts. Fublie Health _ Reports, vol. 4S, so. 32, August 11, 1933. ` Lagan, hL, and Brounutein, IV.: Rational method for calculating records obtained by meant of Owens' Jot Dust Counting Apparatus. Jour. Ind. Hyg, voL 13, no. 1, January 1931. I\ THIS DOCUMENT WAS NOT A R^rn irf SS/RIES',NC- 0,0 wr mm IT s FILES, AND CANNOT 8E AUThfut, BT PPG INDUSTRIES, INC. | BB 0020132_jj 2S26 1G6 30. RkminficM, J. J., and WxHI, It. S.: Tito |nx;iw of lead dust and fumes In tho air of rlrcct*. auUuuobffo rvpalr shut*, and industrial establishments GO. lb of large rtlifs. Jour. lwl. 11 vg., vol. 15, no. 3, May 1033. 40. CUadHd, Iv. M., and Mamhi, C. W.: Uandlwtolc of Cltomteal Microscopy. John Wiley and Sons, Ine., Now York, 1030, p. 402. 41. ThoniiMon, 1* IL, Bnmdaue, D. K., RiumvM, A. E., and Bloomfield, J. J.: The llt-alllt of Workers In Diutv Trades. 7. Health of Workers in a ltoriland Cement Plant. ritiifio Health Bulletin no. 170, 102S- 42. Drrrs*cn, Waldomar C.: 23Trct of inhaled marble duct as observed in Ver ntnt marble finishers. Public Health Report*, voL. 40, no. 25, Juno 22, 1934. 43. llillcltrand. W. F.: The analysis of nfiirate and carbouate rock*. United State* Geological Survey Bulletin No. 700. 1319. 41. Dale, KHsun T.: The etuuinereial granite* of New England. United State* Ct'olxgtcal Survey Bulletin No. 73S, 1923. 45. Knopf, A.: The quantitative determination of quarts (free silica} la ducts. Public Health Reports, voL 4$, 1333. 4C. Bloomfield, J. J- I*ruHnnary surveys of the ioduxtrial environment. FuUie Health ltetMM'b*, vol. 4S, no. 44, November 3, 1033. 47. Bloomfield, J. J.: A study of the efficiency of dust-removal systems in granite-cutting plants. Public Health Reports, voL 44, no. 42, October 13,1929. 4& Bloomfield, J. J,, and Greonburg. Leonard: Sand and metallic abrasive Masting as an industrial health hazard. Jour. Iod. Hyg^ voL 15, no. 4, July 1933. 9. Bloomfield, J. J.: Tho determination and control of industrial dust. Taper given before Dust in Industry Session of tho 12th Annual Midwest Safety Conference, May 10,1934. 50. Hatch, Theodore, Control of the silicosis hazard in the hard-rock industries. IV. Application of tiio Kelley trap to undei-gtound drilling operations- Tho Jur. of 2nd- Hyg* voL 15, no. 1, January 1033. 51. Drury, W. Herbert: The iaeidcnco of tuberculosis among polishers and grinders in an as factory. PubUe Health Reports, February 4, 1321, or reprint no. 540. _____ t I I t ? a l * fit. lit. 1 2 l ' 02. Hat i K U 03. Hal. oil n< Jut 64. Safvt tie 65. WUii. the Feb 06. Terr}*, lag. 67. Owcr. 1921 68. Hill. 1 * MJ 69. Yaglov wi*i 70L Bulk'd; Urtw 71- Hatz, .v struct Bun's 72- Drinker. studyi 52. DailaValle, J. M. and Hatch, Theodore. Studies in the design of local exhaust hoods. Tran*. Am. Soc. Meeh. Rngts., 1332,54. 53. DallaValio, J. hL: Velocity characteristics of hoods under suction. Am. Soc. Heat, and Vent Eagna, Jour. Section, Heating. Piping and Air Con ditioning. 1933, 4. Itf J 2nd. II 73. Barret and rtvoL 9, CL PalinValle, J. M.: The impertanco of velocity characteristics in the design of local exhaust hoods. Jour. 2nd. Hyg., voL 15, no. 1, January 1933. 55. Hatch, Theodore, Drinker, Philip, and Choate, Sarah P- Control of the I * i Mcoai* hazard in tho hard-rock Industries. ' L A laboratory study of the design of dust control systems for uso with pneumatic granite cutting tools. Jour. lad. Hyg* voL 12, no. 3, March 1930. ^ 56. Winslow, C.-E. A-, and Grccuburg, Leonard: Note* on the efficiency of various systems of air-conditioning in a munition factory. Piddle Health Reports, February 10,1022, or reprint no. 729. IblUVdlq J. M.: Determining minimum air velocities for exhaust system*. Joar.^Am. Soc. neat, and Teat, ilngr*., Jour. Section, Heating, Piping and iitioniog. September 1932, moffrey: Chemical Engineering. London, Crosby Lockwood and ,.- a. Ron. neat. and Venk Kugnu, 1034 (12th crb). ,,* , - r\-r -- r T" IV;' ` t 105211* i t THIS DOCUMENT WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID HOT COME FROM IT'S FILES AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. \ eC of leaxl <!wt awl fnuw* i;, ad } '^wlrin! r.ilAJlihnn*t; . * IMIS. > MicniurMfn. p. 402. I L, jwl ]th*mOckl, J, j,: 1. Health f Worker* in Ictin in. J70, 1P2S. tils dust a* olawrved in V*r. rts, Yok 4% no. 33, June 2* d carbonate rock*. Uiiihsi 19. ew Eughuid. United Slat*, quart* (free silica) in dtwiv utral environment. Puldir 1933. if dust-removal systems in U, voL 44, no. 42, Octolxr 'tad and metallic abrasive r. Ind. Hyg-, voL 15, no. 4, j ; t of industrial dust. Pajnr 3tU Annual Midwest Safety < in the hard-rock Industrie* ground drilling operation*. 1933. losis arooi'X polisher* awl 4)1-007}' 4, 1931, or aiWs the d'nign of Utral .,1032,34. iod* under suction. Am. *Un& ripin; and Air Cun- haisctcristies in the deden 13, no. 1, January 1933. Sarah 1'-: Control of Wr A laboratory study of tbr pneumatio granite eutlinc 330. V tes on the efficiency <J as factory. Public Health jetties for exhaust system* tttion. Heating, Piping owl an, Crosby Lockwood aw< !th cd.). 1C7 lilt. Iluffhr*, IIktor J., an>I SAfford. Arthur T.: A treatise mi hydraulic*. New York. The Macmi'l.i'T Co.. 1925. Cl. Jlay. 1*. K-: A uiclhid <>f tra;>|Miu; tiroilu-l prodm-ed by pneumatic drills, l'ajx-r no 2X Wi'ij in Him* JliM-aP'h Ihjar.L t`*it*-d by Moss, K. Kovilliv. Cases. lhi*t and Hint lit Muna, London, Charles Griffin it Co., Ltd. fpbihultfiphia. J.'lt. LippincuU C.) 1927, p. K3. 62. llatvh, Tl.*-ohre, Iv-lhyGcorgo S., nod J-Vhnd, J. William: Control of the silinwis hazard in the. hard-roct inductrtV*. II. An investigation of the Kelley dust trap for u-w with pnoumalw: rock drills of the "Juck-hamnx-r" tyiao. Jour. JiuL llyr., voL 14, no. 2, February 1932. 63. Ilatrh. Tiet*loco, Wt.rr'n, Henry, and Kelley, George S.: Control of tlto silicrsus hazard in tin- liard-rock Inda-dries. III. Dcaien and operation of a dust-control system .'or u*o with pw-nmatic rock drill* in opcu excavation. Jonr, Ind. Hyp., viA.14, no. 7, Scptmitior 1032. 64. Safety code for tlto u- carr, and protection of abrasive wheel*. Bulletin of the United States )*n* of LaUo-SlaiwUoi, no. 4M, J927. C5. TVhiton, Louis C* Jr.: .Research on eyciune dust collectors. Presented at the technical inco(i::g of the ifotnuwWidan section, Kerr York, K. Y., Febnary 13, 1UT.*, #1110 American Society of Mechanical Engineers. GO. Terry, V,'. F.: Opcralloh, maintenance of cioth-scroen duct collectors. Heat ing, Aping, and Air Conditioning, May <uul Juno 1933. 67. Ower, E.: Tlto Measurement of Air Flo**. London, Chapman & HsU, Ltd. 1927. CS. HiU, IBernard: The science of ventilation and open-air treatment, part 1. Medical Research Council; Special RcjKwt Series, no. 32, Loudon. CS. Yagluu, C.F.,and`L>ol.oir, Ivroutm Cali>>ra4ioa of the kata-thermometer over a wide range of air conditions. Jour. Ind. Hyp, voL H, uo. $, October 1929. 70. Bullet in No. 120. University of Illinois Engineering Experiment Station, Urhaua, lib 71. Kata, S. 11., Smith, G. W., and Meitcr, E. G.: Dust respirators, their con struction and fill (.ring efficiency. Technical paper 301, United States Bureau of Mine*. 1926. 72. Drinker, P., Thoinon, IL. M., and Finn, Jam L.: Photometrie methods for studying and cri.'^ atice suspension* nf dusts, fumes, and smokes. Jour. Ind. Hyg., vui. 7, ia 12, December 1925. 73. Barreto J. Ik, Drinker, Philip, Finn, June L., and Thomson, R. M.: Masks and respirator* for protection against dusts and fumes. Jour. Ind. Hyg., voL 0, no. 1, January 1927. i. 163511* THIS DOCUMENT WAS NOT A RECORI PPG INDUSTRIES, INC. DID NOT COME F IT'S FILES AND CANNOT BE AUTHENTIC! BY PPG INDUSTRIES, INC. \ 2GZ8