Document 3J08Ndad22bn4zLjw66rX7ByO

FILE NAME: CERAMICS (CER) DATE: 1944 Nov 15 DOC#: CER030 DOCUMENT DESCRIPTION: Journal Article - Dust Removal and Collection 403 Y:'"*' :: : t-. ' -. - ' - ' .V." - V f.i. - s No. I* 360 (a) 624^6571 710-79 Ih) 780-78 850- 1050-1503 I62O-I63S 1670-168(9 2050-215H 2130-214M . 2250-226M 14- by 1at 5862 :an be taken < ch weari I ; It - ' - '-' : ill:'- s i - i i ? .Dust'Rempal and Collection" n v . . Tspecml machine (see Fig. 6)T' Norton wheels MB 35588 'o, ME 36438, 100 S-M-100, 4 by */u by 0.503 inch, are BseU. The wheel is run at 4711 surface feet per minute; 0.0005to 0.0001 inch is removed per revolution of the gauge [ blank. Soluble oil is used during grinding. Some types. gauges has indicated that they have special advantages in some applications which should make their use profitable after the war. . -, 1 T h * E lectic Auto-Lite C o u r* n v T oledo, O hio Addition! References ' (1) "New Factors in Making Glass Gauges," Tool fir Die Jour., 9 [3] 77-80 (June. 1943); abstracted in Ceram. 'Ind., 42 [3152 (1944). . . ' (2> P. M. McKenna, "Tungsten-Titanium Carbide Hardness," Automotive cf Aviation Indj., 91 (4] 40 (1944). (3) "Gauge Blanks." 3d. ed.. Commercial Standard CS 8-41, National Bureau of Standards, 1941. __ (4) "Gauges and Precision Measuring Hand Tools,'-' Part 1252, General Preference Order E-5-a, Tools Division War Production Board, as amended April 17. 1943. (5) R. Russell, Jr., and L. J. Berberich. "Low-Loss Ceramics," Electronici, 17 (51 136-42, 338 (1944); ab stracted in Ceram. Ind., 43 [3] 78-84, 96 (Sept., 1944). (6) Louis Navias. "Scratch Hardness Tests of CerauJc Materials." Jour. Amer. Ceram. Soc , 12 [2)69-74 (1929). (7) F. H. Riddle, "Ceramic Insulators for Spark Plugs," S.A .E. Jour., 46.236-42T (1940). (8) C. D. Hodgman (editor), Handbook of Chemistry and Physics. 23d ed. Chemical Rubber Publishing Co.. Cleveland.* Ohio, 1939. 2221 pp.; Crrom. Abs., 19 [5] Fjc. 6.- -Method of grinding a ceramic gauge with a ' diamond grinding wheel. such as ring gauges, may also require lapping or polishing with rouge, alumina, silicon carbide, or diamond dust. ' . 127 (1940). ,, (9) International Critical Tables of Numerical Data, Physics, Chemistry, and Technology, 1st. ed. McGraw Hill Book Co., New York, 1926. (10) E. S. Dana, System of Mineralogy, 6th ed.' John Wiley & Sons. Inc., New York. 1892. 1134 pp. (11) Hans Thurnauer, "Ceramic Insulating Materials," Elec. Eng., 59 [11] 451-60 (1940); Ceram. Abs.. 21 [3] 63 . V. Conclusion Ceramic materials of various kinds are a wartime sub stitute for critical tool steel in gauges. The use of ceramic (1942). - (12) G. W. Morey, Properties of Glass. Amer. Chem. Soc. Monograph Series. Reinhold Publishing Corp.. New York. 1938; Ceram. Abs., 18 [2] 4S (1939). DUST REM O VAL AND COLLECTION* By R. R. Robinson `W.-.t-j th handles?^ e. The finish^ >od toolma c ground on 1 ol. 23, No. 1 Abstract The reasons for dust collecting in plants are (a) to protect the health of the workers, (6) to protect machinery and equipment, and (c) to conserve the dust for its economic value. Methods of dust removal and collection are also discussed. 1. Introduction . From the beginning of the industrial revolution in England, during the latter part of the eighteenth century, the presence of fumes and dust in the atmosphere of mines and manufacturing plants has been a cause of as much unrest among employees as has any other single working condition. This is due to the fact that such foreign bodies as dust particles (and many so-called fumes are clouds of minute dust particles) when entering the respiratory organs are not only eventually dangerous to health, but have an immediate irritating effect. . For more than a century, there has been a determined attempt by humanitarians to interest mining and industry in a movement to create clean atmospheres within working * Presented at the Forty-Sixth Annual Meeting, The American Ceramic Society. Inc., Pittsburgh, Pa., April 5, 1944 (Materials and Equipment Division). Received July 13, 1944. spaces. Within the last decade, th a t action has taken hold of the minds of employers so that today the question is not whether the air should be cleaned, bet how shall it be ' done. In fact, many problems are not solved simply because the management of a specific mhastry is unac quainted with the best methods of procedure. .I t seems appropriate at this time to pve reasons for removing dust from working spaces, methods of eradicat ing dust and fumes, and the disposition of those foreign substances after they have been removed. Although the subject has been discussed in former cotetings of The American Ceramic Society, the discussions have b en closely confined to the toxic effects produced by dusts. In the present discussion, no attempt -ill be made to prove a necessity for dust removal The dangers to human health are too well known by informed manage . ment to require explanation. ; ' ' : Dust may be defined as finely divided particles of oc- (1944) - . . //}2 Bulletin of The American Ceramic Society--Robinson ganic and inorganic solids. Drinker and H atch1 have stated: ' . If. 1 cc of quartz is crushed into particles 1 cubic micron in size, there mill be 10ls particles within a total surface area of 6 square meters as compared a ith 6 sq cm. for the original block. Assuming a dust concentration of 100 million particles per cubic foot of air. the 1 cc. of material will be dispersed in an air volume of 10,000 cu. ft. Thus it can be seen that the dispersion of dust particles from manufacturing processes may soon fill an atmos phere to such an extent th at visibility may be reduced, and if the dust is dangerous to human life, toxic effects may result, or if the dust is of a carbonaceous nature, violent explosions may result. The following reasons could, therefore, be given for the removal of dust particles from working spaces: (1) the toxic effects of dust on the human body, (2) the effects on visibility in the atmos phere, (3) the explosive effects of carbonaceous dust, (4) the abrasive effects on machinery, (5) the adulteration of products in process of manufacture, and (6) the general cost of cleaning the premises. The toxic effects of dust are discussed in a bulletin pub lished by the Commonwealth of Pennsylvania Bureau of Industrial Hygiene.1 In many factories, even today, visibility is often de stroyed, or it least seriously impaired, by dust particles floating in the air. This has been the cause of many accidents. It is hardly necessary to make any further remarks on this phase of the subject. In the ca_i of dusts of an explosive nature, it has been found advisable and, in fact, necessary to reduce the dust count to the lowest possible minimum. Buildings which house machinery from which carbonaceous dust or other explosive particles are exuded have been equipped with special dust walls and windows which, serve as escape valves in the event of explosions. Reference can be made to the numerous bulletins published by the Department of Agriculture of the United States Government covering this subject. One of the bad effects of dusty atmospheres is that of abrasion of bearings. There are little data to show the amount of damage that is done, but there is no doubt that if the data could have been collected, it would be found that such damage costs industry many times the value of the equipment necessary to clean the air in working spaces Another serous danger from dust is that of adulterating products manufactured in the plant. ' All the manu facturers of whiteware in the ceramic industry are fully aware of the expense th at is incurred due to foreign bodies becoming mixed with the clays used in their work. Within a few hours, the dust which permeates the atmosphere of a whole plant could discolor or in other ways affect the quality of the ware so as to increase the number of rejects to such an extent th at the loss would be of considerable value. The cost of cleaning plants due to the presence of dusts is another item of considerable expense. One plant, manu facturing a material from which a very abrasive dust was 1Philip Drinker and Theodore Hatch, Industrial Dust McGraw-Hill Book Co., New York, 1938. 316 pp Ceram. Abe., 17 [4] 166 (1938)................... ......._ -, "J ' *"Study of Silicosis in the Silica Brick Industry." Penn Deyi. Hcalih, Bur. Ind. Hyt.-. - ^ . , ... u ... ;r. discharged, did employ, until the outbreak of World W II, a great number of men whose duty it was to clean ti automobiles parked on the plant grounds. It is eas'd' seen that in such a plant the cost of cleaning offices and Other buildings where cleanliness is necessary would be quite an item of expense. II. Methods of Removing Dust . To keep the removal of fumes or dust particles at tie lowest possible cost, it is always best to arTest the ma' terials and remove them before they get into the genera] atmosphere of the plant. Whenever possible, hoods should be placed over the machines or at the source of dust. R would be practical and very profitable to align the machin ery so that duct systems could be extended in as straight lines as possible or so th at separate rooms could be con structed to confine the dusts or fumes and to make possible the removal of these with the least amount of power and machinery. When it is impossible to hood machines jet velocities of air may be directed toward the source of the dust with collecting hoods placed at a strategic posi tion from which the dust-laden air may be exhausted In many cases, water sprays may be used or water may be poured over the machines in such a way that the water may mix with the dust and the mixture drained off so that there is no dispersal of the dust particles into the atmos phere. In almost every case, the removal of dust requires care ful engineering. Good engineering may mean the dif ference between success and failure. III. Collection The removal of the dust from a working space is only part of the problem. The management must decide whether this dust shall be discharged into the open air outside the plant, whether it shall be collected, and, if collected, what means shall be taken to dispose of the residue. If the material is such that it has an economic value which will pay for expensive apparatus, then the dust may be used in process work. In many cases, it may be necessary to grade the dust for particle size. In other cases, the dust may be of little value, but of such a nature that it cannot be discharged into the air without some as surance that it will not be carried over the neighborhood by the winds. There are many types of dust-collecting equipment which can be used and which are employed for various purposes, depending upon the ultimate disposition of the material. Generally speaking, these collectors may be classified as follows: (1) the mechanical type, which includes those making use of cyclonic air action, (2) those which make use of the principal of lutriation, and (3) those of the filter type. The filter-type collectors are of many kinds known as the bag collector, the soft material filter collector, and the screen cloth collector. Under nearly all of these machines there is placed a hopper into which material ultimately drops and from which it is taken for final disposal. Within the last twenty to twenty-five years, there has great development in the electrical-precipitation type of collector. The action of these collectors depends ' upon the fact that dusts can receive and retain an electrical -. 2- . ' Vol. 23, No. I I . .: xge and u b* reo the proper ... eded tb it ta* rx rru ch m ore t f '. t 1 I re stricte d .a s /T he question c/ oe of the co s: '-i [D IS C U S S IC I (A) The eliminatie' operation mvol s 'he point of ? Firbere it is tc Of Suspended. (3) i i 1(4) the disposu ,c __. This is usual %: located at the ;:> , ^collector, ar i u i a The air and c . fat a velocity suf*c The tj'pe of c : ?on many factc's Fteat of the gas t fcolJector, anc *>; i Dust collect.,:'^chambers, c> do c Jters, gas was t precipitators j ( 1) Settling Cba-n' A settling cha n _ Jocity is reduce: of the gas by g-a .. Every coarse pa* i: (2) Cyclone ColU The cyclone t .; ugal forces act.ng he gas In grr e* ^smaller the radius There are rra :\ JoDes uhich n ^dust-collection v. o -equipment. 71 er * A simple rye! . avjngs, sa'*:i.v nt is not worth i -l nail and the dust __A "high-efficH n rhere the terr; e [lection and colic t : T here are mai:> definite place ta . "`The mechanic!1 vts the dual pi ure and a cycle n itions as the cycle ^ilt of the dust-Uc Abrasive mate-iT auseshighmai t J(3) Viscoui Co It :T he viscous t ~ through, a caught or t a *Received Juu ' 1>:. 'g/U'.- ' iv k of World .w2 vas to dtatTtS ' It is easily ling offices S .s a r y would.. articles at t i t arrest the ma? ito tie genenB e, hoods should cc of dust. in the machin? 1 in as straight! could be coir? make possible" of power and! od machiues^j the source of] strategic posi le exhausted!; water may 1 at the waterj ed off so that to the atmos- 'equires careni eaa the dif-j space is only j must decide^ the open air ' cted, and, if^ spose of the : nomic value1 en the dust s, it may be - In o th e r" ich a nature. mt some asighborhood equipment for various ition of the rs may be ype, which i. (2) those, n. and (3) known as >r, and the"! - machines'^ ultimately" L there has icipitation s depends i electrical ` 3 . No. 11. / Barry Discussion r.. v / 413 charge and can be attracted to plates or electrodes when given the proper land of electrical charge. I t is generally conceded that the electricol-preoipitatioa type of collector is much more effective than any other type, but its use has been restricted largely by the'eost of investment. ' IV. Conclusion - The question of cleaning the atmosphere is becoming one of the most widely discussed questions among manu facturers of the present d ay .' The human being breathes at the rate of approximately 56 pounds of air per day while at rest and many times that amount while a t work; it is important, therefore, that the atmosphere which we must use constantly be kept as clean as we can possibly make it. . ' . R obinson V axTiLA rm o Coupant ' Z bubnoylb, P ennsylvania DISCUSSIONS O F ROBINSON PAPER ON DUST REM OVAL AN D COLLECTION (A ) DUST COLLECTION* . By T. J. Barky I. Introduction The elimination of dust generated in any industrial operation involves, as n general rule, (1) its removal from .the point of generation, (2) transportation to the point where it is to be separated from the gases in which it is suspended, (3) its actual separation from the gases, and (4) the disposition of the gases and the/dol!ected material. This is usually taken care of by properly designed hoods located at the point of generation, a duct system, a dust collector, and a fan. ' The air and dust must be removed from their source at a velocity sufficiently high to insure control of the dust. The type of dust separator or collector to use depends on many factors, such as the type of dust, moisture con tent of the gas, temperature, size of particle, location of the collector, and space available. in application and cannot be considered for the collection of industrial dusts. (4) Wet Collectors The wet separator or w asha has been built for many years and is made in many designs, such as the tower washer, the disintegrator, and scrubbers. Blast-furnace gas and coke-oven gas are frequently cleaned by this type of equipment. During the past few years, the wet collector has been applied to other fields, such as foundry dust and dust from metal grinding. Water is usually the fluid used, although it has been' found that many dusts cannot be removed by the water alone and other materials must be added to promote the wetting of the dust particles. The wet systems are limited in application and require attendant equipment, such as pumps and sludge-removal equipment, which add to the opaating cost of the system. II. Classification of Dust Collectors Dust collectors can be classified generally into settling chambers, cyclones and other inertial apparatus, viscous filters, gas washers, cloth collectors, and electrostatic precipitators. (1) Settling Chamber A settling chamber is simply a chamber in which the gas velocity is reduced to a point where the dust w21 fall out of the gas by gravity. Naturally this will only remove the very coarse particles and has a limited application. (2) Cyclone Collector The cyclone type of collector depends upon the centrif ugal forces acting on the dust particle to separate it from the gas. In general, the higher - gas velocity acd the smaller the radius, the higher the efficiency of the cyclone. There are many variations in the design of commercial cyclones which materially increase their application in dust-collection work. They are limited, however, as is all equipment. There is a definite field for each type. A simple cyclone is perfectly satisfactory for separating shavings, sawdust, etc., from a woodworking shop, but it is not worth much on a job where the dust particles are small and the dust is readily``air-borne.'' . A "high-efficiency" cyclone is well adapted to those jobs w han the ternp astu re is a factor, such as fly-ash col lection and collectors for driers and kilns. There are many designs of these collectors which have a definite place in the scheme of things. ' The mechanical separator, of the type in which the fan serves the dual purpose as the source'of suction or pres sure and a cyclone collector, is subject to th *saw limita tions as the cyclone itself and has a bad feature in that all of'the dust-laden air goes through the fan. If it is an abrasive material, the fan wheel takes a beating and causes high maintenance. , (3) Viicoui Collectors The viscous type of collector, where the du.t-liden gas passes through a labyrinth filter and the dust particles are caught or trapped by the viscous su: face, is limited * Received July 13, 1944. ` ' (1944) (5) Cloth Collectors Cloth collectors are made in several designs and are the simplest means of separating the dust from the gas. Their field of application is wide and their limitations are quite well known. Cotton cloth can be used on the gases when the tem perature is below 1>90F. The life of the cotton decreases rapidly as the temperature goes high. Wool cloth can be used up to 25Q'F.; above this temperature asbestos cloth is used. The bags and screens made of glass have not been too successful. If the gas temperature goes below the dew point, trouble is likely to develop with cloth arrestors. In many cases, this can be overcome by heating the gas or by insulating the casing of the collector. The principle of operation of the cloth separator is well known and the factors affecting its design are primarily (1) type of dust, (2) temperature of gases, (3) moisture content of the gases, (4) dust loading, (5) intermittent or continuous use, and (6) method of removal of the dust from the hoppers. The operation simply consists of having a material in the cloth that will stand the temperature and permit a filta cake of dust to build up on the cloth so that the dust will be filtered out of the air by this combination. A micron particle is Vu.o of an inch in maximum dimension, so that when we speak of a particle l/i# of a micron in size, it is only inch in its longest dimension. The filta cake of dust therefore really does the filtering of the small particles, and, as a result, the accumulation of dust must be periodically removed; otherwise the pressure drop through the collector will build up until the flow of air or gas ceases. The three general type of cloth arrestors are (1) the screen type, where the cloth is held on wooden or metal frames by one of several methods, (2) the envelope type, w hae the cloth is more or less in the form of an envelope and fits over a frame to hold it in position, and (3) the bag type, w hae inverted bags are attached to a plate between the dust hoppers and the bag section and are supported from the top, usually by springs attached to the shaking device. In this type, the dust-laden gas en tas u n d a the /I/ Bulletin oj The American Ceramic Society-,Begann Discussion ' " S & T i S f i l t S , ' S T S 'h n i^ rfr 3 ^rcat dcal of atten tio n from the designer and K d 1!ecelve a lo t m o re a tte n tio n from those mho install the equipm ent, as the life of th e filtering m a tm a l a ^ d lh e tthhi"s ffaaccttoodrrr. POOtnhrOsoUmgeh ttybpCeCsOolIfr dtu0srt aarcravt'iotalolyf 1a fcfuebcitce fdoboyt t h k 1* p e r ,st3uar' foot of d o t h m u st be used. A d u s t of this ty p e has a flat surface, such as the flahv tvn* m.* 1 dust W ith carbon black and simHar m a t S i ^ e m rio 3 to 1 " w S 2 `V : " ith foundri- dust and clay dust! in rite d . ' figUreS are tXceeded' m aintenance is A co n tin u o u sly o p erated a rre sto r is m ade in tw o or P e rio d -'^ bC -iD system" ^ ' t W T S - s" a t " sectionsfor o'vet Z e [ m S y byTaht L T ati0n U ^ of-- into a S r To o p o u t S & * J ! ,* ?' a rre st0 r iS PSed W lti a tra d in g or buffing system and there ,s a possibility of sparks or fire being c S If th e d" r t arre5t,or ,ls m.5taIled ahead of th e bag se X o n If th e d u st is explosive (and m any are), the cloUr should p05ltlve' y. ^ P y o d e d to elim inate the possibility of a static spark igniting the dust. y 01 a (6) Electrostatic Precipitation B e g ^ SlatiC p re c ip ita ,o rs "> ^ discussed later by M r. III. Conclusion . A du5t condition in a plant is a cause of is a h o Jth hazard it should be eliminated regardl H U cost. If it is not a heakh hazard, it is a n u is iX " v of causes excessive equipment maintenance rejected " hlch ucts and dissatisfied workers, and, as a'resilt ^ f rod- quahty of workmanship. a lo"ex The question of whether or not to recirculate ,u . aaii?r Tshho3ulMdUnStevceorUb"etorerc?i"rcsulcaateudseudnlmesuschit disiscceurstsaiionn kh<^Ti`r does not contain toxic material and that it is e n tire ly U from all harmful dust a t all times. entirely frtt A plant with an adequate supply of fresh air r,i,i. , it costs more to heat in the " months) v , fewer lost-time accidents than the plant where h * becomes " dead" after a few hours, ^ result! will m a'r than pay for the extra cost of heating the air U re The water has tried to keep this discussion as technical as possible and to refrain from comments a tiTe " the b' 5` or any" ' " . Dust collecting is a combination of art and science t. involves the proper design of the entire system from' o ,' point of dust generation to the final disposal of H 4 ^ collected material and cleaned g a ! P ' b lh There is more engineering in doing a good ioh .v, meeu the eye. When one sees so many j X V h e re ^ T lines are too b,g and fill up with dust or k e to i smaU a^d do not get enough of the dust away from th T so m e and the equipment inadequate or of the wrong type it m i one wonder just how to paint the picture so that be seen that a properly designed system will pay dividends even though ,t seems to be "just a dead o p X t.n g C0X " P ar* B ctL orvc PTTTSB CTtCH, PeNN5kT.VAKla4 (B) ELECTRIC AIR CLEANING* Bv G. F. B egoon II. Electrostatic Precipitation The only effective method known todav for ..m o I. Introduction t e m i X a StatiC a a cIean,inK ^ applied in ventilating sys- \Vhv s i 3Dd re jrUtJOriary d e c trnie development air c li n i S f ' ^ f0r air clean" S' > al ^ electric r a,,t,,T ^ ,,b19MMfto,,nns,sn.pLtrr Psqnua0rUe rmCiilteiepsetromdaoyn'thatin^Pittasmbuarzginhg 163 ons in Chicago, 1450 tons in Baltimore and com' V & and decorations, soil fabrics cause P" ' of industrial m achinery, et" ' exc" s'v' maintenance Toe size of these particles is measured by a minute d s W ace X s t s t S volts causes Such a high generation of zone ho e w that the air thus treated is not safe for b r e a t h ^ mros and hence not suitable for ventilating systems ^ s Tbl lS pr.obIem th a t'w a s solved by scientifi- re tbe dfCtn<:, - r d e a n / t h a t oper'a. X h f X n y ^ 'X " " ^ found" " oidcxws o" ".' direct"crirrent^by^tP*^eJ ^ t o u tC000 a!]!]1recl!ficc! to 7 i 1 by 1 0 tubes. By means of a Scoeucect otorr p!atoe vholtagUebslinagre CoiKbCtUaiint edl.e prop- S r a5 ,, i ! r ^ t l y no practical method had been devisr ! though X c X iiS i' fiU * larger dirt panicles i.e from P m id " ' Al t m o v in g the Received June 22, 1944. -- pprrfaccttiiMcall3uusOeh, aa,,nedi eCatife,Cwaiinr sdtaelilaDt'iTonbsadwreeraecmheaddethaes Pthoeinatior-f. sln e m * compontnt f air-conditioning or ventilating buiidffirsm ThrC" ' St, ^ w h a n k s , and other commercial from Th" e *nstAllations were made to obtain relief mTke X c h n!oa,nd T ? Y air' b o n ,t d irt- dus`- i X a n d shX s Tnbd bo "l d damage merchandise in stores and f e r a w S k " eqUent redCCOration and s i i ^ ^ h V c h yCa? ' fUri ber installations were made in n ^ A ^ bU^hn?" t ? m any other types of busi- nesses, such as cleaning the air in pharmaceutical andl cause imperfectioWnshmtrCpr^oducdtestaensdt'mprioccreosssecso.p ic s p i t s ' air foer 1 ^ C d ean f is to clean the venlilating Dower n if T ILe d ' ctncal machinery in steelmills. power plants, and substaons._ Failures of these machines 1 . - Vol.23.Ko.il Raw Materials for Porcelain Enamels 415 if expense. 1 ed regardless, i nuisance whS rejected prT I result, a lo' circufate the^ iiscussion. is certain thi? it is entirely'f sh air (althoug. mths) will hay t where the"_ results will mo iir. ussion as 'n o comments as'tj :st for any pai and science.'jlt ystem from tiff osal of both t i a good j o b __ . jobs where the re too small and the source and : type, it m a ti|] ; so that it i " II pay dividend operating cost y for removing i is electrostatic; lich have be_ tssfully in sue d cement mil___ The high v o ltl .000 to 100,0001 `zone, however^ athing purpo ` >tems. , )y scientific re?J r that operates^ e that its conj* it of doors on a? on and 6000 forj s of a rectifie volts, 60-cycle and rectified toll By means of i oer ionizer andj ted the point ofa nade as the air or ventilating ler commerc to obtain relie dust, soot, and e in stores and and excessiv s were made i types of busf.^ naceutical and oscopic speck ses. the ventilating / in steelmillsl these machine VoL 23, No. II t often caused by excessive temperature rise or leakage utr the insulation due to dirt on the windings. _ In telephone exchanges, electric air cleaning is used to ,dpmaintain delicate relays by removing the microscopic pit particles which cause faulty operation and noise in le circuits. * . . In textile mills, electric air cleaning has been'applied t eliminate soot, smoke, dirt, and dust during winding, finning, weaving, and drying operations. These micro- Jopic particles damage the yarn and fabric to such an Stent that about 15% of the total production has to be dd as inferior products. Mills equipped with the electric cleaner have reduced this to about 6%. ' Other establishments, such as hospitals, restaurants igbt clubs, radio stations, libraries, and laboratories are feund that investments in electric air cleaning pay tig dividends. . When the war came along, many of our materials were heed on the critical list and purchases were subject to priority control, which brought to an end the peacetime iisiness. On the other hand, the necessity for clean air amany wartime production problems opened the door to aw markets. ./ . . As its contribution to wartime production; electric air deaning is being applied where precision engine parts, sstruments, lenses, and optical goods are manufactured, aspected, and assembled. Tiny unseen abrasive and rorrosive particles that damage superfinished surfaces onnot be removed by mechanical filters, yet the electric drcleaner takes them out of the air and saves many costly ejects. _ Electric air cleaning is applied to catch the oil mist and moke generated from coolants on machine tools. This d mist has become serious enough in some plants to (1) ouse a fire hazard, (2) condense and drip from overhead learns, lighting fixtures, and pipes, and (3) lead to pre suture electrical insulation failures and make the working mvironment unpleasant. Precipitating the oil mist at its xirce not only eliminates these objections, but also re avers the cooling oil for reuse. Also some operators are sowable to use a better grade of coolant oil, which results abetter work and increased production. Another use is the control of welding fumes and smokes. Ill the applications mentioned have been very successful. The total installed electric air-cleaning capacity at the present time is about 50,000,000 cubic feet per minute, 3% of which is associated with air-conditioning systems. Even so, the surface has barely been scratched. These in stallations require only 15 watts of electric power per 1000 c.f.m. of cleaning capacity. III. New Development! In addition to the electric air cleaner as we have known it in the past, there are some new developments in the offing that should substantially increase the potentialities of this device. Right now, work is being done on a combination cyclone dust collector and special-design electric air cleaner for boiler-stack smoke and fly-ash control. No official an nouncement has yet been made in this regard because it is only recently that WPB gave one of the power companies the necessary priority to continue the work. The results so far, however, look quite encouraging. . Another new development involves the home market. We are now making definite plans to provide electric air cleaning for home use, particularly in homes with forced- air heat. We have already built about 100 so-called home central units, the majority of which are now installed as pilot installations in homes around Pittsburgh. The re sults obtained, from the standpoint of keeping the house clean and contributing to the health of the family, par ticularly those suffering with hay fever, have been ex cellent. . . We hope to provide a complete cabinet unit for homes which can be installed at a cost to the user of about $250. `Market research indicates that, if this can be realized, there will be a strong demand to be satisfied,for this type of unit for existing homes equipped with forced-air heal. The housewife will see to that. _ For new construction, in addition to the self-contained unit just mentioned, we are working with the furnace builders to help them incorporate the cells as an integral part of the furnace. This will enable the home to have the advantages of electric air cleaning at much less cost. Ceramic plants in which contamination of the ware is a serious factor may. in the near future, be using the elec trical method of cleaning air, not only to prevent foreign materials in dust particles from spoiling work in process, but also to clean the atmosphere of workrooms without being obliged to heat gTeat quantities of- new outside air. PxxanTEOM Dr*TMX!fT WlSTTNCHOUSE ELECTRIC& Ma.VUTACTUTTSQ CdCTAMY 1216 W est J 8th Steeet C lev elan d 1, O n o RAW MATERIALS FOR PORCELAIN ENAMELS SURVEY OF CURRENT MARKETS AN D ALLO CATIONS* Bv J ohn W. I u pp Abstract Although many raw materials for porcelain enamel have been restricted, either by market shortages or by WPB regulations, all important raw materials except tin oxide are currently available in at least moderate quantity. A group of materials warranting in dividual attention is considered. I. Introduction Conversion, steel, and man power have all put limita lions on porcelain enameling to a far greater degree than '`outages of enamel raw materials. Indeed, the relatively tbt demand for chemicals and minerals has been met with Ettle trouble and with little need for the use of unsatis- betory substitutes. Nevertheless, it is prudent to keep a e watch over material requirements, especially on I *>terials under allocation. ' . *Presented at the Forty-Sixth Annual Meeting. The American Ceramic Society, Inc., Pittsburgh, Pa., April 5 (Enamel Divisiou). Received August 13, 19+4. fl&H) \ II. Availability of Raw Materials (1) Mill Additions ' Tin oxide may not be used (WPB Order M-43), but the zirconium opacifiers and Uverite can be used. Uverite has been available continuously in quantity adequate for con sumption. So have the zirconium opacifiers, although in some cases it has been necessary to change types. (2) Color Oxides Both cobalt and cobalt-free blacks contain substantial amounts of chrome, which is restricted and in very short supply. Cadmium colors, comprising the bnght reds, T