Document 4aZaQVyZNxXwd3wX5aKgv2xEN

;''V>v v Sale fraelites Pamphlet He. 34 i. *- <- ,s Industrial Explosion -- J-f. (Joses, Vapors and Flammable liq Published bjr National Safety Count!, lac 20 North Wacker Drive, Chicago 4 I ij *t ev t t . ..'li'' .) 'I., 1. A serious danger to employees and property in many industries is the use, creation or accidental occurrence of gases, vapors and liquids that may cause an explosion. This danger exists, often unsuspected, b so many plants that it is desirable for every executive to give some consideration to conditions in his own plant and to take steps to prevent fires or explosions before something oc curs to call this danger more forcibly to his attention. tUt pamphlet Is one of more than 190 Safe Practice* and Health Practices Pam phlets. It is a imyiliiiwi of experieaae in accident prevention from many source*. It should not be awnmad, hoeew, that it includes every acceptable procedure In field covered. It must not be confused with American Standard safety codec; federal leers; insurance tsqaueacans: state laws, rule* and tenJsnosw; nan municipal ordinance*. AflMmd cepies of this tiar^Wrt an price, 55 cents nub, __ member prices an refersi, the wrts of the space in which the exploding substance is confined, or to expkptan waves and vibrations set up with the exploding substance, follow ing an eapkvuoa and the original oatrash of sir, there is a reversal and air rubies back to the area. This canes a partial vacuum la the surrounding area that may he stroeg enough to poll win dows out or even cause walls to be sucked over. Also, expiation* of vola tile materials are commonly accom 2. An explosion from a chemical viewpoint is most commonly a rapid chemical reaction, such as combustion or decomposition, that causes a great md sudden evolution of gases, or hearing of gas, or a combination of these. There is an attending sudden violent increase of pressure, usually accompanied by a sharp report, and explosion waves are set up m the air and other gnrj*ovt While not many explosion* . of this nature occur in industrial equipment, they are possible. However, (hey fre quently occur in the laboratory, whan working with glass vessels. 3. The violence or destruction that accompanies or immediately fOBows most explosions is due, primarily, to the development of pressure that, rupture* panied by Same anti, ttibaegueat tires and by destruction due to objects and debris set to motion by the force* cre ated. (Sea ftgare 1.) 4. : Explosives 'may he. divided into (he foQowmg lots general chases: L Explosive mbstaacea. a) Commercial explosives or chemi cal cqloavti fdisenssed in Safe material. While the term "explosion" is employed in this pamphlet to in dude only rapid chemical reactions that produce a sudden violent increase in pressure, it should be recognised that vi olent explosions ef a physical nature can he caused by a sudden release of gases and vapors under pressure, such as the bursting of a steam boiler or other pres sure vessels. It is also possible to create destructive or physical rmxfitisn* of an. explosive nature by ehemiealor physical reaction* tbitproduce a partial oaiaiv^Kla tf uoafinad spnee, us the attain JttlK'sufi" ad W^Hjpi teaccfcm of jam* tiMt fun lesfe qtire ftah tiioaie jRKneiiff'fcto'l!be toiC&n. fh&e sftuatihh the fsgpjoticn pad ac- l-i tnapanyiqf destruction arise from the fact that Oh tte forced fe'fer&e tort k 14.7 pounds p* agree m - `i >.z ..... * RSV0030394 2--S.P.P.-54 SAFE PRACTICES PAUPHLET BO. M Figure 2, VTentberproof fittings for pip**- (See pnagnph 23d.) Practices Pamphlet No. 28). such as dynamite and gunpow der, which contain the oxygen necessary for their rapid com bustion, or, where the weak chemical bonds of the nitrogen tn the compound are easily broken by a chemical or physical shock. b) Chemicals not used as commer cial explosives but which can decompose spontaneously (such as acetylene.) II. Gases and vapors which react rap idly with gases (other than oxygen) when they are ignited by heating or sunlight Examples are chlorine and hydrogen or bromine and fluonne. III. Combustible dusts (discussed in Safe Practices Pamphlet No. 104), which may or may not contain enough oxygen for rapid combus tion. They are explosive when mixed in proper proportion with air. IV Combustible gases and vapors from flammable liquids, when they are mixed intimately in certain propor tions with air or other oxygen con taining gases from which they ob tain the oxygen-necessary for rapid combustion (ammonia, iltantnatntg gas, gasoline, naphtha and prxctkaHy every other flammable gas. vapor or Ikl-id.) 5. This pamphlet contains a sion of the substances included in fee third df fine three major rfassea, vapors, and flammahfr S Jtmmakh It Kaatei to tie cm- ixflarie* hianbly OUyitffUKiegan But an gbm eg by iwc* WpBfs. ft shmdd be reongnjaed feat Out m liquids other feanfeatof feAr gasoline is a flammable liquid whose heat or by spontaneous processes are vapors when mixed with air and ignited - more daqgeraos than either those that in a confined space can produce etfdo- require a positive source of ignition sioos. In the one case, sadden vfchsrt such as t nme'or'qpaih or those that decomposition or ekplosios is caused react fcpmedtaetr on contact. When merely by detonation or sudden hod, positive^gbnifr required the mixtures while in the case of gasoline it is naif the vapors that wifi explode. Niteglycerine is an explosive liquid but gasoline is a liquid whose vapors wifi bum or explode when mixed with air 4a Mb safe mBIb 'an igaition source of unstable i mixture can acreaction may then take jdate frontsnrrrnily. the proportion of 1.4% to 6%. Cap tain other mists or fogs (air-carried droplets or particles of liquid rather than vapors), are explosive in much the sane manner as dusts or particles of com bustible solids. Mist explosions wffl even occur where the liquids are not volatile enough to produce explosive amounts of vapor at ordinary mom temperatures. 9. The gratg> of gases and vapors that are flammable and will produce explosive mixtures with air or oxygen has thebroadest interest from an indus trial explosion hazard viewpoint The number of gases or vapors in this group is so targe that it is not practicable to g?ve a complete list in this pamphlet In general, however, a complete list would include every gas that is com 6. The most unstable of all com mercial combustible gases is acetylene winch will dissociate, (split into its com ponent parts, hydrogen and carbon) if subjected to heat when it is at more than atmospheric pressure. It is for tins reason that the gas, when stored raider pressure, is compressed in vessels con taining a porous substance that w01 prevent dissociation or explosion. In actual practice this porous material is soaked with a solvent, such as acetone, bustible and every liquid that is vola tile enough to create a flammable vapor mixture with air. The list may also in clude substances that alone are not vola tile enough to create a flammable vapor air mixture, hut which'will contribute a significant amount of vapors to com bustible gues or vapors from other sources so (hat the mixture of vapors as a whole makes a flammable vapor-air mixture. For example, if there were time liquids either as a mixture, or sep that will absorb many times its own weight of acetylene. 7. A number of rather common gases will react with each other with ex plosive violence in the absence of air or oxygen- Mixtures of chlorine and hydrogen wifi react violently, tire prod uct of the reaction being hydrogeo chloride. Also, while the reaction in mktmes of hydrogen and chlorine rosy be initiated with a flame, the mixtures are very unstable or sensitive; the reactian may be started by saafight. Tlti ahs chlorine vffl react violeqfer with gaaes and vapora such as acetjtae, cthylpe and otherhydrocarbons e^tedatyeffee arately, each of which was volatile enough to give off only one third the amoimt of vapors required to form an explosive vapor-air mixture, the cumu lative contribution of the three would be explosive. This wfll be discussed in more detail later under the subject of flammable limits of mixtures of vapors. Iff. flu* pciat: This is the too- peratare at vfefeh a combustihiefiquid gws off enough vapors to be jgnfliaWf redetermined ty prescribed test; ftjanwUes i Bar" in and " ^ amafuratad types, Offer eggHaaj^iag. of gases, partknlsriy the otferhilcjem' as'bromine aatf flwfeae^apt. reactive but the that hazards df exrihudaaa df eases wad not coadboi ftrflme dhd- 3> urn decompose and Stem gaseous pat#**-- *. nets feat are explosive. Tor eunfrfe' ' luces of gam But agjf . ifltre-gycerine is an expSosive fiqwd bat very sensitive h> IgriHl01% if - i .4 4X RSV0030395 rINDUSTRIAL EXPLOSION HAZARDS S.P.P.-34--3 gases, vapors, and liquids is important In this pamphlet it is not possible to indicate more than a few of these properties and point out their relation to explosion hazards and their control. Butyl Acetate (Iso) 64 Butyl Formate 64 Croton Aldehyde 55 Crude Petroleum Denatured Alcohols 45 to 60 Diacetone (Technical) 40-57 Dichlorethylene 57 \' Explosive Casts Diethylene dioxide 65 pressures above atmospheric) Ethyl Alcohols 48 to 65 Ethyl Alcohol ft Water (up to 3096 jspebusiible Gases water) 62 to 70 Butane* pherie) Butylene Carbon Monoxide Coal Gas Ethane Ethylene Ethylene Oxide Hydrogen Hydrogen Sulphide Illuminating gas Methane Methyl Chloride Natural Gas Miscellaneous com mercial fuel gases Propane (at atmos pheric pressure) Propylene Ethyl Benzene 59 Ethylene Dichloride 56 Ethyl Methyl Ketone 30 Ethyl Nitrate 50 Ethyl Propionate 54 Lacquer 0-80 Methyl Alcohol 54 Methyl Butyrate 57 Naphtha ("Solvent") Benzol (Coal Tar Naphtha) 60 Nitrocellulose (Wet with solvent) 40 Octane 56 Flammable Liquids Paraldehyde 63 Class 1--Liquids in this class have a flash point below 25* F., closed cup tester Acetaldehyde --17 Acetone 0 Aluminum Paint 0-25 Benzine 0 or less Benzol 12 Butyraldehyde greater than --20 Carbon Disulphide --22 Collodion 0 or less Propyl Acetate 58 Propyl Acetate (Iso) 43 Propyl Alcohol (n) 59 Propyl Alcohols (Iso) 53 Propyl Alcohols (Sec.) 67 Propylene Dichlortde 59 Pyridine 68 Rubber Cement 50 or less Toluol 40 Varnish Shellac 40 to 70 Cyclohexane 1. Cyclohexane Hexahydrobenzol Penatured Alcohol (Govt Formula SD- 13A) lower than 19 Class 3 -- Liquids in this dass have a flash point above 70* F., and below 200* F., dosed cup tester. Diethyl Ether --20 Ethyl Acetate --24 Ethyl Chloride --58 Ethylene Oxide lower than 20 Ethyl Ether 0 or less Ethyl Formate --4 Ethyl Methyl Ether --35 Ethyl Nitrite --31 Gasolme --SO Gasoline (natural) 0 or less Heptane 25 Hexane --7 Lacquer 0 to 80 Lacto! Spirits 7 Leather Cement 0 or less Methyl Acetate 15 Methyl Ether --42 Methyl Formate --2 Naphtha --0 or lower Naphtha, V. M. and P. (Mineral Spirit) --40 to 20 Paint and Grease Eradkators 0-80 Paint, Bmnce or Gold 0-70 ' -O.to 80 Acetic Add 104 Allyl Alcohol 70 Amyl Acetates 77 to 91 Amyl Alcohols 91-109 Aniline 168 Benzaldehyde 148 Benzyl Chloride 140 Brandy 84 Brocaobenzene 149 Bronzing Liquid, below 80 Butyl Acetates 64-72 Butyl Alcohol 84 Butyl Alcohol (Iso) 82 Butylbenzene 126 Butyl "CarbitoT 172 Bufyl "CeEosolve" 141 Butyl Ether 100 Butyl Lactate 160 Butyric Add 170 Butyric Anhydride 190 Bntyrone 120 Carbon Remover Liquid Chlor Benzol 82 Chloroethyl Acetate 129 ^--50 lower than 20 )--18 (Iso) --22 Propyl Formate (normal) 27 Vinyl Acetate --18 1 Vinyl Ether --20 Cleaning Fluid **Coal Tar light OH Coal Tar Oil Creosote Oil 165 Cresol --0 to 178 Crude Petroleum Deeafin 136 Decane 115 , Class 2--Liquids in this dais have a flash point above 25* F, closed cup tester, and below 70 degrees F,, dosed'dtp tester. Diacetnoe (Acetone Free) 131 - , Dibutyl Ether 77 Dichlorethyl Ethel* (Chlorex) -172 Diehlorobenzene 150 '. ~ , Acetyl Chloride 40 - - Diethyl Carbonate 77 ' Aluminum Punt 0-70 \ . Dimethyl AnBine '145 - - Coattesr ShcnriB-Wniim Company Figure 3. Belts equipped with metalbrush static electrioty collectors. (See paragraph 33,) \ Distillate Ethyl Acetanilide 126 Ethyl Alcohol ft Water (more than 30% water) 72 to 144 Ethyl Butyl Acetate 135 Ethyl Butyl Alcohol 137 Ethylene Diamine 93 Ethyl Glycol 104 Ethyl Glycol Acetate 117 Ethyl Lactate 115 Fish Oil 150 Flavoring Extracts Formaldehyde 130 No. 1. Fuel Oil 100-165 No. 2. Fuel Oil 110-190 No. 3. Fuel Oil 125-200 No. 5. Fuel Oil 150 and over No. 6 Fuel Oil 150 and over Furfural 140 Fusel Oil 108 Gas Oil 150 and over Hexyl Alcohol (n) 145 Kerosine 100-165 Lacquer 0-80 Leather Dressing Liquid Metal Polish Liquid Stove Polish Methyl Amyl Alcohol 113 Methyl "CeJlwohre" 107 Methyl "Cellosohre" Acetate 132 Methyl Glycol 97 Methyl Propyl "CarbinoT 105 Nitrobenzol 190 Octyl Acetate 180 Octyl Alcohol 178 Octyl Aldehyde 125 Phenol (Carbolic Add) 175 Fine Oil 172 Pine Tar OS 144 Propylbenzol (a) 86 Pyroxylin Sotsdon 80 Signal Stoddard 'Sdtrcuts ~ (Naphtha High -Flash) -Iglsaftcr-higher Tohn&*'WjH&'-' Tmpen6nera^*;- ' Turpentine 'SmBMIb 90 XVarakti * . WM&ey * - Wines (Sherry aeB Fort) -129 J- . - MyTe below 3E* F depending cm epeet- 1 ~jjtyt be below SO* T dependln* on epect-^ |T*-. M. ' -* RSV0030396 4--SP.P.-34 SAFE PRACTICES PAMPHLET MO. M t .. >. f O ,, '1* tZ. The above brief fist fives the there Is no danger of an erplosloc; also -. i ptacfic* effect on the range of A points of a number of 6e well if It Is above the qpper flask R wfll a*' However, * anted in Known gases, vapors, and flammsMe propagate flame. Ink if it it shove the crease intempetatnre wfll have an ap- liquids that are liable to cause an - qpper limit and lata becomes dButed , iTo propagate flame, the plosion. They were taken from die Na with air or oxygen, it wflB hi rifldi 1 ft M&MiejjjM 0m next to the burn tional Fire Codes for Flammable Cases, published by the 'Protection Association the flammable range. In most industrial ing W* J&IBk tW&L to <* situations where then are flammable Mratare^g^M^fcffaae It Wfll bunt gas or vapor hazards, the conocntratinai late flami|j^MOifl>aed layer is futual Data Sheet No. wfll vary from traces ap through the riready b^Mgsb^ne degree, a smaller 1% the Associated Fac- full range of flammability to the wane amoiastofhNffjjaatobe supplied from The flash points jpvea b of the vapors where 6m amounts may the banikglayer and thus flame propa (he lowest shown in the reference material; reference should be made to these sources for flash points of materials not covered here. It should be borne in mind that flash points of any of the substances given may vary according to the purity. 'Where there is any doubt, either a test should be made to get accurate data on the sub stance used, or the lowest flash point given should be accepted as the prob able correct value. be above the upper range of flanunsMity. 14. Any variation in the annul at air present in a mixture win, of comae, affect the ignition point of the mixture. When the partides of a gas are widely separated by an increased amount of air, the mixture is said to be too lean mad flame will not propagate. While ignition might occur, it will not be supported since the partides of gw or vapor are too far apart for the initial flame to ganda will be aided. TVs dewdoe of tetoperaftue decreases Che lower Emit of flammahffity and raises the upper 17. limits of matures of gases and vapors. Wbea two or more flammable gases or vapors are present in a mixture with air or oxygen, each gas makes its owa contribution to the flammability or eqWM%el the mixture. Each may he presere ia amounts below its lower Sait bat the total of the contributions 13. Flammable limits. Each flam mable gas or vapor has two rather defi nite limits to the proportions in air that wiC propagate flame and become ex plosive. The "lower flammable limit" is the least amount and the "upper flammable limit" is the maximum spread. Conversely when the mixture is deficient in air, the mixture is said to be too rich. Here the gas or vapor partides crowd one another so doaeiy that there is insuffirient oxygen to s*>port combustion. Between the upper and lower Units of the explosion range of each may create an explosive atmos phere. A rather supple formula for esti qifig (he probable explosive character of a mixture from the amount of each gas or vapor and its lower flammable limits was suggested by Le Chateiier. Investigations lave indicated teat tips amount that will propagate flame if ig nited. Here it should be noted that the terms flammable limits and explosive limits are synonymous and each is fre quently used although most references use the term explosive limits. The range of concentrations of gases be tween the lower and upper limits of the particular gas or vapor is its range of flammability or explosibility. When the amount of gas or vapor is below its lower flammable limit and a source of ignition such as a flame or spark is present, a small amount will be burned in the immediate vicinity of the flame or apaxk but the flame will not be arifpropagating through the body of gas, but wQI be extinguished. When the igrddngSMptt is removed, the combustion dfiher words, there is no : away from the Ig- whep fie ma- are found ali the graduations of slower rapid combustion. This provides a com monly used basis for control of explo sions, by maintaining the required de ficiency of oxygen in the mixtures. 15. The slight normal changes of atmospheric pressure have Attic effect on the explosive range of gas or vapor and air mixtures. Marked changes up or down do, however, cause some change, this change being specific for each mix ture. Decreases in pressure for the first few hundred millimeter bdow 760 only minor variation but as the is further decreased the explosive narrows until at a sOfBdeatiy fcwfnaasure the lower explosive bait ephstides rrith the upper Emit. Here noflame trill propagate. Increased praeure, oa fie other hand, does not always imiraaae^flK explosive range, ha " range is narrowed so that a "' formal* is correct lor mixtures of hydro gen, carbon monoxide, and methane taken two at a time or all together, and for water gas and coal gas, also for the simpler paraffin hydrocarbons including natural gas. On the other hand there are some stalked deviations with vapors such as ether and acetone. The formula is thus useful when its applicability has been proved but must not be used indis criminately. In certain cases the law wfll not have commercial application since the normal variations In the major constituents at a mixture may make H uimenemiy to consider the rnffiaenee of minor constituent. Far the purpose of fUi pogfiflet It la srffionre to knbw a gesenl sgatian of life nature -of MMI'fc upper flammable lim win propagate at it, fbeees S&ne combustion If oxygen is aifll not do bo at a present fa* the lame w3Z aat he srif- additional details oa tin propafflflag. In riB proportis'he*wcen the lower and the ^pper SariM the mix ture upon jgdtSaa at me gdfat nOI sure oa common gases IwfUmnuiUBjf gf Gases mE"lVapm^_ --------akrfltw. f sameat Mm vqpors'yiheB pfapf* propagate flame throughout fhe.erdfae mixture. If a gas or vapor in tflriilag*. bdbw the lower Sadi * * Ia1 ' ** ' -' RSV0030397 0 INDUSTRIAL EXPLOSION HAZARDS S.P.P.-34--S % compound vary with the randKIons wf experiment, the values given in (he tafete >ave been selected (Bureau of Mines bulletin 279, 1939 edition) ts those that would be most generally representstive of the conditions of industrial situ ations- Small variations an of no con ?aMei Summarised Data oa Looks of flammahgjty of Gases a . Vapors Limits givd in Per Cent ty Volume. Moisture Free OA*- or vapor ---------- - Qqrgn poroantac* below no mirturs is sequence snce in the control of explo sion V~~afd a considerable safety factor should I Temperature. Refermade to the Igniting a gas or vapor in air, with the understanding that it is the minimum temperature required to initi ate an explosion. While it is true that gases and vapors have rather definite temperatures at which they become ig nited in air, it must be remembered that in each case the recorded temperature of ignition is also closely related to the exact conditions under which the par ticular value was obtained. Ignition temperatures are not definite physical constants under practical conditions. The temperature that will produce ignition of the same gas or vapor may vary considerably for different means of ignition, particularly if they are heated surfaces. Catalytic effects are very im'ortant, particularly those of the type at accelerate surface combustion at comparatively low temperatures. This causes an increase in temperature of the igniting body, which in turn speeds up the reaction so that the surfaoe tem perature continues to rise until it be comes high enough to ignite the mixture. 20. The means by which explosions of gases and vapors may be initiated vary considerably with the particular gas or vapor dealt with and the condi tions under which the explosions occur. With acetylene; for example, only pres sure is required. With hydrogen and chlorine, strong light is sufficient Mix tures of chlorine or bromine with acety lene require no initiator. Same gam such as phosphine ignite spontaneously and umneffiildhr an contact with air. Carbon dMHljjk vapors ht air can he ignited at temperatures below sterna huet^Rbwevcr, for the ruajoitty of gases and vapors, twpperatiaea of around 250 to SOD* C. and frigfrer are required, depending on flat partinalar substance, in addition to oerature of (he igniting gases or vapors lequbaa nrrtato -,-jintity of energy. For Ixrww Vpgte Acetaldehyde ......... 40 Acetooe ...................... 255 Acetylene ..................... 25 AUyl alcohol............... 2.4 Ammonia ..................... 16 Amyl alcohol .............. 12 Amyl chloride ............ U Amylene ...................... L6 Benzene (Benzol) .... 1.4 Butane ......................... 155 Butyl acetate .............. 17tt Butyl alcohol ............. 1.7 Butylene ...................... 1.7 Carbon disulphide----- L25 Carbon monoxide .... 125 Croton aldehyde ........ 21 Cyclohexane ............... 15 Cyclopropane .............. 24 Decane ........................ .7 Dicbloroethylene ........ 9.7 Diethyl peroxide........ 255 Diethyl selemde.......... 25 Dioxan ........................ 20 Fitihnn ................ .. 32 Ethyl acetate............... 20 Ethyl alcohol ............. 35 Ethyl bromide ........... 6.7 Ethyl chloride ........... 4.0 Ethyl ether................. 155 Ethyl nitrile ............... 3.0 Ethyl formate.......... 27 Ethylene ...................... 275 Ethylene dichloride ... 65 Ethylene oxide............ 3j0 Furfural ...................... 21t Heptane ...................... 10 Hexane ........................ 12 Hydrocyanic add .... 54 Hydrogen..................... 40 Hydrogen sulphide.... 45 Iso-Amyl alcohol.......... 12 Isobutene ..................... 15 Iso-Butyl alcohol.......... 15 Isopentane ................... Iso-Propyl acetate----Iso-Propylaknbol .... Lead tetraethyl............ 15 15 24 15 SO Methyl acetate............ Methyl ** ............ M/C-sQl-9---1A D. f_O1-BUtJK. . Methyl butyl ketone... Methyl chloride .......... 35 4.7 35 12 50 Methyl cyclitiryaur ... L2 Methyl ethyl ether___ 20 JKiQyi flQQI BCvBMk U Methyl formate ...... SO Methyl propyl Icetesm.. ts . *- ^ Am uwfBB-j t^y4tB- s^ * *-%' m 15 PQQftlflfc * a-- Ftypaae * U, 20 57 13 to .. 27 ,. ,, .. 67 &4 ,. ,. 90 50 74 155** 15 105 ., 128 , ,. 22** 125 115** *19 115 14.8 48 . 165** 29 15.9** 80 ,, 60 6.9 40 74 455 ,. 8.4 75** V .. a 155** *96 K5 ** 0 a* m. x. 23" ` W* ** - * ' es * 1 % 1 `- (CaOkp* ' -- levs .* * *. 4* 15 79 . #,, . . .. . . ## , , ,, , . . . ,, , . ,, , . ,, . , ,, . , ., 85 ,, 245 63 ,. ,, . ,, . .. ., .. f. ,, 4.1 SO ., ,. ,* ., ,, 21 82 .. .. ,, .. 29 80 ., .. .. .. ,, .. , . ., ,, ., ,, 4.0 94 .. , ., %* ** , , . ., - * % u 59 - * * HU t * tffl ''wrt <* * * v<r " 1 1/ v-y> t .vr? ' "Tf' j * , ? <' .a VS?* "fUS* 13-5 15.6 12.1 ' 145 5.6 5.9 114 13.4 10.0 11.7 11.9 145 si 5.9 12.1 144 iii M4 HI (uap Lii 11 j m IPRWpMIUmil, *i RSV0030398 6-~S.PP.-34 *w SAFE PRACTICES PAMPHLET Nt. M ' Table 1 (Continued from page 5) Units m sir, par eset Limits in oxygen, par Met Lower Upper Lower Upper .. .. .. promtito dkhloride .. Propylene oxide ... .. Pyridine ................... .. Tin tetrametfayl ... . Toluene.................... . Vinyl chloride.......... . Vinyl ether ............. .. Xylene ...................... . L8 23 20 3.4 2.1 10 19 L3 4.0 17 1.0 At 60" C At 100` C. 80** .. 11.1 143** 213 12.4 . 67 220 27 6.0 , . 2.1 . * . . . 10 tAt 125' C ., .. 53 .* . .. 85 Oxygen perrontaxe Mov which no afiias la flammable Nitrogen aa diluent of air Chiton dlostd. ta diluent at air .V ... 113 .*. ... ... ... ... . ... ttAt 30* C a aw 14.1 ... ... . .. .. ... trie sparks, even though at high tem perature, can be so small and of such short duration that they do not bum enough of the gas or vapor-air mixture immediately surrounding them to start a general flame propagation through the mixture. However, ordinary sized sparks and small arcs such as are usually pro duced by electric switches, flame of matches, etc., are sufficient from a prac tical explosion hazard viewpoint to im mediately ignite any flammable mixture of a combustible gas or vapor in air. 21. Volatility. The amount of vapor that will accumulate in the air above a volatile liquid is dependent upon its vapor pressure. Vapor pressure, some times called vapor tension, is a deter minable physical property of all liquids and for a particular liquid it is affected only by changes in temperature. Vapor pressure values as given in standard tables usually are calculated at a tem perature of 0 C. and 760 nun. pres sure (atmospheric pressure) hence, the vapor pressure at normal workroom or higher temperatures will vary. When the ak xxcr above a volatile liquid is satnattKLjiat when all the space is oqqgjHnpf vapor, then the vapor is lb maximum pressure at that aHnwtuse and no more vapor wiS dwpktt hurt is useful in deter mining the maximum amount of vapor that cordd he presort if the air wn saturated under the particular tempera ture and use of the substance. Another physical property of nhe to detetaafeing the relative volatility of snfwtaam is their hoflmg points. These, too, can be found in standard reference tables. 22. Surface evaporation. An impor tant factor related to evaporation is the amount of surface exposed from which vapors may emanate. Evaporation takes place at the surface and, for example, if a gallon of liquid were exposed with a liquid surface of but one square foot the rate of evaporation would be roughly only one-tenth that of a gallon of liquid exposed under conditions of 10 square feet of surface. This is very important from a safety standpoint and points to minimizing surface areas as a means of control of hazards. The temperature is also very important as the potential rate of evaporation increases with an increase in temperature, owing to the increase in vapor pressure. Many substances will not give off enough vapors at ordinary temperatures to be explosive but will give off explosive amounts if the tem perature is raised. A limiting factor exists in that the space over the liquid will eventually become saturated with vapor, especially if the qsace is con fined, as In a portly filled, closed con tainer. Thus at any given temperature a condition of balance is reached and evaporation no longer occurs. Materiah In mist form present very favorable conditions for rapid evaporation, as fire surface exposed is tire total of the sur faces of the individual purffdes of mist ^Preventing Exptaioa 23. fuqfiosiom can be prevented (1) by preventing the development ef ex plosive mixtures and (2) hy preventing the ignition or setting niff of the explo sive mixture. Important steps in carry ing wt these measures are: a) a thorough survey and inven tory of products and processes to de termine the possible ordinary and aci ai explosions or fires. possibility of occurconditons to a inch common proceitutiou of non-explosive : less explosive products: isolation of dangerous products: improved safety is handling and use of volatile ma terials; good local and general ven tilation; use of closed containers; use of inert gases to suppress flammable conditions and elimination of sources of ignition. (Cognizance should be taken of the toxicity of the materials used. In some cases it may be pos sible to substitute a less toxic as well at a less volatile material.) c) Waking thorough inspections at sched uled intervals. d) Designing new plants so the effect of an explosion will be localized (Explosion resisting partitions should separate hazardous and non-hazardoos departments; all stair wells and elevator shafts should be completely enclosed, all pipe holes through walls and Bomb should be sealed and any other floor or wall opening should be dosed to prevent the propagation of flame beyond the immediate site of the fire or explosion. Large outside window spaces should be pro vided and scored glass should be used to relieve the explosion pres sure Vent pipes should be installed ) 24. Common ignition sources. The ignition of an explosive mixture of gas or vapor with air may be prevented by the proper control of flame, fire, fric tion, sparks, static electricity, electric arc, excessive heat or spontaneous igni tion. 25. Smoking. Many explosions have been caused by smoking' and the tinrow ing aside of lighted matches, cigars, pipe adxes, and qgarettes. Smoking, and the lighting or carrying of matches, cigar filters, and attar flame-producing arti cles, sboMte prohibited in every plant are In locations ; f bn wcptoakai is aatyhe advisable to Ifey for men to AiHeW^f hwng j ~ At Are trenrea to arnreaqp or zooms snare QnOHHv reQBHttBDGB SB DpflNBw tiutgar |pa ttmtti lx tibg df thelasrefl, warning against tlx enrty- MM ^ wm RSV0030399 INDUSTRIAL EXPLOSION HAZARDS S.P.P.-3+--7 Table 2 Approximate Limits of Flammability of Some Industrial Mixtures of Gases and Vapors in Air at Ordinary Temperatures and Pressures, per oeut J, Gas or vapor Lower Upper Limit, by Limit, by volume volume Benzol Aflbauwi) .. i.i Water 41'-'-...... Nitiirrfnt ... 4* DhnmdiPljF fu .,. . W BbistdNptoe gas..... 35 86l5 55 to 70 133 31 74 The limit figures in Table 2 apply only to particular samples of mixture. By the use of Le Chateher's law (see paragraph 17) the limits of samples of similar mix tures can be calculated. Much more information is given in Bureau of Mines Bulletin 279, 1939 edi tion, on the conditions under which the values given in Table 1 and 2 were ob tained as well as data on the limits of other gases, vapors and mixtures. The information pertains not only to limits when the gases or vapors are in air but also to other atmospheres, such as those that have either a deficiency or enrich ment of oxygen, or the presence of car bon dioxide or other gases that have a suppressing effect on the propagation of flame. ng of matches or open lights, and pro hibiting the entrance of unauthorized persons. 27. Open flames, lanterns, boilers, etc. The use of open flames, such as lanterns, gas jets, oil lamps, torches, or candles, should not be permitted in plants where there is an explosion haz ard. Neither should boilers, furnaces, or dryers with open flames be installed in those portions of the plant where explosive substances may be present. Gases and vapors may be carried by drafts to a flame several hundred feet away. Heavy vapors may spread across a floor or table to a flame and may flash back and cause an explosion at the point from which the gas or vapor originated. Boilers aad other fires should be in separate iNpffiags without connecting bauds enkSosed walkways and out of the Bae'jplMch explosive gases and vapon1||* travel or be .blown by preuaHsgPwNlt. Hie plant layout should coafenn with state or local re quirements. Welding operations age a source of open flame. Before any weld ing or cutting is done, systems should be purged of all flammable liquids, 'apors or goes. Tests using'a flam mable gas indicator should be made to Brush Contact on Cylinder Shaft icier Bin, or Material. Name Star Material " flaacarr *r*r V.L B 1 a Brush Holder C l Brush 0 1 Brush Srrihs irxrx* Hand Wood nr Corner STEEL c 1 Wire Sorrort r 1 Fulcrum Fa W.l 6 1 Lead to Ghoimd-inskated MaHG Corner H 1 Snhs Bolt *'*3- J 2 Machmc K l RHStove b 1 mm War Figure 4. Bruih contact for removing static from Saftiaf. (Sea paragraph 35.) determine whether or not it is safe to weld or cut 28. Fire hazards. Fire is a serious hazard in practically every industrial establishment, but it is particularly dan gerous in a plant where there are flam mable gases and vapors because any ac cidental fire is almost sure to cause an explosion. Accordingly, in such a plant, every possible precaution should be taken to prevent fire and to extinguish it immediately if one should occur. These problems are discussed in other sections of this pamphlet; also hi Safe Practices Pamphlets No. 24, "Fire Ex tinguishment," No. 31, "Fire Causes and Prevention,'' and No. 36, "Fire Bri- 29. Danger signs on tanks. At tanks and at the entrance to alt buildings or rooms where explosive substances are stored, used, or generated, danger signs should be posted, telling of the hazard, warning against the carrying of wiHdm or open lights, and prohibiting the un trance of unauthorised persons. (See American Standard Safety Specifications for Industrial Accident Prevention Signs Z4S.I.) - ,, 30. Friction sparks. Some tests have indicated that friction sparks might be produced by striking two ordi nary pieces of steel together, do not ignite gaso&ne vapor-air mixtures, but until more conclusive data have been developed regarding the possibility of igniting various vapor-air mixtures from the friction sparks caused by different types of metal, it is desirable to avoid sparks of any kind in locations where combustible vapor-air mixtures are likely to be present. In attempting to avoid friction sparks, care must be ex ercised not to introduce conditions fa vorable to static sparks. (See paragraph 32.) 31. In some operations, the danger of sparks can be somewhat decreased by the we of "non-sparkhag" tools made of a hardened copper alloy, but these must be regularly inspected to make certain that particles of inn or steel are not nriboddart 3a the striking sur- Iddesparks Trill not be of the copper off, they may be created *n**al being struck a1 32. Stafl^HPMby. Static electric ha a numhn f wgys, eadhuf which mat be guarded gainst If fact aan apkaaot are to be prevented* in ntinoq^bena c--ifxwwwstrfl vrtflb ns and ah oruapor and ak ndx- 4 mmmm mrn RSV0030400 8--SJJ.-34 SAFE PRACTICES PAMPHLET MO. M motors and other electric equipment should be' fastened outride those towns where there is an ignition hazard. kctrfc fangs, ffr earn(fle, nay be installed i so as to throw light .cqpinsion-proof win- of any kind rooms, the sof a type that is iniby each an organiza tion as Underwriters Laboratories, Inc., and tie installation should conform to the reqtaxements of that section of the Nathxud Electrical Code relating to Hazardous Locations. Likewise, port able lighting equipment such as handbugs and flash lights should be of approved types. 9) Figure 5. Exploiioo - proof electric inRslIstian. Butane gas pump iin i lugs minufaC' ruring plant. (See paragraph 47.) tures. Static charges are built up when any two dissimilar surfaces are rubbed together, when two pieces of silk are rubbed; where liquid passes through hose; when liquid is violently agitated in a tank or by belt running-over pul leys. This charge as soon as it builds up a sufficiently high potential will dis charge to the nearest grounded metal. It is this discharge which is dangerous. (See Safe Practices Pamphlet No. 52, "Static Electricity.") 33. The best precaution against static electricity sparks is to keep all conductors bonded together and grounded. AH machines, motors, belts, pipe lines, tanks, or other permanently located metal objects or portable elec trical tools or devices should be elec trically grounded. In some plants two separate grounds are provided an belts, pulleys or shafts so that in case one should Mtiie other w31 prevent budd ing charges. These grounds ahodi`^Bwlced frequently to make certain V||e resistance of the tir- cukbMpi' 34. In drawing or pouring gasoline from one container to mother, ft is ad visable to keep the two amtaben hi contact with each other or to attach a chain to the pawing coufafae wm maintain this contact This prevent the formation of static spark*, and conduct away or equalize any static charge that may otherwise cause igni tion of vapor. In making repairs to pip ing systems, wire jumpers should be used when disconnecting unions and couplings, and when cutting pipe. 35. Sparks from static charges on belts. On power transmission belts, static charges may be eliminated by ap plying belt dressing that has been mixed with aluminum or bronxe powder or with a mixture of equal parts of water and glycerine. The surface of the belt trill then conduct a static charge and lead it to the earth through a ground wire connected to the shaft bearing* or shaft hangers, or to brushes on the metal pulleys over which die belt runs. In many installations, belts can be replaced by spur or metal gears which can he encased and operated in oiL Whenever there Is an ignition hazard, both the moving and stationary parts MB machinery should be electrically grounded. (See Safe Practices Psrnptleti No. 29, "Electric Equipment in farias- triri Plants," wadNo. 52, "Static Electricity.") (See Figures 3 and 4.) #> 36. Stray currents. Where' stray currents may exist, and pipe Uses sae to be parted wring can be prevented by bonding across Ok proposed gapha- fore the pipe line is pasted. - 37. Electric ere. When prurlirilM^ all electric wiring, switches, cjfl-oa. 38. Heat. While metals not heated above black heat are generally consid ered unable to cause direct ignition of a mixture of gas or vapor, there are many vapors such as carbon bisulphide, amylene and many hydrocarbons of the heavy molecule type that are ignited at temperaiiires below a viable red heat Abo, excessive heat may ignite other substances, and the flame .or spark thus produced may ignite an explosive mix ture. See the preceding discussion of ignition temperature. \ 39. Hearing rooms. Low pressure steam or -hot water heat is the one form of safe heating in rooms or buildings where there are certain explosive sub stances. Low pressure steam is usually available. The pressure in the mains should not exceed 15 lbs. per square inch. There will be a drop in pressure in the feeder pipes so that the pressure at the radiators will be somewhat lower than 15 fas. per sq. inch. The surface temperature of the radiators will vary therefore from a high of 250.3 F. at 15 fas. per square fadt to 112 F. at atmospheric .pressure. These tempera- tuns should 1>e carefuOy considered m planning fasting system since carbon Stkor and ether oaletMe rot- foutoct noth surfaces The beat at there the indirect type, to a predetermined the room. Tem- he doreiy at any part dt screed 120 f* -A* jWwiWl tiy? temperature It Hkriy to rear* * dangerous point, ifecsrffiqg jgnottrias may be used and \ V>- RSV0030401 INDUSTRIAL EXPLOSION BARA S.P.P.44-* automatic shut-off valves and alarms should be installed. These can be ar ranged to sound an alarm ulise da tofentme reaches a predetermined Galt 40. Ignition by overheated bearings. Overheated bearings can ignite explosive or flsmralMe vapors. Bearings, there fore, dgKfcawe the beat of care, fe- Tlabricatioa. Where nAr t used. It is advisable to of the self-offing type. In mas^Paats, automatic alums see installed to sound if journals or bear ings become overheated. 41. Ignition by belt fires. Friction of belts is liable to start a fire and thereby ignite an explosive or flammable gas or vapor-air mixture. Belts should not be permitted to rub against each other or against other objects. Neither should they be allowed to dip around pulleys which, because of "freezing," excessive load, or other causes, will not revolve. 42. Ignition by the ran and by glass lenses. Defective window glass, bottles, or other articles of glass through which the sun shines may act as lenses and >tart a file. Bottles and other articles should be set out of range of the sun, and the windows can be shaded or painted. 43. Spontaneous ignition. The possi Courtor Ombr-FUce-Foatei "HuSoot of Hie howlo" Figure 7. Well-derigned oil house. Walls bid, store or concrete; Roof--concrete whboot exposed metal; Floor--concrete chained to one point, drain to sewer through properly designed trap or. oil sepa rator; Door Sill--raised about 4 inmea; Door--metal-covered and hung os Iran frame; Windows--metal frame and wire glam. Vent pipe extends from door through tool. (See paragraph 52.) bilities of spontaneous ignition or de composition of gases and vapors has been referred to previously.. In general, none of the mixtures of common gases or vapors with air will ignite or explode spontaneously. On the other hand, dust accumulations or other substances ffice rags containing vegetable oik may ignite spontaneously and in turn ignite an explosive or flammable mixture or a flammable liquid that may be present. Spontaneous ignition is the result of a chemical reaction between the oxygen of the air and the material ignited, or bacterial action, or both. As in most chemical reactions, beat is produced. The heat causes the action to become more rapid until the point is readied at which the material bursts into 1 the flame, in turn, may manganatc and nitric arid which will react with organic matter and produce fires, must not be stored near explosive or flammable mixtures such as gases, vapors and liquids. eve Atmospheres 45. Ttdmg and piping. The use M rubber tubing fa place off .metal pipe riKMtid be pwMbltod; robber deterio 44. Ignition by fire-producing chemi rates with 9ft, mechanical abrasion, cals. Spontaneous ignition, especially in beat, and when is contact with moisture, dust and rags contahfing vegetable oSs, Oti, wadtT^>jljj%iflg, or tf abeefatt^y has undoubtedly caused some toes tied fesdbfe tiffifeg, explosions, but many ilUmiw haveVeen ati attributed to gnataneous ignition ahm), if the truth were known, (hey hne nffiber may mast he*afforded bees caused by a lame, a r en- mdnptoK.-Qto cesshe heat from some other M a avoided, com Acrid apd repaired at ..&K catch fee an egneuw torirajfito easel) tttfeffc* contact with nektoni, and strong *- or sari V unOril on k ri 4* ageres Nti i MAuBtaa par-, moved -to,*** fe n tifatant - ' '. .V ; 'S''*,!'..'-. ' S ' .A RSV0030402 10--SJPJ>.-34 AFE PRACTiCBS PAMPHLET NO. H where there is no danger of igniting the gas, great care should be exercised in Jodng the necessary valves and remov ing aH traces of the gas before starting work. Other points on gases are dis cussed in Safe Practices Pamphlet No. 31, on "Fire Causes and Prevention." 46. ene is discussed in Safe PracticetaRamchleta No. 23, on "Gas and HflCKWeMing," and in No. 95 on "CoiigwHI 'Cases used in Industry." 47. wmaShmetMS commercial gases. A number of commercial g&Ses such as propane, butane, blau gas, pintsch gas, and others are used for lighting, weld ing, and other purposes. These gases should be handled with precautions similar to those observed when handling other combustible gases. (See Figure 5.) 48. Mechanical rupture. Compressed and liquefied gases and vapors are used extensively. Great care should be exer cised in storing and handling containers for these substances; heat or severe blows may cause them to burst with explosive violence. 49. Flammable liquids. Gasoline and other flammable liquids should always be stored in closed containers to prevent endue evaporation and the mixing of their vapors with the air. (See Indus trial Safety Series Pamphlet No. Chem-1 "Pipe Lines and Tanks as Causes of Accidents" and Safe Practices Pamphlet No. 63, "Storage Tanks for Oils, Adds and Dry Materials.") 50. Skipping containers. In shipping flammable liquids, tank cars, binds, cans, and other containers should be used in accordance with the regulation of the Bureau of Explosives, 30 Vesey St., New York City. After portable con tainers are emptied, taps, plugs, and bungs should be tightly replaced im mediately. Some users dean out port able containers before returning them to the manufacturers- It should be recognixed thatapentainer that is empty with only eeiiLtf He whffle liquid adHhe to the inside may be taan^mimm bum the of eqbflp He container Hum tfe contuhaerWea fllled with liquid, owing to the huge volume of explosive ndxture Hat It enrtatoi See Safe Practices Pamphlet No. Fd. 2, "Drums m$ Sarrab.M See abe Industrial Data Shrek No. D-Qem. W, **Dras ad Other atahie Containers Which Have SAd ^lammaMe Substances" aaflNa. D-lkt. 1, "Removing Flammable Vapor Iron Gasoline Storage Tanks." 51. Storage tanks. Large quantities of flammable liquids should be stored in outside tanks preferably below pound and with a barrier to prevent the liquid from flowing into buildings, basements or sewers in event of a leak. The maxi mum capacities of both underground and above-ground tanks depend upon their proximity to buildings and other tanks. Where explosive mixtures are likely to be present in the tanks, the vent openings should be designed to prevent flame propagation through the vent. Safety diaphragms may also be employed to relieve excess pressure. Local ordinances should be consulted for data on clearances, capacity and con struction specifications before work is started on installation of tanks. For details on capacities, material and con struction of tanks, foundations, ground ing, dikes, vents, pumps, piping, fill pipes, freeing tanks of flammable and explosive vapors, repairs, etc, see Safe Practices Pamphlet No. 63, on "Storage of Flammable Liquids," and Industrial Safety Series Pamphlet No. Chem. 1, "Pipe Lines and Tanks as Causes of Accidents," as well as the Regulations of the National Fire Protection Asso ciation. 52.. Oil rooms. Under certain con ditions it may be necessary to provide an oil room inside a building for the storage of limited quantities of flam mable liquids. Such oi! rooms should have walls, floors, and ceiling made of brick or concrete, 8 inches thick, or of reinforced concrete 4 inches thfck. All openings into the room should be pro vided with automatically dosing fire doors; windows should be of wired glas in metallic sash and frames. To prevent the accumulation of vapors in pits and other confined spaces, inside oil rooms should not be below the grade line dor immediately above a cellar or base ment. Door openings should have ribs raised 6 inches. The floor should -he water-proof and this water-proofing ex tended up the ride walk at least J inches. Rounded corners that can easily be washed and cleaned should be pro vided. The floor should pitch to a drake $* leading outside to a cetdi ban <r terminating at a point where proper pracantfons have bare taken so He wrouaffing property wifi not endangered. No drain connections dtoflld be made direct to the sewer. Figure 6 shows a well-designed oil sgmntor. It is neces sary to dean oat an oil separator at regular intervals If this is not done the separator wiD become filled and .will then fta contents into the sewer. In periodic visits to dean out oil separator^, 53. VentSSBm. 'Proper ventilation should be provided lor oil rooms. No system of ventilation is applicable in all cases; the method adopted necessarily varies with the nature of the gas or vapor to be removed and depends upon whether it is heavier or lighter than air. Ventilation may sometimes be secured fay arranging screened openings near the floor or near the ceiling or both. It may be necessary to provide a general system of exhaust ventilation by installing fans. In such cases, care mast be taken to prevent the exhausted gases or vapors from re-entering the room, or from en tering any other place where their presence would be dangerous. Fans should be driven by direct-connected ex plosion-proof motors or by belt or shafting if the motor is not of the ex plosion-proof type and is located outside the danger zone. An exhaust system with hoods which trap the gas or vapor at the point of origin is likely to be more satisfactory than general room ven tilation. To assist in the solution of ventilation problems, certain gases read vapors are classified as follows: Lighter thin Air Acetylene Fit gas (firedamp) Carbon Monoxide Jtlnmmarinff gaa Hydrogen Alcohol Naphtha Gasoline Fad OB Heavier than Air ItUauiaating oils Petroleum Vanufc Aaqyl acetate Carbon hinriphidr The vapor density of a gas, if stand- artfiaed qgn&ntjdr m 1, may be used to determine ~ If its denrity is leas Jtykter Han air, if more t For fsrthar Pamphlets i" and No. Storage cabtnot more then Bqwid. bat no hold H ,* ,v ( C ' w*\ inli Kjeni<v$*jB|pfqi RSV0030403 INDUSTRIAL EXPLOSION HAZARDS S.P.P.-34--11 of at least No. 18 gage sheet iron, with doable walls allowing a 1*4 inch air space. The door should have a three* point lock and be kept dosed when not in use. The door siU should be raised at least two inches above the bottom of the cabinet. Some cabinets of this type are vented and where it is practicable they aMnfataced outside the building. (See PUK*-) 55. MtsMe wheeled tanks and con tainers. n may sometimes be necessary to cany flammable liquids in portable containers. Portable wheeled tanks and safety cans have been designed for tins purpose. No portable wheeled tank should exceed 60 gallons in capacity. The tank should be of iron or steel, at least 3/16 inch thick, with all openings located at the top. Wheels should be rubber-tired and tanks hung so they are not likely to tip over. Liquids should be drawn from the tank by means of a tight-fitting pump. Whenever practi cable, these tanks, when not in use, should be kept outside the building; if they must be within the building, they should not be placed near radiators or other sources of heat. They should be located that they can be removed ..uickly in case of fire. A brake and handles at both ends of the tank are desirable 56. Safety cans. To minimize the hazard in handling flammable liquids in portable containers in plants, safety cans bearing the label of nationally recognized testing laboratories should be used. This suggestion is not intended to apply to the delivery cans used by oil companies and carried on the side racks of trucks. 57. Distingsdskmg colors and labels for containers and piping. AH tanks, cans, and other containers holding flam mable liquids should be marked or painted in some distinguishing manner. Tins dnaOKatto apply to pipe lines wherever IflK&adlcable. Serious mis takes najtiHyflMided If, for instance, gasoline j^Hpiars are painted red, kerosene fHpiMni green, etc. AH coo- tuners nartoviQg contents otherwise designated ahotid bear in large letters a dcarrjptiac of their contents, lire Compressed Gas Manufacturers Asso ciation has promulgated a rule that all mders of coragreaBcd gas be marked, PHIS CYLINDER CONTAINS-------------." (See Safe Practices PampHet No. fl8, "Identification of Piping Systems. ") Special Utilization of Volatile Flammable Liigukis 58. AH rooms or portions of plants in which explosive or flammable gases, vapors, or flammable liquids are used or generated, should comply with the 'recommendations of the National Fire Protection Association and of local ordinances. In the following sections of this pamphlet, several types of special utilization equipment are discussed and a few safety suggestions applying to each one are presented. 59. Dtp tanks. The handling of flammable liquids in open containers should be avoided whenever possible. If open vats or tanks must be used, their openings should be as small as possible, and wherever practicable a cover should be provided. Covers may either be hinged or slide on trades, and should be held open by metal chahts of approved type, containing fusible links. AH covers should be designed and installed so that they can be dosed manually or automatically when re leased by the action of heat on the fusible links. Covers should be dosed when tanks are not in use. If the cover slides on a track, the inclination of the track should not be less than yA of an inch per foot. Where steam pipes are used in viscous material, care should be taken that the temperature does not get too high (regulating devices) and that the steam is shut off at the end of the day. (See Safe Practices Pamphlet No. Chem. 5 "Pyroxylin Lacquer Manufac ture.'') 60. Wherever practicable, yrntflatian should be by natural means throng vents in the btnlding walls at both the ceiling and along the floor. If mechan ical ventilation is provided, the instaQa- tkn should conform to tire NJFPJL Regulations for Blower and Systems. ,( <1 Tanks dwnM have m lean hr steel overflow pipe leading fco a safe place wink the buMiag or to an anatom tank. Thep^e should be as Straight* poMwre. son pipe bkhu corresjiwM in diameter to the requirement* Salad below and &aM be provided wttk a coarse strainer at-the taidc abuntjH- Csnke tMtal Firr Pro*ectwe AmcUm Figure a. A well-constructed storage cab inet for small quantities of flammable liquids. (See paragraph 54.) 3* pipe for area up to 75 sq ft. 4' pipe for area up to 150 sq. ft 5* pipe for area 19 to 225 sq. ft 6' pipe for area up to 325 sq. ft 62. Each tank should be provided with a drain pipe, the dram to be equipped with a valw capable of being operated both manually and automati cally. Tbe valve openings should be at least 60 per cent larger than the crosssectirtnal area of tire drain pipe. 63. Japammg and drying ovens. Drying ovens used for evaporating var nish, japan, and other flammable liquids should have ample provision made for ventilation and explosion venting. If the drying ovens are heated m any way other titan try steam there should be a ventilating pipe laadmg born tire heatlag mwyrtniMU to a sqfejioint outside the buflffiag. This wffl prevent the col lection |wrajf 1 `i'!1 aim of tire gas or vapor used far beatiag. <4. T3K bnrnbtg apdpmmt. Al RSV0030404 12--S.P.P.-34 SAFE PRACTICES PAMPHLET VO. '* ' in many .garages and other places. In normal situations and processeslid as a The appEdattoi of these practices re volves the use of gasoline in open pans stand-by emergency means for qukflfly quires an understanding of the amount for cleaning grease and oft from metal flooding spaces in which an explosive at it material and' procedures to be to parts. Alkaline compounds, high flash mosphere or a fire ni&et adidtntaOy retuitions. It must point solvent* (Stoddard solvent or ker occur. AS Indicated, the objective & to jriintedout that most of osene), carbon tetrachloride mixtures reduce the concentration of oxygen be m very volatile and flammable solvents, or tri low that which will support a fire or ex can be used with safety plosion, or In case of a fire to create an space kr* `i^HqMts In a confined atinospfcere dan- Where these substitutes atmosphere that will quickly another It , for exam- r should be takeh to avoid In addition to diluting and replacing the, 'substance and men enter (caustic compounds or poison oxygen, the physical properties of the ing areas qr vessels where its vapor is ing from wide vapors; and, too, accumu particular inert substances used have present mosj'be supplied with respira lation of eO or grease in (he cleaning some influence, but the important factor tory protective equipment in the form compound should be avoided. For de is the reduction in oxygen. lit this con dl tJ. S. Bureau of Mines approved Type tails, see Industrial Data Sheet No. D- nection it should be pointed out that an B organic vapor masks to low concen Gen. 13 "Removing Oil and Grease from atmosphere that is deficient in amount trations or fresh air hose masks for Metal Parts," Safe Practices Pamphlets of oxygen to support an explosion will concentrations over 2 per cent. Oxygen No. 25, "Adds and Caustics," No. 14, also be deficient in amount required for breathing apparatus (self-contained) "Goggles" and No. 54, "Respiratory life. In all uses of inert gas for preven may also .fae used if men are properly Protective Equipment" tion of explosions and fires, care must trained. More information on this sub 66 Inert gases. A practice that has become popular for the prevention of explosions of gases and vapors or fires from flammable liquids, is to keep the amount of oxygen below that which will support combustion. In vessels that are open to the extent of permitting air to enter, the suggested practice is to exclude the air and consequently oxy gen by purging or flooding with a gas that will not support combustion. 67. The gases are commonly termed "inert" gases. They may be ordinary be taken to prevent exposure of persona to the atmosphere unless they have ade quate respiratory protection in the tom of a U. S. Bureau of Mines approved self-contained oxygen breathing appa ratus or a supplied air base mask 69. The oxygen deficiency or amount of inert gas hi vapor required to pre vent explosions varies to some extent with the combustible gases or vapors dealt with. Table 1 and Bureau of Mines Bulletin 279 (1939 edition) give information on this subject. ject can fae found in Bureau of Mines Bulletin 279 and in Safe Practices Pam phlet No. Cfaqm. 1, "Pipe Lines and Tanks as Causes of'Accidents." Inspection '71. The large majority of explosion* and fires occur in situations where either no hazard was recognized or where It was thoqght that the hazard was negli gible or that it had been taken care of by preventive means. This indicates clearly the need for thorough surveys at regular intervals for the purpose of dis compressed carbon dioxide, nitroged, en 70. Flame-suppressing vapors. An covering and eliminating potential ex gine exhaust gas, flue gas or products of other practice similar to the use of inert plosion hazards- Three inspections combustion from another process; or gas gas, is to add to the combustible vapors should be made by qualified persons made purposely for purging and flood a nan-combustible vapor that dilutes the who, jn addition to a knowledge of the ing by burning gas or ofl in what are oxygen. A common example is carbon dangers of flammable and explosive termed inert gas-making machines. Each tetrachloride vapor or certain other gues, should have an alert mind to situation must be given consideration halogenated hydrocarbons. These sub visualize dangerous conditions where as to the most economical and satisfac stances may be mixed with the oren- none apparently exist at the moment. tory means of providing the gas; afro bustible liquid to produce a non-flam thought must be given to the use of a mable mixture of liquids. Abu fay reflag ACKNOWLEDGMENT gas that will not react with the system or products which it contains. Among the practical situations m which these gases are used are the flooding of vessels in which teria^ of tn ;.Bammabte Squids; for tanks ef volatile flam ^tpd for pwgiag gas fcflJd- i when lairing them at* repairs ^during repair and for,putting then back join nuroice. .6*. Inert ,gasesaro used not only in a volatile non-flammable liquid'of4fce proper physical properties it w evupe-' rate with the combustible component! and render the resulting vflpor-ufr atoture non-flammable. Another paonedure to using these flame-siqipress^jriboreicals is to <pour ihe chemical-ato fle vessel or space which it % desired 4b render safe from explosion of Kamifllr gases or vapors (hit tright^be \xaOM as residues. This may also he done:in an emecgejny such as A* spflUge dt a flammable Squid iqtaa.'Sfffity mwihnfc. T**t PynpWat was. revised by Joist M. Rode* T>irectorf Industrial Division, National Safety CirtmcH, with the assist ed of s special `committee of tokkk W.',, Twit .iparjCiairman. The first submitted for of fins special Safe Practices The astiattemce ly acknowi!iwu approved by of Ok Nol.r ; : . ' r> 'y. <: f" ' ' h'4 -f1 -djivn.'-i pr r;- " ( >V i - > ' - ! - .... i - i. . r*-hs *-'? rr\ *0, . ..{ y'-i [I. f F*r rtj " r . ,j-> ' Nap. 944-3M i - . -r.' 1 .'ssM'-as') RSV0030405