Document Z4MZmLKQaoLNGDYaJGEw7pXkJ

Appendix C to m in u tes o f m eetin g o f CCAP h e ld in. Chicago, O ctober 4 , 19^3 PREPARATION OP TANK VESSELS* ' PRIOR TO ALTERATIONS OR REPAIRS By C. A, Neusbaum** v 1. Introduction The p re v e n tio n o f p e rs o n a l i n j u r i e s and damage to p ro p e rty h as alvrays been a s e rio u s problem in th e a l t e r a t i o n s and r e p a ir s o f tank v e s s e ls . The c le a n in g o f th e tanks and compartments o f a tank v e sse l and th e te s tin g o f th e atm osphere w ith in th e s e ta n k s and com partm ents a r e te c h n ic a l p ro b lem s r e g u la r ly e n co u n te re d when such v essels arc used fo r tra n sp o rta tio n o f crude petroleum and it3 products. 2. Toxic E ffe c t o f Petroleum Vapors Vapors given o ff by crude petroleum , g aso lin e and o th e r petroleum products cause a n a e s th e tic e f f e c ts when in h a le d and, u n le s s p re c a u tio n s a re tak en , such e f f e c t s may be e n co u n te re d by w orkers d u rin g th e c le a n in g o p e r a tio n s . Exposure to petroleum vapors o fte n r e s u lts in i r r i t a t i o n o f the eyes and th e developm ent o f a s e v e re head ach e. When in h a le d i n c o m p a ra tiv e ly sm all q u a n ti t i e s th e se vap o rs produce m erely a m ild e x h ila r a tio n . Upon in h a lin g th e fumes in more c o n c e n tra te d form t h i s c o n d itio n ra p id ly develops in to com plete in to x ic a tio n accompanied by a tendency on th e p a rt o f th e in d iv id u a l to sin g , dance, or o therw ise v ig o ro u s ly e x e r t h im s e lf . As t h i s s tim u la te d a c t i v i t y w ears o f f th e v i c t i m 's l i p s lo s e t h e i r n a t u r a l c o lo r end become so s t i f f th a t p ro p e r e n u n c ia tio n i s no lo n g e r p o s s ib le . At t h i s s ta g e , f u r t h e r exposure c au se s u n c o n sc io u sn e ss an d may r e s u l t in death. * The to x ic e f f e c t o f g a s o lin e vapors in v a rio u s deg rees o f c o n c e n tra tio n i s i l l u s t r a t e d by d a ta from th e U .S.B ureau o f Mines T ech n ical Paper No. 272 a s follow s: A ir c o n tain in g .07 to .22$ vapors by volume causes s l i g h t "symptoms o f d iz z in e s s whon in h a le d f o r 14- l / 2 m inutes. Air c o n ta in in g 1.13 to 2.2 2 $ vap o rs by volume re p re se n ts th e c o n c e n tra tio n which causes severe d iz z in e s s when in h a le d f o r 3 m in u te s. . A ir c o n ta in in g 2 .2 0 to 2.6 0 $ vapors by volume causes i n t o x i c a t i o n a f t e r 10 to 12 b r e a th s . 3* F lam m ab ility o f P etro leu m V apor-A ir M ix tu res " Petroleum vapors a re h ig h ly flammable and co n sid erab le care i s re q u ire d to p re v e n t th e o c c u rre n c e o f f i r e s o r e x p lo s io n s . When mixed w ith th e p ro p e r am ounts o f a i r (oxygen) th e se vapors form ex p lo siv e m ix tu res. The e x p lo siv e m ixture range o f g a s o lin e i n a i r , f o r exam ple, i s g e n ? .ra lly a c c e p te d to be from 1 to 6$ by volum e. The low er f ig u r e c o rre sp o n d s to th e minimum amount and th e h ig h e r f i g u r e to th e maximum amount o f g a s o lin e v ap o r c a p a b le o f p ro d u c in g a flam m able m ix tu r e . The vapor c o n ce n tra tio n below which th e m ixture w ill not burn i s c a lle d th e "lower explosivo lim it" and th e vapor c o n c e n tra tio n above which th e m ixture w i l l not burn Presented a t m eeting o f M arine S ectio n -N atio n al S afety C ouncil-C hicago, O c t.5.19^3 * * A sst.D ire c to r, Standard In sp e c tio n la b o ra to ry , S tandard O il Development Co., New Y ork, N. Y. 2 i s c a ll e d th e "upper e x p lo siv e l i m i t . " For some o f th e more v o l a t i l e h y d ro c a rb o n s, such a s com m ercial propane, th e upper e x p lo s iv e l i m i t i s 9*5$ The e x p lo s iv e ra n g e f o r n a tu r a l g a s i s 4 ,S to 135$* A lthough e x p lo s iv e l i m i t s have "been e s ta b lis h e d d e f in ite ly fo r a number o f hydrocarbons, i t must be remembered th a t petroleum p ro d u cts seldom a re handled a s pure h y d rocarbons, I t i s e s s e n tia l, th e re fo re , to consider the low est and the h ig h est explosive lim its of the hydrocarbons of any products or m ixtures being handled. The fo llo w in g t a b l e l i s t s s e v e r a l o f th e more common c o m b u stib le s w ith th e ir lower and upper explosive lim its : C om bustibles Lim its of Flam m ability Lower Upper Methane Ethane Propane Butane Pentane Hexane Hydrogen Carbon Monoxide N a tu ra l Gas I llu m in a tin g Gas 5.0 3.20 2,40 1.90 1.4 5 1.2 5 4.10 12.50 4 . SO 5*30 15*0* 12.50** 9,50* S.50** 7. 5O** 6. 90*** 74.0** 74.2** 13.50** 31,00** 4 . Oth ;r Gases A ss o c ia te d w ith P e tr o l e um P ro d u c ts Other gases asso ciated w ith petroleum products also a re to x ic i f breathed in s u f f ic ie n t q u a n tity . Hydrogen s u lfid o , th e most prom inent of th o se g ases, i s c o n ta in e d i n somo c ru d e o i l s and i s p r e s e n t a ls o in some u n f in is h e d r e f i n e r y d i s t i l l a t e s as a r e s u lt o f re a c tio n a t high tem perature and p re s su re . Hydrogen s u lfid e i s harmful, and even f a ta l, in re la tiv e ly sm all co n cen tratio n s. I t i s e sp e c ia lly h azard o u s b e ca u se o f i t s p a r a l y t i c e f f e c t on th e sen se o f sm e ll, making d e te c tio n by odor in p o ssib le . The U .S.Bureau o f Hines has found th a t a c o n ce n tra tio n of 0.01$ in a ir w ill produce i r r i t a t i o n of the eyes and o th er p h y sical d istu rb an ces upon exposure f o r two m in u tes, w ith in c r e a s in g ly h a rm fu l r e s u l t s upon c o n tin u o u s exposur. Exposure fo r two m inutes in a c o n c e n tra tio n o f 0 .0 7 $ has r e s u lte d in d e a th . Hydrcg s u lf id e * 1" .also i s e x p lo s iv e i n c o n c e n tr a tio n s from 4 .3 to 4 6 .0 $ i n a i r . 5 Oxygen D e fic ie n c y The atm osphere w ith in c le a n ta n k s w hich have been c lo s e d t i g h t l y f o r some time i s freq u e n tly d e fic ie n t in oxygen due to ru s tin g of the m etal of th e tan k s. Such tonics, th e re fo re , should n o t be e n tered u n t i l they have been v e n tila te d tho ro u g h ly . Normal a i r c o n ta in s about 21$ oxygon. A ir which c o n ta in s l o s s th a n l 6$ w ill not safely sustain lif e . . T able: *G, W, Jo n e s, E, H a r r is and W, E, M ille r - U .S.B ureau o f Minos T e c h n ic a l Paper #544, 1933* pngs 26. **H, F. Coward and G eo.W . Jo n es - U .S .B u reau o f Mines B u l l e t i n #279* ***G. V7, Jo n es, 3. S. B aker, R. E. Kennedy - U .S .B ureau o f Mines R ep o rt on I n v e s tig a tio n s #337 F ebruary, 1937* ** H. F. Coward and Geo. V. Jo n es - U .S .B \ireau o f Mines B u l l e t i n #279 6. E arly Safe ty Measiires 3- P r i o r to 1922 th e c le a n in g o f ta n k s and com partm ents o f S ta n da rd O il Company o f New J e r s e y ta n k e r s was l e t by c o n tr a c t to o u ts id e co n cern s who s u p p lie d t h e i r own labor and supervisors for cleaning the tanks. In order to insure the d etectio n of any e x p lo siv e o r to x ic g a se s, a n a ly se s o f th e atm osphere in th e ta n k s were made by chem ists from a commercial te s tin g la b o ra to ry . . A lthough t h is arrangem ent was re a so n a b ly s a tis f a c to r y , a d e ta ile d study o f th e methods employed brought out th e f a c t th a t too l i t t l e a tte n tio n was p a id to c l inning and too much dependence p u t on th e a n a ly s e s of th e atm osphere w ith in th e tanks. Host in sp ec to rs took samples of the atm osphere w ithout e n terin g the tanks, and could not know, th e re fo re , th e c o n d itio n of th e bottom s and s id e s . U nless th e ta n k s a ro known to bo p r o p e r ly c le a n e d , th e r e i s no a ss u ra n c e t h a t a g a s - f r e e atm os p h e re a t tim e o f in s p e c tio n i s a g u a ra n te e o f s a f e ty d u rin g r e p a i r p e r io d s w hich may extend over s e v e ra l days. Numerous cases have been experienced, whore th e atm osphere i n ta n k s showing no s ig n s o f g as on one day, showed dangerous am ounts tw e n ty -fo u r hours la te r , presum ably because the tanks were not cleaned s a tis f a c to r ily and vapor iz a tio n o f petroleum m a te ria l took pla.ee a f te r th e an aly ses wore made. In t h i s c o n n e c tio n , i t seems d e s i r a b l e to p o in t ou t two fu n d am en tal p r i n c i p l e s which a p p a r e n tly were n o t u n i v e r s a l l y re c o g n iz e d p r i o r to 1922 Che f i r s t i s th a t a c e r tif ic a te of safety is w orthless u n less the inspector has entered the tank or compartment in q u estio n and has examined i t c a r e fu lly fo r d e p o sits o f o i l an d /o r sedim ent which may g e n e r a te v a p o r. W ithout such an ex am in atio n th e a n a ly s is o f th e atm osphere moans n o th in g more th a n t h a t th e tan k i s s a fe f o r a man to e n te r a t th e tim e o f t e s t i n g . Che p r a c t i c e o f ta k in g sam ples by means o f a sam pling tu b e o r sampling b o ttle lowered, from th e dock seems e n tir e ly inadequate except fo r prelim inar;: inform ation. /' Che o th e r fundam ental p r i n c i p l e i s t h a t th e maximum p e r m is s ib le c o n te n t o f p etro leu m vapor i s f ix e d by i t s e f f e c t on men in h a lin g th e atm osphere r a t h e r th an by th e low er l i m i t o f th e e x p lo siv e ra n g e . Che lower e x p lo siv e l i m i t o f d i f f e r e n t h ydrocarbons v a r ie s , b u t 1 .0 $ i s p e rh a p s a r e p r e s e n t a t i v e f i g u r e . On th e o th e r hand, i t i s s ta te d th a t petroleum vapors in c o n c e n tra tio n s o f 0.3;* or more a re in to x ic a tin g to some p e o p le on exposure f o r 30 m in u tes o r lo n g e r, so t h a t th e a c tu a l danger l i n .i t i s f a r below th e e x p lo siv e l i m i t . ' I t h as been ex p erien ced th a t nan a r e a b le to work i n ta n k s fo r i n d e f i n i t e p e r io d s when a maximum o f 0 .2 $ o f p e tro le u m v ap o r c a lc u la te d as pentane is enforced as a lim it. 7 Clcani ng P roc odur es Because o f th e p o s s i b i l i t y o f p e rso n a l i n j u r i e s and damage to p ro p e rty , th e S tan d ard O il Company o f Hew J e r s e y i n J a n u a ry o f 1922 i n s t i t u t e d a s ta n d a rd p la n fo r the p rep aratio n of tank v e sse ls p rio r to a lte ra tio n s and re p a irs . A s ta f f of men was employed f o r t h i s p u rp o se c o n s is tin g o f a s u p e r v is o r , a c h e m ist, s e v e ra l forem en, and a group o f la b o r e r s . Che c le a n in g method employed a t th e c u t s e t i s r e f e r r e d to as th e Manual Method, In th is method h o t w ater i s a p p lie d w ith hand h o se a f t e r a steam ing o p e r a tio n , Che recommended p ro c e d u re to d a y , how ever, i s th e B u tterw o rth Method in which h o t w ater i s a p p lie d m echanically by means o f s p e c ia l equipm ent. A ll th e ta n k v e s s e l s owned by th e Company a re equipped to u s e th e B u tte r w o rth M ethod,, so t h a t th e Manual Method i s u s e d o n ly on v e s s e ls when B u tte rw o rth machines a re n o t a v a ila b le . Coday th e p erso n n el employed fo r c le a n in g o p e ra tio n s h a . in c re a s e d to one c a p ta in - who a c t s a s s u p e r v is o r , 3 c e r t i f i e d c h e m ists , 6 forem en, 5 pump men, 3 tim e k e e p e rs, and a group o f c a s u a l la b o r e r s who a r e e x p e rie n c e d tan k c le a n e r s ra n g in g in number from 50 to 75* Che c h e m ists employed In t h i s work a r e *G. W. Jo n es and M. P . Yant - U .S .B ureau o f Mines T e c h n ic a l P ap er #35* b g ra d u a te s o f re c o g n iz e d c o lle g e s and a r e recommended f o r c e r t i f i c a t i o n "by th e American Bureau o f Shipping only a f te r they have worked a t th e ir p ro fe ssio n in th e o i l in d u stry fo r a t le a s t th re e y e a rs -- s ix months o f which has a c tu a lly been on cleaning of tank v essels used fo r the tra n sp o rta tio n of crude petroleum and i t s products. I t is im possible to specify a r b itr a r ily th a t a tank of a given size sh a ll bo steam ed or machine washed a c e r ta in number o f h o u rs, sin ce th e amount of steam ing o r washing re q u ire d v a r ie s w ith th e n a tu re o f th e o i l which was c a r r ie d l a s t , th e a tm o sp h eric c o n d itio n s , and o th e r f a c t o r s . Tho i n t e n s i t y and d u r a tio n o f each process r e s ts th e re fo re w ith the judgment of th e supervisor and the chem ist, and are governed by th e conditions and circum stances which n e c e s s ita te such clea n in g . (a ) B u tto rw o rth Method . W ith the B u tto rw o rth Method, h eated w ater i s d ire c te d upon th e i n t e r i o r su rfa ce o f ta n k s by means o f h ig h p r e s s u r e stre am s from two re v o lv in g n o z z le s . The n o z z le s a re geared to tu rn sim ultaneously and slowly in a l l planes, h o riz o n ta l to v e r tic a l, sc th a t th e w ater stream s from th e nozzles a re d ire c te d e v en tu ally upon th e e n tire in te rio r surface of the tank. As soon a s th e cargo i s pumped o u t, steam i s fo rc e d th ro u g h th e h e a te r c o i l s and steam sm othering l i n e s . I f condensed steam comes th ro u g h th e h e a te r c o i l s c le a r , in d ic a tio n s a r e th a t th e l i n e s a r e s a t i s f a c t o r y . I f steam f a i l s to come through or i f th e condensate is o ily , i t i s evident th a t th e c o il is ru p tu red , and th a t clean in g i s necessary b efo re a c e r t i f i c a t e can be issu ed fo r th e compartment in which th e q u e stio n a b le c o il i s lo c a te d . Sm othering lin e s a ro steamed fo r apprcxim atoly ten m inutes. B uttorw orth machines a re next placed in the cargo tanks through sp ecial openings or through hatches i f the v essel i s not equipped w ith such s p e c ia l o p e n in g s. G e n e ra lly two m achines a r e o p e ra te d a t th e same tim e , one in each o f two Main, Wing o r Summer ta n k s . The h a tc h and u lla g e c o v e rs a r e c lo s e d b u t n o t dogged down. D uring th e p e rio d o f w ashing, w hich n o rm ally ta k e s from 1 l / 2 to 2 hours per tank, the ship is h eld a t a s lig h t l i s t i f necessary to speed the d rain age of the tanks to th e s u c tio n . The cargo pumps a re o p e ra ted slow ly to withdrawfrom the tan k s th e re fu s e o i l and h o t w ater r e s u l t i n g from th e washing o p e ra tio n . For most e f f ic ie n t clean in g o p eratio n , the w ater i s h eated tc a tem perature o f a p p ro x im a te ly 175 S' The w a ter i s s u p p lie d a t a p r e s s u r e o f a p p ro x im a te ly 175 pounds p e r sq u are in c h from th e v e s s e l 's deck f i r e l i n e s . A fter th e tanks have been washed s u f f ic ie n tly , th e B uttorw orth machines a rc removed and th e tan k s v e n tila te d by means o f wind s a i l s , V enturi tu b es o r a ir blow ers lowered in to the tanks through the h atch , or by steam gas suckers in s ta lle d i n th e s h i p 's deck d is c h a rg e l i n e s . When th e atm o sph ere w ith in th e ta n k s has c o o led s u f f i c i e n t l y f o r men to e n te r , a sample o f i t i s o b ta in e d by means o f a sam pling tube c r sampling b o ttle lowered from tho dock and analyzed fo r to x ic o r com bustible g a s e s . I f th e atm osphere i s found to c o n ta in n o t more th a n 0.2ff ,gaa by volume, th e s u p e rv is o r in c h a rg e o f c le a n in g e n te r s th e ta n k s to make a p r e lim in a r y su rv ey b e fo re men a r e s e n t i n t o th e ta n k s w ith hand h o se to wash tow ard th e s u c tio n any sedim ent or s c a le l e f t in v a rio u s p a r ts o f th e ta n k . Sediment which i s n o t pumped through th e siictio n lin e i s removed m anually. A c a re fu l watch i s m aintained over th e men doing th e work. . (b ) Manual Method When B u tto rw o rth m achines a r e n o t a v a i l a b l e , th e ap p ro x im ate tim e r e q u ir e d fu r scanning i s e stim ate d on th e b a s is o f p rev io u s c arg o es. A fte r th e h e a te r lin e s a rr blown, th e h a tc h c o v ers and u l l a g e h o le s a r e c lo s e d b u t n o t dogged down. St cam a t a l i n e p r e s s u r e o f a b o u t 75 pounds i s a llo w e d to e n te r th o ta n k s th ro u g h th e sm other ing lin o s fo r tho period of tim e considered necessary to s u ffic ie n tly so ften and lo o sen o i l and sedim ent on th e b u lk h e ad s, beams, e t c . , so a s to p e rm it rem oval w ith stream s o f hot w a te r. Upon co m p letio n o f th e stea m in g , th e h a tc h c o v e rs a r e throw open and wind s a i l s , a i r blow ers o r steam gas suckers a re used a s d e sc rib e d above f o r p u rp o se o f e x p e llin g g a se s and steam . When th e ta n k s have c o o le d s u f f i c i e n t l y , a p re lim in a ry t e s t o f th e atm osphere w ith in i s tak en . I f th e gas c o n te n t i s more th a n 0, 2$ by volume, f u r t h e r v e n t i l a t i n g o r steam ing and v e n t i l a t i n g a r e r e q u ir e d . I f th e gao c o n te n t i s 0 ,2 $ o r l e s s , men eq u ip p ed w ith hand hose descend th e la d d e r s slo w ly , w ashing down th e to p , s id e s and beams a s th e y go. The w a te r u s e d fo r wash in g i s a t an ap p ro x im ate te m p e ra tu re o f 100 3?. and a t a p r e s s u r e o f ab o u t 50 pounds. -A c o n v en ien t means o f su p p ly in g h o t w ater f o r w ashing i s p ro v id o d by a "Y" connec tio n which in tro d u ces steam in to a nozzle on the f i r e lin o and provides a p o s itiv e re g u la tio n o f tem perature. A c a re fu l watch i s m aintained from deck fo r the s a fe ty o f th e man below . When th e to p , s id e s and beams have been washed th o ro u g h ly , work i s commenced on th e b o ttom . S t a r t i n g a t th e fo rw ard o u tb o a rd c o rn e r o f th e tan k th e o i l and sedim ent a re washed tow ard th e s u c tio n from w hich p o in t th ey a rc removed to a barge or a slo p tan k a sh o re by means o f th e s h ip 's pumps which a re k e p t in o p e r a tio n th ro u g h o u t th e e n t i r e w ashing p e r io d . Any m a te r ia l w hich i s n o t removed through the su ctio n lin e is removed m anually. (c) Pinal Inspection A fter a l l tanks and compartments in q u e stio n have been washed and cleaned in acco rd an ce w ith e i t h e r o f th e above m ethods, th e main pump room b i l g e s a r e c le a n e d . Next, w ater i s pumped through a l l s h ip 's cargo lin e s and d isc h a rg e d in to th e slo p l i n e . A fte r pumping fo r a predeterm ined p e rio d , th e w ater i s d isch a rg e d on deck where i t i s examined by the chem ist, th e c h ie f o f f ic e r , and th e su p erv iso r in charge of tank clean in g . If th e w ater i s c le a r, the cargo lin o s a re considered to be c lea n e d . Whenever p o s s ib le , depending on th e s h if tin g of b a l l a s t , v a lv e s a re l e f t open to a ir out the cargo lin e s . The ta n k s a r e then e n te re d and in sp e c te d by a c e r t i f i e d chem ist; and, i f found to be c le a r e d to h i s s a t i s f a c t i o n and i f th e g a s c o n te n t i s 0. 2$ o r l e s s , a C e rtific a te is issued sta tin g the tanks (rep o rted in d iv id u ally ) are e ith e r "Safe f o r Men and P ir e " o r "S afe f o r Men - Not Safe f o r P i r e . " . 5* R e p a irs Remote from Cargo Tanks Whenever a v e s s e l must be dry docked fo r a su rv ey on account o f a s e r io u s ly damaged bottom or fo r r e p a ir s confined s o le ly to work on th e ru d d er, p ro p e lle r, t a i l s h a f t or o th e r p a rts rem ote from th e cargo compartments, such tan k s nay be smothered w ith steam and se a le d p r io r to the v e s s e l's a r r iv a l in th e sh ip y ard . In c a s e i t i s found n e c e s sa ry to do any work i n a n d /o r around any o f th e tunics, th e ta n k s in q u e stio n a re clean ed by e ith e r th e B u tto rw o rth Method o r th e Manual Method and c e rtifie d as heretofore described. 10, C leaning Cargo Tanks a t Sea Whenever v e s s e ls a f t e r d isc h a rg in g a t one p o rt a re o rd e re d to p ro ceed to a ship y a rd a t some o th e r p o r t, i t nay be n e c e s s a ry to c le a n th e ta n k s and com partm ents e n ro u te . The same p ro c e d u res o u tlin e d under S e c tio n J a re follow ed e x ce p t, c f c o u rse , no c e r t i f i e d ch em ist i s p r e s e n t. However, each v e s s e l i s p ro v id e d w ith a C om bustible Gas I n d ic a to r by means o f w hich i t can be d eterm in ed i f i t i s s a f e f o r members o f th e crew to e n te r th e cargo ta n k s to remove sedim ent and c o n p lo te th e c le a n in g . Upon a r r i v a l a t th e sh ip y a rd , th e s e r v ic e s o f a c e r t i f i e d c h em ist a re obtained fo r a complete in sp ec tio n . I f the chemist i s s a tis fie d w ith th e condition of the tanks and th e a n a ly sis of th e atm osphere w ithin the tanks in d ic a te s absence of gas, a C e rtific a te is requested, I f fu rth e r cleaning i s necessary th is is dene to the s a tis fa c tio n of the chemist and a C e rtific a te is obtained before re p a irs are started. Whenever i t i s n e c e ssa ry to c a r ry out emergency r e p a ir s ( r e q u ir in g th e use o f spark producing to o ls) in a cargo tank w hile a t sea, the tank in question and a l l ad jacen t tanks are cleaned, and the atmosphere w ith in te ste d w ith a com hustihle gas i n d i c a t o r i n a cco rd an ce w ith th e approved p r a c t i c e . I f th e g a s c o n te n t i s 0 ,2fo o r l e s s , th e n e c e s s a ry r e p a i r s may he c a r r ie d o u t. 1 1 . Chem is ts C e r t i f i c a t e As a convenience f o r r e p o r tin g th e c o n d itio n o f ta n k s o f a v e s s e l, a r u l e d form o f c e r t i f i c a t e w ith b lank spacos resem bling a con v en tio n al diagram o f th e h o rizo n tal cross section of a ship is provided. This c e r tific a te , affirm ing th a t the atm osphere in th e ta n k s in which r e p a ir s a r e to bo made, and a d ja c e n t ta n k s, a rc safe fo r the conduct of tho work, must be signed by th e in sp e c tin g chem ist and given to th e mast-or o r o f f ic e r in charge b e fo re th e sh ip i s d e liv e re d to th e c o n tra c to r o r p erso n charged w ith making r e p a ir s . In o rd e r t h a t no p o s s ib le m is u n d e rsta n d in g can o c c u r, th e c o n d itio n o f ta n k s i s in d ic a te d o n ly by th e n o ta tio n s "S a fe f o r Men and F ir e " , "S afo f o r Men Mot S afe fo r F i r e " , and "Not S a fe " . The n o ta tio n "Safe f o r Men and F ir e " im p lie s t h a t th e ta n k s so d e s ig n a te d a s w ell as th e a d ja c e n t tan k s and com partments have been th o ro u g h ly c l -once o f r e s id u e s and d e p o s its on fram es and on th e bottom which, when d is tu rb e d , m ight produce vapor; and th a t th e gas co n ten t o f th e atm osphere w ith in tho tallies i s not more th an .2 fo 'by volume c a lc u la te d as p e n ta n e . W elding, r i v e t i n g and s im ila r work r e q u ir in g f i r e a r e p e rm itte d i n ta n k s so d e s ig n a te d . The n o ta tio n "S afe fo r Men - Mot S afe f o r F ire " im p lie s t h a t ta n k s so designated but not the adjacent tanks have been thoroughly cleaned o f resid u es and d e p o s its on fram es and on th e bottom which, when d is tu r b e d , m ight p ro d u ce vapor; and th a t th e gas c o n ten t o f th e atm osphere w ith in th e tanks i s n o t more th an ,2'i by volume c a lc u la te d as p e n tan e . Only work n o t r e q u irin g the u se of f i r e or spark producing to o ls is perm itted in such tan k s. The n o ta tio n "Mot Safe" i s u se d when o i l o r dangerous am ounts o f r e s id u e s or d e p o s its a r e p r e s e n t, when leakage from a d ja c e n t tanks i s p o s s ib le , or when th e g a s c o n te n t o f th e atm osphere i s g r e a t e r th a n .2 $ , Under such c o n d itio n s , men a r e p e rm itte d to e n te r th e ta n k s when a n emergency e x i s t s b u t o n ly when eq u ip p ed w ith l i f e - l i n e s and fre s h a i r hose masks, and only when a c o n sta n t w atch i s m aintained on dock fo r th e ir sa fe ty . The o r ig i n a l and one copy o f th e c h e m is t's C e r tif ic a te a re r e ta in e d aboard s h ip and an e n tr y o f t h e i r r e c e i p t made i n th e S h ip 's Log Book. Upon c o m p letio n o f r e p a ir s a statem e n t i s made by th e m aster o r o f f i c e r in charge on th e o r ig i n a l C e r t i f i c a t e to t h i s e f f e c t - and th e C e r t i f i c a t e th e n i s fo rw ard ed to th e Mew York O ffice. 1 2 . C om bustible Gas I n d ic a to r Various types of in d ic a to rs have been used in the p ast fo r th e d etectio n o f petroleum vapors to in su re th a t the atm osphere i s non-toxic and to guard a g ain st f i r e s raid e x p lo sio n s. A ll have employed b a s ic p r in c ip le s , such as d if f u s io n , volume change on com bustion, o r h e a t o f com bustion. Of th e s e , th e l a s t ty p e scorns most s u ita b le fo r th e petroleum in d u s try because o f th e wide v a r ie ty o f g ases which a re !*v ely to be encountered, In th o b e g in n in g , th e S ta n d a rd O il Company o f New J e r s e y employed a p o r t a b le in d ic a to r based on th e volume c o n tra c tio n on com bustion p r in c ip le , designed 0 QC6 6 5 2 . 7. e sp e c ia lly fo r th is type of work. I t req u ired c a re fu l handling and i t s operation involved a f a i r amount of s k i l l and tr a in in g but i t served a u se fu l purpose u n til th e u rg en t need fo r such equipment brought about th e a d a p ta tio n and p e rfe c tio n of the heat of combustion p rin c ip le s in th e form of a p o rta b le in d ic a to r. At p re se n t, sev eral of th e se instrum ents are on th e m arket and a re used alm ost e x c lu siv e ly fo r th is type of work. CAN:HF /