Document RKzneoEoqaJpXD1Jwqkm6aa

LEAD INDUSTRIES ASSOCIATION. INC. o 212 MAOiBON AVCNUC NEW YORK. N. Y. 10017 rVLCPMONC -- ACA COOK K(S OR MOM February 10, 19^5 SUBJECT: RFFPDJT "LEAD IS MODEM* CHEXXCAL CCKSTRUCTICS" Tc Members of the Lead Industries Association, Inc.: The enclosed article "Lead In Modern Chemical Construction" has beer, prepared by L. I .A. and reprinted free the Encyclopedia ef Chemical Procession Equipment. Just published by Felnhcld Publishing Ccrp. The article describes types of lead products, design criteria for lead In stallations, sheet and tended constructions, pipe and coll Installations and Inspection and testing methods. The reprint is being distributed to a list of 1,61*0 chemical ccapanles and chemical engineers. It vill also be distributed at appropriate trade shovs and used to answer Inquiries received by L.I.A. You nay obtain 25 copies of the reprint free of charge, and addi tional copies are available at our cost of 10 cents per copy. Very truly yours, FT:bd (Tc. Robert Travis o d: &ooA wM Lss<f iyj ' fi n n j ;n in iiif ---*-- - ---- - -- - -- ---------^ LIA23233 LEAD IN MODERN CHEMICAL CONSTRUCTION ktpeirtid from The Encyclopedia of 9 CHEMICAL PROCESS EQUIPMENT Pvbhih+d bf *E!NHCHD PUSUSHING CORPORATION. NEW Y0* Otlffibv*^ bf LEAD INDUSTRIES ASSOCIATION, INC. 292 Modiion Av., Nw York, N. Y, 10017 iff MitoMl&fcifti -v N 1693.01 LIA23234 o 3 o 1 LU23235 o o IEAO Lead has been an important material for handling corrosive chemical* sine* the be ginning of the chemical process industries. It w*a used for the first commercial sulfuric kcid chamber constructed in 1749 and sub sequently ha* wen mere than two centuries of aervice in industrial plant* ac a standard corrosion-resistant material. Acid manufac ture, pickling, plating, anodiiing. waste acid recovery, and a boat of other operation* have all made u*c of lead's resistance to eorroaive chemicals--particularly sulfuric acid aod ita derivatives. Although othci materials have been developed to compete with lead in this field, the use of lead haa continued to expand. Of course, this is due to its inherent corrosion resistance and to the growth of the chemical industries. But it i? also due to the experience gained fn m the long and varied use of lead in this field. Although lead is used in a variety of d.apes and forms, by far the major portion of the lead used falls into three general product categories: rolled sheet, extruded pipe, and east shape*. Boiled Lead Products. The major part of all the lead used by industry for handling corrosive chemicals is in the form of rolled heet products. Sheet lead weigh# approxi mately 1 Ib/sq ft for each jo. of thick ness, is usually specified by aright per square foot rather than thickness. For ex ample, 4 lb lead is Vi* in. thick; 60 lb sheet is I in. thick. These sheet products are used for storage and fraction tanks, duct* and flue* for handling corrosive fume*, and launder* to etvnvcy **lutin* fn*m |Mint to point, to name a few application*. Siiert* may be produced in width* up ID ft and in lengths up to 60 ft dej^mding \qin (lie thickness. Sheet# 10 ft wnlr and 20 ft l**ng are usually otftsidercd *-tandard. Extruded Pipe and Cotit. Lend is ex truded readily into van.*u> -hajc*, and large quantities of extruded lead arc utilised in t'r plating. chemical. and related Industrie* Principal uses find it a? pq*c for conducting com*ive solution* and a- ending heating coils submerged in forr*dve cliemicaU. Sites are limited only bv citm-HO equipment; for example, they range fnm fine tubing inside diameter and earn less to 12in. inside diameter. A!m<**t any doirrd wall thickness and ero-s -return- of practically any *hape can be ohtaitv-d An advantage of lead pq*c is that it i* readily Vnt t> con form I*, intrente do-icn q^ifieafion* Joints mar be made by wi lding. .-oMerjng. or by nierlttnoal mean*--the rhoiec depends U|w .q end u-e. WeMing f ''burning" is generally used in chemical c-n>iructi< n Ca*t Lead Products. f.arge quantities of lead are employed by the e!:em:eal indutry in the form of casting*. I^ad and certain of its alloy* are excellent for castings pro vided that high strength is not a requisite ami they are m* for u?e at temperature* higher than the melting point of the alluy. Ordinary chemical <-r acid Wad, usually too soft for this put)"**, t* alloyed with antirm-oy for strength Lead hardened in this manner is cast into pump and valve* a* well as many -|xcul -hapes and fittings. Occasionally reinforcing e!ementi made of stronger materials are cast into the lead to ~* * - w*>-- ^ii4.m-n . f .% * LIA23236 LEAD Ta k j 1. CowrAsiso* <w Tcsua Snurorn -vo CAurvurt* Ou a k ik s 9nM w X-iu i Lm Alleys ro*c tV) Strtrylk (p*i Sire* fe~ycr UJ* Ip*) WC (im'r) rcwt/ {p*l Slnu 90-yHt W# ip*) Purs lead 1,600 no IJXO 760 l*St> s^oo 600 7&0 226 6*Sb 7.T00 1,000 6-200 &20 f- It* Sb 7,700 77$ 6,200 600 i i provide greater strength. Catling qualities MSSSIIWS.1* are excellent, the melting temperature* low, and eotToeion retutance it good under tnoct condition*. Design Criteria for Lead ImtaHatioa The unique mechanical propertiei of lead mutt be considered when detigning lead chemical equipment The mott important consideration* are it* low mechanical trrngth, it* lack of elasticity which rerult* in permanent deformation under rtrea*. it* tendency to creep under any tuttained load, and it* low fatigue limit under repeated stresses. In fact, it could be aaid that lead tend* to act a* a plaatic (olid rather than an elastic or rigid one. There ia evidence that indicate* that there i* no limiting stress below w hich long continued tteady load or continued cycling ttreatea will not ulti mately cause failure through creep or fa tigue. Fortunately, there is a practical itresa level below which, with proper design and adequate *upport, lead construction will last indefinitely. Mechuiical Properties. The apparent ten sile strength, yield point, and hardneaa of lead art strongly influenced by test condi tions, particularly rate of application of load. The data in Table t illustrate thia. Both creep and fatigue properties are increated by alloying. But, the enhancing effect of alloying on creep properties is loet at high temperature*. Fatigue resistance ia raised partially by the grain refining effect Pm. 1. Ma j u b u a sHowibW fibt* ttw ia cbtB* ktl aad 6 pxr c t bI aoumoouJ Wad p*f* it rinau temperature*. of alloying elements. Yet even la Alloys of comparable grim list, it has bees found thftt Additions of Antimony, tin, or other Alloying elements increase fstigue resistAnee. Furthermore, the improvement per sists At clevsted temperature*. Despite the low strength snd plastic prop erties, design stress levels havt been em pirically established that 'ill give indefinite service life (Fig- 1). Consideration must Also be given to the problem of adequately providing for expan sion aod contraction of lead. Lead has a relatively high linear coefficient of *her mat expansion, that is, approximately three tunes that of steel; consequently provision must be made to allow for this expansion (Fig. 2). Q L 14a I LIA23237 o I.MD Fie 2. Liorr tS^rmal ripiiwot o( poll lewd *jyi iDitmooul Wd. Short Lead Construction Because of its low strength, lead is u*ually supported hy some other stronger ma terial uch as steel, wood, or concrete. Sheet (cad construction is probably the ')<le*t method id using lead as a material of chem ical con>truction. Basically, there arc two principal method* of sheet lead c-n-truen.-n Cape construction consi-ts of a lead -hTt supportcd in a sleet of w*h-n frame work, wlictraa lead-lined construction con-i-i.- of a lead sheet lining in a structural -hell such as steel of wood. Nev rt heirs*, there are probably as many moderations a> tlicre are applications for both types of con-truction. Sheet lead construction is generally re garded as the method which require* the hast capital outlay, moreover this method has additional advantages. Should repairs It necessary, they arc easily made in the field, and once the vessel** useful sendee life has expired, the lead can lie reclaimed a? scrap and sold at the highest relative rate of any id the common metal*. Cage Construction. The first chamber* for the manufacture of sulfuric acid mere of cage construction, i e , simply large sheet lead boxes supported by timliers In cage construction the lead sheet chamber is sup ported by a basket or cage-hke framework of steel or wood. Modern methods tend more towards ita u-c d -lei I fl it* mtd angle* welded (*<! Ik f. Tin* ty|c of fon>trurti.*n has -Mira) ndvantage*, however it cannot I* u*cd uivhr condition* of high pressure or vacuum K**r tho>e application* where it can 1* u-nl, it offer* low material co*ls ami usually rn-fc-r assembly in the field, since handling of bulky and heavy *tee| *het t* t* eliminated. In addition, there arc other important advantage*. The spacing U tween the frame work permit* leaks to Ik * easily located and repaired from the outside in a matter of minute*. Thi? type of open construction in which the lead is fully cx(>cd to the at mosphere provide* an extremely effective and inexpensive method for ending liquid* which arc received hot nr where heat i generate*! ly reaction such as battery arid dilution. Very frequently, where the site of the vessel dictate-, ixtra supj*rt i- required which i* accomplish*! hy strapping with long h-ruontal and or vertical steal flat* of ovU t> iIk - outside of the had shirt lining f>r additional -upjwrt ('age con-iruction allow* the slraj* to liC mountid externally. Hccrntly designed chamNrs sUppTt tlie !<ad ihoct wall* m a special tccl fratiHwi rk that jrmnt* a cer tain amount of movement of the lead with l< mjwraturc changes independent of the sterl frame a.1* shown m Kig 3. Lead-Lined Construction. Slicct lead!ini'*i wtKwlin or mild steel tanka arc com monly ux-d and have Urn for many year*. Lining thicknesses usually range between 8 and lh lb. Occasionally two or more differ ent thicknesses are used in the *ame vessel with thicker sections in the areas subject to erosion or where greater strength is re quired Either existing vessels or specially constructed one* of concrete, wood <>r terJ can be readily lined with lead to nuke them suitable for handling excretive chemical*. In other words, by lining any old but struc turally sound vessel with lead, it become* unnecessary toconstruct an rntirelynew one. Lower construction co*U are realiled w len the sheet lead is hung from the (op of a HP TP1 i i i i 4 \ .* LIA23238 LEAD tot Ktc i Wstce-eooWd sulfur* sod chambers eo*irurtnl of ihM W*4 supported by a free ^ mg steel structure. v >m I dicll. but this t* confined to relatively '.malt vr**rl*. A variety of tank design* tini: hanging bad lining have given sati*- f:i< t. fy *rm*e A variety of support meth- ,!* f>r r vcs*cl* have Nvn devchped, i.f m.Tticli the uc depends up<-n the tank design, *ix\ and the u-age I./vi shot* can N* sup|**rtr<l ;-n a *tce! or w*d*-n hell hv large cut *tre! * a*hm and round ln:it n* -rnwn in Fig 4 The cut *-.vb r dotrihuie* *he bad over ft larger area than the bolt alone; *ul-equcntly b^lt and w.vher are covered with ft lead cap burned to the lining Strapping. In deep tank*, or under rendi tion* involving fluctuating temperature* or higher Mre>x** and vibration, a crie* of vertical, and sometime* horizontal, steel straps are used f<*r support. Strapping e*n- *it* essentially of supporting the lead sheet ag.un-t the steel shell with flat steel bar* fastened at frequent interval* ituide the lead lining am! through it to the outer itee! sliell. Tbe*e strap* are Covered with itripa of lead wehini to the lead lining on either *nle. thus pfTM-nting a continuous, mutant bad "irfarc to the eorro*ive chemicalj nntamed Lead Bonded Sheath In addition to the lead lining* previously diM'u*ed, lead can be bonded directly to iron and steel for use with corroaiv* chemi cal*, particularly in high temperature proc ess.*. The thickness id the homogeneously U-mlrtl layer, dc|*nu:ng vn the use, range* from in. to *4 in. 'a relative motion U-luitn the two metal* v conatrained by the plastic flow of the lead, uch lininp are recommcmlcd where: (!) The reaction vessel operate* under vacuum; (2) Rapid or wide tcinjwraiure variation* occur that would cause fatigue am! stress corrosion in I<v*c linings; i3i G<w*i heat transfer char acteristic* are required; *41 High tempera ture operation i* c*ential (bonded lining* will not creep at tcmjHTatures up to 450CF); 5l Lightweight construction, as in tall ves sels. i* required; and (61 Vibration and repeated ?hck* are encountered. Two methods of bonding lead lininp on Tra. 4 Butloo-typ* fsjteniog of *b*t U*d bn mg to steel structure. I 1 '*J5.WW5UfeP *ww.up 4 ? . ,, ................ LIA23239 I 1AD teel are in common u*e, that j, burning 1r and casting Tlie mural tcp in U*th method* if preparation of (lie base metal surface before landing The u>ual method if to clean (hr atrcl initially by *h>t blasting to cx|**c an oxidc-frre surface I'irkhng, usually with 10 jx-r rent ulfune and, i then sometimes used. Fluxing with tine* ammonium chloride and fUnnoui chloride or certain proprietary (luxe* ia carried out jud !<forc U-nding. The oldest method of bonding lead to fieri, ihc turning bar rnrth&i, i* particu larly useful b*r final! area* and irregular hij*cs In this hand operation, lead u ap* plied to t!r prepared surface by melting fr**m a ''burning bar** using a manual burn f'hi $ A<-sl4i(h l.nifv* i(k imprrvKMa le*4 ('* <fa< ntir j I ing torch A skilled operator can check the lond la-fore Continuing to cover the surface inner lining Ftg. 5). This tyjtc of corvdrue* with a layer of lead almut vj$ in. thick. tion h.\- proved if!* vtivc in a largc numlier Casting. Tl>e second method id Landing of in.-talUtn n wl*rr bad alone or otlicr had to steel i? efficient and relatively in- malt rials of chemical c>nstruction have ixjar.Mve After the steel has !<*en cleaned and l**ind. molun lead is carefully poured <n the surface After cooling. tfe steel-lead lien inadxjuatf When pro|*rly designed and installed, they will |*erf*rm admirably undtf the mM m vert* conditions plate * often rolled in a conventional roll Brick linings Itave excellent common re ing mill to reduce grain sue and to incrrae sistance l*ut cannot In- u-ed g*,,ue t*-tau-e dtn-itv. Tlte plate u sul*scquently formed they arc ox-ntially j* rrocablc mat* rial*. la into the do-md shajK* fact, the best grade- of a- ;J-pr<*d brick are Sprayed Costings. I .rad coating* a!>> nuy intentionally made 3 to 4 |er cxnt porous be applied by spraying !>ad wire i.* fed for thermal s!>ch rrsi*tanre Tl*e lead lining, into a prav gun which melt- the tietal nd tl^-reforr, arts ai a membrane between the !>!' it onto the \*rfae to le elated S.nce stall ai.d the brick lining so that any liquid there i* no chemical bond l*etwttn the lead and ba.-c metal. the latter is firt -and* blasted r otherwise roughen*d and eh-aned to provide good mecl.anical anchorage for the coaling. Pinholes may le niinim>i<d hy turning the surface after coating. that jn-rietraU-s the hnck work will l< citairod hy the lead. The .-penal conditi* nj which warrant the selection of lead acid-bnek construction arc discussed below. High Temperatures. Referring to tem peratures !*ey<nd the mechanical limita Lead Acid-Prick ComtroctKW tions of lead, the hnck lining provides an insulating layer resulting in a tcmjnrature An important method of chemical con struction which baa been devised to resist the roo*t severe conditions encountered such aa the handling of corrosive slurries and high (iterating temperature* has ltd to the development of lead acid*brick conftructioo --a lead-lined itcel *hell with an acid-brick gradient. Consequently, although the tem perature within the vcwl at tlc lining may Im* efivwlwrr from Out) to 1300 K, tle temperature of tlie lead membrane Well within its mechanical limits. The u;*pcr temperature limitation oi ihu tyj>e of con struction ia merely t function of the thick* i LIAZ3240 nrt HfM'l (LAP n,.. ,41, 1 llM-rm-iI in-ulatmn properties of </,, Wrick lining For example, (here arc ijmr .1 few applications for sulfuric aeid-ullur dioxide scrubbing nfxralions with ctif, ring temperatures ranging a* high aa li<X)T High Pressure ot Vacuum. Certain arid frcov, rv units arc bnek- and lraddincd and ,,jH rile under vacuum* as low m 0.25 in. of mercury at alniut 250`F. Under these con dition-. the fricx lining affords a uniform -up(M>rt under static or cyclic conditions of vacuum and pressure which would normally c u u k * a great deal of undesirable movement of the lead lining Abrasion and Erosion. Many vessels use itirth*d* of agitation such as steam jet lance*. a hirii would fau>< h TH-u s rfoehm of an unprotected lead lining A brick lining protect. the lead membrane from the strong -ci urine < ffiTt <d ifx agitators or from any other abrasive condition that may be pres r.t -urli as the presence of abrasive slurries. In addition, pickling tanks holding sulfuric and mixture- are frequently lead-brick lined to eliminate tlx possibility of damage due to i*nfeh>s handling of the objects being pjrkleiJ Thermal Insulation. In addition t*> allow ing ambient vessel temj* raturc well alxive the hmjxrature bfml# of tlx lead memhrne. a bnck lining i- de-irab!e in tlx r.ition id ve-M'ls with rapid time-tem|n rafurc flurtuationj in the lead lining, tlureby retlucmg markedly tlx tendency f*r thential fatigue in the b a 1 Severe Corrosion Condition*. In certain c.io -. the pn-%4 nrc of the bnck layer deters drilling*' and ' scabbing" tyjx attack which -cur* when lead is exj-*-<-( to tlx direct action of combinations of sulfuric acid and srtui organic rU-tniral* Such attack, for *XNiitpU. ecurnd in a v--el which eon- t.uiHs| 35 |ef cent sulfuric arid plus coal t.r- at I2UF A comparison f corroded pun- with pieces which Were protected by a I*.in course of hard-burned high silica o id-n-i-iing brick ami barked with aeid- pit-d euiMiit. demonstrated the cffcetive- ness of (he had acid-brick construction ia this application. In general, whether or not an organic material will attack lead in Combination with sulfuric acid apparently is related to the materials* polarity or lack of it. Nonpolar julutanccs such aa gasoline, benxene, and toluene are not corrosive to lead. Evi dently the assistance pruvided by the acidbnck lining is to rrstnet the penetration of the polr fufM.(ancet to the had lining. The nonpolar materials, interestingly, penetrate acid-brick very rapidly; nevertheless, they arc hannlcfs. Lead Pipe and Cod Lead is extruded readily into various shafx*. and large quantities of extruded had pipe arv u m>1 in tlx building chemical, and relatH mdu-tnes. principally a pipe for conducting corr^ive solute r.* and aa fooling r heating roils sulwxfgfd in a corn*-ivc medium. Un* of the great advantage- of Wad piping, in addition to us r rro-:. n rr-i-tance. is it* adaptability and t'r facility with which tt ran lx in-talhd When pipe Ixnd* arc n-quind. straight p:;e may lx f,!li-d and pa*kd with Mind, and U-nt During tlx o|irti-n. tlx outv: wall bermiicj thinner; rn-rrover jf the radius of the Und i- W - ri n f'-ur iiu.ct the in*il< diameter of the ptjw. (ids inter wall o "h-cV is reinforced hr "burning on" an addt-d layer of lead Shorter rxi;us bends may lx made by means of mitred joint* f,,tw<*n short sections of pijx Alterna tively. a variety f pi|x fitting* may lx purehand as t*rk items, east Tt, chemical lead or antimonial lead. These are -uppind in four forms: til With solid lead flanges welded in place. 2 With cast iron or steel slip-* n flanges. 3i With over-length for flar.g.r.g in the field. Hi With plain ends for weldir.g. Honmntal runs of lead ir V*<i alloy pqx are generally continuously -upported LUZ32 Al LEAD In steel or woodm troughs or in specially constructed sheet metal shells Vertical runt 4re supported a( /rrquent interval* ttjch m every 18 in Ing ruru are provided with expansion bend* if they operate at high or fluctuating temperature*. Thia traditional method of supporting pipe ha* the disadvantage* that any leak* age may cause damage to the supports. Free expansion and contraction are hin vehement* is a heat exchanger consisting of two lea<i pipes, <vne within the Tlie larger pipe ha* a 2-in. in*idc diameter with 1 i m. wall and is extruded from 6 per cent antimontal lead. The inside pipe made of soft lead is I in. in diameter with a 'fin. wall at the thin portion The extenor of the inner pipe has been extruded in the shape of a su-pointed star U> provide extra sup port and also to retain concentricity. dered, and the location of any leak is not Ribbed and finned lead pipe are used always evident or easily accessible for re in many systems requiring greater surface pair. area Lead sheathed electric heating devices Thieknea* of lead pipe depends on sev have bom used successfully in place of eral facton, including corroaive attack, ab steam-heated coils in some installations rasion, and pressure to be handled; for where u*ing steam is difficult or haiardous example, if wall thickness is ealrulated io or where electricity is inexpensive. the usual manner to aeeommrvU - given Bonded and Lead Covered ripe. Under pressure, additional wall thick new is al conditions of high temperature or exces lowed to compensate for loss through cor sively high pressure <here greatest strength rosion or abrasion. The velocity at which < essential. lead-1 ted steel or cast iron a corrosive solution flows screw* the surface pij>e or, nuaaibly. I ad-fovrrrd copper pipe of lead is an important factor in the rate may !*e used TW.d *ig techniques similar m of corrosion, but it is difficult to establish those described earlier are utilised in the a definite relationship between the two. Aj manufacture of these pndurts. an illustration, Table 2 shows the effect of In making bonded lead pipe a length of increasing the velocity of a 20 per cent sul steel is first cleaned and fluxed Then m.*l- furic acid solution al 25rC (75;Fl screws ten lead i east on in sections by r<'atmg the surface of lead: the pi(*c A second method uw* uulctd of molten lead a length of extruded lead pipe Ta s c i 2 V# 1 / 5ofWwW Att o ** L*<*d Hot4 of Corona* v /o- which Is inserted m-ide a properly prepared pipe of >tcrl The ends f the lead p*{< art sealed and steam pressure applied to ex pand it against the outer pipe Pressure ts It u raised until the temperature reaches the 17 point where beidmg ccctjr* between the IU U lead and steel, aided by pre-tinmng the 300 86 steel with a thin solder film In this way, the lead is said to be "sweated" to the steel The erosion of lead pipe may be retarded pipe. by designing the system to reduce flow rata friction La much as posib!c, e g, eliminate short benda, use larger pipe, or both. Lead pipe ia especially useful when a high rate of flow is desired because it can be curved and assembled without extra fittings and because extruded lead offers a minimum of surface frictsoo. One of tb more interesting lead coil oe- Impeding and Testing Lead Linings Lead-protected chemical-processing ves sels are normally inspected for the presence nf pinhole* or ponwtty in welded seams nfi sheet-lead linings, hairline cracks, either m the weld or the sheet, resulting from fatigue or itreM corrosion; and pinholes, incbi*iofi, or bond diicontinuilie* in the case of clad .x LIA 2324 2 LXAD Ml vessel*. Defect* falling into any of the abov* classifications, although they may not penetrate the lining completely, do form a potential trouble spot that may shorten the lining'* expected life*-* probVra that can be minimised through the uae ot proper inspection and letting. Testing Sheet-Lead Linings. After the completion of a new installation or exten sive repair* on an old lining all the welded (burned) team# are carefully checked visually by the lead burner and all obviout defect* corrected. If it if necessary to cheek the Kxjndne'* of a lead weld tuch a* on butt joints to determine the depth of fusion, a section of the team can be trepanned with a trepanning dnll to obtain a crow aeetion. On a bonded lining, this technique ha* also been used to cheek the nature of the bond and the thickness of the lining. In either ca*e, however, the test is destructive, whereas radiographic technique* provide a more effective, nondestructive test for weld soundness. For closer and more exacting examination of weldj, a fluorescent of dyt penetrant that is drawn into tiny crack* or pores by capillary action i often used. After the excess is cleaned off. the chemical remaining in the imperfection* can be de veloped or brought to the surface, where it may readily identified, either by a bright glow under uHravivlvt light, in the case of the fluoroeent penetrant, or by a distinctive Color, in the case of the dve j>enetraot. Interpretation of each in Jication is all important. Practically all procedure* in volving the fabrication of lead result in the possibility of confusion between a defect and a simple surface marking; therefore, it mu*t be realised that a high degree of discernment must exist to differentiate be tween a true defect and a harmless surface irregularity. Testing Bonded Lining* Acid-wash test* have been accepted as a standard inspection technique on bonded lead-lined vessel* for the detection of pin hole penetration, surface imperfection*, and porosity. It will not detect svjbsurfset flaws. First, the entire lead surface must be cleaned free of any oil or grease Aims. Then, a dilute solution of hydrochloric acid 45 to IS per cent acid) is freely applied to the en tire surface by brushing or swabbing and is allowed to remain fur 12 to 24 hr Before the acid is cleaned off, (he lead surface may be examined by an inspector for vet spots or discoloration, or, better still, the aeid washed of! with water, and the surface al lowed to dry and then be examined A wet spot indicates either surface porct;*y or a pinhole that has not penetrated the trad. Rusty discoloration indicates a pinhole that has penetrated through to the steel Repairs are usually made on the wet spots by touch ing up with a lead humor's torch. arras are removed and the steel cleaned so that new load can be (winded. Aftir *11 rustsp't indications have been rebccded, the and-wwah test is repeated to give a final cheek. A second melhixl i the same tet in prin ciple, but it is more effective and u restricted to lead-clad pressure vessels. The vessel is heated by internal steam pressure to about 500'F until thermal equilibrium :> reached. At this point, the steam is turn'd off and pro-ure rapidly released from t:e vessel. Air Is subsequently admitted and t.te VCsacl is cooled and ir>;-ectid for bubble* If Done are found, the test is repeated. After the second cycle, if none are found, tie lining is accepted a* 100 jx r rent bonded Ultrasonic tests involving the transmis sion and reflection id ultrasonic saves lend themselves well to the location of --.bonded areas and subsurface inclusion.* And can a!*o provide a simple nonde*lru<*.* means for determining the lead thickness s. bonded linings. Two basic method# of .Itrasontc inspection have been used successfully on bonded lead linings; the resonance method, and the pulse or echo method. In the resonance method, the cryual head on the instrument transmits an .Itrasonie wave into the metal and the wave* reflected from the opposite surface are dt'ectcd au- ItAD dibly in hcAdphonei or visibly on i cali brated eathodr-ray tube or a dial reading. When lead it well bonded to steel, the wave* are not reflected from the steel-lead inter face; consequently no signal it obtained. Small unbonded area*, one half of the crystal-head me or smaller, or semibonded arras, may result in partial reflection of the waves from the interface, indicated by weak signal*. Strong signals reveal a complete lack of bond, lnrgcr in area than the crystal head, whnee outline can be easily traced with the instrument. In the pul>e or echo method, vibration! are sent out through a similar crystal head. The puf.-e travel* through the metal until it >tnke* a flam* and is reflected, wherca* the rr>t of the nave* travel on until they hit the u}>|x*iie surface and are reflected. AUlmiph the vibration* are alternately off, the crystal detects the reflected pulx** and the time difference is converted electroni cally tit readable indication* of depth on a c.itlnde-ray lube. Radiographic Testing. Although, because of its high dvnMty, lead i* normally u-od at a material for shielding against radiation, it i* j*>-Mhle with the higher ra<iiation energies commercially avad.-ible today to obtain practical radiographs of the load in leadlined steel vessel*, to htente entrappetf gaset and subsurface foreign inclusion* not de tectable by acid-mash mctliods. Reference* "leAd (B M(irr& todu*iry," New York. Lead laduairir* Aminat ion, lae. Itt) Zw-ffrM. R L, "How to CVk mt lead Liom* for l*rorro Ymli," Cketn. A`ag (Jan f, 1961). Turner. A. Wellington, J. K, William#, L. "l*# of Lead in CS< mical and Metallurgical Plant Cuftitnjrtios." J, o/ Ckcm. E*f. (Apr, 1959). MulUrker. K. J. *Tar of Lead to Control Re- tnrnr CroA*on,* Ptirultum Refit** (Apr, 195AI "fVx Dr*ign< (or Lead Installation#," Ckcm. fag. (Mar .Mav. ISM). "CofTOaun Rebalance of lead sod Lead Alloya,* dem. fug. (Feb. 1953). Mu.'ta/i*% i\ J. "Lead jod Ju Alloy#,'* fid. fag. Ck. m. 59, 1M? tS-i. 19SH); iM. 51. No. 9, 11^ 1959). Roll K H, "Li)r< Mrtb<xl for ln|<retiD4 Lead LaftiHg*- CAm. (Sov, 19561. WVvM*f| 1( C. 'Miifruli of CostnKtioa for Chemical Plants lead,'* fJkrxicof PracCM > ........... 41. No 6. 247 (June. I960) Or^o-ha*. J G . "Lead a# a Mttrnil of Construc tion fur Chemical I^Unt#.** Clnmcfli aa-f u fayvifr'ing. W No. 10, 550 (Oct. I95M R. B. Tr a v is Cm-idfm>tti Brvk-U**d Rruceu EqwipmctU.