Abrasive Blasting Operations, Engineering Control and Work ...

1 ABRASIVEBLASTINGOPERATIONSE ngineeringControlandWorkPracticesManualE nviro-Management&Research, , "DEPARTMENTOFHEALTH,EDUCATION,ANDWELFARE P ublicHealthServiceCenterforDisceseContro lNationalInstituteforOccupationalSafetya ndHealthDivisionofPhysicalSciencesandEng ineeringCincinnati,Ohio45226 March1976 ForalllebytheSuperintendentofDocuments, , , , , , (NIOSH)76-179iiACKNOWLEDGDAENTSW eacknowledgewithgratefulappreciationthea ssistanceprovidedbytheAmericanFoundrymen 'sSocietyandTheAmericanIronandSteelInsti tute,a l'OUSmanufacturersofabrasl'veblastl'ngeq ul'pment, ,v rEngineeringBranch,DivisionofPhysicalSci encesandEngineering, ~~ ~itsinblastcleaningroomsHand-operatedcab inettypeblastcleaningmachinesAutomaticbl astcleaningmachLTlesWeiblastcleanL~ ~ . 2 SpecificmhC~ ') ,000abrasiveblastersareexposedtosilicadu st,inhalationofwhichcanleadtosilicosis, ; blast. mach. type 107 Generalsafetycontrols125involved;methods toidentifyhazards; , **vi** ,Education,andWelfare'sNationalInstitute forOccupationalSafetyandHealth(NIOSH) , , ,ontheaverage, (ThresholdLimitValue) ,suchasopen-airabrasiveblasting, ;thepotentialsafetyandhealthhazardsinvol vedinthesepractices; :Abrasiveblastingcanbedefinedasaprocesso fcleaningfu~dfinishingofmaterialsbyforce fuldirectionofanabrasivemediaappliedeith erdryorsuspendedinaliquidmedium, **CURRENTMETHODSANDOPERATIONS cleanasurfacebyremovingunwantedrust,scal e,paint,etc.

2 ,inpreparationforpainting,anodizing,weld ing,orotherprocesseswhichrequireacleansu rface;deburr,removetoolingmarks,orotherw isefinishacrudeproduct;changemetallurgic alpropertiesorstressrelieveapartbythepee ningactionofmultipleimpactions;producead esiredmatteordecorativefinish;provideact ualcuttingorinscribingofpartiallymaskedp arts,suchastombstones,or;remove"flashing ll(excessmaterial) ~IOSH surveyundertakenfordevelopmentofthepUbli cation"AbrasiveBlastingRespiratoryProtec tivePractices"--andreferencedhereafteras litheNIOSH surveyll--indicatethatabrasiveblastillf. ! ~gtec~~iquesincludemaso~ry(brick,stone,c oncrete,etc.),sfu,dcastings,alwminum,cop per,brass,WOOd,glass, ~dsessentiallyonthenatureoft~esurfaceinv olved(includingitspre-cleanedsurfacecond itionwhichmayincludebeingcoveredbypaint, rust,etc.),thetypeoftreatmentdesired(cle aning,deburrL~g,etc.) ~ncompetitiveprocessesofpickling,electro chemicalcleaning,orhandfinishing, ,equipmentinvestmentisnotsUbstantiallyin fluencedbymodelchanges,operationalproced ures,orpersonnelturnover;trainingofopera torstakesplaceinaminimumamountoftime,and inmanycases--theabrasivemedia,orsubstant ialportionsofthem, ,shipyards,steelfabricationplants,specia lpurposejobandmachineshops,gastransmissi onstations,steelmills,structuralsteelsup plyyards,buildingcleaners,wineries,brewe ries,canneries,rubbermanufacturers,paint ingcontractors,plasticmanufacturers,weld ers,woodshopsandfurnituremanufacturers,p latingandanodizingshops,aircraftmanufact urers,electronicmanufacturers,petrochemi calcompanies,memorialmonumentmarkers, :Therearetwomethodsusedfordry-blastclean ing; , , (seeFigure11-1) ,generallyairwashedandgraded.

3 Orubbermatsoftenareusedonworktablestocus hiontheimpactanddippervalvewhichmeterst 'lC',0::oQ)t:>V'l,_JV'l-0':':.. )Q)Q). ,,-~o~3'Vi001+=..(1). :,,-~ZVi:2=>0w:r:Z::;-'Cf:.~ww4:0:r:w-'~ ~ 'a=> )wZw=> , ,abrasivevelocity(approximately250feetpe rsecond) , , ,andtocleanstripsteelandautomotivecranks hafts,axleshafts, :Indirectairpressureblasting,theabrasive isfedfromapressurizedcontaLier(pressurev essel)intoablasthose, (usually80to90psi)toboththehoseandpressu revesselareequalthuspermittingthefreefal loftheabrasivethroughanaperture(feedpoin t) ~~ , ~~~~!:~f~=1~C~fr~o~m~compressor,Controll inefilterTankremains~underpressure~atall times; ,SanFrancisco, ,~henabrasivebein gusediseXhsusted, sthenexhaustedfromthepressur evesse~and,whenitreacheszeropressure,the fillervalvedro~ssot !nductjon-SiphonMethod:Theblastgunofindu ction-siphonequipmentisconnectedtoacompr essedairpipeandaflexiblehoseYihichcarrie st ::~ATM05PI1[f',j(A "EfA~~~~~,.:"- ' .AGRASIVEHOPPErIgunwhereitispropelledthr oughthenozzlebythejettheabrasivehosecrea tesapartialvacuuminthehoseofthemachineho pper(seeFigure11-3).]

4 Asaresult, ,inturn,drawsorinducestheabrasiveintothe Therubberabrasivefeedhoseisusuallysix-to eight-feetl ,Figure11-3:Conne ctionofAbrasiveFeedhosetotheAb rasiveHopperpassesthrought heblastnozzlebutdoesnotreachthefullveloc it yoft heabrasiveleavingt henozzleisapproximately40%of - 9 widerangeofhand-operatedabrasiveblastin heyalsoareusedincon-:,inuousoperationaut omatice quipment,theyaregenerall ylimitedtoapplic ationofl i :Induction-gravityequipmentisverysimilar toinduction-siphonequipmentinthatalIgunl lisusedtomixairandabrasivemedia(seeFigur e11-4).Withinduction-gravityequipment,ho wever, , '.BLASTUNITBODYBLASTNOULEABRASIVEFEEDTUB ECO : ,eventhoughtheyallc ! , :Wetblastinginvolves:1i~h-velocity, , . ,take-offconveyors, ,horizontalplaneturntable,shuttlewithrai lorcarextensions,chainorbeltconveyors,se lf-containedturningmechanismsdesignedfor shaftsandtubularparts, , (seeTable11-1)thats&~ ,steelgrit,aluminum,flint/garnet,glassbe ads,carbides,slag,andorganicmaterials( ,groundcorncobsandcrushedpecanshells).

5 AbrasiveBlastingEquipmen~ fabrasiveblastcleaningsystemsnowincommon useare:portableblastcleaningma(?hines;ha nd-operatedunitsinblastc1eaI"lingrooms;- 13-TABLEII-ITheNIOSHS urveyResultsbyAbrasiveUsehand-operatedca binet,--cypeblastcleaningmachines;automa ticblastcleaningmachines,andwet- (Figure11-5):Portableblastcleaningmachin esgeneraRlyrequireahigh- volumeairsupply(usuallyintheAbrasiveSand SteelShotSteelGritAluminaFlint/GarnetGla ssBeadsCarbidesSlagOrganics(Cobs,PecanSh ells,etc.)TotalNumberReported% 'ange);acontain e rorpressurevesseltocontaintheabrasive; a meteringdevicetocontrolair-to-abrasivera tioandflow; aflexibl ehosetodelivertheabrasive,andahand-heldn ozzlet oaimtheabrasiveO:cl~ "pot " machineshavecontr olswhichstartandstopoperationsbyuseofafl owcontrolvalveora"deadman" ,themachinestartsandtheairandabrasivemix tureise heoperatorreleasestheflowcontrolvalve, (NIOSH)74-104-14-intothedryblastdischarg e.'l'hewatersaturatestheabrasiiTeandthus convertsadryblastoperationintoa i t sinBlastCleaningRooms(Figure11-6):Althou ghhand-operatedunitsinb lastcleaningroomsusuallyusealargehopperf orstorageofabrasive,t heunitsthemselvesareessentiallysimilar-1 5-FIGURE11- 5 PortableBlastCleaningUnit C1ementina, , (1)abilitytoprovideanduseadustcontrolven tilationsystem,(2)costsavingsfromrecycli ngtheabrasive,and(3) (inoneofthenation'slargershipyards) , ~chines(Figure11-7) ,semi-automatically, , CourtesyofWheelabrator Frye, ~ ,theabrasive-to-waterratiousuallyis25% (Figure11-$) ~ , ,SwingTableBlastCleaningMachine-20--21- ,heavy-dutycompressorsand0' (300everyfiveminutes).)

6 (Figure11-9):passedthrougha ,wet, , ,specialpurpose(whichisrecycleduntilitca nnolongerbeused). :3-Someofthenewerwater-jetblastcleani ,awaterfilter ,apressuregauge, f 4t 'It_191wae rpressuresplaceconsiderablestr a i lizealimitedsupplyofabrasivedrawnfromano pensupplyht' , ,however,numeroushazardscanbegreatlymini mizedifnoteliminatedaltogetherbyapplying mownoperatingandmaintenancetechniquesand engineeringcontrols, ,noiseandchemical& :Dustsresultfrombroken-downabrasives,pUl verizedsurfacecoatingsandencrustedsubsta nces,andabradedmaterialfTOmtheobjectbein gblasted,Thesolidparticleswhichcompriset hedustsrangeinsizefromlessthanonemicron( 1/25,000inch) , ~ (Si02) }aslowlydevelopinglungdiseasewhichoftenl eadst odeathyearsafterexposurehas~ (referredtoearlier)showssandtobefarandaw aythemostcommonlyusedabrasiveandthatexpo suretosilicadustinmanyoftheindustriesinv olvedisext~emelyhigh(seeTableIII-I).Anot herserioushealthhazardiscreatedwhentoxic metalsoralloyscontainingtoxicmetalssucha slead,cadmium, ~sarenotgenerallyinvolved,italsoshowedth atmanyofthematerialscleanedarelikelytobe coatedbypaintorothersubstanceswhichcould containsuchmetalsorothertoxicsubstances( seeTable111-2).

7 }ears}noseandthroatandcancause,attheleas t, , ;throughingestion(eatingdust-affectedfoo ds),and(rarely) ) 'drla:l.> <P::1H+-'~ooH+-'(f) (.)oorloorlH+-'C/) or--rl Q)rloH+-'Q) '0o~ ~tlc:ou-27-rl(V\ )c:J5oC/)"Becausedustalsoisairborne,heav yconcentrationsmayaffectthosenearthework areaaswellasthoselocatedatevenarelativel yremotedistance,dependingontheventilatio nsystemor,inthecaseofopen-airblasting,pr evailingwindconditions,humidity, ,infact, , , ,particlesonceagainbecomeairborneexample ,unprotectedworkersfrequentlyaregiventhe taskofbeatingandcompositionofblastingare a,thetypeofequipment(includingareas,neit herofwhichenableseasyconfinementorcontro lofdustnozzle)involved,theangleofworkpie ce,andsoon.(seeTable1II-3).Assuch, (intermsoftime)oftypicalblastingoperatio ns(seeTable II1-5). :NumberReported% (brick/stone/concrete/etc.)SandCastingsM etal(notspecifiedorNEC)AluminumCopper/Br assWoodGlassPlasticWithcabinetandautomat icroomtypeblasting,thenoiseproblemisorca nbemaderelativelyminorwithproperengineer ingcontrols,(seeTable111-6).

8 Inalmostallcases,however,abrasiveblastin gSource:"AbrasiveBlastingRespiratoryProt ectionPractices"HEWP ublicationNo.(NIOSH)74-104hand-operatedn ozzles(SeeTable1II-7)presentaseriousnois Rllr(1)lpffibecausethenozzlegenerallyisn eartheoperator' -29-en0~(")CIl0to0c+~'0r:'f-l~::r~(1)c+I IIJ-3CD(1)1-" >-iIi~1-"0c+CDJ-3Il>CDIII01-"~I-'c+f-l>- i~OJC/Q~==::0~00~>-i0g;~S(1)~~III~HH1-'0 CDH'i:l<IIIIg.(1)wf-lto1-"f-l0Il>J-3 IIIOJ::rc+c+(1)~.f-J. ~ZH0Z::Oen0(1)~~;.OJ'0 Zen1-"~r::;..>-i>-iIZIl> <wHC+(1)CD0001\)>-i Ien'iV11\)W\J1\ ::r:: ..00W\ \)::0::0'-"CD(1)'i:l' 'i0r::;+'-0'if-lIc+c+c+f-l(j)CDro00p.+'- c+c:t1-" 0~tof-l'l:lIII'iCIlPlc+01-"c+~1-"()Q0(1) ~CIl'*CD0Il>f-lI\)1\)wI~ \)I\)1\)V' \) >f-lIIATBLASTOPERATORNEARBYAREASBELOWTLV ABOVETLVBELOWTLVABOVETLVMODERATEEXCESSIV EMODERATEEXCESSIVE 2xTLV)(>2xTLV)I 2xTLV)(>2r-TLV) ! ) E 6 ~ 6 ~ 5 E t lTABLE111-4;SummaryofDustExposuresforDif ferentOperation sSurveyedABRASIVEBLASTINGIFEDERALEXPOSUR E--RECORDEDDUSTCONCENTRATIONS1 NSTALLATION*LIMITATIONSFORDUST(OSHA,CFRT ITLE29) *Ea chinstallationlist e drepresent s :"IndustrialHealthandSafetyCriteriaforAb rasiveBlastCleani ngflHEWPubl i cationNo.

9 (NIOSH) \IHHHrz:l~E-tTABLEIII-7 SoundLevelsNearHand-OperatedNozzleshelme ts(seeTable111-8) * :Althoug~nota directelementoftheabrasiveR-4(3)P-5(2)P- 9(2 )P-4(l)p-4(2)P-4(3)P-4(4)R-5(2 )P-2(2)P-2(3)Outside3'--BlastingRoomWall sBlaster6'--NozzleBlaster35'--NozzleBlas ter70'--NozzleBlaster70'--NozzleBlaster3 5'--NozzleBlaster40'--NozzleBlaster3'--N ozzleBlaster8'--NozzleBlaster46'--Nozzle 96/110928792/969990/9190/104102/10594/98 10294929794999097103961-1 , ,visionimpairment,slipping,flyingabrasiv e,fire,explosion, :Becauseofthesignificantdifferencesbetwe enthevariousmachinetypes, :Operatorsofhand-heldequipmentworkintheo penwhencleaningsurfacesofhighbuildings,s wimmingpools,hullsandothersurfacesofship s,highsteelstructures,* :"IndustrialHealthandSafetyCriteriaforAb rasiveBlastCleaningOperations",HEWP ublicationNo.(NIOSH) , ,electrical,andpersonal-35- TABLEIII-8: (hrs/ day) (dbA)MaximumSoundPressureLevel( dbA) ' :rlAbrasiveBlastingRespiratoryProtective Practices",HEWP ublicationNo.(NIOSH)74-104(j)a>::'i()(]) .

10 I~001(j)c+~ ::J(j)rlc+'d~~00t-'(])t-'NW+'-0'ex;.'it-< \J'I\J'IM01\J' ' :HOJ'i'"H'0It-'::r'"rl(])0~OJ>::OJ'it-'rn'l:J(])ro'i(;)~.It-'rnI0'OJW" '.1--'. "INt-''"(])0:z:l-J:ja~1--'.OJt-'(])'"~(j )t-'(])0txJ0OJ ~.'d'" \J'I~OJOJ~~rof-'f-'f-'f-'t-'I-<(])f-'f-'000'"'"'"'"roOJ\.Jl0\J' \J'INat-' ":J>(j)t-'0~ , ,asshownintheNIOSH survey,itisgenerallythemostcommonlyusedb lastequipment(seeTable111-10). :Typicalmechanicalhazardsassociatedwitht heuseofhand-operatedportableandroom-type blastcleanL~ ,fail-safedevicewhich,whendepressedbythe operator, , ,shouldtheoperatoraccidentallydropthebla stgun, :"AbrasiveBlastingRes-piratoryProtective Practices,"HEWP ublicationNo.(NIOSH) ~ ,joints,bends,valves, ,too,arenotinspectedwithsufficientregula ritytoidentifypreventive/correctiveactio nst :Pressurevessels(orpressurepots) ~ardsinvolved, "Pressurevesselsshallbebuiltinaccordance withthecodeforUnfiredPressureVessels,Sec tionVIII oftheAS~mBoilerandPressureVesselCode1968 ." n GHoles/Nois~:Blastcleaningr oomsfrequentlydevelopholes,abradedmetale nclosuresurfaces,anddefectivedoorsealswh ichcanBlastCleaningRoomSurfaces:Wheninte riorfloors,ledgesandshelfsurfacesofblast cleaningroomsarenotcleanedofwasteabrasiv eanddebrisonaregulardailybasis,bothsafet yandhealthhazardscanresult, ,evenonanirregularbasis,anddonotwearsuit ablerespiratoryprotectionforthetasksinVO lved, :Pressurevesselswithoutanupperfillheadof concavedesignorwhichotherwisearepoorlyde signedte~dtointerferewithentryoftheabras ive,inducespilling.