Safety advice for bulk chlorine installations - Cedrec · Safety advice for bulk chlorine...

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Health and Safety Executive

Safety advice for bulk chlorine installations

This is a free-to-download, web-friendly version of HSG28 (Second edition, published 1999). This version has been adapted for online use from HSE’s current printed version.

Youcanbuythebookatwww.hsebooks.co.ukandmostgoodbookshops.

ISBN 978 0 7176 1645 2 Price £14.00

Thisbookletgivesguidanceonthesafehandlingofchlorineatsiteswhichreceivebulkdeliveriesofchlorinebyroadorrailtanker.

Itisaimedatthemanagersoftheseinstallations,butitisalsorelevantforplantsupervisors,designandmaintenanceengineersandsafetyprofessionals.

HSE Books

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© Crown copyright 1999

Firstpublished1987

ISBN9780717616452

Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans(electronic,mechanical,photocopying,recordingorotherwise)withoutthepriorwrittenpermissionofthecopyrightowner.

Applicationsforreproductionshouldbemadeinwritingto:TheOfficeofPublicSectorInformation,InformationPolicyTeam,Kew,Richmond,SurreyTW94DUore-mail:[email protected]

ThisguidanceisissuedbytheHealthandSafetyExecutive.Followingtheguidanceisnotcompulsoryandyouarefreetotakeotheraction.Butifyoudofollowtheguidanceyouwillnormallybedoingenoughtocomplywiththelaw.Healthandsafetyinspectorsseektosecurecompliancewiththelawandmayrefertothisguidanceasillustratinggoodpractice.

Safetyadviceforbulkchlorineinstallations Page3of91


ContentsForeword 5

Introduction 6

Management of health and safety and risk assessment 7Riskassessment 8Design and location of installations 10Potentialincidents 10Sitingofinstallations 10Unloadingarea 12 Design and location 12 Deliveries of liquid chlorine by road tanker or ISO tank container 13 Interlocks 14 Deliveries of liquid chlorine by rail tanker 15Connectionsbetweenthetankerandthefixedlinestothestorageinstallation 16 Types of connection 16 Flexible couplings (semi-rigid loading arms) 16 Flexible hoses 17 Articulated arms 17 Pipeworkforliquidchlorine 17 Permanent pipework at the unloading point 18 Design criteria for pipework transferring liquid chlorine to storage tanks or from storage to point of use 18 Protection of pipework 19 Marking 20 Protectionofliquidchlorinepipeworkagainstoverpressure 20 Provision of relief systems 20 Valves 21 Types of valve 22 Vertical globe valves 22 Conical plug valves (PTFE-sleeved) 22 Ball valves 23 Remotely controlled valves 23 Storagevessels 23 Design criteria 24 Connecting pipework and means for isolation of storage tanks 25 Liquid chlorine inlet 26 Liquid chlorine outlet 26 Vent and compressed dry gas lines 28 Relief system 28 Instrumentation and chlorine detector systems 28 Chlorine detectors and alarms 29Protectionofstoragevesselsagainstoverpressure 30 Relief system 31 Bursting discs 31 Arrangements for relief systems 31 Expansion vessels 33 Pressure alarms 33Arrangementsforunloadingofliquidchlorinefromroadtankerstostorage 34 Unloading using dry compressed air or dry nitrogen 34 Supply of dry padding gas to the system 35 Unloading using chlorine gas pressure 35 Use of re-compressed chlorine vapour 35 Chlorinevaporisers 36



Types 36 Regulation of throughput 37 Methods of heating 37 General installation 38 Hazards 38 Routine and emergency isolation 40 Pressure control valve 41 Corrosion 41Chlorineabsorptionsystem 42 Vent collection system 43 Absorption equipment 43 Instrumentation 43 Disposal of effluent from the chlorine absorption plant 44

Operating and maintenance procedures, training and PPE 45Operatinginstructions 45Maintenance,inspectionandinstallation 45 General maintenance requirements 45 Maintenance of connections 46 Inspection and commissioning of chlorine tank installations 46 Inspection procedure 47 Testing 48Modificationofthechlorinesystemandclearanceprocedures 48Unloadingofliquidchlorinefromroadtankerstostorage 49 UseofISO(demountable)tankcontainers 50Transferofchlorinetotheconsumingunits 51 Transfer of gaseous chlorine 51 Transfer of liquid chlorine using vapour pressure 51 Transfer of liquid chlorine by padding with dry compressed gas 51 Transfer of liquid chlorine using a separate pumping tank 51 Precautions 52 Training 53 Competency and audit 53PersonalProtectiveEquipment(PPE) 54 Selecting suitable respiratory protective equipment (RPE) 54

Emergency arrangements 57 Emergencyequipment 57Controlofleakages 58 Releases inside buildings 59

Appendices 601Toxicologicalpropertiesandfirstaid 602Characteristicsofchlorine 613RelevantlegislationandHSEguidance 644Usefulcontactsandstandards 725Outsideinstallationsandinsideinstallations 756Proceduresfordischargingroadtankersofchlorine 777Typesofvaporiser 808Emergencyplans 83

References 85

List of acronyms and abbreviations 90

Further information 91



ForewordTheaimofthisguidancenoteistohelpthoseresponsibleforthesafeuseofchlorinefrombulkcontainerstomeettheirobligationsunderhealthandsafetylaw.

Thisguidance,likethedocumentthatprecededit,waspreparedwiththehelpofthechlorineproducers,users,tradeunions,theWaterServicesAssociation(WSA),andtheChemicalIndustriesAssociation(CIA).

Wearegratefultothosewhocontributedfortheirassistanceandco-operationinpreparingthisadvice,andtoShawValvesandtoDescoteLtdforpermissiontousethephotographslinkedtoparagraph74,toWestonPointStudiosforpermissiontousethephotographslinkedtoparagraph216andtoZenecaplcforpermissiontotaketheremainingphotographs.

Theguidelinesmaybeappliedtoanybulkchlorineinstallationbuttheyarenotintendedtobeadetaileddesigncode.Someexistinginstallationsmaynotatpresentmeetalltherecommendationsand,insomecases,notalltherecommendationsmaybeappropriate.Itisfortheoccupier,usuallyinconsultationwiththechlorinesupplierand/orspecialistadvisers,tojudgetheneedforfurtherriskcontrolmeasures,followinganassessmentoftheactualrisks.Ifimprovementsareshowntobeneeded,aresponsibledecisionisrequiredfromtheoperatingcompanyonthenatureandtimingofchangessothattheycanbemadesafely.

WherereferencetoBritish,Europeanandotherstandardsismadeinthisdocumentequivalentstandardsareequallyacceptablealternatives.

Youmayneedhelpbeyondthatgiveninthisguidance.Ifyoudo,tradeandemployerassociations,suchastheChemicalIndustriesAssociationandEuroChlor,oryourchlorinesuppliercanofferarangeofadviceandsupport.TheseandothersourcesofinformationaregiveninAppendix4.



Introduction1 Thispublicationgivesguidanceonthesafehandlingofbulkliquidchlorineatsiteswhichreceiveliquidchlorinebyroadorrailtanker,orbyISOtankcontainer.Theguidanceisaimedprimarilyatmanagersoftheseinstallations,butitisalsorelevantforplantsupervisors,designandmaintenanceengineers,andsafetyprofessionals.Applicationoftheguidancewillhelptoensurethattheriskstopeopleon-siteandoff-siteareminimisedsofarasisreasonablypracticable.

2 Therisksarisebecausechlorineisahighlytoxic(seeAppendix1)andreactivesubstance(seeAppendix2).Itformsflammableandexplosivemixtureswithsomeorganicandinorganicsubstances.Whenreleasedfromcontainmentitformsagascloudthatisheavierthanairandwhichmaintainscontactwiththegroundasitdisperses,possiblyendangeringpeopleinitspath.

3 Despitetheserioustoxicandreactivehazards,andthepotentialtoharmpeopleoff-site,thechlorineindustryhasestablishedaverygoodsafetyrecord.Thishasbeenachievedthroughthedevelopmentandpracticeofeffectiveproceduresforhandlingchlorinesafely.Thisguidance,likethedocumentitreplaces,isissuedtohelpmaintainandenhancethatrecord.Guidanceonthesafehandlingofchlorinesuppliedindrumsandcylindersisgivenelsewhere.1

4 TheguidanceisbasedonthecombinedexperienceofthefourUKmanufacturersofchlorine,theircustomers,tradeunionsandassociationsandHSE.Itcoversthesafetyandhealthrequirementsatallstages,fromthereceiptoftheliquidchlorinetothepointofuse,includingthelocation,design,testing,operationandmaintenanceofequipment.Proceduresfordealingwithemergenciesarealsooutlined.



Management of health and safety and risk assessment5 EmployershavealegalresponsibilityunderSections2and3oftheHealthandSafetyatWorketcAct1974(HSWAct)2toensure,sofarasisreasonablypracticable,thehealthandsafetyoftheiremployeesandotherswhomaybeaffectedbytheiractivities.Otherpeople,suchasdesigners,installersandsuppliers,alsohavesimilardutiesundertheHSWActwithrespecttoproducts.Since1974variousregulationshavebeenmaderequiringspecificcontrolsforparticularhazards(egpressuresystems),oractivities(egmanualhandling).Alistoftheseandothercurrenthealthandsafetylegislation,codesofpracticeandguidanceispublishedannually.3Thislistalsocoversamendmentstotheregulations.Referencesinthisdocumentaretothebaseregulations.Appendix3givesanoverviewofthemainlegislationandregulationsrelatingtothesafehandlingofchlorine.

6 YoumustobtainplanningpermissionfornewinstallationsintheusualwayfromtheLocalPlanningAuthority,whowill,whenappropriate,refertoHSEforadvice.Ifyoustore,orplantostore,morethan10tonnesofchlorine,yoursitewillbesubjecttoanumberofspecificregulations.

7 TheNotificationofInstallationsHandlingHazardousSubstancesRegulations19824requireyoutonotifyyouractivitytoHSEifmorethan10tonnesofchlorineisliabletobekept.Youmustalsonotifysubsequentchangestoyouractivity.Newinstallationsover10tonneschlorinecapacity,orproposalstoincreasethenotifiedcapacitytomorethanthreetimestheoriginalcapacity,mustbenotifiedthreemonthsinadvance.TheformofthenotificationisintheRegulations.

8 TheControlofIndustrialMajorAccidentHazardsRegulations1984(CIMAH)5alsoapplytositesstoringorprocessingchlorine.Theseregulationsapplyattwolevels.Thelowerlevelrequirementsapplytositeswhichstore10ormoretonnes.Theyalsoapplyatsiteswherechlorineisinvolvedinaprocessinanyquantity,unlesstheprocessoperationisincapableofproducingamajoraccidenthazard.Youneedtocomplywithtwogeneralrequirements:

(a) todemonstratetoHSE,atanytime,thatmajoraccidenthazardshavebeen identifiedandadequatelycontrolled;and(b) toreportanymajoraccidentstoHSE.

Forsiteswhichstore75ormoretonnes,orwhichprocesschlorineandhaveinventoriesof25ormoretonnes,unlesstheprocessoperationisincapableofproducingamajoraccidenthazard,morestringentregulationsapply.Theserequirethepreparationofasafetyreport,thepreparationofon-siteandoff-siteemergencyplansandtheprovisionofinformationtomembersofthepubliclikelytobeaffectedbyamajoraccident.CIMAHwillbereplacedinFebruary1999bytheControlofMajorAccidentHazardRegulations(COMAH)whichimplementtherequirementsoftheSevesoIIDirective6onthecontrolofmajoraccidenthazards;thethresholdforthelowertierrequirementsis10tonnes,and25tonnesforthetoptier.

9 ThePlanning(HazardousSubstances)Regulations19927applytositeswith10ormoretonnesofchlorine.Undertheseregulationsthe‘consent’ofthelocalHazardousSubstancesAuthority(HSA)isneededforthepresenceofchlorineinsuchquantities.TheHSAmustconsultHSEontheassociatedrisklevels.Toquantifytheoff-siterisksHSEmayrequesttechnicalinformationabouttheinstallation.8



10 Inaddition,anyprocesswhichinvolvesthemanufactureoruseofchlorineoranyprocesswhichislikelytoresultinthereleaseofchlorineintotheairorwater,isaprescribedprocessundertheEnvironmentalProtection(PrescribedProcessesandSubstances)Regulations1991.9OtherprocessesarealsoprescribedintheRegulations.UndertheEnvironmentalProtectionAct199010nopersonshallcarryonaprescribedprocessexceptunderanauthorisationgrantedbytheenforcingauthorityandinaccordancewiththeconditionsintheauthorisation.ApplicationsfortheauthorisationofaprescribedprocessinEnglandandWalesmustbemadetotheEnvironmentAgency(EA)andinScotlandtotheScottishEnvironmentalProtectionAgency(SEPA).InadditioninScotlandwheretheAlkaliandWorksRegulationAct1906,11asamendedbytheHealthandSafety(EmissionsintoAtmosphere)Regulations1983,12isstillinforce,suchprocessesarelistedasScheduledworksandmustberegisteredannuallywithSEPA.

11 Ifyoufillcontainersfromyourbulkinstallationandtransportthemoff-site,youwillneedtocomplywiththeCarriageofDangerousGoods(Classification,PackagingandLabelling)andUseofTransportablePressureReceptaclesRegulations1996,13andtheCarriageofDangerousGoodsByRoadRegulations199614(inthecaseoftransportationbyroad).TherelevantlegislationisoutlinedinanHSEbooklet.15Note:The(legal)termforgascylindersisnow‘transportablepressurereceptacles’.

12 Althoughyoumustcomplywithhealthandsafetylegislation,regulatorycontrolcannotcompensatefordeficienciesinthewaythatsafetyismanaged.Effectivehealthandsafetymanagementismainlyaboutmanagement(atalllevels)takingaproactiveapproachtominimisethechanceofincidentsoccurringratherthanputtingthingsrightaftertheyhavegonewrong.Guidanceoneffectivehealthandsafetymanagementisgivenelsewhere16,17whichadvocatesandelaboratesonthefollowinggeneralprinciplesofgoodmanagementpractice:

(a) setyourpolicyanddemonstratecommitmenttoit;(b) organiseandtrainyourstafftoensureeffectivecommunications,co-operation, andtheircompetencetocontrolrisks;(c) planwhatyouneedtodo,setperformancestandards,andestablishsystems andproceduresforcontrollingrisks;(d) measureyourperformancetoassesswhethertherisksarebeingadequately controlled;(e) conductsafetyauditstoensurethatyoursystemsareworkingasintended; reviewyourfindingsandtakeanycorrectiveaction.

AriskassessmentisessentialtothisproactiveapproachtosafetymanagementandisastatutoryrequirementoftheManagementofHealthandSafetyatWork(MHSW)Regulations1992.18GuidanceontheseRegulationsandriskassessmentiscontainedinanApprovedCodeofPractice.19

RISK ASSESSMENT

13 TheMHSWRegulationsrequireyoutoconductafullriskassessmenttoidentifyallthehazardsandassesstheassociatedrisks.Theriskassessmentneedstoincludeallsourcesofhazards,includingthoseassociatedwithtransportaroundthesite,accesstoplantandsecurity.Theneedforriskassessmentisalsoarequirementofotherregulations(egTheControlofSubstancesHazardoustoHealthRegulations1994(COSHH)20andtheFirePrecautions(Workplace)Regulations1997.21



14 Inoutline,ariskassessmentforyourchlorineoperationsrequiresyouto:(a) lookforthehazardsiepotentialsourcesofchlorinereleases;(b) decidehowseriouseachoftheseloss-of-containmenteventscouldbe,iewho couldbeharmedandhowseriously;(c) decidethelikelyfrequencyofeachofthesehazardousevents;(d) evaluatetheassociatedrisksandconsiderwhethertheprecautionstoprevent releasesofchlorineandtomitigatetheireffectsareadequate,orifmore shouldbedone(thisguidanceandthesourcesofadvicelistedinAppendix4 isrelevanthere;particularlythepublicationsofEuroChlor;22(e) recordyoursignificantfindings;thisisastatutoryrequirementifyouhavefive ormoreemployees;and(f) updateyourriskassessmentatleasteverythreeyears,andbeforemaking significantmodifications.Checkthatyouroperationalexperienceaccordswith anysignificantassumptionsyoumadetocarryoutyourriskassessment. Safetyaudits,aswellasday-to-daymanagementarrangements,should addresstheneedtocheckassumptions.

15 Eachsitewillhaveitsownspecialfeaturesandyouneedtotaketheseintoaccountwhenconductingyourriskassessment.Aproperriskassessmentwillhelpyouto:

(a) decidewhethertherisksarebeingcontrolledsofarasisreasonably practicable;and,ifnot,to:(b) establishadequatecontrolsandsafeworkingproceduresbasedontheadvice inthisnote.

16 Yourriskassessmentwillneedtoconsiderthemainpotentialcausesof releasesofchlorine.Forbulkchlorineinstallationstheseare (seeparagraph20):

(a) plantdamagecausedbyexternalsources(vehicles,hoists,flyingdebrisfrom nearbyaccidents,firesetc);(b) incorrectoperation;and(c) inadequateinspectionandmaintenance.17 Thepeopleconductingyourriskassessmentmusthaverelevantexperienceandknowledge.Ifnecessary,youmust18seekassistancefromexperiencedandknowledgeablepeople.Yourchlorinesupplierwillbeabletoidentifycompetentpeopleabletoconducttheriskassessmentonyourbehalf,andsupplyinformationtohelpyoucarryoutyourriskassessmentandtomanagesafety.

18 Theremainingsectionsofthisbookletprovideguidanceonthearrangementsforpreventionandmitigationofchlorineleaksandspillagesthroughgooddesign,operation(includingemergencyprocedures)andmaintenance.Theguidanceappliesonlytoinstallationsstoringliquidchlorineunderpressureinbulktanksortankcontainers.YoushouldthereforepayparticularattentiontotherequirementsofthePressureSystemandTransportableGasContainerRegulations1989(PSTGC).23Precautionsforthestorageofliquidchlorineinrefrigeratedtanksatlowpressureareoutsidethescopeofthisguidance.AdditionalsourcesofadviceandinformationarelistedinAppendix4.



Design and location of installations19 Bulkchlorineinstallationsoperateunderpressure.Consequently,thedesign,installationandoperation(includingperiodicexaminationandmaintenance)ofthesepressuresystemswillneedtomeettherequirementsofPSTGC.23Pipework,equipmentandprotectivedevicesforliquidchlorinearepartofthesystem.Theregulationsdonotapplytosystemsoperatingatorbelowpressuresof0.5bargauge,exceptforsteamsystems.GuidanceonPSTGCiscontainedinanApprovedCodeofPractice24andthepublicationA guide to the Pressure Systems and Transportable Gas Containers Regulations 1989;25seeAppendix3forbriefdetails.

POTENTIAL INCIDENTS

20 Whendesigningormodifyingyourinstallation,youshouldincludeprovisionstopreventthefollowingpotentialincidentswhichcouldresultinareleaseofchlorine:

(a) Damagetochlorinelinesfromexternalsourcesegbyhoistsorvehicles- includingtheroadtankerwhileitismovingtoorfromtheunloadingpoint. Whenthetankerispositionedforunloadingyouneedtoprovideadequate clearanceforthevalvedomewhenitisopen.Youalsoneedtomake allowanceformovementofthedeliveryvehicleduringthetransferoperation, egthenormalupwardmovementofthetankeronitssuspensioncancause damageifthereisinadequateflexibilityintheconnection,ormovement causedbyinadequatebrakingorwheelchockingorcarelessoperationbythe driver.(b) Damagetotheliquidchlorinedeliveryvehicle,storagetankorconnecting pipeworkcausedbyimpactfromothervehicles.(c) Jointandgasketfailuresduetofailuretotightenjoints,over-tighteningof joints,incorrectlyfittedortheuseofunsuitablejointrings,ortheuseof hydrocarbonbasedlubricantswhichmayburnwhenattackedbychlorine(see Appendix2).(d) Errorsinoperatingprocedures,includingover-fillingofthestoragetankand overloadingoftheventscrubber,failuretoclosevalveswhenremoving containers,orbreakingintothesystemformaintenance.(e) Plantandequipmentfailureduetoinadequatemaintenance,eg‘passing’ valves,orleakscausedbycorrosionorerosion,oruseofplantandequipment beyondtherecommendedlife.(f) Damagecausedbyfireorexplosion.

SITING OF INSTALLATIONS

21 Theguidanceinthissectionrelatestogeneralfeatureswhichaffectthelocationoftheinstallation.Morespecificfactorsarereviewedinthedetailedsectionsdealingwithoff-loading(seeparagraphs134-147)andemergencyprocedures(seeparagraphs247-263).Whendecidingthelocationofyourinstallationanimportantconsiderationisthepotentialriskstopeopleandtheenvironment.Theserisksdecreaseastheseparationdistanceincreases.Thesizeofsuchseparationdistanceswilldependuponanumberoffactors,including:

(a) thenumberandsizeofstoragetanks;(b) whetherthestorageisindoorsoroutside;(c) theoperationalconditionsandthetypeofprocess;(d) thefrequencyofchlorinedeliveries;



(e) thedesignoftheinstallation,eglengthanddiameterofliquidandvapourlines; and(f) thesize,distribution,andtype(egsensitivegroups)ofthesurrounding population.

22 Youshouldcarefullyconsiderthesefactorswhendesigninganddecidingthelocationofyourinstallationandwhenconductingyourriskassessment(seeparagraphs13-17).Youshouldinvolveyourchlorinesupplieratanearlystage.Considerationshouldbegiventomaximisingthedistancebetweenthesiteboundaryandthechlorineinstallation.Itshouldbeemphasisedthatyourriskassessmentandindividualcircumstances(seeparagraph21)willdeterminetheseparationdistances.Thesameconsiderationsalsoapplywhenmakingsignificantchangestoanexistinginstallationwithinasite.

23 Whenchoosingthelocationforyourchlorinearea,youneedtoconsiderthelocationofotheron-sitebuildingsinrelationtotheprevailingwinddirection.Itisrecommendedthatthechlorineareashouldbelocateddownwindofbuildingsthatareregularlyoccupied.Ventilationintakestooccupiedroomsshouldbeatleast25mfromthechlorineinstallation,andpreferablyatahighlevel.

24 Youalsoneedtotakeaccountoftheprevailingwinddirectionwhendecidingthelocationsofemergencyassemblypoints.Twoassemblypointsarerecommended;theseshouldbelocatedsothatatleastonewillbeavailableregardlessofthewinddirectionwhenareleaseoccurs.Forcomplexsites,indoorassemblypointsarerecommended;openairassemblypointsmaybesuitableforsimplesites.

25 Foranewinstallation,fullaccountwillhavetobetakenofanyrequirementsattachedtotheplanningpermissiongrantedbythePlanningAuthority.InadditionthelocalPlanningAuthorityneedstoensurethattheoverallplanwillavoidproblemsarisinginthefuturefromdevelopmentsleadingtoahighdensityofpopulationneartheinstallation,orfromtheintroductionofotherpotentialhazardsinanadjacentarea(seeAppendix3:Planning(HazardousSubstances)Regulations1992).ForsiteswhichmaypresentsuchhazardsHSEmayrecommendthatthehigheststandardsareapplied,beforeconsentcanbegrantedbytheHSA.Insomecasestheconsiderationofoff-siterisklevelsbyHSEmayrequirecontrolmeasuresinadditiontothoserecommendedinthisguidance.

26 Forexistinginstallations,controlofneighbouringpopulationdensitiesisnotpossibleintheshortterm.However,proposeddevelopmentsnearbywhichwouldincreasethenumberofpeoplearecontrollableandwouldbepermittedbythelocalPlanningAuthorityonlyafterdetailedconsideration.SuchconsiderationwillincludetheadvicereceivedfromHSEontherisksfromchlorinereleasestothosewhomayoccupyorusetheproposeddevelopment.

27 Thelocationofanewchlorineinstallationwithinasiteshouldbedecidedfollowingariskassessment.Inmakingyourdecisionyoushouldtakeintoaccountpossibledamagefromfloodingorsubsidence,andthepossibledamagetotheinstallationifneighbouringplantorfactoriessufferacatastrophebyfireorexplosion.Installationsshouldbesitedatasufficientdistance(25mminimum)frompublicroadsormainrailwaylinestoreducetheriskofdamagetotheinstallationifthereisanaccident.Protectivebarriersshouldbeinstalledwherenecessary.

28 Inallcases,suitablefences,togetherwithadequatesecuritysupervision,shouldbeprovidedtominimisethepossibilityofunauthorisedaccess.

29 Hazardsarisingfromaircraftmaynormallyberegardedasminimalwithprobabilitiesbelowthelevelofsignificancerequiredforanyspecialconsideration.



However,attentionmaybenecessaryinexceptionalcircumstances,egiftheinstallationisattheendofanairportrunwayorclosetoabusyairfield.Insuchcircumstancesliaisonwiththeairfieldoperatoronsuitableriskreductionmeasuresisessential.

30 Theinstallationispreferablylocatedintheopenair;butundersomecircumstancesanindoorinstallationmaybeappropriate.Indecidingthis,itisimportantthatariskassessmentismade,takingintoaccountthefactorslistedinAppendix5.Youneedtoconsiderthefollowingpossibleriskreductionmeasuresatanearlystage:

(a) thescopeforreducingthechlorineinventory,egreschedulingofdeliveries;(b) interlockingarrangements(seealsoparagraphs35,39-41)fortheautomatic isolationofleaksandtopreventthedeliveryvehiclemovingduringtransfer operations;(c) minimisingthelengthanddiameterofpipeworkcarryingliquidchlorineand ensuringoverpressureprotection;(d) mechanicallyventilatingchlorinebuildingsanddischargethroughafume scrubbingsystem;theassociatedairinletductsshouldbeatalowlevel;(e) improvingtheleak-tightnessofanychlorinebuildingagainstmajorleaks;and(f) restrictingtransfersofchlorinetodaylighthoursornormalworkinghours(8.00 amto5.00pm)astheweatherconditionsarelikelytobemorefavourablefor thedilutionofchlorineconcentrationsifthereisarelease.

UNLOADING AREA

Design and location

31 Youshouldaimtominimisethepossibilityofchlorineescapeduringthetransferofliquidchlorinefromthedeliveryvehiclestothestoragetank.Detailedattentiontothesiting,designandlayoutoftheunloadingequipmentandoperatingprocedureisessential.

32 Theunloadingareashouldbeonreasonablylevelgroundwithadequatesurroundingspaceprovidinggoodaccessfromdifferentdirections.Thelocationshouldminimisetheriskofimpactdamagefromvehicles,mobileequipmentorfallingobjectsfromliftingequipment.

33 Theunloadingpointshouldbereasonablyclosetothestorageinstallation.Toavoidimpactdamageaprotectivebarrierbetweenthetankerbayandthestorageinstallationisrecommended.Theunloadingpointshouldalsobesitedatasafedistancefromdrains,rivers,drainagecollectionpointsandanyplantorequipmentwhichmightgiverisetofireorexplosion.

34 Satisfactoryaccessshouldbeprovidedtothepermanentpipeworkfordischargeofthechlorinetankersandtoensurethatconnectionstothetankerscanbemadesafely.Wherethisinvolvesworkingfromaplaceabovegroundlevel,apermanentstructureshouldbeprovided.Thisshouldbedesignedsothat,incaseofemergency,escapeispossiblewithminimumrisk.Youcanachievethisbyinstallingasubstantialandnon-flammable(egsteel)structureandensuringthatplatformsarefreeofobstructionsandhavenon-slipsurfaces,adequatetoe-boardsandguard-rails.Alternativeescapewaysshouldbeprovidedwithstairwaysofstandardslope.Verticalladdersorsteepstairwaysshouldbeavoided.Ifverticalladdersareunavoidable,ensurethatsafetyhoops,etc,donotimpedeaccessforpeoplewearingbreathingapparatus.Thedesignofmoveableplatformsgivingaccesstothetopofthetankersneedstominimisethepossibilityofaccidentsduetocollisionwiththetankers.Interlocksystemsmaybeusedforthispurpose,seeparagraphs39-41.



Awelldesignedunloadingarea

35 Youneedtoprovideforthesafeisolationofanyleaksthatmayarise,particularlyfrompipeworkcarryingliquidchlorine.Itisrecommendedthatremotelyorautomaticallycontrolledvalvesshouldbeinstalledonthetransferlinetothestoragetanks.Whenautomaticisolationisemployed,operatedbychlorinesensorsintheunloadingarea,thedetectorsystemneedstocloseboththestoragetankisolationvalveandthatonthetanker.Thepossibilityofliquidchlorinebeingtrappedbetweenclosedvalvesandtheneedforpressurerelief(seeparagraphs61-67)needstobeconsidered.

36 Itisalsogoodpracticetoprovide:

(a) protectionagainsttheweatheronfixedgantriesatunloadingpoints,egby windbreaksoroverheadcanopies;(b) storagespaceforconnectorsusedfortransferoperationssothattheycanbe keptdryandprotectedfromdirtandmoisturegettingin,andpossibleimpact damage;(c) storagespaceforemergencyequipment(egfilterrespirators,breathing apparatus,protectiveclothingandspareequipment)inasafelocationsothat theequipmentisreadilyavailableinanemergency;(d) adequatelightingandemergencylightingcoveringtheunloadingarea,andall escaperoutes;(e) sufficientmanuallyoperatedalarmstationstoenablewarningtobegivenin theeventofachlorineescape.Furtherdetailsonemergencyproceduresare giveninparagraphs247-263.

Deliveries of liquid chlorine by road tanker or ISO tank container

37 TheCarriageofDangerousGoods(CDG)byRoadRegulations199614andtheCDG(DriverTraining)Regulations199626apply.ForsafetyreasonsallUKroadtankersarefittedwithair-operatedshut-offvalvesforthepaddingair(seeparagraphs134-141)andthechlorinedeliveryconnections.Itisalsostronglyrecommendedthatthefollowingmeansofminimisingpotentialrisksareadoptedwhereverpossible:

(a) Provisionofaseparateandprotectedunloadingareaforthesoleuseof chlorinetankers(egbyerectingsideprotectionofthemotorway-typecrash barrier).(b) Restrictionbysuitablemeansofthespeedoftrafficonadjacentroads.(c) Unauthorisedaccessofvehiclesandpersonneltotheunloadingareashould beprevented,egbyplacingwarningbarriers,notices,moveablebarriersor roadcones,orclosinggateswhenthechlorinetankersareinposition.(d) Provisionofaninterlock(seeparagraphs39-41)systemtopreventcoupling ofliquidchlorinelinestothetankersandopeningofthedischargevalve untilthetankerisimmobilised.Inaddition,theair-operatedtankervalves



shouldbeinterlockedwiththechlorinedetectionandshut-downsystem,orbe remotelyoperablefromtheemergencystoppoints.(e) Asystemofworkwherebyoneperson(thedriverforroaddeliveries)ispresent throughouttheunloading(seeparagraphs214-215,andAppendix6),anda secondispresentduringconnectionanddisconnection.Thesecondperson shouldbenearbyandavailablethroughoutunloadingtoprovidehelpon request.(f) Routingofchlorinepipeworkintheareatominimisetheriskofdamagefrom impactbythetanker,othervehiclesormobileequipment.

Tankerwaitingtoenterunloadingarea

38 Whereaseparateunloadingareacannotbeprovided,andtheunloadingpointisonafactorythroughroad,suchroadsshouldbephysicallyclosed(seeparagraph37c)toothertrafficduringthetransferofliquidchlorine.Yourriskassessmentwilldeterminewhetheradditionalmeasuresareneeded.

Interlocks

Thedischargearmandthepadding-airarmconnectorscannotbereleasedfromtheiranchorpointsuntilthebarriersarelockedinpositionandthemechanicalinterlockkeysremovedandusedtounlock

thearms

39 Interlocksshouldbeusedtopreventseriousincidents.Forexample,interlockscanbeusedtoensurethatthevehiclebrakesarefullyappliedbeforetheunloadingpipeisfinallyconnectedupandthetankervalveopened;or,abarrierontheunloadingplatformcanbeinterlockedtotheloadingconnector,sopreventinginadvertentmovementofatankerstillconnectedup.Alternativelythepressureintheunloadingpipecanactivateaflashingsigntoremindthedriverthatthetankerisstillconnected(thelattersystemmaybeappropriateataproducerplantoraconsumerplantwithalargethroughput).

40 Themanoeuvringnecessarytolocatearoadtankerpreciselyinrelationtoasolidpipeconnectormaymakeitmoredifficulttodeviseaninterlocktothehigheststandardofsecurity.Insuchcases,aninterlocktopreventaccessofothertankersisstronglyrecommended,andspecialattentionmustbepaidtothesystemofworkwhicheffectivelypreventsaccidentalmovementofthetanker,andtodrivertraining.Alternativelymovementdetectorsofthelightbeamandreflectortypecanbeusedandinterlockedtoclosetheisolationvalvesandsoundtheaudiblealarm.



41 Interlocksmaybeusedtopreventsomereleasesduetooperatorerror.Forexampletoensurethatliquidchlorineisnottransferredtotheventabsorber,inadditiontoaprocedure(step9ofAppendix6)requiringtheclosureofthemanualventvalveontheliquidchlorinedeliverylinebeforestartingthetankerdischargeprocedure,theventvalveshouldbeinterlockedwiththedeliverypointorthetankeroff-loadingvalve.

Theairsupplytothetruck’sbrakeshastobedisconnectedbeforetheinstrumentair(neededtooperate

thetankerpaddingairandchlorinedischargevalves)canbeconnected

Deliveries of liquid chlorine by rail tanker

42 TheCarriageofDangerousGoodsbyRailRegulations199627apply.Itisstronglyrecommendedthatyouadoptthefollowingmeansofminimisingpotentialrisks.Yourriskassessmentwilldeterminewhetheradditionalmeasuresareneeded.

(a) Closethesidingstoothertrafficduringtransferofchlorinefromtankersto storage,bylockingthepoints.Alternatively,frictionbuffersorade-railermay beused.(b) Controlbysuitablemeansthevolumeandspeedofadjacenttraffic.(c) Closewarningbarriersand/orplacewarningnoticeswhenthechlorinetankers areinposition.(d) Provideaninterlock(seeparagraphs39-41)systemtopreventcouplingor uncouplingoftheliquidchlorinelines,unlessbarriersorwarningnoticesare inposition.Itisrecommendedthattheinterlocksystemextendstoensure thatappropriatepointsontherailsidingsarelockedandwheelstopsraised beforetransferofliquidchlorinecanstart.(e) Establishasystemofworkwherebyonepersonisresponsibleforthe wholeoperationofunloading,andasecondiswithincallduringconnection anddisconnection.Thesecondpersonshouldbeintheareaandavailable throughoutunloading.(f) Routechlorinepipelinesintheareatominimisetheriskofdamagefrom collisionbythetanker,othervehiclesormobileequipment.

Owingtotheverylimiteduseofrailtransport,therestofthisguidancefocusesonchlorinedeliverybyroadtanker.Whenrailtransportisused,thesamegeneralprinciplesforthesafehandlingofbulkdeliveriesofchlorineapply.

Flexiblecouplingstothetankerforliquidchlorineandpaddingair.Noticetheswiveljointandthespring

loadedpipeworksuspensionforthepaddingairandliquidchlorinelines



CONNECTIONS BETWEEN THE TANKER AND THE FIXED LINES TO THE STORAGE INSTALLATION (see also paragraphs 134 -147)

43 Totransferliquidchlorinetostorage,itisnecessarytocoupletheliquidchlorineoutletlineonthetankertotheinletlinetostorage.Itisalsonecessarytoincreasethetankerpressurebyabout1.7barabovethatinthestoragetankbyconnectingasupplyofdrycompressedair,nitrogenorchlorinevapourtothetanker.Theassociatedpipework(seeparagraphs53-79)shouldbeassimpleaspossibletominimisetheriskofpotentialloss-of-containmentaccidents.

44 Connectionsforthetransferofliquidchlorinerequireverycarefulconsideration,astheyareapotentialsourceofloss-of-containmentleadingtoareleaseofchlorinetotheenvironment.Failureoftheunloadingconnectionscanresultfrominadequatedesign,poorweatherprotection,incorrectmaterialsofconstruction,inadequatepipeworksupport,improperuse,orinadequateinspectionandmaintenance.Therefore,youneedtoensurethatthedesignstandardsareadequate,thattestingandinspectionproceduresareregularlycarriedoutandthattheequipmentissatisfactorilymaintained.

Types of connection

45 Threetypesofconnectionareavailable:

(a) Flexiblecouplings(sometimescalledsemi-rigidloadingarms)have: (i)asolidconnectionpipewithswiveljointstofacilitateconnectiontothe tanker;and (ii)adegreeofflexibilitybuiltintothesupportsandhangertoallow movementwhencoupledup,ieacrankedfreelengthofpipeoracoiled pipe.(b) Flexiblehoses.(c) Articulatedarms.

Flexiblecouplingsarenormallyused,butflexiblehosesorarticulatedarmsmaybeusedbyagreementwith,orrecommendationof,thechlorinesupplier.

Flexible couplings (semi-rigid loading arms)

46 Flexiblecouplingsarenormallyconstructedfromsteelpipe.However,HastelloyC(notB)pipeisrecommendeduptothefirstisolationvalve.Thisoffersgreaterlifeinsituationswherethepipeisrepeatedlyexposedtoverysmallamountsofatmosphericmoisturebytheconnection/disconnectionprocess.Flexibilityisprovidedbyacrankedfreelengthofpipe(lessusuallybyacoil)toallowforverticalmovementofthetankerduringdischarge.Screwedconnectionsareusedfortheconnectionstotheroadtanker;screwedconnectionstoBS2128arecommonlyusedateitherendoftheflexiblecoupling.‘Swivel’jointsinthepaddinggaslineandtheliquidchlorinelinefacilitateconnectiontothetanker.Thesejointsaretightenedoncetheconnectionsaremade.Flangedconnectionsareusedforconnectingtorailtankers.

47 Pipinglocaltothetankerberthshouldnotbefixedforthefirst5-7mbutitneedstobesupported.Thesystemofsupportusedshouldensurethatthepipeworkiskeptabovetheheadroomrequiredbythetankerwhenitisbeingputinposition.Thesupportshouldalsoallowthepipeworksufficientverticalmovementtoaccommodatethatinthedeliveryvehicle’ssuspensionsystemduringtheunloadingoperation-typicallyabout150mm.Aminimuminternalpipediameterof25mmisrecommended.



48 Thedesigncriteriaforflexiblecouplingsconstructedfrompipeworkaresimilartothoseforfixedpipework(seeparagraphs56-60).Wheretheconnectionsarescrewedconnections,thegasketshouldbeatrappedjointring,whichisrenewedateveryconnection(seealsoparagraph215).

Flexible hoses

49 Thedesignofflexiblehoses29,30shouldbeagreedwithyourchlorinesupplier.Theyrequiremorefrequenttestingthanflexiblecouplingsandtheirlifeisshorter,butpositioningoftankersiseasier.FlexibleMonelbraidedhoseconnectionsarenormallyconstructedupto50mm(2in)sizefortheliquidchlorinedischarge,and25mm(1in)sizeforthecompressedgasconnectiontothetanker.

50 Theoperatinginstructionscoveringunloadingshouldensurethatvisualinspectionandleaktestingoftheflexiblehosesiscarriedoutbeforecommencingtransferofliquidchlorine(seealsoparagraph215).

Articulated arms

51 Articulatedarms,withswivelledjoints(knuckles),areusuallyusedonhighvolumeinstallations.TheyshouldbedesignedtomeettherequirementsspecifiedintheEuroChlorpublicationGEST75/4431andcertifiedasmeetingthisoranequivalentstandard.Theyshouldbeoperatedandmaintainedasadvisedbythemanufacturer.Armsshouldbevisuallyinspectedfordefectsandtestedforgastightnesseverytimetheyareused.Suspectarmsshouldbeimmediatelywithdrawnfromserviceformaintenance.

52 Wherethesealsatknucklejointsarepurgedbyaflowofdry(dewpointlessthan-40oC)airornitrogen,thisgasshouldbecontinuouslysampledbyachlorinedetectorsystemwithanalarm.Anisolationvalvesuitableforusewitharticulatedarmsshouldbeattachedtothedischargeendofthearmtopreventairenteringthearmafteroperation.Itshould:

(a) ensureagastightsealwhenthearmisnotinusetopreventmoisturegetting in-anendcapshouldalsobeused;and(b) permittheventingdownofthearmanddepressurisationofanyconnection adapter.Thearmshouldbeventedaftereachoperationandpurgedwitha suitabledrygas.

Whenanarmisoutofservicethepurgegasshouldbemaintainedunderasmallpressure(eg0.5bargauge).

Youneedtokeeparegistershowingeachoperationandthequantity(egtonnes)ofchlorinetransferred.

PIPEWORK FOR LIQUID CHLORINE

53 Indesigningyourpipeworkyoushouldtakestepstoguardagainstthefollowingcausesoffailure:

(a) impact;(b) heating,egfire(resultinginareactionbetweenthesteelandchlorine);(c) severeinternalorexternalcorrosion;(d) overpressure(seeparagraphs61-67);and(e) erosionduetorelativelyhighliquidvelocitiesandinadequateinspectionand maintenanceprocedures.Liquidvelocitieslessthan2m/sarerecommended.



54 Routingofpipeworkforliquidchlorineshouldnormallybeabovegroundandshouldbesuchastomaximiseprotectionfrommechanicaldamage,corrosionandfire.Aminimuminternaldiameterof25mm(1in)isrecommendedtoensureadequatemechanicalstrength.

Permanent pipework at the unloading point

55 Thepermanentpipeworkattheunloadingpointusuallyconsistsofthefollowinglines:

(a) pipeworkforpressurisingthetankerwithdryair,nitrogenorchlorine(see alsoparagraph134-147);(b) pipeworkforthetransferofliquidchlorinetostorage;and(c) pipeworkforinstrumentairlines,egtooperatetheremotelycontrolledvalves onthetanker.

Thesourceofcompressed‘padding’airneedstobeindependentfromthatsupplyingotherservices.Detaileddesignrequirementsforthepipeworkandfittingsaredescribedinparagraphs56-79.Thesystemforoff-loadingofliquidchlorineisdescribedinparagraphs134-147.

Design criteria for pipework transferring liquid chlorine to storage tanks or from storage to point of use

56 YourpipeworkwillbepartofapressuresystemandsubjecttotherequirementsofthePSTGCRegulations.23-25Itthereforeneedstobeproperlydesigned,fabricated,inspectedandtestedinaccordancewitharecognisedCode,egANSI/ASMEB31.332,33andshouldbesufficientlyrobustforallforeseeableconditionsofwork.

(a) Designpressure.Shouldnotbelessthan12bargauge(174psig), correspondingtoadesigntemperatureof+45oC.Anypartofthesystem whichmayoperateatahighertemperatureshouldbedesignedtowithstand thecorrespondingvapourpressure(seeAppendix2,FigureA2.1).

(b) Designtemperature.Shouldbelessthantheminimumatwhichthepipeis intendedtooperate,orthetemperaturetowhichitwillbecooledifliquid chlorineboilsoffatatmosphericpressure(-35oC).Thenormaldesignrange is-35oCto+45oC.Incertainuncommonsituationslowertemperatures arepossibleduetochlorinecoolingbelowitsboilingpoint,egwhenpurging systemswithdrygas-locationswhereliquidchlorinehascollectedmay cooltotemperaturesaslow-50oCduetoevaporativecooling.Yourchlorine suppliershouldbeabletoprovideadviceontheneedtodesignforsuchlow temperatures.(c) Materialsofconstruction.Careisneededinselectingsuitablematerials(see Appendix2).Seamlesscarbonsteeltubingisrecommendedforpipework. Allcomponentsofpipes,valvesandfittingsshouldberesistanttotheaction ofchlorinebetweentheextremesofoperatingtemperaturesandpressures. Originalmaterialcertificatesshouldbekeptthroughouttheplant’slife.(d) Corrosionallowance.1mm.(e) Radiusofcurvatureofanyformedbends.Threepipediametersminimum (weldelbowsmustbeusedwheretighterbendsarenecessary).Elbows,tees andreducingpiecesshouldbeforgedorhot-formedwithoutreductioninwall thickness.(f) Bolting.ShouldbedesignedtotherequirementsofBS4882.34

(g) Flanges.Thenumberofflangesshouldbelimitedasfaraspossibleand thoseusedshouldbetotherequirementsofarecogniseddesigncodeeg



BS156035orASME/ANSIB16-5.36Steelusedforfabricationofflangesor weldedconnectionstothepipemustbecompatiblewiththatofthepipeitself.(h) Gaskets.Theuseofincorrectmaterialsforgasketscanbedangerous;ifin doubtyoushouldseektheadviceofyourchlorinesupplier.Rubbergaskets shouldneverbeusedforliquidchlorineservice.Allpackings,gasketsand diaphragmsshouldberesistanttotheactionofchlorinebetweentheextremes ofoperatingtemperaturesandpressures.Provenmaterialssuchasspiral woundMonel,Kel-ForAramidfibrearesuitable.Compressedasbestosfibre (CAF)gasketstoBS1832,37gradeAorO,preferablygraphite-treatedoneach facetofacilitatedismantling,aresuitableforjointsthatareexpectedto remaininserviceforseveralyearswithoutbeingdisturbed.Anyusedasbestos componentsshouldbecollectedanddisposedofsafely.Wherejointsare madeandremaderelativelyfrequentlyCAFisnotrecommendedfor environmentalreasons.Alternativejointingmaterialsuchasaramidfibre shouldbeused.Polytetrafluoroethylene(PTFE)toBS656438gradeUA1/1 maybesuitableprovidedthejointisofanencapsulatedtype(egaspigotted joint)topreventthePTFE‘creeping’.Someusershavefoundleadtobe suitableonsmalldiameterpipework(lessthan25mm).Whereavarietyof gasketmaterialsareusedjointsshouldbetabbedforeasyidentification.(i) Manufacturers’instructionsneedtobestrictlyadheredto.Avoidover- tighteningfittingsasthiscanresultinleaksduetothesubsequentfailureof thefixingnutsorpacking.(j) Lubrication.Normallyinassemblingpipeflanges,boltsandgaskets,no lubricantsarerequired.Wherelubricationisneeded,onlyfullyinertoilsand greasesrecommendedforchlorinedutyshouldbeused.Onnoaccountmust hydrocarbon-basedlubricantsbeusedastheyreactwithchlorineandmay ignite.Theheatgeneratedmaybesufficienttocauseachlorine-ironfire(see Appendix2)whichwouldresultinapipeworkfailureandareleaseofchlorine.

57 Thefollowingcontrolsshouldbeappliedduringconstruction:

(a) Stressrelief.Allfabricateditemsandbuttweldsshouldbestress-relieved beforefinalinspectionandtesting.(b) Inspectionandpressuretesting.Allweldspatter,scaleandotherforeign mattershouldberemoved.Allbuttweldsshouldbefullyradiographedor ultrasonicallyexamined.Allpipeworkshouldbepressure-testedinaccordance withthedesigncode.Wherehydrostatictestsaremadeitisessentialthatthe completepipingsystemisthoroughlycleanedanddriedtoadewpointless than-40oCbeforeintroducingchlorine.Alltracesofoil,greaseandsolvents mustberemoved(egwithsteamoraqueousdetergentsorboth)forthe reasonsstatedunder‘Lubrication’inparagraph56.Ifahydrostatictestis madeafterinstallationitwillbenecessarytochangeallgasketstoensure dryness.Appropriateleaktestswillthenberequiredtocheckthenewlymade joints.(c) Modifications.Anyextension,modificationorrepairstopipeworkshouldbe carriedouttoastandardatleastequivalenttotheoriginaldesignand constructioncodeincludingstressrelief,inspectionandtesting.

Protection of pipework

58 Youshouldinstallpipeworkconveyingchlorinesothatitis:

(a) protectedfromimpactbyvehiclesbydistanceorwithbarriers;(b) protectedfromfallingobjectsegnooverheadhoists.Canopyroofsforweather protectionshouldbeconstructedoflightweightmaterials;(c) separatedfrompipeworkcarryingcorrosiveorflammablematerialsorother sourcesofheat,egsteam-theseparationwilldependonthenatureofthe othermaterialandanestimateofthehazard;



(d) adequatelysupported;(e) accessibleformaintenanceandinspection;(f) preferablyunlagged;and(g) regularlyinspectedunderanylaggingtodetectcorrosionduetofailureof weather-sealing.

Marking

59 Thechlorineareaneedstobeclearlyidentified,marked39-41-seealsotheDangerousSubstancesRegulationsinAppendix3-andsecuredagainstunauthorisedentry.ItisrecommendedthatchlorinepipeworkshouldbeclearlylabelledandpaintedyellowinaccordancewithBS171042(egto08E51-BS480043).TheHealthandSafety(SafetySignsandSignals)Regulations199644requireclearlabellingwheneverriskstoemployeescannotbeavoidedoradequatelyreducedbyothermeans;adviceisgivenintheassociatedguidance.45

60 Itisgoodpracticetomarkvalveswhicharerequiredtooperateinanemergency.Theyshouldbemarkedwithaclearindicationoftheirfunctionandthedirectioninwhichtheyopenandclose.Thesemarkingsneedtobeconsistentwiththemarkingsonanyflowdiagramsoroperationalinstructions.Valvekeysforoperatingtheemergencyvalvesshouldbelocatedneartothevalve.

PROTECTION OF LIQUID CHLORINE PIPEWORK AGAINST OVERPRESSURE

61 Trappingofliquidchlorinebetweenclosedvalves,followedbyariseintemperature,increasestheriskofoverpressure.Evenasmalltemperaturerisecancauseaveryhighhydraulicpressure,becauseofthehighcoefficientofexpansionofliquidchlorine(seeAppendix2).

62 Theriskofliquidchlorinebeingtrappedbetweenclosedvalvesisincreasedbythefollowingfactors:

(a) Isolationvalvesthatarecontrolledbydifferentoperators.Thismaybeaspecial riskwheretherearelonglinesorcomplexpipeworkbetweenunits.(b) Thesimultaneousclosureofautomaticallyoperatedvalvesthathavebeen installedforplantisolation.Thisriskshouldbeassessed.Insome circumstancesitmaybepreferabletoemployatleastonemanuallyinitiated remotelycontrolledvalve.

63 Youshoulddesignyoursystemandoperatingprocedurestominimisetherisksofoverpressurisation.Whenappropriate,pressurereliefdevicesshouldbefitted.

Provision of relief systems

64 Reliefsystemscomplicatepipeworkandintroduceotherpotentialhazards,andshouldingeneralbeavoided.However,ifthecapacityofyoursystemissuchthatreleaseofthechlorinepresentcouldleadtoaseriousincident,automaticmeansofreleasingexcessivepressureinthepipeworkneedstobeprovided.Itfollowsthattheconfigurationofthepipework,positioningofvalves,andvalve-closingmethods(seeparagraph62)havetobestudiedtoseewhetherthehazardcanoccur.

65 Pressurereliefsystemsshouldbedesignedtomeetyouroperatingconditions.Itisrecommendedthattheneedfor,andthedesignof,reliefsystemsisfullydiscussedwithyourchlorinesupplier.



66 Acommonmethodofpressurereliefforprotectionofliquidchlorinelinesisviaaburstingdiscinstalledinaverticalteeonthepipework,dischargingtoasuitablecollectingsystem(seeFigure1)Thereliefvolumeofthepressurevesselshouldbeatleast20%ofthelinevolume.Anyexpansionvesselshouldberegisteredasapressurevesselforexaminationandrecordingpurposes.23

Figure 1 PressurereliefsystemforchlorinepipelinesNote:ValveAshouldbesecuredopenandvalveBclosed.Lockingmechanismsshouldbedefeatableifthevalvepositionneedstobechangedunder

emergencyconditions.

67 Thepressurevesselshouldbefittedwithasuitablealarmwhichoperatesasaresultoftheriseinpressureinthevessel,iftheburstingdiscleaksorruptures.Thevesselandlinecanthenbeventedtoprocess,ortothechlorineabsorptionsystemviaanormallylocked-closedvalve.Theheated‘bottle’systemoriginallyusedonolderinstallationsisnowobsoleteandnotrecommended.

VALVES

68 ItisstronglyrecommendedthatEuroChlorapprovedvalvesareusedonnewinstallations.Careisessentialinthechoiceofvalves(egseethepublicationsonvalvesinreference22)astheyhavetoberesistanttochlorineandabletocopewiththestressestowhichtheymaybesubjected.Thevalvebodyshouldpreferablybemadeofforgedsteel;castironisnotacceptable.Ifthevalvedesignissuchthatliquidchlorinecouldbetrappedwithinthebodywhenthevalveisclosed,provisionshouldbemadetoavoidexcesspressurewhichmaydevelopwithtemperaturerise.Inothersituationstheevaporationofliquidchlorinemaycauseoperatingtemperaturestofallbelow-35oC(seeparagraph56(b));thevalvesshouldbeselectedsoasnottofailifthisoccurs.Problemswhicharespecifictocoldortoliquidchlorinelimittheapplicationofcertaindesignsofvalve.

69 Theselectionoftheappropriatetypeofvalveforeachapplicationshouldbereviewedwithyourchlorinesupplierwhowillbeabletosuggestmanufacturersofvalveswhoseequipmenthasgivensatisfactoryservicewithliquidchlorine.Thiswillreducethepossibilityofunsatisfactoryvalvesbeingusedwhichwillrequirereplacementafterashortperiodandcouldbeapotentialsourceofhazard.

70 Valveswhichare‘permanently’open(egtopreventinadvertentisolationofpressurealarms),or‘permanently’closed(egemergencyventlines)shouldbesecuredinthesepositions.Thelockingmechanismsshouldbecapableofbeingbrokenintheeventofanemergency,egtheleadorplasticsealtype.

Pressure alarm gauge

Locked open valve

Locked shut valve

Vent line to processor to absorption plant

Pressure vessel

Chlorine pipeline

Bursting disc assembly



71 Itisemphasisedthat,duringmaintenanceoperations,relianceonvalvesofwhatevertypeforisolationisinsufficient.Thedesignofthesystemshouldbesuchthatcompleteisolationofthesectionconcernedispossible.Suitablemethodsforachievingthisincludetheinstallationofspoolpiecesinthelineswhichcanberemovedandsubstitutedbyblanks,ortheinsertionofslipplates.46

Types of valve

72 Valvesofthefollowingtypeshavebeendevelopedforusewithliquidchlorineordrychlorinegasunderpressure:

(a) verticalglobevalves;(b) conicalplugvalves;(c) ballvalves.

73 Valveshavetobedegreasedusingsteamordetergentsandthencompletelydriedbeforeuse.Alltracesofanysolventusedshouldberemovedasitcouldreactwithchlorine(seeparagraph57(b)).Itisrecommendedthatafterthistreatmentthevalvesshouldbestoredinindividualgas-tightplasticbagsreadyforinstallationwhenrequired.

Vertical globe valves

74 Thistypeofvalveispreferredtoothertypesandisusedforisolationofliquidchlorinestocktanksorforlargeflowsofchlorinegas.Thebillet-globevalveisrecommendedforinstallationontheliquidchlorineoutletlinefromchlorinestoragetanks(seeparagraph96).Thegassealaroundthevalvespindleinglobevalvesmaybeformedbyapackedgland(preferablyusingringsorchevronsofPTFE)orbyabellowsseal.Thebellowsshouldbebackedupbyasecondaryglandseal.Globevalvesmay,withadvantage,befittedwithabackseatingarrangementwhichisolatestheglandfromlinepressurewhenthevalveisfullyopen.

Glandpackedglobevalve(typical Bellowssealedglobevalve Anglepatternglobevalvesizesavailable15mmto250mm) withpneumaticactuator. Hydraulicandelectrical actuatorsarealsoavailable

Conical plug valves (PTFE-sleeved)

75 Conicalplugvalves,PTFE-sleeved,aresatisfactoryforisolationofliquidchlorinelines,particularlywhenquickisolationmayberequired,buttheprimaryvalveonthestoragetankispreferablyaglobevalve.Rapidisolationcancausepressuresurgesandyouneedtoconsiderthesewhendesigningyourinstallation(seealsoparagraph79).

76 Conicalplugvalvesforusewithliquidchlorinerequireprovisionfortheavoidanceofproblemsarisingfromliquidchlorinetrappedintheborewhenthevalveisclosed.Ifthismakesthevalvesuni-directional,theyneedtobemarkedwithanindicationoftherequireddirectionofliquidflowtoensurecorrectinstallation.Gas-tightnessisprovidedbyaPTFEsleeveinsertedintothebodyofthevalveand



byasupplementarysealalongthelengthofthespindlebetweenthevalvebodyandhead.Careshouldbetakentoavoidtheapplicationofsidethrusttothespindlesofplugvalves.

Ball valves

77 Thistypeofvalvecanbeusedforisolationinliquidchlorinelinesandshouldincorporatethefollowing:

(a) sphericalturninglimitedtoaquarter-turn;(b) straight-throughflanging;(c) PTFEseals.

78 Ballvalvesshouldbeavoidedwhenoperatingconditionsinvolvelargeandfrequenttemperaturechanges.Ifusedwithliquidchlorine,youshouldmakeprovisionforavoidingproblemsarisingfromliquidchlorinetrappedintheborewhenthevalveisclosed.Liquidtrappedintheballshouldbereleaseddownstreamviaasmallholeintheball.Ifthismakesthevalveuni-directionalitneedstobemarkedwithanindicationoftherequireddirectionofliquidflowtoensurecorrectinstallation.(Ballvalvesmaynotsealwhenthesealingpressureandthesystempressureareinoppositedirections).Theremarksaboutpressuresurgesinparagraphs75and79alsoapply.

Remotely controlled valves

79 Therateofclosureofanyactuatedvalveshouldnotbesorapidthatitcausesunduepressuresurgesinthesystem.Thestandardrateofclosureshouldbesatisfactoryforpipeworkupto50mmdiameter.Longrunsoflargerdiameterpipeworkmayrequirelowerratesofclosuretopreventliquidhammer.Youshouldseekadvicefromyourvalvesupplier.

STORAGE VESSELS (see also paragraphs 190-229)

80 Tominimisethedangerofover-fillingyourstoragevessel,itscapacityneedstobesignificantlygreaterthanthatofthelargestdeliveryvehicle.Thechosencapacitywilldependontherateofconsumptionandthefrequencyofdeliveries.InstallationofbulkstoragefacilitiesshouldbeconsideredonlyiftheannualconsumptionofchlorineissufficienttojustifybulksuppliesratherthanpurchaseofliquidchlorineindrumsorISOcontainers(seeparagraphs216-221).Aninstallationconsistingofsmallertankswhichwouldrequiresplitloadsisnotrecommended.NewsitesshouldinvolveHSEatanearlystage.

81 Inconsideringthenumberofindividualstoragetanksforarequiredtotalstoragecapacity,takethefollowingpointsintoaccount:

(a) Theminimumworkingcapacityofthetankshouldbeadequatetosafely accommodatetheworkingstockresidueandthemaximumforeseenunit delivery.(b) Ifcontinuityofsupplyisessential,atleasttwotankswillberequiredtoallow timefornecessaryinspectionsandtofacilitatemaintenance.Thisalsoprovides greaterflexibilityofoperation.(c) Increasingthenumberofstoragetanksleadstoanincreaseintheancillary plantandequipmentwithacorrespondingincreaseincomplexityofoperation.

82 Thedistancebetweenadjacentstoragetanksshouldbeadequatetoprovidegoodaccesstothetanksunderallcircumstances.Thisincludesthoseinwhichbulkyprotectiveequipment(suchasself-containedbreathingapparatus)isbeingused.



Chlorinestoragevesselandbund.Notetheemergencystopbutton(oneofseveral)attheedgeof

thebund.

83 Allchlorinestoragetanksshouldbeinstalledinabundwhichisimpervioustoliquidchlorine.Thebundshouldbecapableoftakingthecontentsofthelargeststoragetankwithadequatefreeboardandasump.Ifthereisasub-divisiontogiveaseparatesectionundereachtank,eachsectionshouldhaveaslopingfloorleadingtoasump,whichmayservemorethanonetank.Sumpsshouldnotbeconnectedtothedrain.Provisionshouldbeincludedforremovalofrainwateroverthebundwall,notviathedrainorthroughvalvesinthebund.

84 Leaksofliquidchlorinearepotentiallymuchmoredangerousthanleaksofgaseouschlorine.Yoursystemthereforeneedstobedesignedsothatsourcesofleakageofliquidarereducedtoaminimum,egbyavoidingjointswhicharecontinuouslyexposedtoliquidchlorinesuchasbottomoutlets,seeparagraph88.

85 Theseverityofaleakisreducedbyloweringthepressurewithinthesystemandthereforeitisimportantthatfacilitiesfortransferringgaseouschlorinetoaconsumingprocessortoawaste-chlorineabsorptionplantareavailable.Youshouldalsoconsiderinyourriskassessmenttheneedforarrangementstotransferliquidchlorinefromaleakingtanktoanothertankwhichcanbeisolated.

86 Layoutofthechlorineareashouldbeplannedtoprovideallfacilitiesnecessaryforgoodhousekeepingandemergencyresponse.Chlorinestoragetanksshouldthereforebeerectedabovegroundlevel.Installationindeeppitsisnotrecommendedbecauseitincreasesthedifficultiesoftreatmentanddispersalofachlorineescapeandofaccessformaintenanceorrepair.Amplestoragespaceisneededformaintenanceandsafetyequipment,whichhastobereadilyaccessibleinanemergency.

87 Thermalinsulationofthestoragetanksisnotnormallyrequired.However,ifyourvesselisrelativelyclosetoafirehazardandlaggingisrequired,thematerialshouldbefire-resistant,chemicallyinerttoliquidorgaseouschlorineandresistanttoatmosphericmoisturegettingin.Periodicinspectionbeneaththelaggingisessentialwhencheckingforcorrosion.

Design criteria

88 Designcriteriafornewliquidchlorinestorageandexpansionvesselsareoutlinedbelow.

(a) Designpressure.12bargauge(174psig)minimum.(b) Designtemperature.Whenliquidchlorineevaporatesatatmosphericpressure itstemperaturefallsto-35oCandthereforetheminimumdesigntemperature shouldnotbeanyhigher,butlowertemperaturesarepossibleifevaporative coolingofliquidchlorineoccurs,seeparagraph56(b).Thenormaldesign rangeis-35oCto+45oC.



(c) Fillingratio.Fillingratiosfortransportableliquidchlorinecontainersare detailedinBS535547forvarioussizerangesofmobilecontainersandfor differenttemperatures.Althoughthereisnoequivalentstandardforfixed tanks,forsimplicityafigureof1.25kgofliquidchlorine/litrecapacityis normallyusedtofixthemaximumleveltowhichthetankmaybefilledand thesettingchosenforthehighlevelalarm.Thisensuresthatthevolume ofliquidchlorinedoesnotexceed95%ofthetotalvolumeofthevessel,even foramaximumtemperatureof50oC.(d) Designcode.NewvesselsshouldbedesignedandmanufacturedtoBS 550048Category1(oranequivalentstandard).(e) Corrosionallowance.Minimum1mm.(f) Supportsandloadcells.Thevesselsupportsshouldbedesignedin accordancewiththedesigncodetopermitthermalexpansionor contractionoverthedesigntemperaturerange.Specialconsiderationmay benecessary(checkwithyoursupplier)whereloadcellsareusedfor determiningthecontentsofthetank,egcertaintypesofweighingdevice requiresecondarysupports.(g) Branches.Dimensionsshouldbelimitedtotheminimumrequired,particularly fortheliquidlines.Allbranchesshouldbemounted,wherepossible,onthe manholecoverorcovers.Manholeaccessshouldbeprovidedontopofthe vessel.Theopeningshouldpreferablybe600mmdiameter,butinnocase shoulditbelessthan460mmdiameter.Bottomoutletsshouldnotbe providedexceptwhererequiredforchlorinetransferbypumping.Any bottomoutletshouldhaveaninternalvalve,preferablyremotely-operable, plusaback-upisolatingvalve(seeparagraph97).(h) Bolting.ShouldmeettherequirementsofBS4882.34

(i) Gaskets.Useofincorrectmaterialsforgasketscanbedangerous,see paragraph56(h)forsuitablematerials.(j) Documentation.Regulation5ofPSTGC23-25requiresdesigners,manufacturers andsuppliersofpressuresystemstoprovidesufficientwritteninformation concerningthedesign,construction,examination,operationandmaintenance toenabletheregulationstobecompliedwith.Youmustretainthisinformation togetherwithanyCertificateofCompliance(egBS550048orsimilar documentationifotherstandardsarebeingused).(k) Marking.ThevesselmustbemarkedwiththedetailsspecifiedinSchedule4 ofthePSTGCRegulations.Allvalvesandpipeworkassociatedwithchlorine storagetanksshouldbelabelledandcolourcoded(seealsoparagraphs59 and60).

89 Paragraph88appliestonewsystemsdesignedandconstructedinaccordancewithacurrentstandard.Whereanexistingtankhasbeenprovidedinaccordancewithadifferentstandard,thesystemsshouldbeassessedaccordingtotherequirementsofthoseoriginalstandards.Inparticular,ifthevessel’ssafeworkingpressureislessthan12bargauge(174psig),thentheairsystempressure,reliefdevicesetcallhavetobealteredtosuit,andthedeliverysystemhastobearrangedsoastobecapableofworkingwithinthestoragetankconditions.Itisrecommendedthatsuchtanksarereplacedwithtanksmeetingtherequirementsofparagraph88.Thetimingofthereplacementshouldbeagreedwithyourchlorinesupplierandthecompetentpersonwhoexaminesyourvessels.

Connecting pipework and means for isolation of storage tanks

90 Themainconnectionstothestoragetanksare:

(a) liquidchlorineinlet;(b) liquidchlorineoutlet;(c) ventlinesandcompresseddrygaslines;



(d) reliefsystem;(e) instrumentationandpressuregauges.

Connectionsatthetopofthechlorinestoragetank.Notethepressuresreliefsystemwithinterlocked

valves(seeparagraphs120to127)

91 Youneedtokeepthenumberofconnectionstoaminimumtoreducethepotentialsourcesofleakage.Thearrangementsofvalvesandpipeworkshouldbemadeassimpleaspossibletominimiseerrorsinoperation.Pipeworkisolationvalvesshouldbefitteddirectlytothebranchesonthemanlidorthetankitself.Thesystemshouldbedesignedandoperatedsothat,ifthejointsbetweenthevalvesandthestoragetanksfail,gaseouschlorineonlywillbereleased(seeparagraphs94-96).

92 Whenevertwovalvesareinstalledinseriesforisolation,itisrecommendedthatthesystemofoperationisplannedsothateachvalveisusedexclusivelyforadefinedperiodduringnormaloperation.Thisensuresthatbothvalvesarekeptinoperableconditionatalltimes.

93 AnapplicationoftheprinciplesinthissectionisshowndiagrammaticallyinFigure2.Notallinstallationswillbetothispattern,andvariations(someofwhicharedescribedinthetext)maybeappropriate.

Liquid chlorine inlet

94 Theliquidchlorineinletshouldnotnormallyextendfurtherintothetankthanthemaximumliquidlevel.Someolderinstallationsuseadip-pipeontheinletline.Toavoidliquidchlorineflowingbackifthefillinglinefails,holesaredrilledinthetopofthedip-pipesothatliquidwillnotsiphonback.Afulldip-pipemaybeprovidedasaninlettoavesselusedforbothimportationandexportation.Suchvesselsneedtobefittedwiththeadditionalcontrolsappropriatetoaliquidchlorineoutlet.Youshoulddiscussthecontrolsneededwithyourproposedchlorinesupplieratanearlystage.

95 Theisolationvalveonthechlorineinletline,directlyboltedtotheflangeonthestoragetank,shouldpreferablybeabilletorhighintegrityglobevalve.Aback-upvalveshouldbeprovided,whichmayberemotelyoperated.Ifamanualback-upvalveisused,theisolationvalveatthedeliverypointendofthepipeworkshouldberemotelyoperablefromtheemergencystoppoints.

Liquid chlorine outlet

96 Theremovalofliquidchlorinefromthestoragetankisbymeansofadip-pipe.Youthereforeneedtomakearrangementstopreventchlorinereleasescausedbythejointbetweentheisolationvalveandstoragetankfailing.Thisismost



satisfactorilyachievedonnewplantbyuseofabillet-typeglobevalve,boltedtotheflangedbranchonthestoragetank,withthedip-pipescrewedintothebottomofthevalve.

97 Youneedtobackupthemainisolationvalvewithanadditionalvalvetoenableisolationifonevalvefailstoseateffectively.Dependingonthelocalpipingarrangement,provisionofoneormoreremotelycontrolledvalvesisrecommendedforemergencycontrol.Aremotelyoperatedvalvewhichisdesignedtogivepositiveisolationandwhichissuitablypositionedmayalsoserveasoneofthetwoisolationvalvesrequired.

98 Inaddition,itisstronglyrecommendedthatyouincorporatearestrictingorificeinthelinetotheconsumingplant.Theobjectofthisistoreducethesizeofareleasefromamajorfailuretoaslowasreasonablypracticable,ieappreciablylessthanthefull-boreflowthroughthepipe.Thesizeandlocationoftheorificeneedscarefulconsideration.Theorificeshouldnotbesosmallastoleadtoproblems,suchaspronenessoftheorificetoblocking,etc.Insomecasesitmaybepracticabletolimittheflowinthelinetothemaximumrequiredbytheprocess.Theorificeshouldnotbelocatedwithinthedip-pipebecauseoftheproblemofremovingtheliquidchlorinefromthetankintheeventofablockageoftheorifice.Insomeplants,theflowrestrictioncanbereplacedbytheremotelyoperableshut-offvalves(seeparagraph111)controlledbyasuitablefloworpressuresensor.Excessflowvalvesmaybeadvisableforlinesnormallytakingaflowofchlorinemuchlessthantheflowwhichcouldpassthroughinfaultconditions.Theyarenotsuitableforlinesinwhichthenormalflowrateishigh,andforwhichothermeansoffaultdetectionandflowisolationshouldbeused.

WIA

All UK road tankers have air-operated shut-off valves.Where practicable theseneed to be linked into theautomatic gas detection and shut down system(para 113 et seq) and /orbe remotely operable from the emergency stop points (para 37d)

Expansion vessel, paras 128-133see para 96

Storage vessel

H

The parts within the dotted line are repeated on every storage vessel

see paras119 -127

H'B' L

H

H

H

H

One of these valves shouldbe remotely operablefrom emergency stoppoints (para 97)

Uilage pipe (paras 107 and 108)

see para 99

Liquid CI to consuming plant(para 98)

2

2

Restricting orificeIf there is any risk of liquid from the vent being suckedback this line should includea preventive device (107, 174)

Vent absorber(para 171-189)

'A'

Dry air or dry Nsupply system atcontrolled pressure(para 134-141)

Valve A or B shouldbe remotely operablefrom emergency stop points (para 95)

Figure 2 AnexampleofthearrangementsfromchlorinetankerstoliquidchlorinestoragevesselsNote:Notallinstallationswillbetothispattern



Vent and compressed dry gas lines

99 Ventlinesandcompresseddrygaslinescanbeconnectedtothestoragetankeitherthroughseparateinletsorthroughacombinedsingleinlet.Ineithercase,thevalvedirectlyconnectedtothestoragetankshouldbebackedupbyasecondvalve.

100 Thepreventionofsuck-backofaqueousliquorintotheventlinerequiressimilarprecautionstothosedescribedforvaporisers(seeparagraph161).Thepreventionofback-diffusionofmoistureisdescribedinparagraphs178-181.Theinlettothescrubbingsystemshouldincludealutepipe(barometricleg)topreventliquidfromthescrubbingsystementeringthechlorinesystem.

101 Theprocedurefortransferringliquidchlorinetothestoragetanksshouldprovidefortheventvalvetobeopenedslightlyattheendofdischargeforaboutaminute(seeAppendix6,paragraph17)toconfirmthatthetankhasnotbeensignificantlyover-filled,ieabovetheextra-highlevelalarm(seeparagraph104).Overfillingisindicatedbyfrostingontheventline,inwhichcasepressurereliefmaybenecessary(seeparagraphs102-132).

Relief system

102 Thespecialrequirementsfortheisolationvalvesonthepressurereliefsystemonthestoragetanksarecoveredinparagraphs123-133.

Instrumentation and chlorine detector systems

103 Controlinstrumentationonstoragetanksandelsewhereintheinstallationshould,whereverpossible,bedesignedtofailsafe.Electricalandelectronicequipment,unlessspeciallyprotectedagainstcorrosion,shouldnotbeplacedinareaswhereitcouldbeaffectedbygasleaks.

104 Storagetankcontents.Thequantityofliquidchlorineineachstoragetankispreferablydeterminedbyinstallingthetankonloadcellsoronaweighbridge.Loadcellsshouldberecalibratedwheneverthevesselisinspectedandpressure-testedwithwater.Accuracycheckscanalsobemadeagainsttheweightofchlorinesuppliedwheneveradeliveryismade,providedtheplantisoff-line.Itisrecommendedthatloadcellsarerecalibratedatintervalsnotexceedingthreeyears.Theweightofliquidchlorineineachtankshouldbeindicatedlocallyandmayberepeatedintheplantcontrolroom.Thecontents-measuringdevicesneedtooperateahigh-contentsalarminthecontrolroom(andoncomplexplants,possiblyanextra-highcontentsalarm)forsafetyreasons.Theextra-highlevelalarmneedstoberunindependentlyofthesystemgivingthehigh-contentsalarm,forreliabilityreasons.Whenfitted,itisrecommendedthattheextra-highlevelalarmisusedtoautomaticallyclosethetankinletvalveandthetankeroutletvalve,seeparagraph105.

105 Asanalternativetothemeasurementofthequantityofliquidchlorinebyweight,measurementbyliquidlevelinthetanksisalsoacceptable.However,selectionofsuitableequipmentisdifficultandyoushoulddiscussitwithyourchlorinesupplier.Suchdevicesarepreferredasthemeansoftriggeringtheextra-highlevelalarm.

106 Tolimittheliquidvolumeinthestoragetanktothatpermittedbythefillingratio(seeparagraph88(c)),anullagepipecanbescrewedintothebottomofthevalveontheventline.Thelengthofthisullagepipeneedstobeconsistentwiththefillingratiosothat,ifliquidchlorinerisesabovethecorrectlevel,itwillflowthroughtheullagepipewhentheventvalveisopenedattheendofadelivery(seeAppendix



6)orinresponsetoanalarm.Theullagepipeshouldbecheckedwhentheroutineinspectionofthestorageinstallationismade.Alowtemperatureorotheralarm(seeparagraph107)shouldbefittedontheventlinefromthestoragetankstowarnifliquidchlorineisenteringtheullagepipeontheventline.

107Onasimpleinstallation,withgoodstaffingandattendanceatthetanks,anullagepipe(seeparagraph106)mayserveastheextra-highlevelalarm.Youneedtobeawarethatthismethodrequirestheventlinetobeleftopen,whichisnotnecessarilythecaseforalternativemethods,seeAppendix6.Ifahighcontentsalarmisignoredduringfillingofthetank,theliquidreachesthebottomoftheullagepipeandevaporatesinthevent-lineabovetheventcontrolvalve,producingfrostingofthepipe.Anullagepipethereforepresentstheriskofliquidchlorinebeingpassedtothescrubberunlessthelinecontainsaknock-outdevicefittedwithahighlevelalarm.Aknock-outpotintheventlinewithlevelalarmsisalsorecommendedforotherreasons(seeparagraph157).Theminimumprotectionfittedshouldbearestrictionorificeplate(seeparagraph98)andalowtemperaturealarm.

108 Ullagepipesarenotrecommendedforcontentsindicationonnewinstallations;insteadanextra-highlevelalarmonthetankshouldbeinstalled,seealsoparagraph105.

109 Alowcontentsalarmmaybeusefulforoperationalreasonsandmayhavesafetyimplicationsif,egtherecouldbeprocessupsetsonfailureofchlorinesupplyorpassageofpaddingair(seeparagraph226)intoadownstreamvessel.

110 Storagetankpressure.Thepressureinthechlorinestoragetanksisusuallymeasuredbygaugesspeciallydevelopedforusewithliquidchlorine;thesehavesilverortantalumdiaphragms.Beforeuse,thegaugesneedtobecompletelydegreased(egwithsteamand/oradetergent),driedandalltracesofsolventremoved,andbepressure-testedusingonlyclean,dry,oil-freecompressedair.Thepressuregaugesmaybefittedwithswitchestogiveanalarmifthepressureexceeds,orfallsbelow,apre-setvalue.Alternatively,pressureswitchesmaybeusedtogiveanindependentsignalforthehighandlowpressurealarms.

111 Wherereferenceismadetofloworpressuresensors‘operating’valves(seeparagraph98)thereisachoicewhethertheoperationisautomaticorviamanualintervention(seeparagraph62(b)).Attheextremes,operationshouldbeautomaticinanunstaffedplant,andmaybeindirectinawell-instrumentedplantwithacontinuouslystaffedcontrolroom.

112 Equipmentassociatedwiththeautomaticpressurereliefsystemisdescribedinparagraphs120and128-133.

Chlorine detectors and alarms

113 Theairinabuildinghousingchlorinestoragetanksshouldbecontinuouslymonitoredusingproprietarychlorinedetectorsystemstogivewarningofchlorineleakage.Detectorsarestronglyrecommendedinbuildingswhicharenotcontinuouslystaffedtoprovideearlywarningofleaks,allowingpromptremedialaction.Foroutdoorinstallations,thevalueofdetectorsystemsneedstobeassessedbyconsideringfactorssuchasthesizeoftheinstallation,thestaffinglevelsandtheresponsetimesachievable.Ondetectingaleak,thedetectorshould:

(a) raiseanaudiblealarminacontinuouslystaffedareaorcontrolcentre;(b) activateaudiblealarmsintheaffectedarea;(c) operatetheautomaticisolationvalves;and(d) controlthemechanicalventilation,iffitted.



114 Audiblealarmsneedtohaveadistincttone.Inaddition,warninglightsoftheamberflashingortrafficlighttypemaybefittedoutsideeachchlorinebuilding.Whereappropriate,egatlarge,remoteorsensitivesites,alarmsshouldbeconnectedtoatelemetrysystemtoprovidewarningatastaffedcontrolpoint.Thecontrolpointshouldbeabletoisolatethechlorinesupply,preferablyviaaremotelyoperablevalvefittedtotheoutletofthetank.

115 Chlorinedetectorsmaybeplacedinstorageandplantareas.Themanufacturerorsupplierofthesystemshouldadviseonthebestlocationforthesensors;typicallysensorsaremountedbetween0.3mand0.5mabovegroundlevel,andattheoutletfromfumescrubbers.Forindoorinstallations,sensorsmayneedtobelocatedinorneartheentrancetoductscarryingchlorinepipework,andtheairintakestoextractorfans.Whereforcedventilationsystemshavebeeninstalled,thedetectorshouldbelocatedattheoutletofthesystem;wherethisisnotreasonablypracticablethedetectorshouldbeplacednearthestorageanduseareas.

116 Detectionsystemsshouldprovideacontinuousmonitoringfunctionwhenchlorineisinstorageorinuse.Chlorinegassensorsshouldbetestedregularlyinaccordancewiththemanufacturer’sinstructionstodemonstratethatthedetectoranditsassociatedcircuitsarefunctioningcorrectly.Arecordofsuchtestsisrecommended.Thedetectionsystemshouldoperatethealarmcircuitsintheeventofpowerloss,sensorfailure,orlowconditionofthestandbybatteries.Allalarmrelayoperationsshouldbeprotectedbyabatteryback-upfacility.

117 Thedetectorsystemshouldactivatethelowlevelalarmatachlorineconcentrationof1-5ppm.Lowersettingsareliabletoactivatethesystemateverytank-fillingoperation,unlessadurationrequirementisalsoimposed.Forexample,somecompaniessetthelowlevelalarmat0.5ppm,butrequirethesensortoregisterthisconcentrationforatleast30seconds,toavoidspurioustripsofthealarmsystemduringfillingoperations.Forindoorinstallations,thelowalarmlevelshouldactivatetheventilationfan,opentheintakelouvers,andactivatelocalaudioalarmsandanyremotetelemetryalarm.

118 Multi-stagedetectorsystemsaresometimesusedtogiveanindicationoftheseverityofthemalfunctiontopersonneloutsideachlorineroom.Itissuggestedthatthehighlevelalarmoperatesataboutthreetimesthelevelofthefirst-stagealarm,ie3-15ppm,dependingonthedurationthatthesensorneedstoregisterthislevel.However,somecompaniessetthehighlevelalarmat2ppmwitha30seconddurationrequirement.

Onactivationofahighlevelalarmtheventilationsystemshouldbeshutoff,theauto-shutdownsystemactivated(wherefitted)andthehighlevelalarmsounded.Thetoneofthealarmatlowandhighlevelsshouldbedifferentandoperatorstrainedtorecognisethedifferenceandhowtorespondineachcase.Localalarmsmaybesupplementedbytelemetrylinkstocontrolrooms,whereappropriate.Theresponsetoalarmsiscoveredinparagraphs247-263.Somesensorscanbedamagedbyhighchlorineconcentrations;detectorsystemsshouldthereforebecheckedafteranyhighlevelalarm.

PROTECTION OF STORAGE VESSELS AGAINST OVERPRESSURE

119 Highpressureontheliquidchlorinestoragetankisindicatedbyahighpressurealarm(paragraph110).Overpressureintheliquidchlorinestoragetankscanresultfromover-fillingorexcessivepaddingpressure.Over-fillingwithliquidchlorineisindicatedbyalarmsontheweighsystemusedtodeterminetheliquidchlorinecontentofthestoragetanks(paragraphs104-109).Overpressureonthecompressedairornitrogensupplytothestoragetankispreventedbythe



installationofareliefvalveonthesupplysourceofthecompressedgas.Thesupplysourceshouldbewellupstreamofthetankandseparatedfromitbyisolationvalves(paragraph139).

Relief system

120 Thestoragetanksneedtobeprotectedagainstoverpressurebyasuitableautomaticpressurereliefsystemwhichissettooperateatapressurebelowthedesignvalue.Thepreferredpressurereliefsystemconsistsoftwoburstingdiscsplacedbacktoback.Aburstingdiscfollowedbyareliefvalvemayalsobeused,butisalwayssubjecttotheriskofcorrosionofthereliefvalve.Protectionofthereliefvalvefromcorrosionmustbecarefullyconsiderediftheburstingdiscreliefvalvesystemisused.Theuseofreliefvalvesaloneisnotrecommendedbecauseofthecorrosionorblockagewhichcouldoccurifareliefvalvewereleftcontinuouslyexposedtochlorine.Whicheversystemisused,youshouldprovideapressurealarm/indicatorbetweenthetwodiscsorbetweenthediscandreliefvalve(seeparagraph133).Inthelatterarrangementitisgoodpracticetoremoveandoverhaulthereliefvalvewhenevertheburstingdiscisreplaced.

121 Thedischargelinefromthepressurereliefsystemnormallyentersaclosedexpansionvessel(exceptinafewspecialisedarrangements).Anypressureintheexpansionvesselorbetweencomponentsinthereliefsystemreducestheprotectiongiventothestoragevessel(seeparagraphs85,128-133).Specialreliefarrangementsareusuallyrequiredwhenthereisasignificantriskofoverpressurefromcontinuouspressuresourcessuchasradiantheatorbypumpingchlorine.Underthesecircumstancesreliefintoaclosedexpansionvesselmaybeinadequate.Reliefarrangementsbasedonreliefvalvesintoan‘open’system(egaventscrubber)maybepreferabletoburstingdiscs,asthevalvesreseatoncethesourceofoverpressurehasbeenremoved.Thisarrangementisnormallyonlyfoundonlargerinstallations;youshouldconsultyourchlorinesupplier.

Bursting discs

122 Burstingdiscs(whicharedesignedtofailatorbelowthedesignpressureofstoragetanks)arecommonlymadeofnickel,althoughtantalum,silverorothercompatiblematerialsmaybeused.Uncoatedgraphiteisnotrecommended.DiscsshouldcomplywithBS291549(orequivalentstandard)andshouldbecarefullyselectedfortheoperatingtemperaturerange,astherupturepressureistemperature-dependent.

Arrangements for relief systems

123 Onsimpleinstallations,suchasthosewithasinglestoragevesselandassociatedexpansionvessel,asingleburstingdiscsystemwithoutanyisolatingvalves,installeddirectlyonthestoragevessel,maybeacceptable.Inpractice,however,itismoreconvenienttoinstallavalvedsystemtoallowreplacementofdiscsunderacontrolledsystemofwork,withoutneedingtocompletelyemptyandpurgethesystem.Wheretwoormorestoragevesselsshareanexpansionvessel,thereliefarrangementsshouldallowpromptreplacementofdiscsandventingofallexcesspressureoutoftheexpansionvessel.

124 ThepreferredarrangementsareshowninFigures3and4andshouldbeusedonallnewinstallations.Theisolatingvalvesmaybemechanicallyinterlocked(recommendedfornewinstallations)sothatonepairofdiscsisalwaysoperative,ortheisolatingvalvesmaybeindividuallylocked.TobeeffectivetheburstingdiscsneedtobeofthesimpledomedunsupportedtypewiththeconcavesidefacinginthedirectionsshowninFigures3,4,and5.Theidentifyingtagsshouldbeleftattachedtoeachdiscsothattheycanbeidentifiedashavingbeeninstalled



correctly.ExistingolderinstallationsusingthearrangementshowninFigure5shouldreplaceitwithapreferredarrangement(Figure3or4)whenmajormodificationsareinhand.

125 Thevalveswhichremainopenmustpermittheoperationaldevicestodischargeattherequiredratetoanexpansionvessel.Pipeworkbeforetheisolatingvalvesshouldbeasshortandsimpleaspossibletominimisetheriskofchlorineleakagefromjointsandpipework;theisolationusingvalvesbeforetheburstingdiscsshouldpreferablybefitteddirectlyonflangedconnectionsonthemanlidofthestoragetanks.

Figure 3 Pressurereliefsystem(preferred Figure 4 Pressurereliefsystem.Doublearrangement).Doublestreamwithinterlocked streamwithlocked-openvalvesvalves

Figure 5 Pressurereliefsystem.Singlestreamwithlocked-openvalves

126 Yourproceduresfordealingwithafailureofaburstingdiscshouldbeclearlydefined.Basethemontheprinciplethatatnotimeshouldpressuresbeyondthedesignrangebeallowedtodevelop(seealsoparagraph127).

127 Atanyinstallationwherea‘locked’-openisolatingvalveprecedesaburstingdisc,asafesystemofworkshouldbedefinedtopreventunacceptablepressuresfromanysourceoccurringinthevesselwhiletheisolatingvalveisclosed.Theproceduresneedtocoverthesaferemovalofthevesselfromnormalservice,stabilisingthepressure,changingtheburstingdisc,ventingtheexpansiontankandreturningthevesseltonormaluse.Suchsafesystemswillvarywithplantdesignbutshould:

To expansion vessel

Mechanicalinterlock

Bursting discs Bursting discs

Pressure alarm gauge Pressure alarm gauge

(Test connections for pressure gauge not shown)

To expansion vessel

Locked open valve

Pressure alarm gauge

Locked open valve

Bursting discs

To expansion vessel

at least one lineneeds to be locked open

Locked valves

Locked valves

Bursting discs Bursting discs

Pressure alarm gauge Pressure alarm gauge

(Test connections for pressure gauge not shown)



(a) beinawrittenform,unambiguousandreadilyavailable;(b) includeapermit-to-worksystem;(c) beincludedinplantpersonneltrainingprogrammes;(d) beproperlysupervisedwithresponsibilitiesclearlyallocated;(e) beregularlyupdatedandperiodicallysubjectedtoHAZOP50review, particularlywhenplantdesign,operatingproceduresormanagementsystems aremodified;and(f) berigidlyadheredto.

Expansion vessels

Expansionvesselmountedinabund

128 Thedesignrequirementsfortheconstructionoftheexpansionvesselaresimilartothoseforthestoragetanks;thecapacityoftheexpansionvesselshouldbeatleast10%ofthelargeststoragevessel.

129 Theexpansionvesselshouldbecapableofbeingventedmanuallytoanabsorptionsystem;theventvalveisnormallylockedclosed.Controlledventingshouldbethroughasuitableflowrestrictiondevice,eganorificeplatetopreventoverloadoftheabsorptionsystem.

130 Theexpansionvesselshouldbeprovidedwithapressure-sensingdevicewhichgivesanalarmifpressurebuildsupinthevessel.Thealarmsystemneedstobecapableofbeingtestedregularlytoensurethatitisoperable(seeparagraph133).

131 Arrangethecompressedairornitrogenconnectiontotheexpansionvesseltoavoidthepossibilityofinadvertentlypressurisingthevessel.Thismaybeachievedbyphysicaldisconnection,isolatingblankingplates,orbydoubleblockvalvessupportedbyasafesystemofwork.Ifanexpansionvesselservesmorethanonestoragevessel,makearrangementsforpromptresponsetoapressurealarmsignalfromit.

132 Whiletheriskoftheexpansionvesselitselfbeingover-pressurisedwithchlorineisminimalbecauseoftheprecautionsdescribedinparagraphs128-131,youshouldestablishproceduralormechanicalmeanstoensurethatthiscannotoccur.

Pressure alarms

133 Thereshouldbeahigh-pressurealarmoneverystoragevessel,andanadditionalpressureindicator/alarmateachimportantsafetylocationonthereliefarrangement.Thismeansthatoneadditionalpressurealarmmaysufficeoneachstoragevesselthathasitsownexpansionvessel,andthatalarmmaybeeitherinthereliefline(ifthereisasingleburstingdisc)orontheexpansionvessel.Whenoneexpansionvesselservesseveralstoragevessels,thereshouldbeanadditional



pressurealarmwithineachreliefassemblyandalsooneontheexpansionvessel.Testalarmsregularly(atleastmonthly)bygasinjectionormovingcontacts.

ARRANGEMENTS FOR UNLOADING OF LIQUID CHLORINE FROM ROAD TANKERS TO STORAGE

Unloading Using Dry Compressed Air or Dry Nitrogen

Aircompressorunit

134Therecommendedsystemfortransferringliquidchlorinefromchlorinetankerstostoragevessels,by‘padding’withdryairordrynitrogen,isoutlinedinFigure2andinAppendix6whichprovidesasoundbasisfordevelopinglocalprocedures.Detailedrequirements,whichsupplementinformationgiveninprevioussections,arereviewedinparagraphs135-147.Youneedtoagreeyourarrangementswithyoursupplieranddesignthemtominimisetheriskofoverpressure.

135Aseparateandindependentdrycompressedairornitrogensystemshouldbeusedforchlorineduty,tominimisethepossibilityofback-diffusionofchlorinewhichcouldleadtodangerousconditionsinotherair-consumingunits,particularlyinstrumentation.Compressednitrogenmaybeproducedinaliquidnitrogenevaporationunit.

136 Ifyouusecompressedair,yoursupplyneedstobeoil-freeandhaveadewpointbelow-40oC.Normally,airshouldbecompressedtoaround10bargaugeusingatrulyoil-freecompressor(1.5m3/minfreeaircapacity);ifanoil-lubricatedcompressorisuseditmustbefittedwithanoilfilterwhichmustberegularlymaintained.

Hygrometeralarm.Atthisinstallationthecompressedairdewpointislessthan-60ºC

137Thecompressedairiscooledtoremovepartofthemoisturecontentandfinallydried,usingaregenerative-typedryingsystem,toadewpointbelow-40oC.Thedewpointshouldpreferablybemonitoredcontinuouslyusingamonitorprovidedwithanalarmthatgiveswarningifthedewpointexceedsapre-setfigure.



Itisimportanttorechargeorregeneratedryingagentsaccordingtotheequipmentandchlorinesuppliers’advice.

138Aguardtower,filledwithanhydrouscalciumchlorideorothersuitablematerial,maybeinstalledaftertheregenerativesystemasafurthersafeguard.Forsmallinstallationsadrieraloneusinganhydrouscalciumchlorideorotherdryingagentmaybeadequate,providedthatproperchecksontheconditionofthedryingagentaremade.

Supply of dry padding gas to the system

139 Thecompresseddryairordrynitrogenshouldbestoredinapressurereceiver.Thisshouldbefittedwithareliefvalvesettooperateatthechlorinestorageplant’ssafeworkingpressureor10bargauge,whicheverislower.Fromthereceiverthegasshouldpassthroughanon-returnvalve,orapressure-actuatedshut-offvalve,followedbyareducingvalvetogiveasupplyatthepressurerequiredforunloadingthetankers.Thissupplywillalsobesuitableforotherpurposesonthechlorineplant,suchasdryingoutorpurgingofpipelinesandvesselsprovidedprecautionsaretakentopreventbackflowofchlorineintotheairsystem.Pressuregaugesshouldbeinstalledupstreamanddownstreamofthepressurereducingvalvesothatcheckscanbemadethatthepaddinggaspressureisgreaterthanthechlorinepressure.Itisimportanttoprovidesafeguards23-25toensurethatexcessivegaspressurescannotbeappliedtothechlorinesystem.Thismaybeparticularlyimportantifthepaddinggasissuppliedfromhighpressurecylinders.

140 Theliquidchlorinedischargelineonthechlorinetankershouldbeconnectedtothepermanentpipeworkattheunloadingpoint(seeparagraphs43-55).Thepipeworkconnectingtheunloadingpointtotheliquidchlorinestoragevesselsshouldbereasonablyshort(seealsoparagraphs(53-60).Ifitisnecessarytousealongliquidchlorinelinetostorage,youmustconsidertheneedtoprotectthislineagainstoverpressure(seeparagraphs61-67).

141 Apressuregauge,aventlinetotheabsorberandaconnectionfordrycompressedgasshouldbeinstalledclosetotheendofthepermanentpipeworkattheunloadingpoint,withthenecessaryisolationvalves,asdetailedinFigure2.

Unloading using chlorine gas pressure

142 Liquidchlorinemaybetransferredfromthechlorinetankerstothestoragevesselsbypaddingwithdrychlorinegas.Thegasisnormallytakenfromoneofthestocktanksbutthisshouldpreferablynotbetheoneintowhichthetankerisbeingunloaded.Thesupplyofdrychlorinegasattherequiredpressuremaybeobtainedbyre-compressingchlorinevapourfromastoragetankorbyvaporisationofliquidchlorine.Asourceofdry,compressed,oil-freeairornitrogenisstillrequired,fordryingoutandpurgingthesystem.

Use of re-compressed chlorine vapour

143 Selectionoftheappropriatecompressorforre-compressionofchlorinevapourrequirescarefulconsiderationtoensurethattheequipmentcanoperatesatisfactorilyonanintermittentbasis.Diaphragmcompressorsordrycarbonringreciprocatingcompressorsaresuitableforthisdutyprovidedthatmaintenanceiscarriedoutonaregularbasis.

144 Diaphragmcompressorsshouldusestainlesssteeldoublediaphragmswithinertfluidbetweenthem.Drycarbonringcompressorsshouldpreferablybepurgedwithdryairafteruse,toavoidproblemsresultingfromresidualchlorineinthe



compressorleakingfromshaftglands.Duringoperationofthecompressor,theshaftglandsshouldbepressurisedwithdry,compressed,inertgas.

145 Ifcoolingofthecompressorbodyisrequired,thisshouldpreferablybeaccomplishedbyaircooling.Ifjacketcoolingisnecessary,thisshouldbeachievedbycirculationthroughanexternalheatexchangerwithprovisiontodetectleakageofchlorineintotheheatexchangefluid.Directwatercoolingshouldbeavoided.

146 Thecompressorneedstobefittedwithabypasssothatthechlorinecanberecycleduntilitstemperatureisraisedsufficientlytopreventliquefactioninthedeliverylines.Thetemperatureofthechlorineshouldbemonitoredusinganindicatorwhichisfittedwithanalarm,settosoundifitexceeds90oC.

147 Apressurereliefsystemonthecompressordeliverylineshouldalsobeprovidedtopreventthedeliverypressureexceedingapre-setfigure(seeparagraph139).

CHLORINE VAPORISERS

148 Vaporisers(alsoknownasevaporators)convertliquidchlorineintogas.Amajoruseofchlorinevaporisersisinwatertreatment,tocontrolweedandalgaeincoolingwaterandtosterilisedrinkingwater.Theseunitsarefrequentlysuppliedaspartofapackagewithotherdosingoranalyticalequipment.Vaporisersarealwaysrequiredwithafixedordemountablebulktank,toobtainaregular,steadysupplyofgastoprocess.Thedrawingofgasfromthevapourspaceofabulktankisunsatisfactoryandunsafe.Thereistheriskofprocessliquidspassingbackintothetank,irregularityofsupplyandthepossibleaccumulationoflessvolatile,dangerousimpurities,suchasexplosivenitrogentrichlorideinthetank.51Thesafehandlingofchlorinecontainingnitrogentrichlorideisdiscussedelsewhere.52

Types

149 Therearefourmaintypesofvaporiser(seealsoAppendix7):

(a) Verticaltubebundle.Theseresembleordinaryheatexchangers,usuallywith thechlorineinthetubes.Alternativeformatsincludethecommonvaporiser usedinwatertreatment(acylinderwithadip-pipeliquidchlorineinlet immersedintheheatingbath)orashellandtubeheatexchangerwiththe chlorineontheshellside.Abayonetvaporiserisverysimilar.(b) Coil.Thechlorineisevaporatedinacoilofsteeltubingrunninginsideawet steambathorawaterbathheatedbysteamorelectricity.(c) Concentrictube.Theheatexchangesurfaceisatube,typicallyfourinchesin diameter,surroundedbyaheatingjacket.(d) Kettle.Kettleevaporatorsareusedonlargecapacitysystems.Theycontaina heatersystem(usuallyatubebundleofhotwaterorheatedfluid-notsteam) passingthroughavesselcontainingliquidchlorine.Kettleevaporatorsdonot superheatthechlorinevapour,othersystemsdo.

Coilinbathvaporiserheatedbylowpressuresteam



Coilinbathvaporiserheatedbylowpressuresteam

Regulation of throughput

Self-regulating vaporisers

150 Insometypesofvaporisertheliquidchlorineisfedinatthebottomandgasisdrawnoffviaacontrolvalveatthetop.Whendemandishigh,theliquidchlorinelevelrisesinthecontainer,andagreaterheatexchangesurfaceareaispresentedtotheliquid.Whendemandislow,thegreatervapourpressureatthetemperatureoftheheatingmediumdrivestheliquidchlorineoutofthevaporiserbackintothestoragevesselandtheevaporationratefalls.Thissystemisusuallyapplicabletovaporiserswitharelativelysmallchlorinecapacity,ieverticaltubebundles,coiltypesandconcentrictubetypes.Bayonetvaporiserscanbeusedforhighvaporisationrates.Onwatertreatmentplantsaself-regulatingvaporiser,withanelectricallyheatedwaterbathisusuallyused.

Constant level vaporisers

151 Othertypesofvaporisers,usuallyfoundonlyinlarge-capacityplants,sacrificecertainadvantagesoftheself-regulatingtypestoachievemuchlargervaporisationrates.Thesevaporisersrequireseparateinstrumentationandcontrolarrangementstoprovideaconstantlevelofliquidchlorineinthekettleorshellwithhighandlowlevelalarms.Insuchtypes(wheretherecanbepartsoftheliquidchlorinepoolwhicharenotwell-mixed),thereisagreatertendencytoconcentratethelessvolatileimpuritiesthaninaself-regulatingvaporiser.Aseparatepurgeandvaporisercircuitmayberequiredtodealperiodicallywiththeresidues.Thedesignandoperationoftheselarger-capacityvaporisersisaspecialisedtopic,andrequiresconsultationbetweentheuser,thedesigner,andthechlorinesupplierastheriskofnitrogentrichlorideenrichmentandsubsequentexplosionisincreased.51,52Youshouldinvolveyoursupplierwhenassessingthisrisk.

Methods of heating

152 Themethodsofheatingthevaporisershouldminimiseboththeriskofcorrosionandvaporiserfailure.Theseinclude:heatingwithhotwater;heatingwithlowpressuresteam;andusingclosedcircuitheatingwithheattransferfluidsotherthanwater.Directelectricalheatingshouldnotbeusedbecauseoftheriskoflocaloverheatingandchlorine/ironfires(seeparagraph158andAppendix2).

(a) Heatingwithhotwater.Thisisthemostfrequentlyusedmethod;thenormal workingtemperature(60-70oC)iswellbelowthatatwhichanysignificant reactionofcarbonsteeloccurswithdrychlorine.(b) Heatingwithsteam.Thesteamshouldbesaturatedanditspressureshould belimitedtolessthan1bargaugetoavoidoverheating,particularlyifthe vaporiserismadeofmildsteel.Anysmallleaksofchlorinetothewaterside ofhotwaterorsteamtypesleadtoveryrapidcorrosionofthesteelbymoist chlorine(seeparagraph169).Steamsystemsmustmeettherequirements



ofthePSTGCRegulations.23-25Thegreaterflexibilityofsteamheatingisuseful onplantsusingchlorinegasathighoratveryvariablerates.(c) Heattransferfluids(otherthanwater).Electricalorsteamheatcanbeapplied toaheattransferfluidwhichisrelativelyunreactivetowardschlorine.The availablefluids(eghexachlorobutadiene)arethemselveshazardous,sothat thehazardsofusingwaterasheattransfermediumareinpracticeaccepted, withsuitablesafeguards.

General installation

153 Thevaporisershouldbeinstalledinthestorageareaorinanadjacentspaceascloseaspossibletothechlorinestoragetanksinordertokeeppipelinescarryingliquidchlorineshort.Longpiperunswillrequirepressurerelief(seeparagraphs61-67).Changeoverofliquidchlorinesupplyfromonestoragetanktoanothercanaffectoperatingconditionsinthevaporisersystemandanysuchdifficultieswillbereducedifthespacingisnottoogreat,eglessthan5metres.Nevertheless,thespacebetweenthevaporiserandthestoragesystemshouldbesuchastoallowadequateaccessforemergencyactionintheeventofanincidentatthevaporiser.

Hazards

154 Thequantityofchlorineinachlorinevaporisersystemisrelativelysmallcomparedwiththatnormallycontainedinthemainchlorinestoragetanks.Nevertheless,thesystemdesignshouldbesuchthatfailureofequipmentcanbedetectedandrectifiedquicklyandthatanyconsequentreleaseofchlorinetotheenvironmentisminimised.

155 Potentialhazardsassociatedwithchlorinevaporisersinclude:

(a) Pinholeleaksleadingtorapidcorrosionandincreasedlossofchlorine.(b) Rapidcorrosion,ifanymoistureisallowedintothechlorinesystem.(c) Possibleconcentrationofimpuritiesinthechlorineasitisevaporated,suchas explosivenitrogentrichloride.Thisneedstobediscussedwithyourchlorine supplier.(d) Reverseflowofreactionfluids,causedbyafallinpressureinthevaporiser, orbyexcesspressureintheprocess,orbysolutionofchlorinegasinthe fluid.Thepresenceofthefluid(water,solventorreagent)inthevaporisercan causecorrosionorlocalviolentreactionleadingtorapidoverpressureand possibleruptureofthevaporiser.(e) Carry-overofliquidchlorineasbulkfluidordropletsintothegaslineorinto theprocessitself.Thiscan(dependingonthematerialsofconstructionandon theprocess)causedamageorhazard.(f) Excessivegaspressuretothesystemduetooverheatingavaporiser,since thevapourpressureofchlorinerisesverysteeplywithtemperature (seeAppendix2,FigureA2.1).(g) Excessivehydraulicforces,ifthesystemisclosedupandfullofliquiddueto theexpansionofliquidchlorinewhenheated.

Thesebasichazardsareconsideredinmoredetailinparagraphs156-161,butgroupedaccordingtothetypeofhazard.

Flooding and liquid carry-over

156 Flooding(filling)ofthechlorinevaporiserwithliquidchlorinemayresultfromoperationoftheequipmentaboveitscapacity,inadequateheating,orfoulingoftheheattransfersurfaces.Thetemperatureoftheheatingmediumisusuallycontrolledthermostatically.Ifthetemperatureoftheheatingmediumfallstoolowin



aself-regulatingevaporator,itispossiblefortheoutgoinggastobeinadequatelysuperheated,orforfloodingtooccur.Floodingresultsincarry-overofliquidchlorineintothevapourlines,andapotentialhazard(dependingontheprocessandplantmaterials).Thesamemayhappenifthelevelofwaterinawaterbathfalls.Intheextreme,ifchlorineisdrawnoffbutnoheatissuppliedtothevaporiser,itispossibleforicetoformontheheatexchangersurfacesanddamagethemseverely.Youshouldconsiderinstallingagasflowrateindicator.Thismaybeofvaluetotheoperatorforroutinepurposes,andwillalsoindicateexcessivewithdrawalrates.

157 Youshouldconsiderfittingaknockoutpot(orspraycatcher)topreventchlorinedropletsandsprayfrompassingintogaspipeworkwhenliquidchlorinemightdamagethematerialofthepipes,orcausetheprocesstobecomeunstable.Inallcaseswherethepossibilityofliquidpassingtoprocessisunacceptable,itisstronglyrecommendedthatalowtemperaturealarmbefittedneartheknockoutpotandarrangedtocutofftheliquidchlorinesupplytothevaporiseror(inself-regulatingtypesonly)thegaseouschlorineoutletmaybeclosed,drivingtheliquidchlorinebackintothestoragevessel(s).Adequateinstrumentationandalarmsshouldalwaysbeprovidedtogiveimmediatewarningofthiscondition.Highandlowbathtemperatureandlevelalarmswithshut-downfacilitiesarerecommended.

Accelerated corrosion and reaction (high temperature)

158 Toavoidrapidcorrosionofthewatersideofheatexchangesurfacesmadefromgalvanisedsteel,operatingtemperaturesshouldnotexceed70oC.Ifoperationathighertemperaturesisrequired,vaporisersmadeofnickelornickelalloys(suchasMonel400orInconel)shouldbeused.Insuchcases,thedownstreamchlorinegaspipeworkmayalsoneedupgradingtoensureadequateresistancetocorrosionatelevatedtemperatures.

159 Iftheheatingmediumissteam,thetemperaturecanbemonitoredbylowpressureandhighpressurealarmsonthesteaminlet.Thepressureofsteamshouldnormallybelimitedto1bargauge(120oCequivalent)andthesteamhastobesaturated,notsuperheated.

High pressure

160 Precautionsmust23beinplacetoprotectthesystemagainstover-pressurisation,egapressurereliefdevice.Pressurereliefdevicesandhighpressurealarms,wherefitted,shouldbeproperlydesignedandinstalled,maintainedinaneffectiveworkingorder,andtestedregularly.Theymustbeperiodicallyexaminedbyacompetentperson.53Atypicalworkingtemperatureforavaporiseris70oC.Thevapourpressureofchlorineat70oCexceeds21bar,(seeFigureA2.1,Appendix2).Itfollowsthatyouneedtotakethefollowingstepsto:

(a) Ensurethatthevaporiserisnotisolatedwhenfullofliquidchlorine.Strict observanceofwrittenproceduresforshut-downisvital.(b) Avoidaccidentallyisolatingthevaporiseronbothsides.Careneedstobe takentoensurethattheclosingarrangementsfortheemergencyvalvestake thisintoaccount(seeparagraphs162-165).(c) Designthevaporisershellandpipestowithstandtheworkingpressureand duty.(d) Implementoperationalcontrolswhichminimisetheriskoftheworkingpressure beingexceeded.

Ifyourchlorinevaporiserisnotsuppliedwithapressurereliefdeviceyouwillneedtoadoptprocedures,orfitsuitablepressurerelief,toensurethattheconditionsin(a)to(d)aremet.



Reverse flow

161 Youshouldeliminatethepossibilityofsuck-backintothevaporisersbysuitabledesign.Forexample,waterchlorinatingpackagesystemsusuallyincorporateasetofvalvesinthecontrolsystemtopreventsuck-backorpush-back.Thearrangementsvary,andcareneedstobetakentoensurethatthesystemprovideddoesgiveprotectionintheeventof,eg,aleakattheejectornon-returnvalve.Youshouldalsoconsiderfittingalowpressuregasalarmtotheoutletgasline.Thisgiveswarningoflossofsupplytotheprocess,andmayindicateaneedtostartpurgingthesystem,usingdryairorothersuitabledrygas(dewpointlessthan-40oC)topreventsuck-back.Whatevermethodisused,thesystemneedstoberegularlyinspectedandmaintained,andadequaterecordskept.

Emergencyshutdownpushbuttonatthevaporiser.Alsoshowninoneofsixchlorinedetectorsatthis

installationwhichcanalsoautomaticallyshutdownthechlorineinstallation(seeparagraphs113-118)

Routine and emergency isolation

162 Thevaporiserhastobecapableofbeingisolatedformaintenance,orinanemergency,suchasafailureofthevaporiseritselfthroughleakageorafailureofthegaslinedownstream.Inadditiontoamanualvalveontheliquidinletandonthegasoutlet,remotelyorautomaticallyoperablevalvesarestronglyrecommendedonbothinletandoutlet.Apressure-reducingorflowcontrolvalvewillalmostalwaysbefittedontheoutletanditissometimespossibleforthisvalvetobetheremotelyoperableshut-offvalve.

163 Yourriskassessmentshouldconsidertheneedforadditionalprotectionintheeventthatautomaticvalvesfailtooperate(orremotelyoperablevalvesarenotactivated)inanemergency.Forexampleaflowrestrictionintheliquidinlet(typicallyontheexitfromthestoragetank(s)),willlimitthereleasewhichcouldoccurintheeventofamajorplantfailure.

164 Thehazardsoftotallyisolatingthevaporiserareconsiderableandwillbemostseverewhentheevaporatorisfull(egifthevalvesclosetogetherinaconditionofmajorgaslinefailure).Ifthereisagasspaceabovetheliquidchlorinewhenthevaporiserisisolatedandheated,theinternalpressurewillreachthatofchlorineattheheatingmediumtemperature.Thevaporiser,linesandvalvesneedtobedesignedtowithstandsuchpressureorincorporatearrangementstorelievetoasafeplace.Thecontrolofautomaticvalvesneedstobearrangedsothatthevalvesdonotclosetogetherwhenanalarmisraised(seealsoparagraph160).Oneapproachistoarrangeforthegascontrolvalvetocloseonalarmsrelatedtoimproperworkingofthesystem(eglowgaspressure,downstreamprocessalarms,lowtemperature)andtheliquidcontrolvalveatthestoragetanktocloseonchlorinerelease(egdetectorslocaltothevaporiserandstorage,ormanualalarms).Iftheplantiscontinuallystaffed,manualinterventionmaybeasuitablealternativetoprovidingwhollyautomaticoperationofshut-down.However,proceduresneedtobeestablishedtoensurethatthisdoesnotintroducesignificantdelaysintotheresponsetoanalarm.Analternativeapproachistouseapressurecontrolglobevalveforremoteisolationoftheoutletlinesothatexcessivepressureswillliftitslightlyoffitsseat,preventingexcessiveoverpressures.



Reliefpressuresandvalvedirectionneedcarefulconsiderationandshouldbediscussedwiththevalvesupplier.

165 Isolationofthevaporiserisstillpossible,butinterlocksbetweentheinletandoutletvalvestopreventtotalisolationarerarelyfitted.Thisisbecauseitisoccasionallynecessarytoclosebothvalvesduringcleaningandoverhaul.Asafesystemofworkformaintenanceandoperationisthusavitalpartofthesafetyarrangements,andisarequirementunderthePSTGCRegulations.23

Pressure control valve

166 Allvaporiserdesignsincorporateanelementofsuperheatingofthevapour,eitherinthevaporiseritselforasaseparateunit.Thisisnecessarytopreventchlorinereliquefyinginthecontrolvalves,whereitcouldcauseproblemsofirregularpressureinoperation.Theseproblemsareavoidedbyreducingthegaspressureattheexitfromthevaporiser.Asuitablepressure-reducingcontrolsystemisrecommended.

Corrosion

167 Corrosionofthevaporisertubesorcoilscouldleadtoaloss-of-containmentaccident.Theconsequenceofaminorchlorineleakfromthechlorinesideofavaporiserheatingbathcouldbeveryserioussincethemixtureofchlorineandmoisturewillleadtorapidcorrosionoftheevaporatorsurfacesandasubstantialreleaseofchlorine.

168 Youmustarrangeforacompetentpersontoperiodicallyexamineyourvaporiserandotherpressuresystemsinaccordancewithyourwrittenschemeofexamination.54Acompetentperson53mustcertifythatthewrittenschemeforexaminationissuitableforthepurposeofpreventingreasonablyforeseeabledangertopeoplefromtheunintentionalreleaseofstoredenergyfromthesystem.Thewrittenschemeofexaminationshoulddescribethenatureandfrequencyoftheexamination.Thisshouldbebasedonriskassessmentandgivedueconsiderationtothedutyandtheconditionofthevaporiserwhenitwaslastinspected.Thecompetentpersonwilladviseonsuitableexaminationandtestregimes,andwhenthevaporisershouldbereplaced.Examinationintervalsbetweenoneandfiveyearsaretypical.Coil-in-bathevaporatorsarecommonlygivenarigorousinspectioneverytwoyears,andthecoilsarediscardedifseriouslypitted.Somemanufacturersadvisethatthecoilsshouldberenewedeverytwoyears.Followingexaminationtheequipmentshouldbethoroughlydriedtoadewpointlessthan-40oCbeforerecommissioning.Moistureleftinthesystemcanleadtoveryrapidcorrosion.Theprocedureshouldbecoveredbyawrittenoperatingprocedure.

169 Corrosionoftheheatexchangersurfacesisnotdirectlymonitored.Insteadtheevaporatorvesselortubesarefrequentlyprotectedagainstwatercorrosionbycathodicprotection.Typicallytheanodesshouldbecheckedvisuallyeverythreetosixmonths.Thefrequencyshouldbeestablishedbyexperienceoftherateatwhichtheanodesareconsumedandreplaced.Iftheanodesarefoundwhollyconsumedatinspection,athoroughexaminationofthevaporisershouldbeundertaken.Thewaterbathorcondensateoutletshouldbemonitoredforchlorineleaksbyredoxorconductivitymeasurements.Thisearlywarningofminorleaksishelpfulinallcases,andisverystronglyrecommendedifcathodicprotectionisnotprovidedornotmaintained.

170 Accumulationofsoliddepositsreducestheeffectivenessofavaporiserandcanalsoenhancecorrosion.Thevaporiserneedstobecleanedanddriedtoadewpointlessthan-40oCregularly.Closeattentiontothecleaningprocedurewillminimisecorrosionbuttypically,thechlorineevaporatorcylinderinahotwaterbath



(seeAppendix7,type1csystem)shouldberenewedafterfiveyears.Theoldonemaybesubmittedtoacompetentinspectionbodyforcertificationforfurtheruseifrequired.

CHLORINE ABSORPTION SYSTEM

171 Youshouldgivedetailedconsiderationtoensurethatinallchlorine-usingoperationschlorinecan,inanemergency,beventedtoanabsorberwithoutemissiontotheenvironment.

172 Controlofchlorineemissionsfromprescribedprocesses(seeparagraph10)mustbethesubjectofconsultationswiththeEnvironmentAgencyinEnglandandWalesandSEPAinScotland.

173 Insomeinstallations,thenatureoftheconsumingprocessissuchthatabsorptionofthechlorineispossiblewithoutaspecialabsorptionunit.However,insuchcircumstancesoperatorsneedtoensurethatduringmaintenanceperiodsadequateabsorptioncapacityisalwayskeptavailabletoaccommodateanychlorineemissions.Aseparateabsorptionplantmaynotbeessentialin,forexamplecooling-watertreatmentplantsandbleachliquorproductionplants.

Lutepipe(baromaetricleg)andventforabsorptionsystem

174 Formostbulkstorageinstallations,however,aseparatechlorineabsorptionplantisrequiredanditshouldalwaysbemaintainedinastateofreadiness.Thequantityofreagentsavailableintheabsorptionsystemneedstobeadequatetodealwithanyforeseeableemergency.Theinlettothescrubbingsystemshouldincludealutepipe(barometricleg)topreventliquidfromthescrubbingsystementeringthechlorinesystem.

175 Theresponsibilityfortheinstallationofanadequatechlorineabsorptionsystemrestswiththeconsumer,butyoushouldobtainthechlorinesupplier’sadviceontheproposedinstallation.

176 Considercarefullytheprovisionofadequateinstrumentationwithalarmsandthedisposalofeffluentfromthechlorineabsorptionplant.

177 Adequatestandbyequipmentshouldbeprovidedtocoverbreakdownsandroutineoverhauls.Essentialcirculatingpumps,fansandinstrumentationshouldbeamongthoseitemswhichareconnectedbothtothemainsandtothefactoryemergencypowersupplyifthereisone.Whentheabsorptionfacilityisrequiredtobecontinuouslyavailable(egventsfromreactors)itisessentialtoprovideemergencypowerandstand-bycirculatingpumpsoranemergencygravity-fedsupplyofabsorbingsolution.



Vent collection system

178 Thepipelinesforthecollectionoftheventgasescontainingdrychlorinemaybemadeofmildsteelbutback-diffusionofmoisturefromtheabsorptionsystem,whichmayoccurifventingsareintermittent,hastobeprevented.

179 Ventsystemsfromreliefsystems,whicharelikelytooperateonlyinfrequently,maybeprotectedfromback-diffusionofmoisturebytheuseofprotectivemembranes.Insomecasesitmayhelptoprovideacontrolleddrygaspurgethroughtheventlines.

180 Ifthereisanyriskofmoisturecontamination,thepipeworkhastobemadeofrubber-linedorplastic-linedcarbonsteel,orplasticresistanttowetchlorine(egPVC,HetronorAtlac382),orglass.

181 Ifthereisanypossibilityofliquidchlorinecarry-over,liquidgasseparatorsshouldbeinstalledonthelinestoavoidexcesspressureoroverloadingoftheabsorptionsystem;theseseparatorsarefittedwithatemperaturealarmtoindicatethepresenceofliquidchlorineintheseparator.Furthermore,ifitispossibleforliquidchlorinecarry-overtotakeplace,plasticpipeworkshouldnotbeused.Pipeworkshouldbesizedtotakeaccountofthemaximumpossibleflowsunderthemostunfavourableconditions.

Absorption equipment

182 Varioustypesofabsorbersareusedforthetreatmentofventgases;suitableabsorbersmaybebasedontheuseofpackedtowers,ventinjectorsorspargeabsorbers.Itcanbeanadvantageifthesystemselectedgivesasuctionontheplant.

183 Causticsodaliquoristhemostconvenientreagentforabsorptionofchlorineinwastegases.Theconcentrationofcausticsodashouldnotexceed21%NaOHbecauseoftheriskofsaltdepositcausingblockagesintheabsorptionplant.Itisrecommendedthattheflowofchlorineiscontrolledorrestrictedbyanorificeplatetoanacceptablemaximum,sothatthetemperatureriseintheabsorberdoesnotreduceitseffectiveness.

184 Alternatively,forinstallationswherethereisnobulkstorageforcausticsodaliquorandwherelimeorsodaashisavailableonthesite,alimeslurryorasodaashsolutionmaybeused.

Instrumentation

185 Itisessentialthatfaultsaredetectedquickly.Adequateinstrumentationwithalarmsshouldbeprovidedontheventabsorptionplanttoensurethereisawarningifequipmentfails.Significantfaultsare:

(a) Lossofcirculation.(b) Chemicaldepletionoftheabsorbingsolution.Depletionofthesolutioncanbe monitoredbytheuseofredoxorconductivitymeasurement.

186 Considerprovidingapressureindicatorfittedwithanalarmtoshowifthereisexcessiveventingorablockageintheabsorptionsystem.

187 Amonitortodetectchlorineshouldbeinstalledontheoutletfromtheabsorber.Ondetectingchlorinethefollowingactionsareneeded:

(a) raisethealarm.



(b) isolatetheflowofchlorinetoprocess;and(c) increasetheflowofliquortotheventscrubber.

Theflowfromtheventlinetothescrubbershouldbemaintained.Isolatingtheflowtothescrubbermayputpeopleatrisk.

Chlorinedetectoralarminventlinefromabsorber

Disposal of effluent from the chlorine absorption plant

188 Thedisposaloftheliquorfromthechlorineabsorptionplantrequirescarefulconsideration,asthepresenceofhypochloritemaycreateproblems.Ifthewasteliquorisdischargedwithouttreatment,thepossibilityofinteractionwithothereffluentsshouldbeinvestigated(egamixturewithacideffluentcanleadtoevolutionofchlorineintheeffluentmains,andwithammoniacaleffluentcanleadtoformationofnitrogentrichloride).

189 Undersomecircumstancesitmaybenecessarytotreattheeffluenttoreducehypochloritecontenttoanacceptablelevelbeforedischargingtoasewer.YourchlorinesupplierandyourlocalEnvironmentalHealthOfficershouldbeconsultedonanenvironmentallyacceptablemeansofdisposal.ForhighlycontaminatedeffluentyoushouldconsulttheEnvironmentAgencyorinScotland,theScottishEnvironmentalProtectionAgency.



Operating and maintenance procedures, training and PPEOPERATING INSTRUCTIONS

190 Oneofthemainrisksofchlorineescapetotheenvironmentisfromincorrectoperationoftheplant.Operatingproceduresandtheselectionandtrainingofprocessoperatorsarethereforeextremelyimportantconsiderationsfortheefficientandsafeoperationofchlorineinstallations.Youroperatingproceduresneedtocovereachprocessoperationandmeetlegalrequirementsegseereferences18,23,and55-60andthestandardsrecommendedinindustryguides(seeAppendix4andreference22).191 Writteninstructionsarerequiredfor: (a) plantmaintenance(seeparagraphs193-198);(b) plantcommissioninginspectionandtesting(seeparagraphs199-209);(c) plantmodificationandshut-down(seeparagraphs210-213);(d) allprocessworkandproceduresinvolvedintheunloadingofliquid chlorinetankers(seeparagraphs214,215);(e) operationofthestorageinstallationandutilisationofthechlorine (seeparagraphs214-229);and(f) emergencyactiontodealwithchlorinespillagesandgasescapes (seeparagraphs247-263).

Thesemaytakedifferentformsdependinguponthecomplexityoftheinstallation,egfromsimpleguidecardsforstraightforwardoperationstocompletemanualsforcomplexoperationsandinstallations.

192 Youshouldmakethesitemanagerorotherdesignatedpersonresponsibleforauthorisinganyamendmentstotheproceduresorschedules.Youneedtoensurethatcopiesoftheinstructionsincludeaflowsheetandindicatethevalvestobeclosedinanemergency.Instructionsneedtobeavailableintheworkingareaforoperators,andinthecontrolroomorcontrolcentreforoperatorsandsupervisors.Supervisorsshouldcheckregularlythatoperationsarecarriedoutpreciselyaccordingtothewritteninstructions.

MAINTENANCE, INSPECTION AND INSTALLATION

General maintenance requirements

193 Satisfactorymaintenanceofplant,equipmentandinstrumentationisessentialtominimiserisks.ThemainRegulationsthatyouneedtocomplywithare:COSHHRegulations20,MHSWRegulations18,andPSTGCRegulations(regulation12).23-25TheCIMAHRegulations5(tobereplacedinFebruary1999bytheCOMAHRegulations-seeAppendix3),willalsoapply,dependingonthesizeoftheinstallationandtheoperatingconditions.

194 Youwillneedtopreparemaintenanceschedulesdefiningtherequiredfrequencyforservicing,testingandinspection.Theseschedulesshouldbestrictlyadheredto.AppropriaterecordsoftheresultsmustbekeptasrequiredbythePSTGCRegulations1989andCOSHHRegulations.Theneedforawrittenschemeofexamination(WSE)54isaseparaterequirement(ieregulations8and9)ofthePSTGCRegulations.Otheraspectsofmaintenanceareindicatedinparagraphs19,44,51,56-58,71,81,86-89,98,127,136,143,160-162,165,169,173,174,225,232,233,237,and255.



195 Youneedtoensurethatdetailedwritteninstructionscoveringallroutinemaintenanceoperationsareavailable.Theseshouldbeformallyapprovedandissuedbytheresponsiblemaintenanceengineer.Supervisorsshouldcheckregularlythatworkiscarriedoutaccordingtotheseprocedures.Payparticularattentiontocorrosion(seealsoparagraphs167-170),especiallywherelaggingisused;andtochlorinedetectorsystemstokeepsuchmonitoringequipmentineffectiveoperation.

196 Closeliaisonisnecessarybetweenthemaintenanceengineerandtheprocessmanager,toensurethatmaintenanceworkisstartedonlyaftertheequipmentconcernedhasbeenadequatelypreparedbyprocesspersonnelandisfreefromchlorine.

197 Adequatetrainingisrequiredforallmaintenancepersonnel.Thisshouldincludebasicinformationonthepropertiesofchlorine,safetyprecautionsandemergencyprocedures(seealsoparagraphs231-234).

Maintenance of connections

198 Theinspectionandreplacementproceduresforhosesandconnectionsmustbedocumentedinaccordancewiththewrittenschemeofexamination.54Recordsoftheinspectionsandreplacementsshouldbekept.Youneedto:

(a) Carryoutengineeringinspectionsofhosesatleastonceayear,orperevery 1000operations.

(b) Renewconnectionsatregularintervals,orasrequiredasaconsequenceof theengineeringinspection.Flexiblehosesshouldberenewedoneitherafixed timescheduleornumberoftransfersasadvisedbythehosesupplier.(c) Hydraulicallypressuretestreplacementflexibleconnectionsanddrythemwith dryairtoadewpointlessthan-40oCbeforeuse.

Inspection and commissioning of chlorine tank installations

199 Itisyourresponsibilitytoorganiseandcontrolinspections,testingandthecommissioningofyourstoragetank.Yourchlorinesupplier,asamatterofpolicy,willgiveadviceifrequestedtodosoandvisittheplantbeforeitiscommissioned.Theydeliverchlorineonlyiftheyconsideryourinstallationtobesatisfactory.YourequipmentinstalleralsohasresponsibilitiesunderSection6oftheHealthandSafetyatWorketcAct.YouandyourinstallerhaveresponsibilitiesunderthePSTGCRegulations;inparticularthewrittenschemeofexamination(WSE)mustbeinplacebeforethepressuresystemgoesintoservice.

200 Youshoulddeterminethescopeoftheschemefortheexaminationofthepressuresystem,withexpertadvicebeingobtainedifrequired.TheWSEmustspecifyallinspectionandtestingtechniquesemployedasrequiredbyRegulation8ofPSTGCRegulations.TheWSEreportmustcontainspecificdetailsofanydeteriorationfoundinthevesselorvesselancillaries(seeRegulations9ofPSTGCRegulations).Itshouldstatewhichpartsofthesystemhavebeenexamined,theconditionofthosepartsandtheresultsoftheexamination.

201 Initialinspectionandtestingshouldbecarriedoutinaccordancewiththedesigncode(seeparagraph88).Thefirstthoroughin-serviceexaminationofavesselspecifiedforliquidchlorinedutyshouldbemadebyacompetentinspectingauthority24withinfiveyearsofcommissioningandpreferablywithintwoorthreeyears.ThereafterthefrequencyoffurtherthoroughexaminationsshouldbedeterminedbytheinspectingauthorityandnotedintheexaminationreportasrequiredbyRegulation9ofthePSTGCRegulations.



TheWSEcanonlybemodifiedafteranexaminationiscomplete.Theexaminationintervalshouldnotnormallyexceedfiveyears.

202 Acompetentperson53tocarryoutsuchexaminationshouldhavetheknowledge,experienceandresourcestosearchfor,detectandassessparticulardefectsassociatedwithsystemscontainingchlorine.Resourcesshouldincludeaccesstoappropriatenon-destructivetestingandlaboratoryfacilities,togetherwithprofessionaltechnicalabilitytorelateinspectionfindingstoappraisalofvesselintegrity,safeworkingparametersandfutureuse.Thecompetentpersonmustassessthevesselforcontinuedusewithchlorinewithrespectto:

(a) maximumandminimumsafeworkingpressures;(b) maximumandminimumsafeworkingtemperatures;and(c) safeworkingloadsatsupportsandfoundations.

Suchinformationshouldbenotedontheexaminationreport,togetherwiththelatestdateforthenextexamination.

203 Forlaggedtanks,youneedtoremovesufficientlaggingtoenabletheconditionoftheexternalsurfaceofthetanktobeassessed.

204 Routinehydrostatictestingisnotnormallyrecommended.Itis,however,recommendedifanymodificationsaremadetothestoragevessels.Suchmodificationsrequireafurtherexaminationbythecompetentperson.

Inspection procedure

Preparation for internal inspection

205 Beforeopeningthestoragevesselforinspection(seealsoparagraph168),thevesselneedstobeemptiedofliquidchlorineandpurgedtoremovealltracesofchlorine.Proceduresforthisshouldbecoveredbypreciseoperatinginstructions46andnormallyinclude:

(a) breakingofallpipeworkconnectionstothevesselbyremovalofspoolsorby blankingoff;(b) removingthemanlidandfillingthevesselwithwatertowhichsodaashhas beenaddedtoneutraliseacidicmaterialwhichformswhenwaterisadded toferricchloride-thecontentsofthevesselshouldbestirredthoroughly throughouttheprocess;(c) siphoningoffthewaterandcheckingtheatmosphereinthevesselforchlorine andoxygencontent;(d) controllinginternalinspectionofthevesselinaccordancewiththeconditions setoutintheConfinedSpacesRegulations199759andtheCodeof Practice60(seeAppendix3).

Re-assembly after inspection

206 Proceduresforthisinclude:

(a) drainingoffallwater;(b) thoroughlydryingthevesselbydryairornitrogenandremovingandreplacing jointsonallconnectionstothevessel;(c) re-fittingthemanlid;(d) pressurisationofthevesselwithdryairandmeasurementofthedewpointof theairreleased;(e) successivepressurisationwithdryairandreleaseuntilthedewpointoftheair leavingthevesselislessthan-40oC.



207 Itisgoodpracticetooverhaulallvalvesonthevesselatthetimeofinspection.Followingoverhaultheyneedtobedriedoutandstoredinindividualplasticbagspendingreinstallation.Ancillaryequipmentshouldalsobeoverhauledateachinspection.Burstingdiscsshouldalwaysberenewed.

Testing (See current version of HSE Guidance Note GS 4 Safety in Pressure Testing)61

208 Followingcompletionofre-assemblyoftheequipmentanddryingouttotherequiredlevel,youneedto:

(a) leaktestwithdrycompressedairornitrogenataround8bargaugeforseveral hours;then(b) introduceasmallquantityofchlorinetothestoragevesselandpressurisewith compressedairornitrogentoaround8bargauge;(c) testalljointsforleakagebyreleasingammoniavapourfromanammonia bottleandobservingtheabsenceoftheformationofwhitefumesof ammoniumchloride(thisisaverysensitiveandwell-establishedmethod).

Ifthereisnosignofleakage,youshouldleavethetankunderpressureforaboutafurther12hoursandthenrepeattheleakagetest.

209 Allassociatedpipelines,whichneedtohavebeendriedouttoadewpointlessthan-40oC,arethengas-testedforleakage.Anyleakingjointsneedtobemadegas-tightbeforeintroducingliquidchlorineintothesystem.

MODIFICATION OF THE CHLORINE SYSTEM AND CLEARANCE PROCEDURES

210 Youshouldonlymodifythechlorinesystemafterconductingariskassessment(andpossiblyHAZOP).50Thisensuresthatapprovalisgivenbyresponsiblestaffcoveringtheoperatingandengineeringsectionsinvolved,andthatappropriateproceduresareputinplacetodealwithanyrequiredalterations.Proposedmajormodificationsshouldpreferablybediscussedwithyourchlorinesupplier.

211 ThePressureSystemsandTransportableGasContainersRegulations198923require(Regulation4)youtomakearrangementsforpropercontrolofrepairsandmodificationstopressuresystems.Anymodificationsorrepairswhichcouldaffecttheintegrityofthesystemhavetobedefinedandoverseenbyacompetentperson.

212 Formalclearanceproceduresneedtobeestablishedaspartofapermit-to-worksystem46for:

(a) ensuringthattheplantisinasatisfactoryconditionformaintenanceand internalexamination,appropriatelyisolatedandfreefromchlorine;(b) coveringallworkinthechlorineareawhichrequirestheuseofcranes,mobile equipment,weldingsetsorotherplantwhichcouldleadtoaccidentaldamage tothechlorinesystem.Thissafeguardisnecessaryeveniftheworkdoesnot directlyinvolvethechlorine-containinglinesorequipment;(c) formallyacceptingthattheplantissafeforoperationaftertheworkhasbeen completed.

213 Thestorageinstallationmustbeemptiedofliquidchlorineduringinspectionandmaintenanceoftheexpansionvesselunlessprovisionhasbeenmadeforalternativemeansofreleaseofpressure.



UNLOADING OF LIQUID CHLORINE FROM ROAD TANKERS TO STORAGE

214 Transferofliquidchlorinefromtankerstoliquidchlorinestoragemaybeachievedeitherbyuseofdrycompressedairordrynitrogenorbyuseofchlorinegaspressure.Themethodsemployingdrycompressedairornitrogenaresimplerandtheuseofchlorinegaspressureisnormallyencounteredonlyinspecialcircumstances.Thegassupplypressureneedstobeabout1.7barabovethepressureinthestoragevessel(iethesaturatedvapourpressureofchlorineatambienttemperature)toeffectthetransferofliquidchlorinefromthetransportvehicletostorage.

215 YoushouldbaseyouroperatingproceduresforunloadingontheoutlinegiveninAppendix6.Theproceduresshouldspecifyrequirementsforinspectionandtestingofcouplingsbeforeuse(seeparagraph198).Someoperationaldetailsaresummarisedinpoints(a)-(f):

(a) Visualinspection,beforeuse,withparticularattentiontothreads.(NB hydrocarbonoilsorgreasesmustnotbeusedonthreadedorother connections-seeAppendix2,andparagraph56(j).)(b) Useofnewgaskets(seeparagraph56(h))eachtimeconnectionsaremade tothetanker.Compressedasbestosfibre(CAF)gasketsarenot recommendedforenvironmentalreasons.IfCAFisusedthediscarded gasketsshouldbecollectedanddisposedofsafely,bearinginmindthatthey containasbestos.(c) Provingofthetightnessofallconnectionsbeforeintroducingliquidchlorine.A gaseouschlorinetestisrecommended(seeparagraph208c)afteradryair/ nitrogentest.(d) Cappingpipesafteruseandprotectingpipestoreducethepossibilityof accidentaldamagetothreadsoringressofmoisture,andprovidean additionalsafeguardagainstanaccidentalreleaseofchlorineduetoanerror invalveoperation.

(e) Considercontinuouspurgingwithdryairornitrogen(dewpointlessthan -40oC).(f) Itisimportanttovent‘paddinggas’totheabsorptionsystem(seeparagraphs 171-184)afterthetransferoperationiscomplete,torestorethepressureinthe tanktoaboutthevapourpressureofchlorineatthetemperatureofthetank contents.Ifthisisnotdone,thetankmayover-pressuriseasitwarmsup,and causethereliefsystemtooperate.

Testingforleakswithammoniabottle(seealsopara208c).Thedriverteststhejointsnearthetankerdome



USE OF ISO (DEMOUNTABLE) TANK CONTAINERS

ChlorineISOtankcontaineronroute ISOtankcontainer:detailoftheconnectionpoint

216 AnISOtankcontainerisapressurevesselmountedinasubstantialsteelframe.Theyareusedpredominantlyforrailandseatransportandwherecontainersneedtobestacked.Theyvaryincapacity,andinthecaseofchlorinethelargestvesselscanholdabout14tonnes.ISOcontainersareusuallysizedtomeetcustomerrequirementsandinvariablyeachtankisdesignatedtoaspecificcustomer.Ifyourplannedconsumptionofchlorineisnotenoughtojustifyinvestmentinabulktankandtoogreatfortransportablecontainers1tobeused,anISOcontainermaybeappropriate.Ifthecontainerchangeoverperiodexceedsfourweeksyoushoulddiscusstheuseofonetonnedrumswithyourproposedsupplier.

217 ThedriverisresponsibleforensuringthattheISOcontainertraileriscorrectlyberthed,themotiveunitisuncoupled,andthatthelandinglegsonthecornersofthetrailerareinplace.

218 ThedesignoftheISOberthshouldbesimilartotherequirementsforanoff-loadingbayforroadtankers(seeparagraphs31-41)egthegroundmustbelevelandtheareawell-lit,awayfromtrafficetc.Thegroundsurfaceneedstoberesilientenoughtopreventthelocalloadsfromthelandinglegsdamagingthesurfaceorallowingsinking.Considerspillcontainment(egusekerbing,semi-bundingorcollectionsumps)intheeventofanyincident.Althoughtheframeprovidessubstantialimpactresistance,topreventdamagetothetankanditsfittingsyoushouldprovidecrashprotectionsimilartothatrequiredforfixedtanks.Similarly,youshouldprovidecrashprotectionforyourplantagainstinadvertentmovementduringtheberthingoperation.

219 Youwillneedtoprovidesuitableflexiblehoseconnectionstoconnectthetanktoyourprocess.Theseshouldbeofsufficientlengthandunobstructedroutingsothatalegcollapsewouldnotstressthehoseorconnectingjoint.

220 Youwillalsoneedtodrawupproceduresforconnectinganddisconnectingthetanktoyourprocess.Theseproceduresandtheassociatedinterlocksareeffectivelythesameasforroadtankerunloadingoperations(seeparagraphs35,39-41,214,215andAppendix6).Theyneedtobecarriedoutwiththemotiveunituncoupledandalwayswiththedriverpresentasitisthedriverwhoisresponsibleformaking/breakingandtestingtheintegrityofthejoint.BarriersshouldbeloweredwhentheISOisberthedandthebarrierlinkedmechanicallyorbysoftwaresequencetotheflexiblehoseconnectionasdriveawayprotection.AstheISOtankerisnotfittedwithareliefvalve(aregulatoryrequirement14)measuresmustbetakentopreventoverpressurefromradiantheatsourcessuchasstoredflammables,orfrominertgassuppliedtoraisethepressureinthetankertransferringchlorinetotheprocess.

221 YouwillneedtoagreeprecautionswithyoursuppliertoensurethereisnopotentialforreverseflowfromyourplantintotheISOtank(seeparagraphs224-229)andimplementthem.



TRANSFER OF CHLORINE TO THE CONSUMING UNITS

222 Transferofliquidchlorinefromthestoragetankstotheconsumingunitsmaybeachievedby:

(a) usingthevapourpressureoftheliquidchlorinealone;(b) paddingthechlorinestoragetankwithdrycompressedgas;(c) transferingtheliquidchlorinetoaseparatetankfromwhichitispumpedusing apumpspeciallydesignedforusewithliquidchlorine.

Methods(a)and(b)arenormallythemostsatisfactoryforcustomerinstallations.

223 Underexceptionalcircumstancesandbyagreementwithyourchlorinesupplier,liquidchlorinefromthetankersmaybetransferreddirectlytoyourprocessortoachlorinevaporiser.Thisisaspecialandunusualarrangement;theadequacyofthecontrolsystemsandproceduresshouldbeverifiedbyariskassessment.IfyouseearegularneedforthisarrangementyoushouldconsidertheuseofISOtankcontainers(seeparagraphs216-221).

Transfer of gaseous chlorine

224 Withtheexceptionofventing,youshouldavoidthedischargeofgaseouschlorinefromtankersorstoragevesselsdirectlytoaprocess.Suchaprocedurecancauseapotentialhazard51byconcentratingthetraceamountsoftheunstablesubstance,nitrogentrichloride,normallypresentinthechlorine-seealsoAppendix2,paragraphs15,20.Inaddition,ariskofsuck-backofmoistureorothermaterialsintothevesselortankerexists(seealsoparagraphs100,161).

Transfer of liquid chlorine using vapour pressure

225 Formanyapplications,thevapourpressureoftheliquidchlorineinthestoragetankisadequatetotransfertheliquidchlorinetotheconsumingunit,althoughtheremaybeproblemsincoldweatherwithoutdoorinstallations,asthevapourpressurewillfallastheliquidchlorinecools.Ifthedemandrateislikelytocauseproblemsincoldweatheroneofthemethodsbelow(paragraphs226,227)shouldbeused.Whentheliquidhasbeenremovedfromthetank,itmayalsobeacceptableforpartoftheremaininggastobeusedonprocess.However,aminimumpositivepressureshouldalwaysbemaintainedinthestoragevessels;thisshouldbedefinedforeachsystem.Youshouldbeawarethatthismethodincreasestheriskofnitrogentrichlorideaccumulationinthetankandyoushouldimplementadditionalmonitoring.52

Transfer of liquid chlorine by padding with dry compressed gas

226 Transferbypaddingthestoragetankswithdrycompressedgasisstraightforward;theactionandprecautionswhichwillberequiredaresimilartothosedetailedinparagraphs134-141.

Transfer of liquid chlorine using a separate pumping tank

227 Completelyenclosed‘canned’pumpshavebeendevelopedfortransferofliquidchlorine:theseareusedwhenthechlorineisrequiredathigherpressure,typicallyabove7bargauge,orwhentheuseofdryinertcompressedgasisnotacceptable.Theliquidchlorineisfirsttransferredfromstoragetoaseparatepumpingtankwhichusuallyconsistsofapressurevesselwithabottomconnection.Theliquidchlorineiswithdrawnfromthebottomofthepumpingtanktothesuctionofthepump.Aremotelyoperatedvalveispreferablyinstalledinsidethetankorbetweenthepumpingtankandthepumpforisolationinemergency.Thedesignof



thissystemshouldensurethatthenett-positive-suctionhead(NPSH)isadequatetomeettheminimumrequirementsforthepumpused.Ifyouseeaneedforthisarrangementyoushouldseekadvicefromyourchlorinesupplieratanearlystage.

Precautions

228 Youshouldmakearrangementstorapidlystoptheflowofliquidchlorinefromthestoragevesselintheeventoffailureatthechlorineconsumingplant(seeparagraphs35,79,95-97).Longliquidchlorinepipelinestoconsumingunitsmayneedtobeprotectedagainstoverpressure(seeparagraphs61-67).

229 Youneedtodesigntheinstallationtoprevent,orminimisetheriskofsuck-backofaqueoussolutionsorprocessliquidsfromanabsorptionsystem.Thisrequiresdetailedconsiderationatthedesignstageandmightinvolvetheinstallationofanon-siphoningbarometriclegorareverseflow/pressure-measuringdevice.

General guidelines for training

Peoplehavelegaldutiestocomplywiththesafetyproceduresassociatedwiththeirwork.However,itisneversufficientsimplytopresumethatstaffwillknowandunderstandwhattodo.Positiveinstructionandtrainingisneeded.Healthandsafetytrainingshouldtakeplaceduringworkinghoursandshouldbepartofthejob.

Trainingisvitalinhelpingtopreventincidentsandtominimisetheconsequencesiftheydohappen.Thinkaboutwhoshouldbetrained,inwhat,andtowhatlevelofcompetence.

Trainingwillhelpemployeesunderstandthehealthandsafetyaspectsoftheirwork.Initialtrainingfornewstaffshouldbefollowedupwithneworrefreshertrainingasrequired.

Trainingmustincludeanyonewhoworksonthesite.Operators,managers,staffandoccasionalvisitors,suchasmaintenancecontractors,mayallneedsometraining.

Trainingcantakemanyforms,rangingfromon-the-jobtraininglinkedtoinformationnotices,writteninstructionsetc,toformaltrainingcourses.Thetypeoftrainingshouldbeappropriatetotheactivitiesanddutiesofthosetobetrainedandthehazardsatthesite.

Involveandconsultstaff.Wherethereisarecognisedtradeunionsafetyrepresentative,theywillneedtobeconsulted.Theywillknowmanyofthehazardsoccurringineverydaysituations.Caterforunusualoccurrences.

Information,instructionandtrainingmustbeunderstoodbythosetowhomtheyaregiven.Ifpoorperformanceshowsthattrainingisnotworking,thetrainingwillneedtobereviewedandimproved.Donotassumethatpreviousexperienceorformalqualificationswillmeanthatnewemployeesdonotneedtraining.(Youareadvisedtokeepatrainingrecordforeachstaffmember,sothatitisclearwhattrainingtheyhavereceivedand,therefore,whichdutiestheycanbeexpectedtoperform.)

230 Itisessentialthatthepersonnelselectedareofadequatephysicalfitnessandtheyshouldpassamedicalexaminationbeforeengagement.Operatorsneedtobecapableofeffectivecommunicationandbereliableunderstressconditions.Previousexperienceinthechemicalorsimilarindustryisverydesirable.



TRAINING

231 Youneedtoensurethatsitepersonnelareproperlytrainedandpractisedineachprocedure.Youshoulddevelopandimplementatrainingprogrammewhichincludesboth‘off-the-job’and‘on-the-job’aspects.Youshouldregularlyassesstheprogrammeforitseffectiveness.

232 Off-the-jobtrainingneedstoincludebasicinformationonthefollowing:

(a) statutoryrequirements,ACOPsandguidance;(b) Physical,chemical,andtoxicpropertiesofchlorine;(c) safetyprecautions;(d) personalprotectiveequipment;(e) processoperationsandsystemconfigurations;(f) safesystemsofworkincluding‘permits-to-work’;(g) containertypes,methodsofhandlingandsecurity;(h) operationalprocedures;(i) maintenanceprocedures;(j) defectrectification;(k) automaticcontrolsystems;(l) leakagedetectionsystems;(m) emergencyprocedures,includingleakagecontainment;and(n) chlorinesuppliers’supportfacilities.

Maintenanceengineersneedtobeprovidedwithmoredetailedtrainingonthesetopics,togetherwithtrainingonsystemintegritytesting,pressurereduction,andsafetydevices.

233 On-the-jobtrainingneedstobecarriedoutundertheguidanceofanexperiencedoperator/maintenanceengineerwhoisfamiliarwiththeprocess,withanemphasisonsafetyprecautionsandmethodsofdealingwithemergencies.Giveparticularattentiontothefollowingaspects:

(a) thehazardsandcharacteristicsofchlorine;(b) safemethodsofplantoperation,includingconnectiontoanddisconnection fromsupplysystems,andregularmonitoringandverificationoftheadequacy ofthesystemsadopted;(c) methodsofmaintenanceandinspection,inparticulartheapplicationof relevantstandardsandcodes(seealsoparagraphs193-198).(d) specialoperations;eg,plantshut-downandstart-up,methodsofisolation46 andpreparationofequipmentforperiodicmaintenanceandinspection;(e) thelocationandoperationofemergencyshut-offvalves,ventilationequipment, alarms,leakdetectorsetc;(f) theprocedurestobefollowedifareleaseoccurs,theseshouldinclude isolationandcontainmentofthereleaseandemergencyplans;theprocedures willneedtobesite-specificandcoverdifferentscalesofrelease(seealso paragraphs247-263);(g) trainingintheuseofallpersonalprotectiveequipment(PPE)supplied (seeparagraph237).Maintenancestaffshouldalsocoverdefectrectification.

Competency and audit

234 Competenceintheabovetopicsneedstobeassessedthroughpost-trainingassessmentsusingdocumentedprocedures.Itisrecommendedthattrainingandsafetyproceduresareauditedannuallybymanagementoranauditteamwithrelevantexperienceaspartofyourcompany’sauditprogramme.InternalauditsmaybesupplementedbyexternalauditsfromchlorinesuppliersundertheCIA’sinitiativeforresponsiblecareandproductstewardship,orbyothercompetentpeopleatintervalsofapproximatelythreeyears.



PERSONAL PROTECTIVE EQUIPMENT (PPE)

235 Chlorineisahighlytoxicsubstance;acuteexposurecanbefatal(seeAppendix1).Youthereforeneedtoestablishsafeworkingpracticesandcontrolmeasures(includingPPE)andensurethattheyareunderstoodbyoperatives.Safeproceduresarevitalwhereitisnecessarytoenteranenclosedstoragespaceoraroomwhereachlorineleakhasoccurred.WorkinsuchconfinedspacesissubjecttoTheConfinedSpacesRegulations1997.59GuidanceonhowtocomplywiththeRegulationsisgiveninanApprovedCodeofPractice.60Theprecautionsidentifiedmustbeimplementedandsuitabletraininggiventooperators.

236 Acommonsourceofexposuretochlorineisinoperationsinvolvingthemakingandbreakingofchlorinepipeworkconnections,particularlytocontainers.Stepsshouldbetakentopreventor,wherethatisnotreasonablypracticable,reducepersonalexposuretochlorine20bymeansotherthanpersonalprotectiveequipment.WhenPPE,includingrespiratoryprotectiveequipment,needstobeworn,equipmentmanufacturedafter30June1995shouldcarrythe‘CE’mark,toindicatethattheequipmenthasbeendesignedandtestedtomeetthebasicrequirementsofCouncilDirective89/686/EEC.

237 Respiratoryprotectiveequipment(RPE)thathasbeenapprovedbytheHSEorisclaimedbythemanufacturertoconformtoastandardapprovedbyHSE,andwhichwasmanufacturedbefore1July1995,cancontinuetobeusedatwork,providedthatitisstillsuitableandmaintainedingoodcondition.AllpersonnelwhoarerequiredtouseRPE(eg,respirators,breathingapparatus,orescapebreathingapparatus)mustreceiveadequateinstructionandtraininginitssafeandcorrectuse.TheRPEmustbethoroughlyexaminedandtestedinaccordancewiththemanufacturer’srecommendations(typicallyatleastonceeverymonth)andrecordskept.20

Selecting suitable respiratory protective equipment (RPE)

238WherePPEincludingrespiratoryprotectiveequipment(RPE)needstobeworn,youmustensurethatitisproperlyselectedandthatitprovidesadequateprotection.63,64WhenselectingRPEyoushouldconsultrelevantguidance65,66andbaseyourselectionontheresultsofariskassessment.20TheselectedRPEmust:

(a) provideadequateprotectionforyourparticularcircumstances(egforspecific tasksorforemergencyescape);and(b) becompatiblewithotherdemandsofthejobandtheworkingenvironment.

TheselectedRPEshouldmaketheoverallriskofinjurywhilewearingRPEaslowasreasonablypracticable.

239 WhenselectingRPEforaparticularapplication,atwo-stageselectionprocedureisthereforerecommended:(a) Basedontheresultsofyourexposureriskassessment: (i)decidewhetherarespiratororBA,oreithermaybeused;then (ii) determinetheminimumprotectionrequiredfromtheRPE.Thisisdone usingtheequationbelow.Indecidingthemaximumallowable concentrationinsidethefacepieceyouwillneedtotakeaccountof recognisedexposurelimits(seeAppendix1)ortakeaccountofyourin- houselimits.

MinimumProtectionRequired=WorkplaceconcentrationoutsidethefacepieceoftheRPE

MaximumallowableconcentrationinsidethefacepieceoftheRPE



Foremergencyescapepurposeswheretheexposurewillbelessthan15minutes,themaximumallowableconcentrationintheaboveexpressionistheShort-TermExposureLmit(STEL)(seeAppendix1).NowcomparetheMinimumProtectionRequiredvaluewiththeAssignedProtectionFactors(APF)indicatedinHSG5366andidentifyaselectionofequipment.(APFsshowninHS(G)53havebeenpublishedbytheBritishStandardsInstitution).67TheseAPFfiguresareaguide,notahardandfastrule.Indeed,itshouldberecognisedthatprotectionlevelsbelowtheAPFarepossiblewhenRPEisunsuitableforthetaskandisnotsuitedtothewearerandtheenvironment.WhereadvicegiveninHSG53isproperlytakenintoaccount,itispossibletoachieveprotectionatorabovethepublishedAPFvalues.YoumayusehigherAPFsifyouhavegoodqualityinformation(egsatisfactoryface-fitresultsforthosewearingRPE)todemonstratethattheyapplyinyourworkplaceconditionsandtotheselectedRPE.YoucanusetheAPFfortheequipmentselectedtoestimateconcentrationinsidethefacepiece.

Concentrationinsidethefacepiece=Workplaceconcentrationoutsidethefacepiece

APF

Note:‘Nominal Protection Factors’ (NPF) values have been used in the past, for identifying a selection of equipment. This procedure is no longer valid because workplace studies have shown that many wearers may not achieve the level of protection indicated by NPFs.

(b) Thenextstageistotakeaccountofthefactorsdetailedinparagraphs36-47ofHSG53tohelpnarrowdownthechoice.Alwaysinvolvethewearersintheselectionprocess,andwherepossibleprovidethemwithachoiceofsuitableRPE.Thiswillhelptoensurethatitissuitedtothemindividually,andincreasethechancesthatitwillbeacceptedandworncorrectly.

Wherethereisdoubtaboutthechoice,youneedtoconfirmwiththemanufacturerorsupplierthatthechosenequipmentissuitableforthetaskandtheconditionsinwhichitistobeused.TheyhavedutiesundertheHealthandSafetyatWorkActetc1974toprovideinformationonthelimitationsandcapabilitiesoftheirRPE.

240 Atsomechlorineinstallationsitiscommonpracticeforpersonneltocarryhalfmaskrespiratorsfittedwithsuitablefilters(eg:typeandclass:B1;colour:grey)forprotectionagainstchlorine.Thepurposeofthistypeofrespiratoristoprovideanimmediateprotectionintheeventofanincidentinvolvinglowconcentrationsofchlorinegassothatthewearercanescapeintofreshair.ThistypeofhalfmaskrespiratorhasanAPF=10,iethemaximumallowableworkplaceconcentration=10xSTEL=10ppm.

Driverwearingfullfacemaskfittedwithafilter.(Helmetremovedfordemonstrativepurposes)

241 AfullfacemaskwithcartridgeorcanisterhasanAPFof40.Theuseofthistypeofrespiratorwouldtypicallybeinorveryneartheopenairduringthe



connectingupordisconnectingofcontainersorbreakingintopreviouslypurgedchlorinesystems.Theoperatingproceduresspecifictothesiteshouldstatewhethertherespiratorhastobewornforeachoperation,orbe‘attheready’tobeputonincaseofneed.Arespirator(egamaskfittedwithafilterorcanister)isnotsuitableforuseinatmosphereswhichareimmediatelydangeroustolifeorhealth.Inotherwords,respiratorsarenotsuitableforoperationswherethereisapotentialforasignificantreleaseofchlorinegas.Inthesecircumstancesasuitablebreathingapparatus(BA)shouldbeworn.

242 Filtershaveashelf-lifespecifiedbythemanufacturersbeyondwhichtheyshouldnotbeused.Oncefilter-canistersealshavebeenbroken,filterlifewilldependonusage,contaminentconcentrations,breathingrateetc.Yourriskassessment,combinedwithinformationfromthefiltermanufacturer,willdeterminetheusefullifeofrespiratorfilters;yourdecisionsneedtobecommunicatedtothewearers.Onceunsealed,filtersshouldnotbestoredforre-use,buttheymaybeusedoveranumberofconsecutivedays,providedtheyhavenotbeenexposedtoconcentrationsofchlorinesimilartoorabovethosetheyareprovidedfor.

243 AnegativepressuredemandBAwithfullfacemaskhasanAPFof40.FormajorleaksapositivepressuredemandBAwithfullfacemask(ieaself-containedBA)wouldbeappropriate,providedtheminimumprotectionrequiredwasconsistentwiththeAPF(2000),seeparagraph253.Aself-containedbreathingapparatus(SCBA)shouldalwaysbeworn(possiblywithagas-tightchemicalprotectivesuit)whenenteringanenclosedspaceorchlorineroomwhereasignificantleakhasbeendetectedorsuspected.Thisisbecausethechlorinedetectormaybesomedistanceawayfromthesourceoftheleakorpocketsof‘trapped’gaswhicharenotdispersedbytheventilationsystem.Theconcentrationinsuchareasmaybemuchhigherthanthosedetectedbythealarmsystem.

244 Incertaincircumstances,compressedairlinebreathingapparatus(CABA)maybesuitable.However,theserestrictthemovementofthepersonnelandthetrailinghosecanaddtotheriskinareaswithobstructions.Insuchsituationsaself-containedbreathingapparatusmaybeappropriate.

245 Forindoorinstallationswithmulti-stagealarms,theforcedventilationsystemwillhavebeenswitchedoffonactivationofthehigherlevelalarm.PeopleenteringtheareatoidentifyandeliminatethesourceoftheleakshouldwearsuitableBA,seeparagraphs252-255).Nopersonshouldworkaloneinthesecircumstances.Anyback-upstaffinattendanceforemergencyactionshouldwearsuitableBA‘attheready’.

246 EmergencyescapeBAisnotintendedforuseduringnormalworkandthereforeitisnotrecommendedbyHSEforanythingotherthanemergencyescapeuse.



Emergency arrangementsNote: Further guidance will be available when the COMAH Regulations come into force in February 1999.

247YouneedtoinformtheappropriateFireAuthorityandPoliceForceofthepresenceofchlorineatyoursite.Youshouldalsoinvolvethemandyourchlorinesupplieratanearlystagewhendevelopingandupdatingyouremergencyplanandprocedures.Youremergencyarrangementsshouldbebasedonariskassessmentandincludeproceduresonhowgasreleasesmaybedealtwithsafelybysitepersonnelandonwhethertocallforassistancefrombeyondthesite.68,69,70Yourriskassessmentshouldalsoaddressfiresafetyoftheprocessorinstallationandpossibleimpactsfromneighbouringsites.GeneralfireprecautionsshouldcomplywiththerequirementsoftheFirePrecautions(Workplace)Regulations1997.21248 Youremergencyplanshouldcovertheforeseeablerangeofchlorinereleasesforyoursite;asummaryofsomeoftheimportantelementsofaplanisgiveninAppendix8.Acopyoftheplanshouldbemadeavailabletoallpersonnelinvolvedinitsimplementation.Itisrecommendedthattheplanincludesthenamesorpositionsofthepersonswhowillsoundtheoff-sitealarm.Thismaybesomeoneon-site,oritmayundersomecircumstancesbetheresponsibilityofthefirstFireOfficeronthesiteintheeventofanemergency.Theplanshouldalsoincludefirst-aid(seeAppendix1)andevacuationarrangementsbothon-siteand,ifappropriate,off-site(seeAppendix8).

249 Eachinstallationneedstohavemeansofwarningallworkersthatagasescapehasoccurred.Awinddirectionindicator,mountedinahighlyvisiblelocation,needstobeprovidedtohelppersonneldecidethebestdirectioninwhichtoescape.Theappropriateactiontobetakenfollowingagasescapewarningshouldbedefinedinwritteninstructions,andappropriatetraininggiven.

250 Foraminorgasescape,youmayonlyneedtoplansimpleactions.Inothercircumstanceshowever,afurthersystemofspecialwarningsmayberequired,whichinitiatestheemergencyplanand,ifnecessary,theoff-siteemergencyplan.Thefirstcallforassistanceshouldbetotheemergencyservicesforincidentcontrolandrescue,andthentoChlor-Aid,throughyoursupplierwhowillofferadviceonhowtodealwiththerelease.UnderChlorAidthechlorineproducersandsuppliers(seeAppendix4)collaborateindealingwithchlorineemergenciesatbulkinstallationsthroughouttheUK.ThearrangementsareoutlinedinabookletpublishedbytheCIA71underthechemicalindustry’sResponsibleCareinitiative.

251 Arrangeregularpracticesoftheemergencyplan.Someoftheseshouldinvolvetheemergencyservices,whowilladviseonasuitablefrequency.

EMERGENCY EQUIPMENT

252 Yourriskassessmentshouldconsidertheextent,type,andlocationoftheemergencyequipment,includingtheneedforchemicalprotectionsuitswhichprovidetotalencapsulation.Thesecanbecompressedairlinesuppliedfullsuitsorfullprotectivesuitswornoverself-containedbreathingapparatus(SCBA).

253 SCBAwithfullfacemaskconformingtoBSEN137(SCBA)72orairlineBAconformingtoBSEN13973hasanAPFof2000(butseeparagraphs238-246).Self-containedequipmentwillsupplyairforuptoabout40minutess(seethemanufacturer’sdetails).Thesesetsareprovidedwithawarningsystemtoalertthewearertoleavethecontaminatedareawhentheaircylindersarebecomingempty.



Compressedairlinebreathingapparatusprovidesthesameprotectionwithoutatimelimit,butdoesrestrictfreedomofmovementinsearchandrescueoperation.254 AswithotherRPE,emergencyescapebreathingapparatusshouldbeCE-markedandincorporatefaceprotection(egintheformofahoodorfullfacemask).SuitableHSE-approvedescapeequipmentmayalsobeusedifitwasmanufacturedbefore1July1995.Suchequipmentisforescapeonlyandnotforuseduringroutinework.

Emergencyandrescueequipment

255 Emergencyandrescueequipmentshouldbeavailableandreadilyaccessibleinallchlorineplantareas,anditslocationsuitablymarked.Suchequipmentneedstoberegularlyinspectedandmaintained.Aninventoryoftheequipmentshouldbekeptandattachedtotheplantoperationalandemergencyprocedures.

CONTROL OF LEAKAGES

256 Localalarmstationstoprovideearlywarningofchlorineescapesareanessentiallinkintheemergencyprocedure.Theuseofchlorinedetectorsandalarmsiscoveredinparagraphs113-118.Localalarmstations(push-buttontypepreferred)shouldbelocatedatstrategicpointsnearchlorinestorageinstallations;generallytwoalarmstationsonconvenientescaperoutesfromthechlorineunloadingterminal/storagetankareaaresufficient.Thelocalalarmstationsmayactuatetheworksemergencyalarmdirectlyorindirectlybyraisinganalarmintheemergencycontrolcentreandthemaincontrolroom.Preferablyinlargeworksthelocalalarmstationshouldactuateadistinctlocalchlorinealarmtowarnpeopleofffromtheaffectedarea.

257 Thealarmstationsmayalsoactuatetheremotelyoperatedshut-offvalvesonthechlorinestoragetankswherethisisconsistentwiththesafeoperationoftheuserplant.

258 Materialsandequipmentincludingsandandplasticsheetstocontainspillsofliquidchlorineshouldbereadilyavailable.Coveringastabilisedspillwithplasticsheetsisoftenthebestaction.Applicationoffoamwouldcauserenewedevolutionofvapourbecauseoftheheatsupplied.Theneedforfoamandwaterspraysshouldbediscussedwiththechlorinesupplierandlocalfireauthority,sincetheuseoffoamandwatermay,incertaincircumstances,aggravatetheproblem.Thefireauthoritymaycarrystocksofsuitablefoam,butthedecisiontouseitshouldbetakeninconjunctionwiththeseniortechnicalmanageronsite.

259 Watershouldneverbeaddedtoaspillageofliquidchlorineorsprayedontoaleakingtank.However,waterhosesorfogspraysdirectedatachlorinegascloudcanhelpdiluteitasaresultoftheairentrainmentgeneratedbythejetsofwater.



Releases inside buildings

260 Ifthespillisindoorsandcontainedbytheuseofsandorabunditwillrapidlycoveritselfwithacoatingofslushychlorinehydrateandacoldvapourlayer.Suchastabilisedspillshouldbecoveredwithaplasticsheet(seeparagraphs258and259).Forasevereleak,possiblyarisingfromafailureofpipework,thechlorinebuildingwillprovidesomedelaytothereleaseofthegastotheopenair,providedventsandaperturesareclosedorsealed.Thiswillgivemoretimeforthetechnicalstaffandmanagementtoidentifyanddealwiththesourceoftherelease.Indispersingthecontainedreleasefromachlorineroomitisstillessentialtoconsidertheoff-siteconsequencesanditmaybenecessarytosoundtheoff-sitealarm(whenfitted)toalertpeopletogoindoorsandremainthere.Itisfortheemergencyservicestoconsiderclearingpeoplefromtheareaimmediatelydownwindoftheinstallationaftersucharelease.

261 Asignificantreductioninthereleaseofchlorinefromabuildingisonlyobtainediftheleakisquicklycontrolledandtherateofairchangeinthechlorineroomislow.Theventilationsystemshould,therefore,beswitchedoff(unlessascrubbingsystemisinstalledtoremovechlorinefromtheexhaustgas)andallaperturesneedtobeclosedorsealed.262 Considerusinganadditionalsensorcapableofmeasuringconcentrationsupto500ppmandgivingavisualdisplayoutsidethechlorineroomandintheworkscontrolroom.Suchadisplayisusefulforassessingthesignificanceoftheleakandwhetheritcanbeisolatedsafely.Onceconcentrationsexceed1000ppm(thisisaboutthethresholdconcentrationforthecloudtobevisible),personneldealingwiththereleaseshouldtakeadditionalprecautionsandshouldwithdrawtoasafeareaassoonastheyareawarethattheyarebreathingcontaminatedair.

263 Afteraleakorsubstantialreleasehasbeendealtwithitwillbenecessarytoventilatethechlorineroomthoroughly.OperatorsshouldnotremoveanyRPEuntiltheyhaveremovedclothing(whichmaybecontaminatedwithchlorine)andareinasafeenvironment.



Appendix 1 Toxicological properties and first aidTOXICITY

1 Chlorinehasaperceptibleodourthatcanbedetectedbymostpeopleataconcentrationof0.3ppm(v/v)andbysomeatconcentrationsaslowas0.02ppm.TheOccupationalExposureStandard(OES)74forexposuretochlorineis0.5ppm;thisisatime-weightedaverageconcentrationoveraperiodof8hours.TheShort-TermExposureLimit(STEL)74is1ppm;atime-weightedaverageover15minutes.

2 Itproducesclearsensoryirritationatconcentrationsof0.5-1ppmandabove.75Irritationofthemucousmembranesoftheeyeandnose,andespeciallyofthethroatandlungs,iscausedbyexposuretochlorineatlevelsofaround1-15ppm.Ingeneral,irritationbecomesintolerableatconcentrationsofabout4ppm.76Concentrationsof50ppmormorearedangerousevenforexposuresofabout5-10mins;theymaycauseinflammationofthelungswithaccumulationoffluid.Occasionallythedevelopmentofrespiratorysymptomsmaybedelayedforuptotwodaysafterexposure.However,thereisnoconvincingevidenceofseriouslong-termsequelaefollowingrecoveryfromasingleexposuretochlorine.75

3 Exposureto1000ppmmaybefatalafterafewbreaths.77Deathresultsfromlungdamage.Itcaneitheroccurrapidly(fromwithinhourstoacoupleofdayspost-exposure),duetooedemaandcongestion,oritcanbesomewhatmoredelayed(severaldays)duetosecondarypneumonia.

4 Theharmfromexposuretochlorineisproportionaltothe‘toxicload’definedastheproductofthesquareoftheconcentrationandexposuretime.Forriskassessmentwork,HSEusesa‘dangeroustoxicload’78(DTL)of:DTL=108000ppm2minwhichispotentiallyfataltothemostvulnerablemembersofthepopulation.Thusexposuresto104ppmfor10minutesor73ppmfor20minutesetcarepotentiallyfatal;thechanceoffatalitydependsonmanyfactors.78

FIRST AID

5 Whenliquidchlorinecomesintocontactwiththeskinormucousmembranesitcanproduceseriousburnswhichneedtobetreatedbyamedicallycompetentperson.Peoplewhohaveinhaledchlorinegasshouldbemovedasquicklyaspossibleinto‘freshair’,laidinarestfulpositionwiththeheadandchestraised,andkeptwarm.Itisessentialthatqualifiedmedicalattentionisobtainedquickly,asserioussymptomsmaydevelopupto48hourslater.Anyonewhohasbeenaffectedbychlorinegasshouldbeexaminedlocallybyamedicallycompetentpersonorsenttohospitalbyambulance.

6 First-aidattendantsshouldbeawareofthedangersarisingfromgassingbychlorine.Thefollowingbasicrulesshouldbeobserved:

(a) ifchlorinehasaffectedtheeyes,theyshouldbeirrigatedwithplentyofclean (preferablytap)water;(b) contaminatedclothingshouldberemovedinawell-ventilatedareaandaffectedskin washedwithplentyofwater;(c) mouth-to-mouthresuscitationshouldnotbegivenifthepatientisbreathing, becausethereisariskoftheattendantbeingharmed.However,oxygenmaybe administeredorresuscitationequipmentusedbysuitablyqualifiedpersonnel.

Morecomprehensiveguidanceisgivenelsewhere.79



Appendix 2 Characteristics of chlorine 1 Chlorineisagreenish-yellowgasatambienttemperatureandpressure.Itissuppliedcommerciallyasaliquidunderpressure.

2 CommercialliquidchlorineconformstoBS3947:1976.80ThisStandardspecifiesaminimumlimitforthechlorinecontentandmaximumlevelsforwatercontentandresidueonevaporation;detailsofthemethodsofanalysisforgaseousimpurities(carbondioxide,oxygenandnitrogen),watercontent,nitrogentrichloride,andresidueonevaporationarealsogiven.

3 Tracesofdissolvedgaseousimpuritiesinchlorinearenotnormallysignificantformostapplications;moisturecontenthoweverisextremelyimportantbecauseofthecorrosivenatureofwetchlorine.

4 Traceresidueswhichareleftonevaporation,usuallychlorinatedorganicproductsorferricchloride,mayleadtoblockageofpipelines,valvesorinstruments.Nitrogentrichloridecanbepotentiallydangerous51,52ifthevaporisationprocessleadstoitsconcentrationinresidues,butthisisgenerallynotconsideredtobeaproblemindrumandcylinderinstallations.

5 Physical properties

Atomicweight 35.46

Molecularweight 70.91

Density liquid 1561kg/m3at-35°C 1468kg/m3at0°C 1410kg/m3at20°C

gas 3.173kg/m3at0°Cand1barabsolute(relative density2.490at20°Crelativetoair)Boilingpointat1.0133barabsolute -34.05°CMeltingpoint -101.6°CCriticaltemperature 144°CCriticalpressure 77.1barsabsoluteVapourpressureat20°C 6.7barsabsoluteViscosity:liquidat20°C 0.35cp

1volumeofliquidchlorine=463volumesofchlorinegasat0°Cand1barabsolute

1kgofliquidchlorine=0.319m3ofchlorinegasat0°Cand1barabsolute

ThevariationofthevapourpressureofliquidchlorinewithtemperatureisgiveninFigureA2.1.

Thermal properties

Specificheat(liquidchlorinebetween1°Cand27°C)0.236kcal/kg/°C

Specificheat(gasatconstantpressureat6.9barsabsoluteorlessandbetween1°Cand27°C)0.113kcal/kg/°C

Ratioofspecificheatatconstantpressuretospecificheatatconstantvolume1.355



Latentheatoffusion 21.6kcal/kg

Latentheatofvaporisationat0°C 63.2kcal/kg

Coefficientofcubicexpansion(liquidchlorineat20°C)0.0021per°C

Thiscoefficientissufficientlylargetoresultinexcessivepressureshouldliquidchlorinebetrappedinpipeworkbetweentwoclosedvalveswithnogasspace.

Heatofreactionofchlorinegaswithsodiumhydroxideliquor348kcal/kgofchlorine.

6 Whiletheabovedatagiveageneralsummaryofthephysicalandthermalpropertiesofchlorine,moredetailedinformationisneededforuseinplantdesigncalculations.

Figure 1 Variationofchlorinevapourpressurewithtemperature

Solubility of chlorine in water

7 Chlorinedissolvesslightlyinwatertogiveasolutionwhichhasoxidising,bleachingandgermicidalproperties.Thesolubilityofchlorineinwaterincreaseswiththepartialpressureofthechlorine.Thetablebelowgivesthesolubilityofchlorineinwateratdifferenttemperaturesforatotalpressureof1barabsolute:

Temperature °C 10 15 20 25grams of chlorine per litre of water 9.97 8.5 7.29 6.41

Foratotalpressureof1barabsolute,thepartialpressureofchlorinereducesasthewatertemperature(andhencethepartialpressureofwatervapour)increases.

8 Oncoolingbelow9.6°C,crystalsofchlorinehydrate(Cl2.8H20)aredeposited.Forthisreason,wetchlorineinprocessmustalwaysbekeptabovethistemperaturetoavoidtheblockageswhichwouldotherwiseoccurasaresultoftheformationofsolidchlorinehydrate.

9 Asolutionofchlorineinwaterformshydrochloricacidandhypochlorousacid: Cl2+H20HCl+HOC1

g



Chemical properties

10 Drychlorineatambienttemperaturesreactsdirectlywithmanyoftheelementsproducingchloridesbothofnon-metals(egsulphurorphosphorus)andofmetals(egironinafinelydividedform,aluminiumortitanium).Drychlorineatambienttemperaturedoesnotattacksteel,copperornickel,butthesemetalsareattackedathighertemperatures.Steelcombineswithdrychlorineabove200°Cand,sincethereactionisexothermic,therateofreactionmayincreaserapidly.Reactionwithnickeldoesnottakeplaceuntilthetemperatureexceeds500°C.

11 Tracesofmoistureinchlorineleadtorapidcorrosionofsteel,copperandnickel.12 Titaniumisresistanttowetchlorinebetween15°Cand100°Cbutreactsviolentlywithdrychlorineandshouldnotbeused;butseeparagraph18.

13 Chlorinedissolvesincoolaqueoussolutionsofalkalistoproducesolutionsofhypochlorites;inhotorboilingaqueousalkalis,chloratescanbeproduced.

14 Chlorinereactsvigorouslywithmanyorganiccompoundsincludingmineraloilsandgreases,producingchlorinatedproducts.Themechanismiseitherdirectadditiontounsaturatedbondsorsubstitutionofhydrogen.Inthelattercase,hydrogenchlorideisformedasaby-product.

15 Mixturesofchlorineandhydrogenareexplosiveoveralargerangeofconcentrations;theexplosionmaybeinitiatedbyaspark,byphotochemicalactionorbyacatalyst.Undercertainconditionschlorinereactswithammoniatoproducenitrogentrichloride,whichisspontaneouslyexplosive.Thisisnotariskwhentestingforleakswithabottleofammonia.

Selection of materials of construction

16 Thechoiceofappropriatematerialsofconstructionforchlorinesystemsisconsideredindetailelsewhere.81Youroptionsshouldbeselectedonlyafteradetailedsurveyofallpossiblevariationsinoperatingconditions,andyourpreferredoptiondecidedinconsultationwithyourchlorinesupplier.

17 Asystemconstructedofsteel,whichisappropriatefordrychlorine,mustitselfbedriedadequatelybeforecommissioning.Thismaybedonebypurgingwithdryairorinertgasuntiltheexitpurgehasadewpointbelow-40°C.However,theupperoperatingtemperaturemustbelimited.

18 Theuseoftitaniummetalforwetchlorineissatisfactory,81providedthatthemoisturelevelisalwayskepthighandthatcontrolisexercisedovertheupperandloweroperatingtemperaturelimit.Maintenanceandinspectionproceduresmustincludeawarenessofthepossibilityofcrevicecorrosion.However,wheretitaniumisusedinplantscontainingwetchlorine(gasorliquid)considerationshouldbegiventothepossibilityofafaultconditiongivingrisetocontactbetweentitaniumanddrychlorinegasorliquid.Ifsuchafaultcouldpossiblyariseitmaybebesttoconsideralternativeconstructionmaterials.

19 Materialswhichareresistanttoattackbybothwetordrygaseouschlorineatambienttemperaturesincludeglass,stoneware,porcelain,tantalum,eboniteandcertainplastics.Theuseofplasticmaterialswithliquid chlorineisunsatisfactory.

LEARNING FROM INCIDENTS

20 Aninterestingselectionofincidents,whichillustratesomeoftheabovehazards(includinganitrogentrichlorideexplosion,atitanium/chlorinefireandexternalcorrosion)andthemeansforcontrollingthem,isreviewedinGEST/AP1.82



Appendix 3 Relevant legislation and HSE guidance1 ThebasisofhealthandsafetylawintheUKistheHealthandSafetyatWorketcAct1974.Thissetsoutgeneraldutieswhichemployershavetowardsemployeesandmembersofthepublic,andthosethatemployeeshavetothemselvesandeachother.ThesedutiesarequalifiedintheActbytheprincipleof‘sofarasisreasonablypracticable’;ietheextentofthemeasurestakentoavoidorreduceaparticularrisktohealthandsafetyneedstobebalancedagainstthetime,trouble,cost,andphysicaldifficultyinvolved.Thisbalancingprocess83isoftenreferredtoasmakingrisks‘aslowasisreasonablypracticable’(ALARP).

2 Inessence,whathealthandsafetylegislationrequiresiswhatgoodmanagementandcommonsensewouldleademployerstodoanyway:thatistolookatwhattherisksareandtakesensiblemeasurestomakethemALARP.ThisbroadrequirementismadeexplicitintheManagementofHealthandSafetyatWorkRegulations199218,19(referredtoastheManagementRegulations).LiketheAct,theseRegulationsapplytoeveryworkactivity.Otherregulationsaremorespecific,egtheManualHandlingOperationsRegulations(MHO)57ortheControlofSubstancesHazardoustoHealthRegulations(COSHH).20

3 Afulllist3ofcurrentlegislation,ApprovedCodesofPracticeandsomeguidanceispublishedannually.Thelistcontainslegislation,which,althoughinexistence,isspentorhaslapsed.Apricelist84ofallavailableHSEpublicationsispublishedannuallybyHSEBooks.Contactdetailsareontheinsideofthebackcover.

4 Anumberofregulations(egCOSHH,MHO,PPE,64ManagementRegulationsetc)specificallyrequireyoutoundertakeariskassessment.Aleaflet85isavailabledescribinghowtheseassessmentsarelinkedtogetherandwhattherequirementsare;however,itdoesnotdealwithhighlyspecialisedriskssuchasmajorhazards.

5 Underthebasiclegalrequirementsyoumust:

(a) haveawritten,up-to-datehealthandsafetypolicyifyouemployfiveormore people;(b) carryoutariskassessment(andifyouemployfiveormorepeople,recordthemain findingsandyourarrangementsforhealthandsafety);(c) notifyoccupationofpremisestoyourlocalinspectorifyouareacommercialor industrialbusiness;(d) displayacurrentcertificateasrequiredbytheEmployers’Liability(Compulsory Insurance)Act1969ifyouemployanyone;(e) displaytheHealthandSafetyLawposterforemployeesorgiveouttheleaflet;86

(f) notifycertaintypesofinjuries,occupationaldiseasesandevents(seeparagraph23); and(g) consultemployeesandanyappointedunionsafetyrepresentatives87oncertain issues,suchasanychangeswhichmightaffecthealthandsafetyandany information,instructionandtrainingwhichhastobeprovided.

6 TheALARPprincipleandtheneedforriskassessmentenablestheHealthandSafetyCommission,whereappropriate,tomakeRegulationsinagoal-settingform:iesettingoutwhatmustbeachieved,butnothowitmustbedone.Sometimesitisnecessarytoprescribeindetailwhatmustbedoneandsetabsolutestandards.



7 Someactivitiesorsubstancesaresoinherentlyhazardousthattheyrequireadditionalarrangements.Forexample,chlorineinstallationswhichstore10tonnesormoreneedtomeetthegeneralrequirementsoftheCIMAHRegulations(seeparagraph9).

THE NOTIFICATION OF INSTALLATIONS HANDLING HAZARDOUS SUBSTANCES (NIHHS) REGULATIONS 1982 4

8 TheseRegulationsimplementanotificationschemeforinstallationswithinventoriesgreaterorequaltospecifiedquantities(10tonnesforchlorine).NotificationistotheHealthandSafetyExecutiveviayourLocalAreaOffice(seeAppendix4).UnderNIHHSthefollowingrequirementsapply:

(a) beforechlorineisusedorstoredatasite,atleastthreemonthsnoticemust begiventoHSEandcertaindetailsspecified;(b) thenotificationmustbeupdatedwheneverthereisachangeinactivityon siteorthereisanincreaseorreductionintheoperationalquantityofchlorineonsite; and(c) theamountofchlorineonsitemustnotbeincreasedtothreeormoretimesthe quantityoriginallynotified,unlessanewnotificationismade.(Anyincreasesin inventorylevelsmustofcoursecomplywithotherlegislation,inparticularsection3of theHSWAct,iethattheriskstopeopleoff-siteareALARP).

THE CONTROL OF INDUSTRIAL MAJOR ACCIDENT HAZARDS (CIMAH) REGULATIONS 1984 5

9 TheseRegulationsimplementtherequirementsoftheEuropeanDirective(82/501/EEC)onthemajorhazardsofcertainindustrialactivitiescommonlyreferredtoasthe‘Seveso’Directive.Theyapplytothestorageandprocessingofhazardoussubstances.TheRegulationshavebeenamendedanumberoftimes.3Theseincludethe1988amendment(revisionofthresholdquantitiesforcertainsubstances)andthe1990modificationofthecontrolsonstoragefollowingaseriouswarehousefire.Twolevelsofactivityaredefined.Thelowerlevelrequirementsrequirecompaniestotaketheprecautionsthatarenecessarytopreventamajoraccidentandtolimittheconsequences,andgenerallytodemonstratesafeoperation(regulation4),andtoreportanymajoraccident(regulation5).InstallationsinwhichchlorineisinvolvedinaprocessunderSchedule4aresubjecttothesegeneralrequirementsregardlessofthequantitypresent,unlesstheoperationisincapableofproducingamajoraccidenthazard.Larger(ietop-tier)installationswhichstore75ormoretonnes,orinstallationswith25tonnesormorewhichcarryoutprocessactivitiesunderSchedule4,additionallyrequirethepreparationofsafetyreports,emergencyplansandtheprovisionofinformationtothepublic(regulations7-13).GuidanceontheCIMAHRegulationsisavailable.69,88TheseRegulationswillbewithdrawnwhentheproposedControlofMajorAccidentHazards(COMAH)RegulationsareimplementedinFebruary1999.

THE COMAH REGULATIONS

10 TheseRegulationswillimplementtherequirementsofTheControlofMajorAccidentHazardsInvolvingDangerousSubstancesDirective(96/82/EC)whichwasadoptedbytheEUon9December1996.TheDirectiveisreferredtoasthe‘SevesoII’Directive.TheRegulationsfollowtheDirectivecloselyandmirrortheSevesoI/CIMAHregime,inhavingtwolevelsofduties:

(a) generaldutiesonalloperatorssubjecttotheRegulations:tonotifythecompetent authoritiesoftheiractivities,totakeallmeasuresnecessaryforthepreventionand mitigationofmajoraccidents,toprepareamajoraccidentpreventionpolicy,and reportmajoraccidents;



(b) top-tierdutiesonoperatorsofsiteswherethequantitiesofdangeroussubstances exceedthehigherthresholds.Theseoperatorsmust,inadditiontothedutiesinthe aboveparagraph,submitsafetyreports,prepareandtestemergencyplansand provideinformationtothepublic.

Inthecaseofchlorinethethresholdquantitiesare10tonnesforthegeneraldutiesand25tonnesforthetop-tierduties.Applicationdependssolelyonthepresenceoranticipatedpresenceofthethresholdquantitiesofdangeroussubstances,includingdangeroussubstanceswhichmightbegeneratedinthecourseofanaccidentduetolossofcontrolofanindustrialchemicalprocess,withnodifferentiationbetweenstorageandprocessing.Thegeneraldutyforoperatorstotake‘allmeasuresnecessaryforthepreventionandmitigationofmajoraccidents’issimilartotheCIMAHRegulationswhichrequiremanufacturersto‘takeadequatestepstoprevent...majoraccidents...andlimittheirconsequences...’.Injudginghowthisdutyshouldbecompliedwithinpractice,thecompetentauthoritieswillbasetheirviewonwhetherriskshavebeenreducedtoALARP.Themainnewrequirementsare:

n AlloperatorswithinthescopeoftheDirectivemustproduceamajor-accidentpreventionpolicy(MAPP)andensurethatitisproperlyimplementedtoguaranteeahighlevelofprotectionforhumansandtheenvironmentbyappropriatemeans,structures,andmanagementsystems.

n Land-useplanningisbroughtwithinthescopeoftheDirective.n Safetyreports(top-tiersitesonly)havetobemadeavailabletothepublic,but

companiescanrequestthatcertaininformation,includingcommercialand personalconfidentialinformation,iswithheld.

n Thecompetentauthorities,HSEandtheEnvironmentalAgency(EA)in EnglandandWales,andHSEandtheScottishEnvironmentalProtection Agency(SEPA)inScotland,mustprohibitoperationswherethemeasures takenbyoperatorstopreventandmitigatemajoraccidentsareseriously deficient.

TheSevesoIIrequirementsplacemuchmoreemphasisonthemanagementofsafetyandtheroleofthesafetyreportthanintheoriginalSevesoDirective(implementedbytheCIMAHRegulations).Paragraphs11-23summarisethemainrequirementsofotherlegislationthatisrelevanttothecontrolofrisksposedbyinstallationshandlingchlorine.

THE PLANNING (HAZARDOUS SUBSTANCES) ACT 1990 AND PLANNING (HAZARDOUS SUBSTANCES) REGULATIONS 1992 7

11 TheActandRegulationsintroduceplanningcontrolswhicharedesignedtoensurethathazardoussubstancescanbekeptorusedinsignificantamountsonlyaftertheresponsibleauthoritieshavehadtheopportunitytoassessthedegreeofrisktopeopleinthesurroundingareaandaresatisfiedthattherisksaretolerable.InessencetheActandRegulationsrequiresitestoapplyfor‘hazardoussubstancesconsent’forinventorylevelsatorabovespecificamountsknownasthe‘controlledquantity’-10tonnesinthecaseofchlorine.Neighbouringsiteswithin500m,andcontrolledbythesameperson,mustbetakenintoaccountwhendecidingthemaximuminventory.Newsitesmustobtainhazardoussubstancesconsentatanearlystageinthelifecycle.

12 InEnglandandWalesthecontrolsareenforcedbytheHazardousSubstancesAuthority(HSA),usuallytheDistrictorLondonBoroughCouncilforthelandinquestion,ietheLocalPlanningAuthority(LPA).InScotlandtheequivalentregulationsareTheTownandCountryPlanning(HazardousSubstances)(Scotland)Regulations1993.TheyareenforcedbytheScottishOffice,EnvironmentDepartment(SOED).HSEisastatutoryconsulteeundertheActandadvisesHSAsandSOEDonthenatureandseverityoftheresidualrisk.TheActrecognisesthatsafetymustbeanoverridingcontrol.Thecontrolsapply,regardlessofwhetherplanningpermissionisrequiredunderotherlegislation.



13 GuidanceonapplyingforhazardoussubstancesconsentinEnglandandWalesisgiveninHazardous Substances Consent: Guidance for Industry(producedbytheDepartmentoftheEnvironmentandtheWelshOffice,92PLAN0001).SOEDhasissuedcircular16/1993Hazardous Substances Consent: Guidance for Industry.

THE DANGEROUS SUBSTANCES (NOTIFICATION AND MARKING OF SITES) REGULATIONS 1990 39,40

14 Wheremorethan25tonnesofdangeroussubstancesarepresentonasite(includingchlorine)notificationmustbemadetothefireauthorityandappropriatesignsplacedatsiteaccesspoints.TheenforcingauthorityisthefireauthorityexceptinspecifiedcircumstanceswhenitisHSE.TheRegulationsrequireallsignstoconformtoBS537841andtobekeptcleanandfreefromobstructions.

THE MANAGEMENT OF HEALTH AND SAFETY AT WORK REGULATIONS 1992 18

15 TheseRegulationsimplementCouncilDirectives89/391/EEC(OJNoL183,29.6.89,p1)and91/383/EEC(OJNoL206,29.7.91,p19)ontheintroductionofmeasurestoencourageimprovementsinsafetyandhealthofworkersatwork.UndertheRegulationsyoumust:

(a) assesstheriskstothehealthandsafetyofyouremployeesandnon-employees arisingin,orfrom,youractivitiesandreviewtheassessmentwhenthereis significantchange.Recordsofsignificantfindingsoftheassessmentmustbekept wheretherearefiveormoreemployees;(b) plan,organise,control,monitorandreviewthepreventativeandprotectivemeasures takenasaresultoftheassessment;(c) appointanycompetentperson(s)neededtohelpyoucomplywithlegalobligations, forexample,whenhavingpressuresystemsexamined;(d) setoutwhatshouldbedoneincaseofseriousandimminentdangeratyour premises,suchasthespillageofanappreciableamountofchlorine;(e) tellemployeesabouttherisksandprecautionsinvolvedintheirwork;and(f) providehealthsurveillancewherenecessary.

THE LIFTING PLANT AND EQUIPMENT (RECORDS OF TEST AND EXAMINATIONS ETC) REGULATIONS 199289,90

16 Youmust:

(a) havecertificatesoftestandexamination(normallyprovidedbymanufacturersand suppliers)specifyingsafeworkingloadsbeforefirstusingchains,ropesandlifting tackle;(b) havechains,ropes,liftingtackle,hoistsandliftsthoroughlyexaminedeverysix monthsbyacompetentperson(oftenemployedbyaninsurancecompany)and obtainandkeepthereport;(c) ensuretestsandthoroughexaminationsofcranesarecarriedoutbeforetheyare firstusedandobtainacertificateoftestandexaminationspecifyingsafeworking loads.Periodicthoroughexaminationsatleastevery12monthsarealsorequired, forwhichareportshouldbeobtainedandkept.

HSEguidanceisavailable.90

Note:TheseRegulationswillberevokedandreplacedinDecember1998bytheLiftingOperationsandLiftingEquipment(LOLER)Regulations(SI1998/2307).GuidancewillbepublishedinanApprovedCodeofPracticeonSafeUseofLiftingEquipment.TheProvisionandUseofWorkEquipmentRegulations1998(seeparagraph19)alsoapplytoliftingequipment.



THE MANUAL HANDLING OPERATIONS REGULATIONS 1992 57

17 TheseRegulationsimplementthesubstantiveprovisionsofCouncilDirective90/269/EEC(OJNoL156,21.6.90,p9)onthehealthandsafetyrequirementsforthemanualhandlingofloadswherethereisariskofbackinjurytoworkers.Employersmust:

(a) avoidtheneedforhazardousmanualliftingandhandlingifreasonablypracticable;(b) assesstheriskofinjuryfromanyhazardousmanualliftingandhandlingwhich cannotbeavoided;and(c) reducetheriskofinjuryaccordingly.

Employeesmust:

(a) followsafesystemsofworklaiddownbytheiremployers;(b) usemechanicalaidsprovidedbytheiremployersproperly;and(c) remembertousethetrainingprovidedonlifting.

THE CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH REGULATIONS 1994 20

18 Theseregulationsre-enact,withminormodifications,theCOSHHRegulations1988(SI1988/1657).Theyimposerequirementsonemployersusingsubstanceshazardoustohealthtoprotectemployeesandotherpeoplewhomaybeexposedtosuchsubstances.Theyalsoimposecertaindutiesonemployeesconcerningtheirownprotectionfromexposure.

Employersmust:

(a) assessriskstohealth;(b) preventexposure;(c) wherepreventionisnotreasonablypracticable,controlexposureby,forexample, isolatingorenclosingtheprocessor,ifthisisnotreasonablypracticable,local exhaustventilation;(d) maintaincontrolmeasuresinefficientworkingorderandensurethatathorough testandexaminationofengineeringcontrolsarecarriedoutatsuitableintervals. Recordsofsuchmaintenancemustbekeptforatleastfiveyears;(e) wherepreventionorcontrolisinsufficientonitsown,providepersonalprotective equipmentandmaintainit;(f) inform,instructandtrainemployees;and(g) carryoutairmonitoringandhealthsurveillancewherenecessary.

THE PROVISION AND USE OF WORK EQUIPMENT REGULATIONS (PUWER) 1992 55,56

19 TheseRegulationsimposehealthandsafetyrequirementswithrespecttotheprovisionanduseofworkequipment(machinery,appliances,toolsetc).Theyimposerequirementsuponemployers,includingtheneedto:

(a) provideworkequipmentthatissuitableforthepurposeforwhichitisusedor supplied;(b) takestepstoensurethattheequipmentisnotusedunderconditionsforwhichitis notsuitable;(c) maintainworkequipmentinanefficientworkingorderandgoodrepairandthatany maintenancelogiskeptuptodate;(d) providepeoplewhouseworkequipmentwith:



(i) clearhealthandsafetyinformationand,whereappropriate,written instructions;and (ii) adequatetraining,includingtherisksinvolvedandtheprecautionstobe taken.(Thisalsoappliestosupervisorsandmanagersofsuchpeople.)(e) protectpeoplefromdangerouspartsofmachinerybysuitableprotectiondevices;(f) providesuitableandsufficientlightingatanyplacewhereapersonuseswork equipment;(g) ensurethatworkequipmentismarkedinaclearandvisiblemannerwith appropriatehealthandsafetyinformationandwarnings;and(h) ensurethatanywarningdeviceisunambiguousandeasilyperceivedand understood.

Note:TheseRegulationswillberevokedandre-enactedinDecember1998.ThenewPUWERRegulations(SI

1998/2306)includenewprovisionsformobileworkequipment.

THE CONFINED SPACES REGULATIONS 1997 59,60

20 TheseRegulationsapplywhenitisnecessaryforworkerstocarryoutworkinaconfinedspaceincludingachamber,tank,flueorasimilarspace,which,byvirtueofitsenclosednature,givesrisetoa‘foreseeablespecifiedrisk’.Inthecaseofchlorineinstallationsthemostlikelyforeseeablespecifiedriskis‘thelossofconsciousnessorasphyxiationofanypersonatworkarisingfromgas,fumevapourorthelackofoxygen’.TheRegulationsprohibittheentryintoaconfinedspaceforthepurposeofcarryingoutworkwhereitisreasonablypracticabletocarryouttheworkbyothermeans.Inothersituations(forexample,theisolationofaleakinachlorineroom)theyimposerequirementsonemployersincludingtheneedto:

(a) establishsafesystemsofworkforentryto,orcarryingoutworkin,orleavinga confinedspacethatrenderstheactivitiessafeandwithoutriskstohealth;(b) establishsuitableandsufficientarrangementsfortherescueofpeopleinthe confinedspaceintheeventofanemergency;(c) ensurecompliance,sofarasisreasonablypracticable,withtheprovisionsofthe Regulationsinrespectofanyworkcarriedoutbyemployees,orotherpeople-in whichcasethemattersneedtobewithintheemployer’scontrol.

THE PRESSURE SYSTEM AND TRANSPORTABLE GAS CONTAINERS REGULATIONS 1989 23,24,25

21 TheseRegulationsimposerequirementsforpressuresystemscontainingagasorliquefiedgasatapressuregreaterthan0.5baraboveatmosphericpressure.Theyimposerequirementsondesigners,suppliersofpressuresystemsandonemployersofpeoplewhomodifyorrepairsuchsystems.TheintentionoftheRegulationsistopreventtheriskofseriousinjuryfromstoredenergyasaresultofthefailureofapressuresystemorpartofit.Ameasureofthestoredenergyisgivenbymultiplyingthesystempressure(bargauge)andvolume(litres).Apressuresystemis:

(a) asystemcomprisingoneormorepressurevesselsofrigidconstruction,any associatedpipeworkandprotectivedevices(systemswithastoredenergyof250 barlitreorlessareexemptfromsomerequirements,egthewrittenschemeof examination);(b) thepipeworkwithitsprotectivedevicestowhichatransportablegascontaineris,or isintendedtobe,connected;or(c) apipelineanditsprotectivedevices.

Thetransportablegascontainerisnotpartofthesystem.Employersmustensurethat:

(a) allplantandsystemsaredesigned,constructedandinstalledtopreventdanger;(b) systemsareproperlymaintained;



(c) modificationsorrepairsdonotcausedanger;(d) thereisawrittenschemeforexamination54ofcertainpressurevessels,suchas chlorinevaporisers,fittingsandpipework,drawnupbyacompetentperson;(e) examinationsassetoutinthewrittenschemearecarriedoutbyacompetent person;and(f) recordsarekept.

Note:The transportable gas container (TGC) part of these Regulations was revoked in 1996 and incorporated into The Carriage of Dangerous Goods (Classification, Packaging and Labelling) and Use of Transportable Pressure Receptacles Regulations 1996. These PSTGC Regulations will be replaced in November 1999 by The Pressure Equipment Regulations and The Pressure Systems Safety Regulations.

THE PERSONAL PROTECTIVE EQUIPMENT AT WORK REGULATIONS 1992 63,64

22 TheseRegulationsimposehealthandsafetyrequirementswhenprovidingPPEandusingittoprotectpeopleintheworkplace.Employersmust:

(a) providesuitablePPEfreeofchargetoprotectemployeesagainstriskswhich havenotbeencontrolledbyothermeans;(b) takeallreasonablestepstoensureitisproperlyused;(c) beforeprovidingPPE,assessriskstohealthandsafetywhichhavenotbeen avoidedbyothermeansanddefinethecharacteristicsrequiredbyPPEtomakethe risksALARP;thenselectsuitablePPEbymatchingthosecharacteristicswiththose ofPPEavailable;(d) maintainthePPEprovidedincleanandefficientworkingorderandprovidesuitable storageforitwhennotinuse;and(e) giveinformation,instructionandtraining.

Employeesmust:

(a) usePPEprovided;and(b) reportanylossorobviousdefecttotheemployer.

THE REPORTING OF INJURIES, DISEASES AND DANGEROUS OCCURRENCES REGULATIONS (RIDDOR) 1995 91,92,93

23 Theseapplytoallemployersandself-employedpeopleandcovereveryoneatwork.Themainpointsarethatyoumust:

(a) notifyyourinspectorimmediately,normallybytelephone,ifanybodydies,receives amajorinjuryorisseriouslyaffectedby,forexample,anelectricshockorpoisoning;(b) notifyyourinspectorimmediatelyifthereisadangerousoccurrence,egafireor explosion,whichstopsworkformorethan24hours;(c) confirmtelephonenotificationsinwritingwithintendaysonF2508;(d) reportwithinsevendays(onformF2508)injurieswhichkeepanemployeeoffwork orunabletodotheirnormaljobformorethanthreedays;(e) reportcertaindiseasessufferedbyworkersonformF2508A;and(f) keepdetailsofreportedincidents.

ENFORCING THE LAW

24 HealthandsafetylawsrelatingtoyourfirmwillusuallybeenforcedbyahealthandsafetyinspectorfromHSE.Insomecases,egapublicswimmingpool,healthandsafetylawisenforcedbythelocalauthority.

25 Inspectorsmayvisitworkplaceswithoutnoticebutyouareentitledtoseetheiridentificationbeforetheycomein.Theymaywanttoinvestigateanaccidentorcomplaint,orinspectsafety,healthandwelfareatyourpremises.Theyhavetherighttotalkto



employeesandsafetyrepresentatives,takephotographsandsamples,andevenincertaincasestoimpounddangerousequipment.Theyareentitledtoco-operationandanswerstoquestions.

26 Inspectorswillbeawareofthemainrisksinhandlingchlorineandwillgiveyouhelpandadviceonhowtocomplywiththelaw.Ifthereisaproblem,theymayissueaformalnoticerequiringimprovementsor,whereseriousdangerexists,onewhichprohibitstheuseofaprocessorequipment.Inspectorshavepowerstoprosecuteafirm(oranindividual)forbreakinghealthandsafetylaw.



Appendix 4 Useful contacts and standardsCHLORINE PRODUCERS AND SUPPLIERS

Hays Process ChemicalsSandbach,CheshireCW113PZ

Imperial Chemical Industries plc, Chlor ChemicalsPOBox13,TheHeath,Runcorn,CheshireWA74QF

Rhodia LtdStaveley,ChesterfieldS432PB

The Associated Octel Co LtdPOBox17,EllesmerePort,Wirral,CheshireL654HF

BOC Ltd Special Gases24DeerParkRoad,LondonSW193UF(Note:BOCsuppliesonlycylinders.)

Air Products (GB) LtdSpecialityGasesDepartment,WestonRoad,CreweCW11DF(Note:AirProductssuppliesonlydrumsandcylinders.)

OTHER USEFUL CONTACTS

Chemical Industries Association(CIA)KingsBuildings,SmithSquare,LondonSW1P3JJTel:01718343399

TheCIArunsachlorinecommitteedealingwithtechnicalandliaisonissues.

Water Services Association of England and Wales1QueenAnne’sGate,LondonSW1H9BTTel:01719574567;Fax:01719574666

HSE

YoucanfinddetailsofyourlocalHSEofficeinyourlocaltelephonedirectoryorthecurrenteditionofHSE35The Health and Safety Executive: Working with employers,availablefromHSEBooks.

YoucanfinddetailsofHSEBooksandHSE’senquiryserviceontheinsidebackcoverofthisbooklet.

Chlorine InstituteInc.2001LStreet,NW,WashingtonDC20036USA

Euro ChlorAvenueEVanNieuwenhuyse4,Box2,B-1160Brussels,BelgiumTel:+3226767211;Fax:+3226767241

EuroChlorpublishesawiderangeofrelevantreports.22Thenewseries(AP)ofpamphletsonlearning from accidentsisessentialreading(egseereference82).

UK suppliers of Euro Chlor approved globe valves

Descote Ltd19SandyLane,WestonPoint,Runcorn,CheshireWA74EXTel:01928565666;Fax:01928565646



Shaw, Son & Greenhalgh Ltd AlbertStreet,Lockwood,HuddersfieldHD13QGTel:01484532425;Fax:01484512426

British Standards Institute

BSISalesandCustomerServices,389ChiswickHighRoad,LondonW44ALTel:01819967000;Fax:01819967001

BritishStandardsareavailablefromtheaboveaddress.

Standards relevant to chlorine

Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions)BS21:1985

Specification for liquid chlorineBS3947:1976(1997)

Specification for filling ratios and developed pressures for liquefiable and permanent gasesBS5355:1976

Specification for unfired fusion welded pressure vesselsBS5500:1997

Specification for flat products made of steels for pressure purposesBSEN10028:Parts1,2,3:1993and4:1995

Specification for tolerances on dimensions, shape and mass for hot rolled steel plates 3 mm thick or aboveBSEN10029:1991

Circular flanges for pipes, valves and fittings. Part 3: Section 3.1 Specification for steel flanges. Part 3 Section 3.3 Specification for copper alloy and composite flangesBS1560:Part3:1989

Specification for bolting for flanges and pressure containing purposesBS4882:1990

Specification for compressed asbestos fibre jointingBS1832:1991(1997)

Specification for bursting discs and bursting disc devicesBS2915:1990

Transportable gas containers. Part 1 Specification for seamless steel gas containers above 0.5 litre water capacityBS5045:Part11982;Part 2 Specification for steel containers of 0.5 L up to 450 L water capacity with welded seamsBS5045:Part21989

Specification for filling ratios and developed pressures for liquefiable and permanent gasesBS5355:1976

Safety signs and colours. Part 1 Specification for colour and designBS5378:Part11980(1995);Part 3 Specification for additional signs to those given in BS 5378: Part 1BS5378:Part31982(1995)

Polytetrafluoroethylene (PFTE) materials and products. Specification for fabricated unfilled polytetrafluoroethylene productsBS6564:Part21991(1996)

Specification for identification of pipelines and servicesBS1710:1984(1991)

Schedule of paint colours for building purposesBS4800:1989(1994)



Guide to implementing an effective respiratory protective device programme BS4275:1997

Specification for respiratory protective devices: self-contained open-circuit compressed air breathing apparatusBSEN137:1993

Respiratory protective devices: compressed airline breathing apparatus for use with a full face mask, half mask, or mouthpiece assembly. Requirements, testing, markingBSEN139:1995

Steels for pressure purposes. Part 3 Specification for corrosion and heat-resisting steels: plates, sheet and stripBS1501:Part31990

Specification for steels for fired and unfired pressure vessels: sections and bars BS1502:1982(1990)



Appendix 5 Outside installations and inside installations1 Bulkchlorineinstallationsshouldpreferablybelocatedintheopenair.Sometimesitmaybeappropriatetolocatetheinstallationinabuilding.

2 Thebuildingmayenclosetheentireinstallationorpartofit,egthemanlids,valves,associatedpipework,gaugesandotherequipment,leavingthetankitselfoutside.

3 Theadvantages,disadvantagesandconsequentrequirementsforoutsideorinsideinstallationsarelistedinparagraphs4-8.

OUTSIDE INSTALLATIONS

4 Theadvantagesofoutsideinstallationsarethat:

(a) leakagesarenotconfined,sothesourceofleakageismoresafelyaccessiblefrom upwind;(b) itiseasiertoidentifythepointofleakageandtakeimmediatelocalcorrectiveaction;(c) accessforinstallationandformajormaintenanceissimpler;and(d) buildingcostsarelower.

5 Thedisadvantagesofoutsideinstallationsarethat:

(a) leakagesmaybedetectedatanearlystageonlyfromdownwindpositions;(b) smallleakages,particularlythosearisingfromcorrosion,candevelopunnoticed;(c) maintenanceandrepairworkmayhavetobecarriedoutinadverseweather conditions;(d) thereisnocontainmenttoreducetherateofreleasetotheatmosphere;(e) surfacecorrosionismorelikely;anyleakmayrapidlyescalate;and(f) thereislesssecurity.

6 Itfollowsthatoutdoorinstallationsrequire:

(a) strictvigilanceandprotectionagainstcorrosion;(b) protectionagainstpossiblemechanicaldamageandunauthorisedaccess;(c) anappropriateemergencysystem,possiblyincludingproceduresfortheuseof waterspraysforgasclouds(seealsomaintextparagraphs247-263);(d) weatherprotectionformaintenanceincriticalareas;thiscouldbeeitherapermanent canopyortemporarysheeting;and(e) continuousstaffingonthesiteifachlorinereleasecouldpresentserious consequencesonoroffsite.

INSIDE INSTALLATIONS

7 Theadvantagesofinsideinstallationsarethat:

(a) valvesandotherequipmentareprotectedfromrainandsnow,andprovided thebuildingiskeptdry,therewillbelessriskofcorrosion;(b) backgroundheatingispossible,tohelpprovidedrysurroundingsand increasedchlorinevapourpressureforprocesseswhereinertgas/airpadding isnotacceptable;(c) controlledventilationispossible,limitingtheexternaleffectsiftheleakis fairlysmall;



(d) thereisgreaterlikelihoodofamonitoringdevicedetectingaleak;thisisa particularadvantageonanunattendedplant;and(e) theinstallationisprotectedfromaccidentalmechanicaldamage,explosionorfirein adjacentplantorinterferencebyunauthorisedpersons.

8 Thedisadvantagesofinsideinstallationsarethat:

(a) followingamediumormajorleak,emergencyaccessmayhavetobemadetoa closedroomwithahighchlorineconcentration;(b) thepointofleakagemaybedifficulttoidentify,owingtolackofdispersion,andmist formation;(c) ifthebuildingisheated,therewillbegreatergroundevaporationandflashfroma liquidleak;and(d) accessformaintenanceislikelytobemoredifficult.

9 Itfollowsthatindoorinstallationsrequire:

(a) adequateforcedventilationsystems,includingstart-upfromoperatingpoints outsideaswellasinsidethebuilding;and(b) carefulconsiderationofplantlayoutandprovisionofadequateescaperoutesand escaperespiratoryequipment.



Appendix 6 Procedures for discharging road tankers of chlorineNote: This typical procedure assumes that the storage tanks and associated items of equipment have a safe working pressure of at least 12 bar gauge. If this is not the case, then steps will need to be taken (eg adjust the air system pressure, and relief valve settings) to ensure that the safe working limits for the storage vessels and delivery system are not exceeded. It is important that more detailed and site-specific procedures are developed and agreed by the customer, haulier and chlorine supplier.

Action by Action needed

Joint 1Theproceduresneedtobedesignedtominimisepotentialleaksbyensuringthatallnewlymadejointsaretestedbygaspressurewith,atmost,onlyasmallamountofliquid.Duringthesetestoperationsagasmaskmustbeworn.Similarly,asuitablegasmask(seeparagraphs235-246)mustbewornduringthedisconnectingoperationwhenthereisapossibilityoftheescapeofasmallquantityofresidualvapour.Duringtherestoftheoperationsitshouldbekeptreadilyavailable.

Customer 2 Willoperateallvalvesonthebulkstorageinstallation,includingthe fillingpipe.

Driver 3 Onarrivalattheworks,willweighoffonthesiteweighbridgeand proceedtothedischargeberth.

Driver 4 Willpositionthetankeratthedischargeberthandemploythe drive-awayprotection.Avarietyoftechniquesmaybeused,eg interlockstothetankerbrakes,wheelchocks,andtheremovalofthe vehicleignitionkeytoacontrolledlocation.Theseareinaddition (seeparagraph7below)toanydrive-awayprotectionbarriersandany interlockstoshutdownthedischargeshouldmovementofthevehicle orshouldchlorinebedetected(seemaintext,paragraphs39-41).

Driver 5 Presentsthedeliverynotestoaresponsibleofficial.

Insigningthesenotesthecustomeracceptstheresponsibilitythat thereissufficientspaceavailableinthestoragetanktoreceivethe fullloadfromtheroadtankandthattheinstallationisfitandreadyfor thedischargetoproceed.

Driver 6 Willtelltheplant operatortheweightofchlorineinthetankerso thattheoperatorcandeterminewherethefinalreadingwillbeonthe weighingmachinedialorloadcellindicator.

Customer 7 Willensurethatanywarningnoticesaredisplayedandbarriers areerected,andwilloperateanysafetyinterlocksassociatedwith theroadvehicleberth.



Customer 8 Wheretherearetwoormoretanksthe customerwilldetermine whichtankistoreceiveandcheckthatthestoragetankcannotbe overfilled.Thepressureonthetankbeforestartingthedischarge shouldnotnormallybegreaterthan5.9bargaugebutinveryhot weatheritmaybehigher.

Customer 9 Thecustomerwillensurebeforedischargethattheventvalve onthestocktankfillingpipeisclosed.Whenfitted,thebarrier mechanicalinterlockkeyisusedtoactivatethecontrolpanel sequenceforthedischargingoperationandreleasetheoff-loading arm.

Driver 10Establishthevehiclemovementdetectioninterlockandactivate interlockstothechlorinedetectionsystembeforeoperatingvalves onthetankerandinstallation.Wearingagasmask,removebothcaps fromtheroadtankvalvesandthecustomer’sfillingarmsandtestfor leaks.UsingnewPTFE,aramidfibreorothersuitablematerialforjoint rings(preferablynotCAF,seeparagraph56),connectbothairsupply andliquiddischargearmstotheappropriatevalvesonthetanker.

Joint 11Wearingagasmask,applypressuretothedischargeconnection, preferablybybrieflyopeningthevalvetothestocktank.Analternative butlessdesirablemethodistoopenthetankerdischargevalve momentarily.Thedriver(wearingagasmask)teststhejointsonthe dischargepipeusingammoniawater.Ifsatisfactory,thedrivercan removehisgasmaskandthenrequesttheplantoperatortoopenthe valveonthestockfillinglineafterthedroparm.Theliquidvalveonthe tankercanbeslowly openedtofillthedeliveryline:thepressure observedwillbethepressureontheroadtanker.Alternatively,and onlywhenthedriverissatisfiedwiththeintegrityoftheconnections, theinstrumentairconnectionsaremadewhichwillallowthe dischargevalvestobeoperated.Thismayalsoactivateabrake interlockwhichisintegralwiththecustomer’sshutdownsystem.

Joint 12Starttheaircompressorandwhenthelinepressureis8.3 bargaugeopenittotheroadtanker.Whentheroadtankerpressure (asindicatedonthefillingpipetothestocktank)is1.7bargauge abovethatofthestocktankrequesttheplant operatortoopenthe valvetotheappropriatestocktankandcommencedischargeofthe roadtanker.

Joint 13Observethedischargeoftheroadtankerisproceeding satisfactorilybyreferencetotheweighingmachinedialorloadcell indicator.

Joint 14Observethestocktankpressureasthedischargeisproceeding. Shouldthisrisesto6.2bargaugethedriverrequeststhecustomerto crackopentheventvalveonthetanktoreducethepressure.

Joint 15Indicationthattheroadtankerhasbeencompletelydischargedis:

(a) fluctuationofpressuregaugeontheliquidchlorinedeliveryline; (b)equalisationoftankerandlinepressurereadings.Joint 16Theplantoperatorclosesthestoragetankinletvalveandthe paddingairsupplyvalve.Ventexcesspressurefromthetankerviathe ventvalvetothescrubber.Thedriverthenclosesthepaddingairinlet tothetankerandtheliquidchlorineoutletfromthetanker,and



disconnectstheoperatingairleadstothemsothetankervalves cannotbereopened.Theconnectingpipeforpaddingaircan nowbeventedanddisconnectedandthetankerpaddingair connectioncapped.Theoperatorcracksopentheventvalveonthe liquidchlorinedeliverylinetothestocktankfillingpipe.Whenthe pressuregaugeontheliquidchlorinedeliverylineshowszero(and anyhoarfrostontheventvalvehasbeguntodisappear)the operatorclosesthevalveonthechlorinedeliverylineatthetanker dischargepoint.Closethedeliverylineventvalve.

Customer 17 Crackopentheventvalveonthestocktankforaboutoneminute inordertocheckthatthelevelofliquidchlorineinthetankisbelow thebottomoftheventdippipe(nofrostingshouldappear).This operationalsoventsnon-condensablegases.Checkthatthepressure inthetankisreasonableforthetemperatureofthechlorine.The storageisnowisolatedfromthedischargelinetothescrubberand thedeliverylineispurgedbypressurisinganddepressurising(open ventvalveandcloseitwhenpressuregaugeshowszero)withdryair foraminimumoffivecycles.Theoperatorcannowshutdowntheair compressorifitisnotneededforotheroperations.

Driver 18Wearingagasmask,disconnecttheliquiddischargepipefromthe tanker,replacethesealingplugtopreventtheentryofmoistair,and swivelbacktothestaging.Telltheplant operatorthattheventcanbe closed.Theshortconnectingpipesfromtheliquidandairvalvescan bedisconnected,bothvalvescappedandthetankerdomesecurely fastened.TheRPEcannowberemoved.

Customer 19 Under no circumstances allow any section of the pipeline to be left unvented with liquid chlorine trapped between closed valves.

Driver 20Beforeleavingthestorageplantaskthedesignatedresponsible persontosigntheadvicenoteandconsignmentnoteafterthewords ‘alloperationsconnectedwiththedischargeoftheroadtankhave beencompletedsatisfactorily’.Handonecopytotheresponsible person.Onleavingtheworksweighagainonthesiteweighbridge.



Appendix 7 Types of vaporiserChlorinevaporisersmaybedividedintofourbasictypes:

(a) Verticaltubebundle.(b) Coiledtubeimmersedinaheatingbath.(c) Concentrictube.(d) Kettle-typeevaporator.

VERTICAL TUBE BUNDLE (TYPE 1)

1c Hotwaterbath

1b Steambayonet

1a Shellandtube

Advantagesofthistypeofsystemare:

(a) smalloverallsizeforrelativelylargeheattransfersurfaces;(b) easymaintenance;and(c) forthemodeofoperationinwhichthechlorineisintubes,theliquidchlorineis automaticallydisplacedbyover-pressurewhenthevapoursupplytotheconsuming plantisshutoff.

Disadvantagesofthistypeofsystemare:

(a) forthemodeofoperationinwhichthechlorineisinthetubes,thereisariskof instabilityathighthroughputowingtovariationofliquidlevelsandapossibilityof corrosionintheregionoftheliquidsurface;and(b) forthemodeofoperationinwhichthechlorineisintheshell,itisdifficulttodryout theshell.

COILED TUBE IMMERSED IN A HEATING BATH (TYPE 2)

2 Coilinbath

Steam

Condensate

Liquid chlorine

Chlorine gas Liquid chlorine

Electric heater

Water bath

Chlorine gas

Liquid chlorine

Chlorine gasCoil

Steam

Hot water bath

Hot water outlet



Advantagesofthistypeofvaporiserare:

(a) itissimpletomaintainandoperate;(b) thelongcoilgenerallyensuresadequatesuperheating;(c) therearenoproblemswithdifferentialthermalexpansion;(d) plugflowoperationavoidsconcentrationofhighboilingimpurities;(e) dryingoutofequipmentbeforeuseisrelativelyeasy;and(f) liquidchlorineisautomaticallydisplacedwhenthevapoursupplytotheconsuming plantisshutoff.

Disadvantagesofthistypeofvaporiserare:

(a) lowthroughput;(b) externalcorrosionofthetubecaneasilyoccur,especiallyneartheliquid surface;(c) irregularinternalerosionofthecoilmayoccur;and(d) internalinspectionandcleaningofthecoilisdifficult.

CONCENTRIC TUBE UNITS (TYPE 3)

3 Concentrictubeunit


(a) simpleconstructionwithminimumweldingrequirements;(b) easymaintenanceandoperation;(c) easyprovisionofadequatecorrosionallowance;(d) automaticdisplacementofliquidchlorinewhenthevapoursupplytotheconsuming plantisshutoff;and(e) plug-flowoperationaboveacertainminimumflowavoidsconcentrationofhigh boilingimpurities.


(a) potentialinstabilityofoperationathighandlowthroughput;(b) limitationofunitcapacityowingtorelativelysmallheattransfersurfacearea;and(c) greaterdifficultyinobtainingadequatesuperheatingofthechlorine.

Liquid chlorine

Chlorine gas

Condensate

Steam



KETTLE-TYPE EVAPORATOR (TYPE 4)

4 Kettle-typeevaporator


(a) itcanbedesignedforlargethroughput;(b) allowanceforthermalexpansioncaneasilybemade;and(c) operationisstable,providedthateitherthelevelofchlorineinthekettleorthe pressureofchlorinefedtothevaporiser,iscontrolled.


(a) sincethevesselcontainsarelativelylargeamountofliquidchlorine,leakageor excesspressureinthevesselposeagreaterpotentialhazard;(b) areliefsystemwithalargecapacityisrequired,unlessthevaporiserisdesignedfor highpressure;(c) operationcanresultinconcentrationofnitrogentrichloride;thepurgingprocess requiredtoreducethishazardmaybedifficulttocarryoutonconsumerpremises;(d) dryingoftheequipmentonthechlorinesideisdifficult;and(e) dismantlingofthetubesisdifficultandrequiresalargespace.

Liquid chlorine Chlorine gas

Liquid CI

Heating medium in

Heating medium out

Heating Coil

Control to inlet

Levelmeasuringdevice

2



Appendix 8 Emergency plans(Note:A fuller discussion of emergency plans appears in HSE’s HSG2569 and references 17, 70 and 71. Additional guidance will be issued to support the COMAH Regulations.)

1 Theworksshouldhaveanon-siteemergencyplanfordealingwithamajorchlorinerelease.Theplanshouldincludeinstructionsfortheemergencyteamandfornon-essentialpersonnel,andforliaisonwiththeemergencyservices.Theemergencyplanshouldbebasedonparagraphs247-263.Yourplanwilldependontheresultsofyourriskassessmentandtheneedtocomplywithhealthandsafetylegislation,egsection3oftheHSWAct.2Thefollowingparagraphscontainsomeelementsofaplan.

2 Theplanmayincludedetailedinstructionsfor:

(a) raisingthealarm;(b) investigatingandassessingthesourceandextentofthechlorinerelease;(c) alertingallpersonnelon-siteorinneighbouringpremisesandtheemergency services;settingupemergencycontrolcentres,assessmentbykeypersonnelofthe incidentandconsequentemergencymeasuresonandoff-site;(d) methodsforcontrollingthechlorinerelease;(e) searchsystemsforcasualties,andaccountingforpersonnelon-site;(f) methodsforassessingthedirectionalspreadandconcentrationofthegascloud;(g) criteriafordeterminingwhethertoevacuatenon-essentialpersonnelortoadvise themtostayinsidebuildingswithdoors,windowsandventilationshut;(h) methodsforassessingwhethercorrespondingactionsareadvisableforpeople off-siteand,inparticular,liaisonwiththemanageratanyadjacentunderground workingswherechlorinecouldentertheventilationsystem;advicetoemergency servicesonthedirection,spreadandconcentrationofthegascloud;and(i) firstaidtoon-sitecasualties,andarrangementsforevacuationwhereadvisableand practicable;advicetoambulanceserviceonroutestouse.

3 Sinceeachinstallationwillhaveitsownspecialfeatures,adetailedplanrelatingtotheparticularplantwillberequired.Localmanagementshouldberesponsibleforpreparationoftheplanwhichshouldbedevelopedinco-operationwiththelocalauthority,thepolice,fire,hospitalandambulanceservices,andthechlorinesupplier.SpecificdutiesarelaidonsomeofthesepeoplebytheControlofIndustrialMajorAccidentHazardsRegulations1984.ThesewillbesupersededbytherequirementsoftheCOMAHRegulationsin1999.

EMERGENCY CONTROL CENTRES

4 Basicrequirementsforasatisfactorysystemtodealwithanemergencyresultingfromaseriousescapeofchlorineareoutlinedasfollows:

(a) twocontrolcentresshouldbeprovidedsothat,intheeventofagasescape, operationscanbecontrolledfromthecentrewhichisleastaffectedunderprevailing atmosphericconditions;(b) eachcentreshouldbeprovidedwithaseparateexternaltelephoneline,aswellas withconnectionstothefactory’sexternalandinternaltelephonesystem;(c) adequateemergencyequipment(self-containedbreathingapparatus,suppliesof suitablefoamasagreedwiththeemergencyservices,protectiveclothing,etc) shouldbeavailable(seesectiononemergencyequipment);(d) emergencyfirst-aidfacilities,includingequipmentforadministeringoxygen,needto beprovided;(e) alarge-scalemap(1:25000or1:10000)ofthesurroundingareashouldbeavailable tohelpdeterminewhichpartsofthefactoryandthelocalneighbourhoodarelikely tobeaffected;



(f) winddirectionindicatorshavetobevisiblefrom,orindicatedin,eachcontrolcentre; and(g) equipmentandinformationareneededtoassessthelikelyextentofthegascloud forvarioussizesofreleaseandvariousweatherconditions.

5 Theemergencyplanshouldspecifyinadvancetheindividualsanddeputiesresponsiblefortheactionnecessarytodealwiththeemergency.

SITE EMERGENCY TEAM

6 Thereshouldbeatrainedemergencyteamwiththefollowingkeypersonnel:

(a) Site incident controller-theseniorpersonon-siteresponsibleforthedirection ofon-siteoperations;

(b) Site main controller-normallytheworksmanagerordeputywithoverall responsibilityfortheoperationoftheemergencyplan,maintainingclose liaisonwiththepoliceandfireservices,andforadvisingthemontherisk; and

(c) Other key personnel -including:

(i) theteamresponsibleforthecontrolofthechlorinerelease; (ii) theteamresponsibleforthesearchforcasualties,forfirstaidandforthecontrol ofevacuation.

7 Thepolicewillberesponsiblefordealingwithmembersofthepublicwhomightbeaffectedbythechlorineescape;theywillneedtobeadvisedofthesizeandexpecteddurationofthereleasetogetherwiththeareaswhichcouldbeaffected,toallowthepoliceandthesitemaincontrollertoagreewhetherthepublicshouldremainindoorsorbeevacuated.

EMERGENCY ASSEMBLY AREAS

8 Emergencyassemblyareasshouldbedesignatedforuseinachlorineemergencybypersonnelnotinvolvedintheemergencyteam.Theassemblyareasallowforcountingofpersonnelandforcontrolledevacuationiftheneedshouldarise.Preferably,theassemblyareashouldbeattheperipheryoftheworkssitewithgoodexitforevacuation.Abuildingwithupperstoreysatalocationupwindofthechlorinereleasemayoffersufficientprotectionwhilethereleaseisbroughtundercontrol.Evacuationofpersonneltotheassemblyareasshouldbedirectedbyaseniormemberoftheemergencyteamwhowilltakewinddirectionintoaccount.Therewillbeoccasionswhenevacuatingoff-siteisnotthebestaction,forexample,whenthereleaseissuddenandoflimitedduration.

CASUALTIES

9 First-aidtreatmentforcasualtiesisdiscussedinAppendix1.



References1 Safe handling of chlorine from drums and cylindersHSG40HSEBooks1999 ISBN0717616460

2 Health and Safety at Work etc Act 1974

3 List of current health and safety legislation1996HSEBooks1997 ISBN0717613119

4 The Notification of Installations Handling Hazardous Substances Regulations 1982SI1982/1357HMSO

5 The Control of Industrial Major Accident Hazards Regulations 1984 SI1984/1902HMSO

6 Council Directive 96/82/EC Control of major-accident hazards involving dangerous substancesOfficialJoftheECNoL10/40CECJanuary1997

7 The Planning (Hazardous Substances) Regulations 1992SI1992/0656HMSO

8 Risk criteria for land-use planning in the vicinity of major industrial hazards HSEBooks1989ISBN0118854917

9 Environmental Protection (Prescribed Processes and Substances) Regulations 1991SI1991/0472HMSO

10 EnvironmentalProtectionAct1990

11 AlkaliandWorksRegulationAct1906

12 Health and Safety (Emissions into the Atmosphere) Regulations 1983 SI1983/0943HMSO

13 The Carriage of Dangerous Goods (Classification, Packaging and Labelling) and Use of Transportable Pressure Receptacles Regulations 1996 SI1996/2092HMSO

14 The Carriage of Dangerous Goods by Road Regulations 1996 SI1996/2095HMSO

15 Are you involved in the carriage of dangerous goods by road or rail?INDG234 HSEfreeleaflet1996

16 Successful health and safety managementHSG65HSEBooks1997 ISBN0717612767

17 Formula for health and safety: guidance for small to medium-sized firms in the chemical manufacturing industryHSG166HSEBooks1996 ISBN0717609960

18 The Management of Health and Safety at Work Regulations1992 SI1992/2051HMSO

19 Management of health and safety at work. Approved Code of Practice. Management of Health and Safety at Work Regulations 1992L21HSE Books1992ISBN0717604128



20 The Control of Substances Hazardous to Health Regulations 1994 SI1994/3246HMSO

21The Fire Precautions (Workplace) Regulations 1997SI1997/1840TSO

22 Publications: Literature and technical documentationEuroChlor1997*

23 The Pressure Systems and Transportable Gas Containers Regulations 1989 SI1989/2169HMSO

24 Safety of pressure systems. Pressure systems and Transportable Gas Containers Regulations 1989. Approved code of practice COP37HSEBooks 1990ISBN011885514X

25 A guide to the Pressure Systems and Transportable Gas Containers Regulations 1989HSR30HSEBooks1990ISBN0717604896

26 The Carriage of Dangerous Goods by road (Driver Training) Regulations 1996 SI1996/2094HMSO

27 The Carriage of Dangerous Goods by Rail Regulations 1996 SI1996/2089HMSO

28 Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions)BS21:1985

29 GEST75/45FlexibleMonelhosesforthetransferofgaseousorliquidchlorine 5thEdMay1996EuroChlor*

30 GEST75/43Flexiblesteelcoilsforthetransferofgaseousorliquidchlorine 7thEdMay1996EuroChlor.

31 GEST75/44Articulatedarmsforthetransferofgaseousorliquidchlorine 9thEdMay1996EuroChlor*

32 Process pipingB31.3AmericanSocietyofMechanicalEngineers1996

33 Chemical plant and petroleum refinery pipingSupplementtoB31.3American SocietyofMechanicalEngineers1995

34 Specification for bolting for flanges and pressure containing purposes BS4882:1990

35 Circular flanges for pipes, valves and fittings.Part3Steel,castironand copperalloyflangesBS1560:Part3Sections1-3:1989

36Pipe flanges and flanged fittingsB16-5NPS1-2throughNPS24American SocietyofMechanicalEngineers1988

37 Specification for compressed asbestos fibre jointingBS1832:1991(1997)

38 Polytetrafluoroethylene (PFTE) materials and products Part 2 Specification for fabricated unfilled polytetrafluoroethylene productsBS6564:Part2 1991(1996)

39 The Dangerous Substances (Notification and Marking of Sites) Regulations 1990SI1990/0304HMSO



40 Notification and marking of sites. The Dangerous Substances (Notification and Marking of Sites) Regulations 1990. Guidance on RegulationsHSR29 HSEBooks1990ISBN0118854356

41 Safety signs and colours. Part 1 Specification for colour and designBS5378: Part1:1980/(1995);Part 3. Specification for additional signs to those given in BS 5378 Part 1BS5378:Part31982(1995)

42 Specification for identification of pipelines and servicesBS1710:1984(1991)

43 Schedule of paint colours for building purposesBS4800:1989(1994)

44 The Health and Safety (Safety Signs and Signals) Regulations 1996 SI1996/0341HMSO

45 Safety signs and signals. The Health and Safety (Safety Signs and Signals) Regulations 1996. Guidance on RegulationsL64HSEBooks1997 ISBN0717608700

46 HSCOilIndustryAdvisoryCommitteeThe safe isolation of plant and equipmentHSEBooks1997ISBN0717608719

47 Specification for filling ratios and developed pressures for liquefiable and permanent gasesBS5355:1976

48 Specification for unfired fusion welded pressure vesselsBS5500:1997

49 Specification for bursting discs and bursting disc devicesBS2915:1990

50 KletzTA Hazop and Hazan: Identifying and assessing process industry hazards3rdedIChemE1992ISBN0852952856

51 GEST76/55Maximumlevelsofnitrogentrichlorideinliquidchlorine1990 EuroChlor*

52 SafehandlingofchlorinecontainingnitrogentrichlorideChlorineInstitute Pamphlet152**

53 Introducing competent persons. Pressure Systems and Transportable Gas Containers Regulations1989INDS29HSEfreeleaflet1990

54 Written schemes of examination. Pressure Systems and Transportable Gas Containers Regulations 1989INDG178HSEfreeleaflet1994

55 Provision and Use of Work Equipment Regulations 1992SI1992/2932HMSO

56 Work equipment. Provision and Use of Work Equipment Regulations 1992 Guidance on RegulationsL22HSEBooks1992ISBN0717604144

57 The Manual Handling Operations Regulations1992SI1992/2793HMSO

58 Manual handling. Manual Handling Operations Regulations 1992. Guidance on RegulationsL23HSEBooks1992ISBN071760411X

59 The Confined Spaces Regulations 1997SI1997/1713TSO

60 Safe work in confined spaces. Confined Spaces Regulations 1997. Approved Code of Practice and Guidance L101HSEBooks1997ISBN0717614050



61 Safety in pressure testingGS4(rev)HSEBooks1992ISBN0717608115

62 Permit-to-work systemsINDG98(rev3)HSEfreeleaflet1998

63 The Personal Protective Equipment at Work Regulations 1992 SI1992/2966HMSO

64 Personal protective equipment at work: Personal Protective Equipment at Work Regulations 1992. Guidance on regulationsL25HSEBooks1992 ISBN0717604152

65 GEST92/171Personalprotectiveequipmentforusewithchlorine1995 EuroChlor*

66 The selection, use and maintenance of respiratory protective equipment: A practical guideHSG531998HSEBooksISBN0717615375

67 Guide to implementing an effective respiratory protective device programme BS4275:1997

68 Prepared for emergencyINDG246HSEfreeleaflet1997

69 Control of Industrial Major Hazards Regulations 1984 (CIMAH): Further guidance on emergency plansHSG251985HSEBooksISBN0118838318

70 RobinsonBWandUKChlorineProducersGeneral guidance on emergency planning within the CIMAH Regulations for chlorine installations1986†

71 Inter-company collaboration for chlorine emergenciesCIA1992 ISBN0900623†

72 Specification for respiratory protective devices: self-contained open-circuit compressed air breathing apparatusBSEN137:1993

73 Respiratory protective devices. Compressed airline breathing apparatus for use with a full face mask, half mask or mouthpiece assembly. Requirements, testing, markingBSEN139:1995

74 Occupational exposure limitsEH40/98HSEBooks(updatedannually) ISBN0717614743

75 WHOInternationalProgrammeonChemicalSafetyEnvironmental Health Criteria 21 Chlorine and hydrogen chlorideWorldHealthOrganisation, Geneva,1982

76 Summary criteria for occupational exposure limitsEH64HSEBooks(updated annually)ISBN0717615766

77 LewisRJSax’s dangerous properties of industrial materials(9thed)Van NostrandRheinhold1996ISBN0442020252

78 TurnerRMandFairhurstSToxicology of substances in relation to major hazards: ChlorineHSEBooks1990ISBN011885528X

79 GEST89/145Guidelinesformedicalmanagementofchlorineexposure (3rded)1995EuroChlor*

80 Specification for liquid chlorineBS3947:1976(1997)



81 GEST79/82Choiceofmaterialsofconstructionforuseincontactwith chlorine(7thed)EuroChlor1995*

82 GEST/AP1Learningfromaccidents1996.EuroChlor*

83 The setting of safety standards: A report by the interdepartmental group and external advisors 1996HMTreasury††

84 Price listHSEBooks(publishedannually)

85 A guide to risk assessment requirements: Common provisions in health and safety lawINDG218HSEfreeleaflet1996

86 Health and Safety Law. What you should know(poster)HSEBooks IBSN0717613801

87 The Health and Safety (Consultation with Employees) Regulations 1996 SI1996/1513TSO

88 A guide to the Control of Industrial Major Accident Hazards Regulations 1984 HSR21(rev)HSEBooks1990ISBN0118855794

89The Lifting Plant and Equipment (Records of Test and Examination etc) Regulations 1992SI1992/0195HMSO

90 A guide to the Lifting Plant and Equipment (Records of Test and Examination etc) Regulations 1992L20HSEBooks1992ISBN0717604888

91 The Reporting of Injuries,Diseases and Dangerous Occurrences Regulations 1995SI1995/3163HMSO

92 A guide to the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995L73HSEBooks1996ISBN0717610128

93 Everyone’s guide to RIDDORHSE31HSEfreeleaflet1996

Thefutureavailabilityandaccuracyofthereferenceslistedinthispublicationcannotbeguaranteed.CurrentRegulations,guidanceandACOPs,andcurrentHSEpublicationsarelistedinthelatestversionofreferences3and84respectively.

* AvailablefromEuroChlor,seeaddressinAppendix4.** AvailablefromCIA,seeaddressinAppendix4.† AvailablefromCIAorchlorineproducers,seeaddressesinAppendix4.†† AvailablefromThePublicEnquiryUnit,HMTreasury,ParliamentStreet, LondonSW1P3AGTel:01712704558

FordetailsonhowtoobtainHSEpricedandfreepublications,seeinsidebackcover.



List of acronyms and abbreviationsACOP ApprovedCodeofPracticeALARP AsLowAsReasonablyPracticableANSI AmericanNationalStandardsInstituteAPF AssignedProtectionFactorASME AmericanSocietyofMechanicalEngineeringBA BreathingApparatusBS BritishStandardCABA CompressedAirlineBreathingApparatusCAF CompressedAsbestosFibreCEC CommissionoftheEuropeanCommunitiesCIA ChemicalIndustriesAssociationCIMAH ControlofIndustrialMajorAccidentHazards(Regulations)COMAH ControlofMajorAccidentHazards(Regulations)COSHH ControlofSubstancesHazardoustoHealth(Regulations)DTL DangerousToxicLoadEA EnvironmentAgencyEEC EuropeanEconomicCommunityEU EuropeanUnionHAZOP HazardandOperabilityHMSO HerMajesty’sStationeryOfficeHSA HazardousSubstancesAuthorityHSE HealthandSafetyExecutiveHSR HealthandSafetyRegulations(Booklet)HSW HealthandSafetyatWorkISO InternationalStandardsOrganisationLOLER LiftingOperationsandLiftingEquipmentRegulationsLPA LocalPlanningAuthorityMHO ManualHandlingOperations(Regulations)MHSW ManagementofHealthandSafetyatWork(Regulations)NIHHS NotificationofInstallationsHandlingHazardousSubstances (Regulations)OEL OccupationalExposureLimitOES OccupationalExposureStandardOJ OfficialJournal(oftheEuropeanCommunities)PPE PersonalProtectiveEquipmentppm Partspermillion(byvolume)PSTGC PressureSystemsandTransportableGasContainers(Regulations)PTFE PolytetrafluoroethylenePUWER ProvisionandUseofWorkEquipmentRegulationsRIDDOR ReportingofInjuries,DiseasesandDangerousOccurrence (Regulations)RPE RespiratoryProtectiveEquipmentSCBA SelfContainedBreathingApparatusSEPA ScottishEnvironmentalProtectionAgencySI StatutoryInstrumentSOED ScottishOffice,EnvironmentDepartmentSTEL Short-TermExposureLimitTGC TransportableGasContainerTSO TheStationeryOfficeUK UnitedKingdomUPVC UnplasticisedPolyvinylChlorideWSE WrittenSchemeofExaminatio

Further informationForinformationabouthealthandsafetyringHSE’sInfolineTel:08453450055Fax:08454089566Textphone:08454089577e-mail:[email protected],CaerphillyBusinessPark,CaerphillyCF833GG.

HSEpricedandfreepublicationscanbeviewedonlineororderedfromwww.hse.gov.ukorcontactHSEBooks,POBox1999,Sudbury,SuffolkCO102WATel:01787881165Fax:01787313995.HSEpricedpublicationsarealsoavailablefrombookshops.

BritishStandardscanbeobtainedinPDForhardcopyformatsfromtheBSIonlineshop:www.bsigroup.com/ShoporbycontactingBSICustomerServicesforhardcopiesonlyTel:02089969001e-mail:[email protected].

TheStationeryOfficepublicationsareavailablefromTheStationeryOffice,POBox29,NorwichNR31GNTel:08706005522Fax:08706005533e-mail:[email protected]:www.tso.co.uk(Theyarealsoavailablefrombookshops.)StatutoryInstrumentscanbeviewedfreeofchargeatwww.opsi.gov.uk.

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