ESS Guideline for Oxygen Deficiency Hazard (ODH)

GuidelineDocumentNumber ESS-0038692Date Apr15,2016Revision 1State ReleasedClassification Page 1(17)

ChessControlledCoreEd:1.0TemplateActiveDate:11Mar2014

ESS Guideline for Oxygen Deficiency Hazard (ODH)

Name

Owners B.Winér;OccupationalHealth&SafetyEngineer,ES&HDivision

Reviewers D.Phan;AcceleratorSafetyEngineer

Approvers P.Jacobsson;HeadofES&HDivision

GuidelineDocumentNumber ESS-0038692Date Apr15,2016Revision 1State ReleasedClassification

2(17)

TABLEOFCONTENT PAGE

PURPOSE..............................................................................................31.

SCOPE..................................................................................................32.

DEFINITIONS........................................................................................33.

REGULATORYFRAMEWORK................................................................34.

MANAGINGODH-SITUATIONS.............................................................45.

Step1:ODHassessment......................................................................55.1. ODHassessment#1:Steady-statecalculationmodel(CERN).............65.1.1. ODHassessment#2:Dynamiccalculationmodel(FERMILAB)............75.1.2.

Step2:Definitionofcontrolmeasures..............................................105.2. ODHcontrolmeasuresrequirements................................................115.2.1. ODHTraining.....................................................................................115.2.2. EmergencyEvacuationandRescue...................................................125.2.3.

Step3:Reviewandapproval.............................................................125.3.

ODHIMPLEMENTATION....................................................................126.

Rolesandresponsibilities..................................................................126.1.

Safetydocumentation.......................................................................136.2.

Contacts.............................................................................................136.3.

Examplesofcasestudies...................................................................146.4.

REFERENCEDOCUMENTS..................................................................147.

APPENDIX..........................................................................................148.

EquipmentFailureratesestimates....................................................148.1.

HumanErrorRateestimates.............................................................168.2.

DOCUMENTREVISIONHISTORY........................................................179.


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PURPOSE1.

Thepurposeofthisguidelineistospecifyrequirementsandtoprovideguidanceonmethodologiesforassessingthepotentialriskandtoreduceriskassociatedwithhazardsduetoapossibleoxygendeficientenvironment.ThisguidelineisalignedwithESSProcedureforSystematicWorkEnvironmentManagement,ESS0051380[1]

TheuseofcompressedandliquefiedasphyxiantgasessuchasheliumandnitrogeniscommonatESS.Thereleaseoftheseelementsintotheatmospherecanpresentarisk,inparticulartopersonsexposedtoreduced-oxygenatmospheres.Undertheseconditionspersonsmayexperiencereducedabilities,unconsciousness,ordeath.

TwofactorsmakeOxygenDeficiencyHazards (ODH)sodangerous.Thefirst is the largevolumeratiobetweenacryogenicliquidanditsgaseousstateatroomtemperatureandpressure.Asanexample1litreofliquidnitrogenwillresultin700litresofnitrogengasatroomtemperatureandpressure.Thus,ittakesasmallamountofcryogenicliquidventedinto a space to reduce the oxygen concentrations to dangerous levels. Second, in lowenough oxygen concentrations the first physiological symptoms of a problem can beunconsciousness,comaanddeath.Unconsciousnesscanoccurinlessthan30seconds.

SCOPE2.

ThisODHsafetyprocessappliestoanyactivity/area/equipmentatESSinvolvingtheuseofasphyxiantfluidsthatcouldhaveanimpactonpeople’ssafety.

DEFINITIONS3.

Oxygendeficiency:anyconditionunderwhichthepartialpressureofatmosphericoxygenislessthan135mmHgorabout18%oxygenconcentration.

Oxygenconcentration: themolar fractionofagaseousmixture representedbyoxygen.Foramixtureofidealgases,itisalsoequaltotheratioofthepartialpressureofoxygeninthemixture.Theoxygenconcentrationinnormalambientatmosphereis20.9%.

OxygendeficiencyHazard: any activity thatmay expose personnel to an increased riskduetooxygendeficiency.

REGULATORYFRAMEWORK4.

Anyactivity/area/equipmentinvolvingtheuseofasphyxiantfluidsshallcomplywiththefollowingregulationsandstandards:

• ESSODHSafetyprocess&implementation-ESS-0038692[2].


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• AFS2014:43ChemicalHazardsintheWorkingEnvironment.• AFS1997:7Gases.• EN13458-3-Staticvacuuminsulatedvessels-Operationalrequirements[3].

MANAGINGODH-SITUATIONS5.

NouseofasphyxiantcryogenicfluidsorcompressedgasesispermittedatESSwithoutaformal evaluation of the ODH Class which shall be conducted through a specific ODHprocessforallactivitieswhicharephysicallycapableofexposingindividualstoanoxygendeficiency.

The ODH process can be divided into three main steps as shown in the followingflowchart (Figure 1). Note that the process is built around quantitative assessmentfollowed by independent expert review that will provide final clearance of theactivity/area/equipmentbeforeoperation.


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Figure1-ESSODHprocess

Step1:ODHassessment5.1.AnyareaatESSknowntohaveanoxygenconcentration<18%(duringnormaland/oroff-normal operation) is considered to be an oxygen deficient area. All areas intended forhumanoccupancyatESSshallhaveanenvironmentorenvironmentalcontrolsthatwillnormallyensurethattheconcentrationofoxygenremains≥18%.

If an area contains equipment or sources of inert gas that could lead to a significantdecrease inoxygenconcentration, additionalmeasures shallbe taken to reduce risk topersonnel.ThegoalsofanODHassessmentaretoevaluatetherisklevelinagivenarea,

Activity leader/installation owner/equipment owner

Activity/equipment/installation involving the use of ashyxiant fluids

ODH assessment #1(CERN methodology)

Area subject to ODH in case of accident?

ODH Class 1 or higher?

Implementation of control measures

Review from the "Cryogenic Safety

Committee"

Area subject to ODHin case of accident?

O2 < 18%

ODH assessment #2(Fermilab methodology)

Activity leader/installation owner/equipment ownerYes

No

No

Activity leader/installation owner/equipment owner +

ICS + ES&H

ES&H + designated persons from other divisions

Yes

Final clearance from the "Cryogenic Safety Committee"

Activity/equipment/installation considered as acceptably "safe"?

Yes

No

STEP 1: ODH Assessment

STEP 2: Definition of control measures

STEP 3: Final review and approval

*

*

* For specific and complex cases, further ODH analyses such as Computational Fluid Dynamics (CFD) might be necessary

ES&H + designated persons from other

divisions


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toclassifytheareabasedupontherisklevel,thatis,toassignanODHClasstothearea,andtospecifyadditionalsafetymeasurestobetakentoreducerisks1.

ODHassessment#1:Steady-statecalculationmodel(CERN)5.1.1.

Thepurposeof theCERN’sODHassessmentmethodology [4] is toprovide toanynon-cryogenic expert with a fast and simple steady-state calculation model aiming atassessingtheO2concentrationremainingintheatmosphereofaspecificareaincaseofacompletereleaseofasphyxiantfluidwithoutconsideringanyventilationrate,leakrateortimeparameter.

ODHAssessmentEquations5.1.1.1.

TheO2 concentrationestimation ina confinedvolume is calculatedusing the followingequation(Table1):

Table1-ODHAssessmentequation(CERN'smodel)

Formula Definitions

C=oxygenconcentrationaftertherelease[%]V=confinedvolume[m3]Vgas = volume of gas discharged at room’s temperatureandpressure[m3]

Remark:forlargeenclosurespacessuchasexperimentalhalls,ODHmightnotrepresenta direct threat for people safety considering an entire homogenousmixture.However,there could be some localized areas with oxygen depletion. Therefore, wheneverapplicableasmallerenclosurespacecouldbeconsideredfortheODHassessment.

ODHClass5.1.1.2.

The ODH assessment carried for every activity/area/installation involving the use ofasphyxiant fluids allows determining an ODH Class that is calculated based on theselectionofthe“mostcrediblescenario”definedwiththehelpoftherelevantexperts.

TheclassificationoftheODHClassaswellastheassociatedactionsarelistedinthetablebelow(Table2):

Table2-ODHClass(CERN'smodel)

ODHClassO2concentration

incaseofhomogeneousmixture

Actions

1Theclassificationofanareacanchangedependingontheactivitiesbeingperformed.Ifconditionsand/oractivitieschangeinwaysthatsignificantlyincreasetherisk,theassociatedquantitativeassessmentmustbeaccordinglyrevised.

C = 0,21(V −Vgas)V


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0 O2≥18% Refertocontrolmeasuresin5.2.12

“notsafe” O2<18%A further ODH assessment shall be done accordingtotheODHprocess

ODHassessment#2:Dynamiccalculationmodel(FERMILAB)5.1.2.

Thepurpose of the FERMILAB’sODHassessmentmethodology [4] is to provide to anynon-cryogenic expert with a dynamic calculation model aiming at assessing the O2concentration remaining in the atmosphere of a specific area during and after anaccidentalreleaseofasphyxiantfluidconsideringtheventilationrate,leakrateandtimeparameter.

ODHAssessmentEquations5.1.2.1.

Oxygenconcentrationestimation,inaconfinedvolume,duringandafterreleaseofaninertgascanbecalculateddependingonthecase,asfollows(

Table3):

Table3-ODHAssessmentequation(FERMILAB'smodel)

Definitions:

C=oxygenconcentration[%].Cr=oxygenconcentrationduringtherelease[%].Ce=oxygenconcentrationafterthereleasehasended[%].Q=ventilationrateoffan(s)[m3/s].

2AccordingtotheODHprocess,dependingofthecomplexityofthecasetheCryogenicSafetyCommitteecanrequireafurtherODHanalysisandadditionalcontrolmeasuresevenifthesituationhasbeeninitiallyassessed as “ODH Class 0”, e.g whenever ventilation, leak rate, time parameter or confined volumeconfigurationhaveanimpactonthefinalODH

# Time Mixing Ventilation Type Diff.eq. Concentration

ADuringRelease

Perfectmixing

Intoconfinedvolume

V dCdt

= 0.21Q − (R+Q)C

C t( ) = 0.21

Q+ R!

"#

$

%& Q+ R e

−Q+RV

!

"#

$

%& t(

)**

+

,--

BDuringRelease

Perfectmixing

Fromconfinedvolume

Ventilationrategreaterthanspill

V dCdt

= 0.21 Q − R( ) −QC

C t( ) = 0.21 1− RQ 1− e

−QVt"

#$

%

&'

"

#$$

%

&''

CDuringRelease

Perfectmixing

Fromconfinedvolume

Ventilationrate lessthanspill

V dCdt

= − R C

DAfterRelease

Perfectmixing

C t( ) = 0.21 e−RVt

V dCdt

= 0.21Q −QC C t( ) = 0.21− 0.21−Cr te( )"# $% e−QV

t− te( )


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R=spillrateintoconfinedvolume[m3/s].t=time[s](beginningofreleaseisatt=0).te=timewhenreleasehasended[s].V=confinedvolume[m3].

ODHClass5.1.2.2.

TheODHClassisbaseduponthemostsevererisk:thelikelihoodthatafatalitywilloccur.Sincethe levelof risk is tiedtotheareaandthenatureof theactivity, thefatalityrateshallbedeterminedonanactivity-by-activitybasis.Foragivenactivity/area/equipment,several events may cause an oxygen deficiency. Each event has an expected rate ofoccurrence and each occurrence has an expected probability of causing a fatality.However,forthesakeofsimplificationonlythe“mostcrediblescenario”isconsideredforthe ODH assessment of every activity/area/equipment involving the use of asphyxiantfluids.Theoxygendeficiencyhazardfatalityrateisdefinedasfollows:

Table4–ODHfatalityrate(FERMILAB'smodel)

Formula Definitions

𝜙=theODHfatalityrate(perhour)Pi = the expected failure rate of the “most crediblescenario”(perhour)Fi = the probability of a fatality due to “most crediblescenario”

When possible, the value of Pi shall be determined by operating experience at ESS;otherwise data from similar systems elsewhere or other relevant values shall be used.EstimatesofequipmentfailureratesaregiveninAppendix8.1.

The value of Fi is the probability that a personwill die if the “most credible scenario”occurs.Thevaluedependsontheoxygenconcentration.Forconvenienceofcalculation,an approximate relationship between the value of Fi and the lowest attainable oxygenconcentrationhasbeendeveloped(Figure2).

φ = PiFi


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Figure2:Fatalityprobabilityasafunctionofthelowestoxygenconcentration(partialpressure)

Thelowestattainableconcentrationisused,ratherthananaverage,sincethatminimumvalueisconservativeandthetimedependenceoftheconcentrationisnormallynotwellknown.

Ifthelowestoxygenconcentrationisgreaterthan18%,thenthevalueofFiiszero,thatis,allexposuresabove18%aredefinedtobe"safe"andtonotcontributetofatality.

Itisassumedthatallexposuresto18%oxygenorlowerdocontributetofatalityandthevalue of Fi is designed to reflect this dependence. If the lowest attainable oxygenconcentrationis18%,thenthevalueofFiis10-7.Thisvaluewouldcause𝜙tobe10-7perhouriftheexpectedrateofoccurrenceoftheeventwere1perhour.

At decreasing concentrations, the value of Fi should increase until, at some point, theprobability of fatality becomes unity. That point was selected to be 8.8% oxygen, theconcentrationatwhichoneminuteofconsciousnessisexpected.

TheclassificationoftheODHclassdependsontheODHfatalityrateasφasshowninthetablebelow(Table5):

Table5-ODHClass(FERMILAB'smodel)

ODHClass [φ](hr-1) Actions

0 ≤10-7 Refertocontrolmeasuresin5.2.13

1 >10-7…but…≤10-5 Refertocontrolmeasuresin5.2.1

2 >10-5…but…≤10-3 Refertocontrolmeasuresin5.2.1

Forbiddenarea >10-3No access to the area is allowed. Immediate controlmeasuresshallbeimplemented.

3AccordingtotheODHprocess,dependingofthecomplexityofthecasetheCryogenicSafetyCommitteecanrequireafurtherODHanalysis(e.g.ComputationFluidDynamics)and/oradditionalcontrolmeasures.


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The risk assessment should also consider thebenefit of existing active control systemssuchasforcedventilationoranysupplyshut-offvalvesthatareautomaticallyactivatedby area monitor readings or system failure indicators. The control systems must bedesignedtobeactivatedbeforetheoxygenconcentrationintheareadropsbelow18%.

Step2:Definitionofcontrolmeasures5.2.Controlmeasures appropriate to theODHClass shall be implemented as stated in theODHassessmentandTechnicalAppendix.

ODHClass0istheleasthazardous.ODHClass2isthemosthazardous.Therequirementsmentionedin5.2.1aretobefollowedtocontrolpotentialODHevents.

Equipment at ESS shall be designed and installed to ensure that areas intended forhumanentryduringnormaloperationarenothigherthanODHClass2.Nohumanaccesswill be allowed in areaswith anODH Class higher than 2 unless controlmeasures areimplementedinordertoreducetheODHClasstoanacceptablelevel,i.e.ODHClass0,1or2.

Asfaraspossible,preventiveandprotectivemeasuresshallbeimplementedinafashionthatreducestheexcessriskoffatalityfromexposuretoanoxygendeficientatmosphereto no more than 10-7 per hour. In parallel of the ODH assessment, it is highlyrecommendedtocoverthefollowingtopicsinaworkinggroupinvolvingalltherelevantstakeholders:

1-EnvironmentalControls

A–Ventilation-withConventionalFacilitiesDivisioni)Forcedii)Natural,includingairmakeup

B–Monitoring-withIntegratedControlSystemandAcceleratori)Areaoxygenmonitoringii)Cryogenicsystems

2-PersonnelControls-withEnvironmentSafetyandHealthDivisionA-PostingB-Entrycontrol(locks,fencing,etc.)

3-EmergencyProcedures-withEnvironmentSafetyandHealthDivision4-SpecialRequirements-withEnvironmentSafetyandHealthDivision

A-Self-rescuesuppliedatmosphericrespirators(escapepacks)B-Unusualprocedures


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ODHcontrolmeasuresrequirements5.2.1.

OncetheODHassessmenthasbeencarriedout,controlmeasuresshallbeimplementedaccordingtothefollowinglist(Table6):

Table6-ODHcontrolmeasuresrequirements

ODHClass 0 1 2

TechnicalSafetymeasuresWarningsigns X X XVentilation * *Area(fixed)OxygenMonitoring * X X

OrganizationalSafetymeasuresMedicalapprovalasODHqualified * *ODHtraining(e-learning) X X XPersonaloxygenmonitor X XSelf-rescuemask * *Presenceofminimum2persons X

AdministrativeSafetymeasuresAccessrestrictedtoauthorizedpersonnelonly X XEmergencyprocedure X XOperatingprocedure X X X*TobeevaluatedcasebycasewiththehelpofES&H

Remark:Note that theabove-mentionedtable isnon-exhaustiveandadditionalcontrolmeasurescanberequiredbytheCryogenicSafetyCommitteeorES&Hforspecificcases.

ODHTraining5.2.2.

IndividualsengagedinODHclass0orgreateroperationsshallreceivetraininginoxygendeficiency hazards and associated safety measures. The following topics should becovered.

1–IntroductiontoactivitiesatESSinvolvingOxygenDeficiency2–DefinitionofOxygenDeficiencyHazard3-EffectsofExposuretoReducedAtmosphericOxygen4-ODHSafetyawareness

A-ExposureLimitatESS B-ODHClassificationSchemeC-RequiredControlMeasuresD–Emergencyprocedureandevacuation

NotethatanODHe-learningcoursewillbesoonavailable.


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EmergencyEvacuationandRescue5.2.3.

The following flow chart (Figure 3) shows the process for conducting emergencyevacuationand rescue.Underno circumstances shall staff enteror re-enter a space inwhich an ODH alarm is sounding. Entry under these conditions shall only be done byqualifiedrescuepersonnelsuchastheFireDepartment.

Figure3:Emergencyevacuationandrescueflowchart

SelfRescueSuppliedAtmosphereRespirator(SRSAR)orescapepack

Step3:Reviewandapproval5.3.Every ODH assessment carried out at ESS; independently from its results, shall besubmittedtoaCryogenicSafetyCommitteeforreviewandapprovalinordertoaddressthefollowingaspects:

• Validatetherelevancyofthehazardousscenariosconsideredforthestudy.

• ValidatetherelevancyoftheODHcalculationmodelchosenforthestudy.

• Validatethelistofcontrolmeasuresforeseentoguarantythesafetyoftheactivity/equipment/installation.

• Provideanofficialclearanceforthestart-upoftheactivity/equipment/installation.

ODHIMPLEMENTATION6.

Rolesandresponsibilities6.1.ThevariousrolesandresponsibilitiesofthemainstakeholdersintheimplementationoftheODHprocessaredefinedasfollows:

Review Operaration with participants

Begin operation

ODH ALARM

Put on SRSAR

Someone trapped?

Get SRSAR

on victim in 1min

Put SRSARon victim

Evacuate area

Initiateemergency response

count # of participants who escaped

Assist Fire Department

each participant should know the #

or participantsYes

Yes

No, or don't know

No, or don't know

Leave any victims for Fire

Department

Dial 112


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Activity leadersandequipment/area responsible: responsible for theODHassessmentandimplementationofcontrolmeasuresrelatedtotheiractivityandequipment/area.

Operators: provide relevant information and knowledge to the ODH assessmentregardingtheactivity/equipment/areatobeanalysed.

ES&HDivision: provides help and support on theODHprocess from the choice of therelevantmethodologytobecarriedoutfortheODHassessmenttotheimplementationofcontrolmeasuressuchastrainingandPersonalProtectiveEquipment.

ICSDivision:providehelpandsupportfortheimplementationofODHdetectionsystem.

CryogenicSafetyCommittee(CSC):reviewsandapproveseveryactivity/equipment/areainvolving the use of asphyxiant agents. The review and approval covers the ODHassessment, the selection of control measures as well as the content of the Safetydocumentation.

Safetydocumentation6.2.Everyactivity leaderandequipment/arearesponsibleshalldemonstratethecomplianceof their activity/equipment/area involving the use of asphyxiant agent with applicableregulationsandstandards.Forthispurpose,theyshallprepareandsubmitthefollowingsafetydocumentationtotheCryogenicSafetyCommitteeaswellastoES&Hforreviewandapproval:

• ODHassessmentincludingthelistofcontrolmeasurestobeimplemented.

• EmergencyprocedureincaseofanODHevent.

• MaterialSafetyDataSheet(MSDS)ofthefluidsinvolved.

• Trainingrecords.

Contacts6.3.Qualifiedpersonscanbecontactedforadviceandexpertiseonthefollowing:

• StuartBirch([email protected])–ODHdetectionsystem

• NunoElias([email protected])orDuyPhan([email protected])-ODHassessmentmethodology

• BertilWinér([email protected])-ODHcontrolmeasures


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Examplesofcasestudies6.4.Table7-ODHcasestudiesatESS

Activity/equipment/installation Reference

Acceleratortunnelhttps://ess-

ics.atlassian.net/wiki/display/ASR/ODH+Assessment+Accelerator+Tunne

UtgårdLaboratoryhttps://ess-

ics.atlassian.net/wiki/display/ELFAS/ODH+Assessment+TBP+Laboratory

REFERENCEDOCUMENTS7.

[1]

[2]

ESSProcedureforSystematicWorkEnvironmentManagement,ESS0051380

N.Elias,“ODHSafetyprocess&implementation,”ESS-0038692.

[3] “EN13458-3-Staticvacuuminsulatedvessels-Operationalrequirements”.

[4] D.Phan,“ODHCalculationtool,”ESS-0043310.

APPENDIX8.

EquipmentFailureratesestimates8.1.System FailureMode FailureRateCompressor(Two-stageMycom) Leak 5x10-6/hr Componentrupture 3x10-7/hrDewar Lossofvacuum 1x10-6/hrElectricalPowerFailure(unplanned) TimeRate 1x10-4/hr DemandRate 3x10-4/D TimeOff 1hrFluidLine(Cryogenic) Leak 5x10-7/hr Rupture 2x10-8/hrCryogenicMagnet(Powered,unmanned)

Rupture 2x10-7/hr

CryogenicMagnet(Notpowered,manned)

Rupture 2x10-8/hr

HeaderPipingAssembly Rupture 1x10-8/hr


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System FailureMode FailureRateU-TubeChange(CryogenRelease) SmallEvent 3x10-2/D LargeEvent 1x10-3/DBatteries,Power(UPC)supplies Nooutput 3x10-6/hrCircuitBreakers Failuretooperate 1x10-3/D PrematureTransfer 1x10-6/hrDIESEL(Completeplant) Failuretostartondemand 3x10-2/D(EmergencyRunLoads) Failuretorun 3x10-3/hr(EngineOnly) Failuretorun 3x10-4/hrELECTRICMOTORS Failuretostartondemand 3x10-4/D Failuretorun-normal 1x10-5/hr Failuretorun-extreme 1x10-3/hrFANS(fan,motor&starter) Failuretorun 9x10-6/hrFUSES Prematureopen 1x10-6/hr Failuretoopen 1x10-5/DFLANGES Leak,10mm2opening 4x10-7/hr

Withreinforced&preformedgaskets Rupture 1x10-9/hrFLANGES Leak,10mm2opening 4x10-7/hrWithpackingorsoftgaskets Packingblowout 3x10-8/hr Rupture 1x10-9/hrINSTRUMENTATION FailuretoOperate 1x10-6/hr(amplification,transducers,calibration,combination)

Shifts 3x10-5/hr

MOTORIZEDLOUVER Failureincontinuousoperation

3x10-7/hr

PIPING Smallleak10mm2 1x10-9/hr-m Largeleak1000mm2 1x10-10/hr-m Rupture 3x10-11/hr-mPIPINGWELD Smallleak10mm2 2x10-11(D/t)/hr-mD=Diametert=wallthickness

Largeleak1000mm2 2x10-12(D/t)/hr-m

Rupture 6x10-13(D/t)/hr-mPUMPS Failuretostartondemand 1x10-3/D Failuretorun-normal 3x10-5/hr Failuretorun-extreme 1x10-3/hrRELAYS Failuretoenergize 1x10-4/D FailureNocontacttoclose 3x10-7/hr Short 1x10-8/hr OpenNCcontact 1x10-7/hrSOLIDSTATEHiPwrapplication Failstofunction 3x10-6/hr Shorts 1x10-6/hrSOLIDSTATELowPwrapplication Failstofunction 1x10-6/hr Shorts 1x10-7/hrSWITCHES Limit:Failtooperate 3x10-4/D Torque:Failtooperate 1x10-4/D Pressure:Failtooperate 1x10-4/D Manual:Failtotransmit 1x10-5/D Contactshorts 1x10-8/hrTRANSFORMERS Opencontact 1x10-6/hr Shortcontact 1x10-6/hrVALVES(motoroperated) FailstoOperate(plug) 1x10-3/D


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System FailureMode FailureRate Failstoremainopen 1x10-4/D Externalleak 1x10-8/hr Rupture 5x10-10/hrVALVES(solenoidoperated) FailstoOperate 1x10-3/DVALVES(airoperated) FailstoOperate 3x10-4/D Failstoremainopen 1x10-4/D Externalleak 1x10-8/hr Rupture 5x10-10/hrVALVES(check) FailstoOpen 1x10-4/D Reverseleak 3x10-7/D Externalleak 1x10-8/hr Rupture 5x10-10/hrVALVES(Orifices,flowmeter) Rupture 1x10-8/DVALVES(manual) FailstoremainOpen(plug) 1x10-4/D Externalleak 1x10-8/hr Rupture 5x10-10/hrVALVES(relief) FailstoOpen 1x10-5/D PrematureOpen 1x10-5/hrVESSELS(pressure) SmallLeak,10mm2 8x10-8/hr DisruptiveFailure 5x10-9/hrWires Open 3x10-6/hr

ShorttoGND 3x10-7/hr ShorttoPWr 1x10-8/hr

HumanErrorRateestimates8.2.EstimatederrorrateD-1

ACTIVITY

1x10-3 Selection of a switch (or pair of switches) dissimilar in shape or location to the desiredswitch(orpairofswitches),assumingnodecisionerror.Forexample,operatoractuateslargehandledswitchratherthansmallswitch.

3x10-3 Generalhumanerrorofcommission,e.g.,misreadinglabelandthereforeselectingwrongswitch.

1x10-2 General human error of omissionwhere there is no display in the control room of thestatusof the itemomitted,e.g., failuretoreturnmanuallyoperatedtestvalvetoproperconfigurationaftermaintenance.

3x10-3 Errorsofomission,where the itemsbeingomittedareembedded in aprocedure ratherthanattheendasabove.

1/x Giventhatanoperatorisreachingforanincorrectswitch(orpairofswitches),heselectsaparticularsimilarappearingswitch(orpairofswitches),wherex=thenumberofincorrectswitches(orpairofswitches)adjacenttothedesiredswitch(orpairofswitches).The1/xapplies up to 5 or 6 items. After that point the error ratewould be lower because theoperatorwouldtakemoretimetosearch.Withupto5or6itemshedoesn'texpecttobewrongandthereforeismorelikelytodolessdeliberatesearching.

1x10-1 Monitor or inspector fails to recognize initial error by operator. Note: With continuingfeedbackoftheerrorontheannunciatorpanel,thehigherrorratewouldnotapply.

1x10-1 Personnelondifferentwork shift fail to check conditionofhardwareunless requiredbycheckorwrittendirective.

5x10-1 Monitor fails to detect undesired position of valves, etc., during general walk-aroundinspection,assumingnochecklistisused.


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0.2-0.3 General error rate given veryhigh stress levelswheredangerousactivities areoccurringrapidly.

2(n-1)x Givenseveretimestress,as in trying tocompensate foranerrormade inanemergencysituation, the initial error rate, x, for an activity doubles for each attempt, n, after apreviousincorrectattempt,untilthelimitingconditionofanerrorrateof1.0isreachedoruntil time runs out. This limiting condition corresponds to an individual's becomingcompletelydisorganizedorineffective.

DOCUMENTREVISIONHISTORY9.

Version Reasonforrevision Date

1 FirstRevision 2016-04-14

ESS Guideline for Oxygen Deficiency Hazard (ODH)

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