fgs assessment

KENEXIS

Fire & Gas System (FGS)Integrity Analysis

KENEXIS

Background Fire&GasDetectionandSuppressionsystemsarecriticalinstrumentation/controlsystems

FGSSystemscanbeakeysafeguardusedtoreducerisktotolerablelevels SafetyRisk EnvironmentalRisk AssetRisk(Commercial/Business)

Allcriticalinstrumentation/controlsystemsrequireabasisofsafetyforspecifyingadequateequipmentdesignandfunctionaltestingrequirements Option1:PrescriptiveBasisofSafety,NFPAstandards,etc. Option2:PerformanceBasis/RiskAssessment

Option2workswithCustomerCorporateRiskTolerancecriteria

2

KENEXIS

Typical FGS Components

FGS Logic Solver

Process

Safetyvalve

Logic solverProgrammable

or non-Programmable

OutputInput

AreaFire or Gas

Detector

Final Element(s)Detector(s)

SV

IAS

KENEXIS

Safety Integrity Level (SIL)

PFD concept is highly relevant to design of Fire and Gas System Functions

However, component equipment failures are not the only consideration!

KENEXIS

Rules for Layers of Protection Independent Protection Layers (IPLs) MUST Completely

Prevent Hazard More credit given to Hazard Prevention versus

Mitigation Systems

KENEXIS

FGS Design & Analysis Challenges WhenTryingtousetypicalRiskAnalysistechniquesforcompliancewithISA84/IEC61511StandardforSIS Fire&GassystemsMitigateConsequence TheyarenotPreventativesafeguards DetectorPlacementandCoveragecantbeignored UK/HSENorthSeadataindicatemorethan30%ofgasreleasesarenotdetectedbyautomatedsystems

FireandGasHazardsaregeneralinnature,difficulttocharacterizeincontextofLayersofProtectionAnalysis(LOPA)

HowtomakedecisionsabouttolerableriskwithrespecttoFire&GasSystems?

WhenisitappropriatetotakecreditforFireandGasdetection/suppressioninthecontextofLOPA?

6

KENEXIS

0

0

0

0

0

0

3

2

1

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4

3

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6

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7

6

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0 1 2 3 4 5

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LIKELIHOOD

S

E

V

E

R

I

T

Y

-

S

A

F

E

T

Y

LOPA works well for Hazard Prevention

KENEXIS

IPL 2 Success

Fail

Initiating Event Occurs

(Fi per yr)

IPL1 Success

Fail

F2

S2

S1

F1

TypicalRiskModelforLOPA

No Hazard

No Hazard

No Hazard

Hazard Occurs

Fi * F1* F2*F3 = Hazard Frequency (per yr)

IPL 3 Success

Fail

S3

F3

Based on QRA / Event Tree Analysis

By definition: Only one branch results in hazard

Hazard is a single event of definable magnitude, severity

IPL = Independent Protection Layer

Conditional Outcome

KENEXIS

FGS Effectiveness(PFD)

Hazard occurs(Fi per yr)

DetectorCoverage

F2

S2

Fi * (F1 + S1* F2) = Unmitigated Hazard Frequency

S1* S2 = Effectiveness of FGS Function

S1

F1

SimplifiedRiskModelforFire&GasSystemIntegrityAnalysis

Mitigated Hazard

Unmitigated Hazard

Fi * (S1 * S2) = Mitigated Hazard Frequency

Conditional Outcome

KENEXIS

SimplifiedRiskModelforFire&GasSystemIntegrityAnalysis

HazardsofvaryingmagnitudeoccuronseveralbranchesofFGSeventtree

Possiblehazardousoutcomesareofdifferentmagnitude,severity

FGSdetectorcoverageandsafetyavailabilityareimportantfactorsinoutcomes,buthavepracticallimits,especiallyondetectorcoverage.

Initiatingeventsincludeleaks,rupturesduetocorrosion,erosion,externalimpact.TypicallynotincludedinLOPA.

EffectivenessofFGSfinalelementactionsneedstobeconsidered.

KENEXIS

0

0

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6

5

4

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7

6

5

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0 1 2 3 4 5

5

4

3

2

1

0

LIKELIHOOD

S

E

V

E

R

I

T

Y

-

S

A

F

E

T

Y

LOPA does not work well for Hazard Mitigation

- Multiple outcomes of same hazard scenario

Unmitigated Hazard

Mitigated Hazard

KENEXIS

FGSIntegrityAnalysisGeneralApproach1. UseaRiskModelthataccountsforboth

MitigatedandUnmitigatedHazards2. SamelevelofanalysisasLOPA...butOptionalfullQRA3. CalibratetoRiskToleranceCriteria4. UseRiskModeltoEstablishPerformanceParameters

forFGSDesign Target:DetectorCoverage Target:FGSFunctionSafetyAvailability(PFDavg)

5. Verifyperformancetargetshavebeenachieved Achieved:DetectorCoverage>Target Achieved:FGSFunctionSafetyAvailability(PFDavg)>TargetNote:QRA/safetycaseanalysisassumes probabilityvaluesfor

DetectorCoverageandFGSAvailabilityFGSIntegrityAnalysisdoesnotassumeprobabilityvalues,it

establishesdesigntargetsthataresubsequentlyverified

KENEXIS

FGSIntegrityAnalysisProcedure

1. DefineFireHazardZonesandGasHazardZones2. ClassifyFire&GasZoneHazardRank3. DetermineFGSPerformanceRequirements

FireDetectorPlacementandPerformance FlammableGasDetectorPlacementandPerformance

4. DetectorcoveragemappingandDetectorPlacement5. Detector/FGSPerformanceVerification6. ModificationofFGSdesign,asnecessarytoachieve

performancetargets

KENEXIS

DefineFireHazardZones

KENEXIS

HazardZonesConsiderations GroupSimilarEquipmenttogetherinZone Considerdifferentiatingzonesby:

Deck FGSsystemactions Segregationofhazards ClassifiedElectricalEquipment Specialoccupancies

SeparateZonesfordifferenthazards: FlammableHazards(fireandcombustibleGas) ToxicHazards(H2S)

KENEXIS

ListofZones

KENEXIS

CategorizeZonesZone

Category AreaDefinition Examples

HHydrocarbonPossessingArea,GeneralFire/GasHazard

wellbay,productionseparation,gascompression,

N NonHydrocarbonFireHazard

CombustibleLiquidStorageLubricationOilSystem

DGeneralOccupancy,NoHydrocarbonFireHazard

AccommodationsModuleControlModule

ENonHydrocarbonSpecialEquipmentProtection

NonclassifiedElectricalEquipment

T GasTurbineorEngineEnclosuresGasTurbineandTurbineEnclosures

V CombustionAirIntake/VentilationAirIntakesReboilerCombustionAirblower,

KENEXIS

CategorizeZonestodetermineObjectivesofFGSIntegrityAnalysis

ZoneH(Hydrocarbon)andZoneN(Nonhydrocarbon) AnalysisObjective:Determineadequacyofgeneralareacoverageofhydrocarbon/nonhydrocarbonfireandgasdetectionsystems

ZoneD(GeneralOccupancy) Conformancewithapplicable,prescriptivestandards,NFPA72,EN54orequivalent

ZoneE,ZoneT,ZoneV(ProtectionofNonhazardousAreas) AnalysisObjective:Determineadequacyofseparationofzonefromotherhydrocarbon/nonhydrocarbonfireorgashazards.

KENEXIS

FGSRiskModel SemiQuantitative(SimilartoLOPA)versusFully

QuantitativeRiskAnalysis(QRA)

DesireaRiskModelthatissensitiveto: DetectorCoverage FGSSystemProbabilityofFailureonDemand

AnalysisConsiderationsinclude: AssessmentofHydrocarbonProcessingEquipment AssessmentofFireandGasConsequences AssessmentofReleaseLikelihood AssessmentofLevelofHumanOccupancyofZone AssessmentofProductionValueforProcess

KENEXIS

SelectFGSRiskMethod

ZoneCategory HazardofConcern

PrimaryRiskAnalysisMethod

AlternateRiskAnalysisMethod

H HydrocarbonFire SemiQuantitative Quantitative

H CombustibleGas SemiQuantitative Quantitative

H ToxicGas Quantitative (none)

N NonhydrocarbonFire SemiQuantitative Quantitative

EAirintakeforSpecialEquipment Quantitative

(none)

TCombustibleGasatAirIntake Quantitative

(none)

VCombustibleGasatAirIntake Quantitative

(none)

Where no FGS is in place, then fully-quantitative method is used to determine if risk is acceptable without the benefit of any automated FGS.

KENEXIS

HydrocarbonvsNonHydrocarbonZones

Step 1:Define Zone Category

NO YESStep 2:Select Processing Unit

Use Prescriptive Standards

Step 3:Adjust ForOccupancy

Step 4:Adjust ForProduction Rate

Step 5:Adjust ForConfinement Criteria

Zone Category N or H ?

KENEXIS

SemiQuantitativeMethod:AssignedGrades

Hazard Grades assigned to Hydrocarbon Zones (fire and gas) and Non-Hydrocarbon Fire Zones

Grade ExposureDefinition

A HydrocarbonProcessing,HighExposure

B HydrocarbonProcessing,

ModerateExposure

C HydrocarbonProcessing,LoworVeryLowExposure

Semi-Quantitative Method

KENEXIS

Grade ExposureDefinition HazardRank

(Risk)

FGSPerformance

Targets


HighRisk HighCoverageVeryLowPFD


ModerateExposure

MediumRisk ModerateCoverageLowPFD,SIL1


LowRisk Min.CoverageLowPFD,SIL1



KENEXIS


(Risk)

FGSPerformance

Targets


3+ HighCoverageVeryLowPFD


ModerateExposure

1or2 ModerateCoverageLowPFD,SIL1


0 Min.CoverageLowPFD,SIL1



KENEXIS

ProcessingUnitsZoneHazard

Rank ProcessingUnitsZoneHazard

Rank

ProductionWells 1 GasCompression(2500) 3

GasLiftWells 2 FuelGas(

KENEXIS

Occupancy ZoneHazardRankAdjustment

NUI=NormallyunmannedInstallation +0

MannedInstallationANDZone=

KENEXIS

ProductionAdjustment

ProductionRate(Oil/Gas) ZoneHazardRankAdjustment

Oil40,000BPDorGas>150MMSCFD +1


KENEXIS

SpecialFactorsAdjustment

DeckTypeZoneHazardRank

Adjustment

Grated +0

Solid +1


KENEXIS

HydrocarbonZonesAssignedGrades


(Risk)

FGSPerformance

Targets


3+ HighCoverageVeryLowPFD


ModerateExposure

1or2 ModerateCoverageLowPFD,SIL1


0 Min.CoverageLowPFD,SIL1


KENEXIS

FireGrade FireDetectionCoverage FGSSafetyAvailability

A 0.90 0.97

B 0.85 0.90

C 0.60 0.90

GasGrade GasDetectionCoverage FGSSafetyAvailability

A 0.90 0.97

B 0.85 0.90

C 0.60 0.90

FGSPerformanceTargets


KENEXIS



DetectorCoverage

F2 = 0.03

S2 = 0.97



S1 = 0.90

F1 = 0.10

ApplicationFireGradeA HighExposure(NotehighcoveragetargetsandFGSEffectivenessTargetsforGradeA)

Mitigated Hazard

Unmitigated Hazard


High-SIL 1 Equivalent Effectiveness

KENEXIS



DetectorCoverage

F2 = 0.10

S2 = 0.90



S1 = 0.85

F1 = 0.15

Mitigated Hazard

Unmitigated Hazard


ApplicationFireGradeB ModerateExposure(NotelowercoveragetargetsandFGSEffectivenessTargetsallowedforGradeB)

SIL 1 Equivalent Effectiveness

KENEXIS



DetectorCoverage

F2 = 0.10

S2 = 0.90



S1 = 0.60

F1 = 0.40

Mitigated Hazard

Unmitigated Hazard


ApplicationFireGradeC LowExposure(NotelowercoveragetargetsandFGSEffectivenessTargetsallowedforGradeC)

SIL 1 Equivalent Effectiveness

KENEXIS

OptionalAnalysisMethod:FullyQuantitativeAnalysis Applicationsinclude:

ToxicGasZones duetohighlylocationspecificanalysis

SpecialExposureZones(E,T,V) AlternativeprocedureforHydrocarbonFire&GasZoneswhereSemiquantitativeMethoddoesnotprovideadequateresults

Usedexclusivelywhenno(orlimited)FGSsystemexistsanddesiretojustifyadequacyofexistingsituation

KENEXIS

HazardScenarioIdentification Hazardscenariosshouldincludegeneralrelease/firescenarios

Identifyallcrediblereleasescenarios,including: Vessels, process piping, flanges, instruments, wellheads, pumps,

compressors, heat exchangers, launchers/receivers, risers and pipelines

Identifyspecificfactorseffectingreleasescenario Holesize,location,orientation,phase,toxicity(H2S),occupancy

ReleaseScenarioswithextremelylowlikelihoodand/orconsequenceneednotbeconsidered

Resultshouldbeadetailedlistofreleasescenarioswithenoughdetailtoundertakeconsequenceandlikelihoodanalysis

Fully-Quantitative Method

KENEXIS

HydrocarbonFireConsequenceAnalysis

TwoConsequenceTypes: JetFire(EarlyIgnition,Turbulentdiffusion,momentum

driven)

PoolFire(LateIgnition,consequenceseverityisdefinedbypoolsizeandfueltype)

Radiantheatoutputisbasisforsafetyconsensuses:

Requiresdispersionandconsequencemodelingusingpurposebuiltsoftware(PHAST)


KENEXIS

HydrocarbonGasConsequenceAnalysis

Consideroneormorepotentialhazardousoutcomes JetFire VaporCloudExplosion(VCE) VaporCloudFlashFire ToxicExposure(H2S)

Sensitivetoatmosphericconditions(i.e.prevailingwinds,relativehumidity,ambienttemperature)

Requiresdispersionandconsequencemodelingusingpurposebuiltsoftware(PHAST)


KENEXIS

FlashFireConsequenceAnalysis Resultofdelayed,unconfinedignitionofcombustiblegasrelease Intense,shortdurationfire Burnsfrompointofignitionbacktopointofrelease Potentialtoresultinresidualfireatpointofrelease(i.e.jet

fire)

LELisflammableendpointforvaporcloud Analysismustaccountforpocketsofflammablevaporwithin

thevaporcloudathigherconcentrationthanthebulkvapor


KENEXIS

VaporCloudExplosionConsequenceAnalysis

Ignitionofsemiconfinedhydrocarbongasreleaseinacongestedenvironment. Flamefrontaccelerationresultsindamagingoverpressure Transientblastfollowedbyresidualfireatpointofrelease

AnalyzeFGSZonetodetermineifVCEispossible Overlayvaporclouddispersionresultswithplatformdeck

plantoidentifyareasofpotentialconfinement

Factorsforanalysisinclude: Considerationofdimensionalconfinement(1D,2D,3D) Considerationofblockageratio(low,medium,high) Sufficientvolumeofconfinedvapor(50m3,UKHealth&SafetyExec.) OverpressuregeneratedbyVCE(LethalBlastOverpressurethreshold) Presenceorabsenceofblastwalls


KENEXIS

ToxicGas(H2S)ConsequenceAnalysis

Gasreleasewithoutignitionresultsintoxicexposure Analysisisextremelysensitivetometeorological

conditions Modelingofmultiplereleaseorientations Considerationofgasdetectionsindownwind,upwindand

crosswind

Analysisrequirestoxicendpoints Lethalconcentrationendpoint ImmediatelyDangeroustoLifeandHealth


KENEXIS

LikelihoodAnalysis

BasedonHistoricalOffshoreData: OffshoreReleaseStatistics,2001.UKHealth&SafetyExec.

PARLOC2001:TheupdateofLossofContainmentDataforOffshorePipelines.UKHealth&SafetyExec.

Sensitivetoholesizedistribution SensitivetoEquipmentType


KENEXIS

RiskIntegration

JoinConsequenceandLikelihoodtogeneratealistofpossiblescenariooutcomes Eachoutcomehasanassociatedlevelofrisk(PLL,Financial

Loss)

EventTreesareusedtodetermineriskforeachoutcome

EventoutcomesareintegratedtodetermineriskforaFGSzoneorPlatform RiskforFGSzone/platformiscomparedagainstCustomer

tolerableriskcriteria

Initiallyselectlowdetectorcoverageandprogressivelyincreaseuntiltolerableriskachieved.


KENEXIS

RiskIntegration EventTree


KENEXIS

Application WellheadPlatform

KENEXIS

DetectorPerformanceVerificationApplication WellheadPlatform

Baseline case includes two optical fire detectors in opposite corners of wellbay

No Coverage

2+ Detector Coverage

Single Detector Coverage

KENEXIS

FireGradeB,requires85%coverage AchievedGeographicCoverageof62% Largeportionofobstructedby:

WellheadsPipingControlEquipment

Designonlyused2detectors InsufficientcoverageasperguidelinesforFireGradeB


KENEXIS


Improved coverage due to addition of flame detector for total of three.

No Coverage

2+ Detector Coverage

Single Detector Coverage

KENEXIS

FGSDesignModificationsObjectiveistoSatisfyFGSPerformanceTargets

ImproveCoverage Increasenumberofdetectors Changesensororientation Changevotingarchitecture(2ooN,1ooN)

ReduceProbabilityofFGSFunctionFailureonDemand ChangeDetectorTechnology, ChangeLogicSolverTechnology, IncreaseFunctiontesting,etc.

KENEXIS

RiskToleranceCriteria

RiskAcceptancedecisionsbasedonCustomerRiskManagementGuidelinesSemiQuantitativeRiskMatrixIndividualRiskBenchmark

KENEXIS

CalibrationofSemiQuantitativeMethodtoCorporateRiskTarget


Gas Release Occurs

(0.01 per yr)

DetectorCoverage

F2 = 0.10

S2 = 0.90

Fi * (F1 + S1* F2) * Pignition = Unmitigated Hazard Frequency

S1 = 0.85

F1 = 0.15

Fi * (S1 * S2) * Pignition = Mitigated Hazard Frequency

1-Pignition = 0.95

Pignition = 0.03

Ignition Probability1-Pignition = 0.99Pignition = 0.01

1-Pignition = 0.95

Pignition = 0.03

Fatality PLL

0.0

0.1

0.0

1.0

0.0

1.0

0E-0

8E-6

0E-0

3E-5

3E-5

0E-0

PLL Sum = 7E-5

KENEXIS

FGSIntegrityAnalysisConclusion

1. RiskModelallowsforperformancespecificationsonFire&GasSystemDesign:

DetectorCoverage FGSFunctionSafetyAvailability(PFDavg)

2. SamelevelofsimplifiedriskanalysisasLOPA,withoptionforfullyquantitativeanalysis

3. CalibratedtoCorporateRiskTargets4. Allowsperformancetobeverifiedanddesign/

testingmodifiedaccordingly5. AllowsanalysisofexistingFGSsystemstodetermine

theiracceptabilityforcontinueduse.

Fire & Gas System (FGS)Integrity AnalysisSlide Number 2Slide Number 3Slide Number 4Slide Number 5FGS Design & Analysis ChallengesSlide Number 7Slide Number 8Simplified Risk Model for Fire & Gas System Integrity AnalysisSimplified Risk Model for Fire & Gas System Integrity AnalysisSlide Number 11Slide Number 12FGS Integrity Analysis ProcedureDefine Fire Hazard ZonesHazard Zones ConsiderationsList of ZonesCategorize ZonesCategorize Zones to determine Objectives of FGS Integrity AnalysisFGS Risk ModelSelect FGS Risk MethodHydrocarbon vsNon-Hydrocarbon ZonesSemi-Quantitative Method:Assigned GradesSlide Number 23Slide Number 24Baseline Zone Hazard RankOccupancy AdjustmentProduction AdjustmentSpecial Factors AdjustmentSlide Number 29Slide Number 30Application Fire Grade A High Exposure(Note high coverage targets and FGS Effectiveness Targets for Grade A)Application Fire Grade B Moderate Exposure(Note lower coverage targets and FGS Effectiveness Targets allowed for Grade B)Application Fire Grade C Low Exposure(Note lower coverage targets and FGS Effectiveness Targets allowed for Grade C)Optional Analysis Method: Fully-Quantitative AnalysisHazard Scenario Identification Hydrocarbon Fire Consequence AnalysisHydrocarbon Gas Consequence AnalysisFlash Fire Consequence AnalysisVapor Cloud Explosion Consequence AnalysisToxic Gas (H2S) Consequence AnalysisLikelihood AnalysisRisk IntegrationRisk Integration Event TreeApplication Wellhead PlatformSlide Number 45Slide Number 46Slide Number 47Slide Number 48Risk Tolerance CriteriaCalibration of Semi-Quantitative Method to Corporate Risk TargetSlide Number 51

fgs assessment

Documents

hazard preventionkenexisipl

unmitigated hazard frequencys1

f1 s1

gas system functions

branch results

component equipment