fgs assessment
Post on 25-Nov-2015
49 Views
Preview:
DESCRIPTION
TRANSCRIPT
-
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
0
0
0
4
3
2
1
0
0
5
4
3
2
1
0
6
5
4
3
2
0
7
6
5
4
3
0
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 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
0
0
0
0
3
2
1
0
0
0
4
3
2
1
0
0
5
4
3
2
1
0
6
5
4
3
2
0
7
6
5
4
3
0
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
A HydrocarbonProcessing,HighExposure
HighRisk HighCoverageVeryLowPFD
B HydrocarbonProcessing,
ModerateExposure
MediumRisk ModerateCoverageLowPFD,SIL1
C HydrocarbonProcessing,LoworVeryLowExposure
LowRisk Min.CoverageLowPFD,SIL1
SemiQuantitativeMethod:AssignedGrades
Semi-Quantitative Method
-
KENEXIS
Grade ExposureDefinition HazardRank
(Risk)
FGSPerformance
Targets
A HydrocarbonProcessing,HighExposure
3+ HighCoverageVeryLowPFD
B HydrocarbonProcessing,
ModerateExposure
1or2 ModerateCoverageLowPFD,SIL1
C HydrocarbonProcessing,LoworVeryLowExposure
0 Min.CoverageLowPFD,SIL1
SemiQuantitativeMethod:AssignedGrades
Semi-Quantitative Method
-
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
Semi-Quantitative Method
-
KENEXIS
SpecialFactorsAdjustment
DeckTypeZoneHazardRank
Adjustment
Grated +0
Solid +1
Semi-Quantitative Method
-
KENEXIS
HydrocarbonZonesAssignedGrades
Grade ExposureDefinition HazardRank
(Risk)
FGSPerformance
Targets
A HydrocarbonProcessing,HighExposure
3+ HighCoverageVeryLowPFD
B HydrocarbonProcessing,
ModerateExposure
1or2 ModerateCoverageLowPFD,SIL1
C HydrocarbonProcessing,LoworVeryLowExposure
0 Min.CoverageLowPFD,SIL1
Semi-Quantitative Method
-
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
Semi-Quantitative Method
-
KENEXIS
FGS Effectiveness(PFD)
Hazard occurs(Fi per yr)
DetectorCoverage
F2 = 0.03
S2 = 0.97
Fi * (F1 + S1* F2) = Unmitigated Hazard Frequency
S1* S2 = Effectiveness of FGS Function
S1 = 0.90
F1 = 0.10
ApplicationFireGradeA HighExposure(NotehighcoveragetargetsandFGSEffectivenessTargetsforGradeA)
Mitigated Hazard
Unmitigated Hazard
Fi * (S1 * S2) = Mitigated Hazard Frequency
High-SIL 1 Equivalent Effectiveness
-
KENEXIS
FGS Effectiveness(PFD)
Hazard occurs(Fi per yr)
DetectorCoverage
F2 = 0.10
S2 = 0.90
Fi * (F1 + S1* F2) = Unmitigated Hazard Frequency
S1* S2 = Effectiveness of FGS Function
S1 = 0.85
F1 = 0.15
Mitigated Hazard
Unmitigated Hazard
Fi * (S1 * S2) = Mitigated Hazard Frequency
ApplicationFireGradeB ModerateExposure(NotelowercoveragetargetsandFGSEffectivenessTargetsallowedforGradeB)
SIL 1 Equivalent Effectiveness
-
KENEXIS
FGS Effectiveness(PFD)
Hazard occurs(Fi per yr)
DetectorCoverage
F2 = 0.10
S2 = 0.90
Fi * (F1 + S1* F2) = Unmitigated Hazard Frequency
S1* S2 = Effectiveness of FGS Function
S1 = 0.60
F1 = 0.40
Mitigated Hazard
Unmitigated Hazard
Fi * (S1 * S2) = Mitigated Hazard Frequency
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)
Fully-Quantitative Method
-
KENEXIS
HydrocarbonGasConsequenceAnalysis
Consideroneormorepotentialhazardousoutcomes JetFire VaporCloudExplosion(VCE) VaporCloudFlashFire ToxicExposure(H2S)
Sensitivetoatmosphericconditions(i.e.prevailingwinds,relativehumidity,ambienttemperature)
Requiresdispersionandconsequencemodelingusingpurposebuiltsoftware(PHAST)
Fully-Quantitative Method
-
KENEXIS
FlashFireConsequenceAnalysis Resultofdelayed,unconfinedignitionofcombustiblegasrelease Intense,shortdurationfire Burnsfrompointofignitionbacktopointofrelease Potentialtoresultinresidualfireatpointofrelease(i.e.jet
fire)
LELisflammableendpointforvaporcloud Analysismustaccountforpocketsofflammablevaporwithin
thevaporcloudathigherconcentrationthanthebulkvapor
Fully-Quantitative Method
-
KENEXIS
VaporCloudExplosionConsequenceAnalysis
Ignitionofsemiconfinedhydrocarbongasreleaseinacongestedenvironment. Flamefrontaccelerationresultsindamagingoverpressure Transientblastfollowedbyresidualfireatpointofrelease
AnalyzeFGSZonetodetermineifVCEispossible Overlayvaporclouddispersionresultswithplatformdeck
plantoidentifyareasofpotentialconfinement
Factorsforanalysisinclude: Considerationofdimensionalconfinement(1D,2D,3D) Considerationofblockageratio(low,medium,high) Sufficientvolumeofconfinedvapor(50m3,UKHealth&SafetyExec.) OverpressuregeneratedbyVCE(LethalBlastOverpressurethreshold) Presenceorabsenceofblastwalls
Fully-Quantitative Method
-
KENEXIS
ToxicGas(H2S)ConsequenceAnalysis
Gasreleasewithoutignitionresultsintoxicexposure Analysisisextremelysensitivetometeorological
conditions Modelingofmultiplereleaseorientations Considerationofgasdetectionsindownwind,upwindand
crosswind
Analysisrequirestoxicendpoints Lethalconcentrationendpoint ImmediatelyDangeroustoLifeandHealth
Fully-Quantitative Method
-
KENEXIS
LikelihoodAnalysis
BasedonHistoricalOffshoreData: OffshoreReleaseStatistics,2001.UKHealth&SafetyExec.
PARLOC2001:TheupdateofLossofContainmentDataforOffshorePipelines.UKHealth&SafetyExec.
Sensitivetoholesizedistribution SensitivetoEquipmentType
Fully-Quantitative Method
-
KENEXIS
RiskIntegration
JoinConsequenceandLikelihoodtogeneratealistofpossiblescenariooutcomes Eachoutcomehasanassociatedlevelofrisk(PLL,Financial
Loss)
EventTreesareusedtodetermineriskforeachoutcome
EventoutcomesareintegratedtodetermineriskforaFGSzoneorPlatform RiskforFGSzone/platformiscomparedagainstCustomer
tolerableriskcriteria
Initiallyselectlowdetectorcoverageandprogressivelyincreaseuntiltolerableriskachieved.
Fully-Quantitative Method
-
KENEXIS
RiskIntegration EventTree
Fully-Quantitative Method
-
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
DetectorPerformanceVerificationApplication WellheadPlatform
-
KENEXIS
DetectorPerformanceVerificationApplication WellheadPlatform
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
FGS Effectiveness(PFD)
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
top related