xviii Contents2527.4.2EscapeTimeAnalysis.2527.4.3 Impairment Analysis.2557.4.4EscapeFatalityAnalysis2567.5AnalysisofEvacuationRisk2567.5.1OverviewofEvacuationMeans.2617.5.2 ImpairmentAnalysis..2617.5.3EvacuationFatalityAnalysis7.6AnalysisofRiskAssociatedwithRescueOperations263.2647.6.1RescueTimeAnalysis2667.6.2RescueCapacity2697.6.3RescueFatalityAnalysis....2717.7TransportationFatalityRisk...2727.7.1FatalityDistribution...2727.7.2ComparisonofRiskAssociated withShuttling2737.8DivingFatalityRisk7.9FatalityRiskDuringCessationWork273.2778Fire Risk Modelling..2778.1Overview.2778.1.1CaseswithOppositeResults2788.1.2Types of Fire Loads..2798.1.3StructuralFireImpact.2808.1.4FireandExplosionLoadsonPeople2808.2TopsideFireConsequenceAnalysis.2808.2.1Mechanisms of Fire.2828.2.2 Fire Balls ..2828.2.3Gas Fires...2838.2.4AirConsumptioninFire...2838.2.5ChoiceofCalculationModels2838.2.6AnalysisofTopsideFireEvents2848.3FireonSea.2858.3.1DelayedIgnitionofanInstantaneousRelease.2868.3.2IgnitionProbabilityofan InstantaneousRelease2868.3.3WhatDetermines theLikelihood of Fireon Sea?2888.3.4LoadsfromSeaLevelFire.2908.4Analysisof SmokeEffects.2908.4.1MethodsforPredictionofSmokeBehaviour2938.4.2SmokeFlowandDispersion.2948.5StructuralResponsetoFire2948.5.1Manual Methods.2948.5.2Uninsulated Steel2958.5.3InsulatedSteel2978.6 Risk Reducing Measures.2978.6.1Overview.2988.6.2RecentR&DExperience...2988.7Dimensioningof StructuralFireProtection2988.7.1CaseIllustration
xviii Contents 7.4.2 Escape Time Analysis. 252 7.4.3 Impairment Analysis. 252 7.4.4 Escape Fatality Analysis. 255 7.5 Analysis of Evacuation Risk. 256 7.5.1 Overview of Evacuation Means. 256 7.5.2 Impairment Analysis. 261 7.5.3 Evacuation Fatality Analysis . 261 7.6 Analysis of Risk Associated with Rescue Operations . 263 7.6.1 Rescue Time Analysis . 264 7.6.2 Rescue Capacity . 266 7.6.3 Rescue Fatality Analysis. 269 7.7 Transportation Fatality Risk . 271 7.7.1 Fatality Distribution. 272 7.7.2 Comparison of Risk Associated with Shuttling . 272 7.8 Diving Fatality Risk. 273 7.9 Fatality Risk During Cessation Work . 273 8 Fire Risk Modelling . 277 8.1 Overview. 277 8.1.1 Cases with Opposite Results. 277 8.1.2 Types of Fire Loads. 278 8.1.3 Structural Fire Impact. 279 8.1.4 Fire and Explosion Loads on People . 280 8.2 Topside Fire Consequence Analysis. 280 8.2.1 Mechanisms of Fire . 280 8.2.2 Fire Balls . 282 8.2.3 Gas Fires. 282 8.2.4 Air Consumption in Fire. 283 8.2.5 Choice of Calculation Models . 283 8.2.6 Analysis of Topside Fire Events. 283 8.3 Fire on Sea . 284 8.3.1 Delayed Ignition of an Instantaneous Release . 285 8.3.2 Ignition Probability of an Instantaneous Release. 286 8.3.3 What Determines the Likelihood of Fire on Sea?. 286 8.3.4 Loads from Sea Level Fire. 288 8.4 Analysis of Smoke Effects. 290 8.4.1 Methods for Prediction of Smoke Behaviour . 290 8.4.2 Smoke Flow and Dispersion. 293 8.5 Structural Response to Fire. 294 8.5.1 Manual Methods . 294 8.5.2 Uninsulated Steel. 294 8.5.3 Insulated Steel. 295 8.6 Risk Reducing Measures. 297 8.6.1 Overview . 297 8.6.2 Recent R&D Experience. 298 8.7 Dimensioning of Structural Fire Protection . 298 8.7.1 Case Illustration. 298
Contentsxix2998.7.2DimensioningFire3008.7.3FireDurationDistribution3018.7.4DefinitionofDimensioningFire3018.7.5USFOsModelling.3048.7.6QRAModelling3068.7.7QRAResults.3078.7.8Observations8.8BlastandFireDesignGuidance3073099Explosion Risk Modelling3099.1Overview....3099.1.1Introduction..3099.1.2Explosion Loads on Structure3109.1.3ExplosionLoadsonPeople.3109.2ExplosionFrequency9.2.1EventTreeAnalysis.3109.2.2HistoricalFrequencies.311.3139.3ExplosionConsequenceAnalysis.3139.3.1Types of Explosion Loads.3159.3.2GasExplosion3169.3.3BlastWave...3179.3.4Pressure..3179.3.5FormationofExplosiveCloud.3199.3.6Deflagration.3219.3.7Confined/Semi-confinedExplosion3239.4ProbabilisticApproachtoExplosion LoadAssessment3239.4.1Basis.3249.4.2ApproachtoProbabilisticEvaluation3259.4.3ProbabilisticEvaluation3299.4.4Example.3309.4.5UseofLoadFunction3319.4.6StructuralResponseCalculations3319.4.7 Is a Probabilistic Approach the Best WayForward?3329.5ExplosionRiskReduction3329.5.1EstablishingBasisforDesign9.5.2BFETSR&DExperience3333349.5.3MainExperience,Mitigation9.5.4RiskReductionPossibilities3343389.6Example,DimensioningAgainst Blast Load.3389.6.1Introduction.3409.6.2Basis forDimensioning.3409.6.3DesignCapability ....3409.6.4 Load Distributions..3429.6.5GasExplosionFrequency.3439.6.6ReinforcementCosts.3439.6.7Optimisation
Contents xix 8.7.2 Dimensioning Fire . 299 8.7.3 Fire Duration Distribution . 300 8.7.4 Definition of Dimensioning Fire. 301 8.7.5 USFOS® Modelling . 301 8.7.6 QRA Modelling . 304 8.7.7 QRA Results. 306 8.7.8 Observations . 307 8.8 Blast and Fire Design Guidance . 307 9 Explosion Risk Modelling . 309 9.1 Overview. 309 9.1.1 Introduction . 309 9.1.2 Explosion Loads on Structure. 309 9.1.3 Explosion Loads on People . 310 9.2 Explosion Frequency . 310 9.2.1 Event Tree Analysis. 310 9.2.2 Historical Frequencies . 311 9.3 Explosion Consequence Analysis . 313 9.3.1 Types of Explosion Loads . 313 9.3.2 Gas Explosion. 315 9.3.3 Blast Wave. 316 9.3.4 Pressure. 317 9.3.5 Formation of Explosive Cloud. 317 9.3.6 Deflagration. 319 9.3.7 Confined/Semi-confined Explosion. 321 9.4 Probabilistic Approach to Explosion Load Assessment . 323 9.4.1 Basis . 323 9.4.2 Approach to Probabilistic Evaluation . 324 9.4.3 Probabilistic Evaluation. 325 9.4.4 Example. 329 9.4.5 Use of Load Function . 330 9.4.6 Structural Response Calculations . 331 9.4.7 Is a Probabilistic Approach the Best Way Forward? . 331 9.5 Explosion Risk Reduction. 332 9.5.1 Establishing Basis for Design. 332 9.5.2 BFETS R&D Experience. 333 9.5.3 Main Experience, Mitigation . 334 9.5.4 Risk Reduction Possibilities . 334 9.6 Example, Dimensioning Against Blast Load. 338 9.6.1 Introduction . 338 9.6.2 Basis for Dimensioning . 340 9.6.3 Design Capability . 340 9.6.4 Load Distributions . 340 9.6.5 Gas Explosion Frequency . 342 9.6.6 Reinforcement Costs. 343 9.6.7 Optimisation . 343
ContentsxX3449.7CaseStudy,ReductionofBlastLoad3459.7.1 Layout and Geometry.3459.7.2Casesand ConfigurationsAnalysed3469.7.3VentilationResults..3479.7.4ExplosionStudies.3479.7.5FLACSResults3489.7.6DemonstrationofParameterSensitivities3499.7.7ImplicationsforQRAModelling.3509.7.8ORASensitivityResults3519.7.9Discussion and Evaluation.35310 CollisionRisk Modelling35310.1 Historical Collision Risk35310.1.1SignificantCollisions35410.1.2NorwegianPlatformCollisions.34610.1.3AttendantVesselCollisions..35710.2ModellingOverview..35710.2.1Introduction.35810.2.2Merchant Vessels35910.2.3Naval Traffic35910.2.4Fishing Vessels.10.2.5OffshoreTraffic...360.36110.2.6FloatingUnits36110.3PassingTraffic36110.3.1Introduction.36210.3.2PoweredPassingVessel Collisions-Model Overview.36410.3.3TrafficPatternandVolume..36610.3.4Probabilityof CollisionCourse....37010.3.5ProbabilityofFailureof ShipInitiatedRecovery.10.3.6ProbabilityofFailureofPlatformInitiatedRecovery373.37410.3.7ExampleResults.10.3.8COASTR.37437510.3.9Model Validation.37610.4CollisionEnergy ..37610.4.1ImpactEnergyandPlatformEnergyAbsorptionCapacity10.4.2Mass of CollidingVessels37710.4.3ImpactVelocityofCollidingVessel37737810.4.4Critical Collisions..37910.5CollisionConsequences.37910.5.1FailureCriteria.38010.5.2CollisionGeometry38010.5.3LocalCollisionDamage...38110.5.4GlobalDamage..38110.6RiskReducingMeasures.38110.6.1OverviewofRiskReducingMeasures.38210.6.2PassingVessels.38310.6.3EffectofRiskReducingMeasures
xx Contents 9.7 Case Study; Reduction of Blast Load . 344 9.7.1 Layout and Geometry . 345 9.7.2 Cases and Configurations Analysed . 345 9.7.3 Ventilation Results. 346 9.7.4 Explosion Studies . 347 9.7.5 FLACS Results . 347 9.7.6 Demonstration of Parameter Sensitivities. 348 9.7.7 Implications for QRA Modelling. 349 9.7.8 QRA Sensitivity Results. 350 9.7.9 Discussion and Evaluation. 351 10 Collision Risk Modelling . 353 10.1 Historical Collision Risk. 353 10.1.1 Significant Collisions . 353 10.1.2 Norwegian Platform Collisions . 354 10.1.3 Attendant Vessel Collisions. 346 10.2 Modelling Overview . 357 10.2.1 Introduction . 357 10.2.2 Merchant Vessels. 358 10.2.3 Naval Traffic . 359 10.2.4 Fishing Vessels. 359 10.2.5 Offshore Traffic. 360 10.2.6 Floating Units. 361 10.3 Passing Traffic . 361 10.3.1 Introduction . 361 10.3.2 Powered Passing Vessel Collisions - Model Overview. 362 10.3.3 Traffic Pattern and Volume . 364 10.3.4 Probability of Collision Course . 366 10.3.5 Probability of Failure of Ship Initiated Recovery. 370 10.3.6 Probability of Failure of Platform Initiated Recovery . 373 10.3.7 Example Results . 374 10.3.8 COAST® . 374 10.3.9 Model Validation. 375 10.4 Collision Energy . 376 10.4.1 Impact Energy and Platform Energy Absorption Capacity . 376 10.4.2 Mass of Colliding Vessels . 377 10.4.3 Impact Velocity of Colliding Vessel . 377 10.4.4 Critical Collisions. 378 10.5 Collision Consequences. 379 10.5.1 Failure Criteria. 379 10.5.2 Collision Geometry. 380 10.5.3 Local Collision Damage . 380 10.5.4 Global Damage. 381 10.6 Risk Reducing Measures. 381 10.6.1 Overview of Risk Reducing Measures . 381 10.6.2 Passing Vessels. 382 10.6.3 Effect of Risk Reducing Measures . 383
Contentsxxi.38710.6.4ExperiencewithCollisionAvoidance.38810.6.5Example38910.7Collision Risk Case Study.38910.7.1Installation.38910.7.2Routes..39210.7.3Results39310.7.4EnergyDistributions.39410.7.5InterventionOptions10.7.6CollisionGeometry.39539911MarineSystemsRiskModelling.39911.1BallastSystemFailure39911.1.1Background39911.1.2RegulatoryRequirements..40011.1.3RelevantHazards.40011.1.4PreviousStudies.40111.1.5RecentStabilityIncidentsandAccidents.40211.1.6ObservationsfromIncidents andAccidents.40311.1.7EvaluationofTypicalQRAStudies40411.1.8ProposedApproachtoAnalysisofStabilityHazards.40811.1.9ComparisonofQRAResultswithExperiencedEvents...40811.1.10Observations.40911.2AnchoringSystemFailure.40911.2.1Incidents InvolvingMoreThanOneAnchorLine41011.2.2Release of Chains inWinches41111.2.3Failures inAnchor Lines.41211.2.4Dragging ofAnchors41211.2.5OtherRiskswithAnchoringSystems.11.2.6Risk Analysis of Anchoring Systems on MODUs on the NCS ...41241211.2.7UseofFaultTreesinQRAofAnchoringSystems41311.2.8Summary.41411.3FailureofDrillingDPSystems..41411.3.1BarrierFunction1-Prevent Lossof Position41611.3.2BarrierFunction2-ArrestVessel Movement11.3.3BarrierFunction3-Prevent Loss of Well Integrity41611.4ShuttleTankerCollisionRisk41741711.4.1Background.41911.4.2TandemOff-loadingConfigurations..42011.4.3OverviewofCurrentFieldConfigurations.42111.4.4CharacterizationofShuttleTankerCollisionHazard42311.4.5Barrier Modelling....42411.4.6AnalysisofRiskAspects.42511.4.7TrendsinOccurrenceFrequencies42611.4.8CollisionEnergy andConsequences...42611.4.9Accidentsand IncidentsforTautHawserConfigurations.42711.4.10Main Contributors to CollisionFrequency,inDrive-off42811.4.11 Experience Data
Contents xxi 10.6.4 Experience with Collision Avoidance . 387 10.6.5 Example. 388 10.7 Collision Risk Case Study . 389 10.7.1 Installation . 389 10.7.2 Routes. 389 10.7.3 Results . 392 10.7.4 Energy Distributions. 393 10.7.5 Intervention Options. 394 10.7.6 Collision Geometry. 395 11 Marine Systems Risk Modelling. 399 11.1 Ballast System Failure . 399 11.1.1 Background. 399 11.1.2 Regulatory Requirements . 399 11.1.3 Relevant Hazards. 400 11.1.4 Previous Studies . 400 11.1.5 Recent Stability Incidents and Accidents . 401 11.1.6 Observations from Incidents and Accidents . 402 11.1.7 Evaluation of Typical QRA Studies . 403 11.1.8 Proposed Approach to Analysis of Stability Hazards. 404 11.1.9 Comparison of QRA Results with Experienced Events. 408 11.1.10 Observations. 408 11.2 Anchoring System Failure . 409 11.2.1 Incidents Involving More Than One Anchor Line . 409 11.2.2 Release of Chains in Winches . 410 11.2.3 Failures in Anchor Lines . 411 11.2.4 Dragging of Anchors . 412 11.2.5 Other Risks with Anchoring Systems. 412 11.2.6 Risk Analysis of Anchoring Systems on MODUs on the NCS . 412 11.2.7 Use of Fault Trees in QRA of Anchoring Systems. 412 11.2.8 Summary. 413 11.3 Failure of Drilling DP Systems. 414 11.3.1 Barrier Function 1 - Prevent Loss of Position . 414 11.3.2 Barrier Function 2 - Arrest Vessel Movement. 416 11.3.3 Barrier Function 3 - Prevent Loss of Well Integrity . 416 11.4 Shuttle Tanker Collision Risk. 417 11.4.1 Background. 417 11.4.2 Tandem Off-loading Configurations . 419 11.4.3 Overview of Current Field Configurations. 420 11.4.4 Characterization of Shuttle Tanker Collision Hazard. 421 11.4.5 Barrier Modelling . 423 11.4.6 Analysis of Risk Aspects. 424 11.4.7 Trends in Occurrence Frequencies . 425 11.4.8 Collision Energy and Consequences. 426 11.4.9 Accidents and Incidents for Taut Hawser Configurations. 426 11.4.10 Main Contributors to Collision Frequency, in Drive-off . 427 11.4.11 Experience Data. 428
xxiiContents42911.4.12AccidentFrequency43011.4.13AverageCollisionFrequency.43011.4.14Trends in CollisionFrequencies.43211.5LossofBuoyancy.43311.6Accidental WeightCondition.43512RiskduetoMiscellaneoushazards43512.1Crane Accidents...43712.1.1ModellingofDroppedObjectImpact43712.1.2PhysicalAspectsofFallingLoads43912.1.3ProbabilityofDroppedLoads.43912.1.4ProbabilityofHittingObjects.44012.1.5ConsequencesofImpact44212.1.6ImpactEnergyDistributions.44412.2Accidents During Tow..12.3Man-0verboardAccidents....444..44512.3.1FrequencyofMOBAccidents12.3.2Scenarios involvingMOBAccidents..446.44712.4HelicopterDitchingAccidents.44812.5StructuralFailure12.6Subsea Gas Release44945113ApproachtoRiskBasedDesign45113.1Overview...45113.1.1AbouttheNeedforRiskBasedDesign45213.1.2ScopeforRiskBasedDesign13.1.3 Challenges for Design.453.45513.2AuthorityRegulations andRequirements.45513.2.1NorwegianInstallations45613.2.2UKRegulations.45613.3RelationshipwithRiskAnalysis.45713.3.1SuitableRiskAnalysis.45913.3.2 Use of Event Trees .13.3.3UseofConsequenceModels.460.46213.3.4SensitivitytoChanges inActiveSafetySystems46313.4ApproachtoRiskBasedDesignofTopsideSystems46313.4.1 Basis for Approach..13.4.2FundamentalsofProposedApproach.464.46513.4.3OverviewofSensitivities.13.4.4What Shouldbe theTarget ProtectionLevel46613.5RiskBasedDesignof Structural andPassiveSafetySystems467..46713.6PracticalConsiderations....46713.6.1 Design Against Fire Loads.47213.6.2DesignAgainstExplosionLoads..47313.6.3DesignAgainstCollisionImpacts47413.6.4DesignAgainstDroppedLoad Impact47413.7 Safety Integrity Levels
xxii Contents 11.4.12 Accident Frequency. 429 11.4.13 Average Collision Frequency . 430 11.4.14 Trends in Collision Frequencies . 430 11.5 Loss of Buoyancy . 432 11.6 Accidental Weight Condition . 433 12 Risk due to Miscellaneous hazards. 435 12.1 Crane Accidents. 435 12.1.1 Modelling of Dropped Object Impact. 437 12.1.2 Physical Aspects of Falling Loads. 437 12.1.3 Probability of Dropped Loads . 439 12.1.4 Probability of Hitting Objects. 439 12.1.5 Consequences of Impact. 440 12.1.6 Impact Energy Distributions. 442 12.2 Accidents During Tow. 444 12.3 Man-overboard Accidents. 444 12.3.1 Frequency of MOB Accidents. 445 12.3.2 Scenarios involving MOB Accidents . 446 12.4 Helicopter Ditching Accidents. 447 12.5 Structural Failure . 448 12.6 Subsea Gas Release . 449 13 Approach to Risk Based Design. 451 13.1 Overview. 451 13.1.1 About the Need for Risk Based Design. 451 13.1.2 Scope for Risk Based Design . 452 13.1.3 Challenges for Design . 453 13.2 Authority Regulations and Requirements . 455 13.2.1 Norwegian Installations. 455 13.2.2 UK Regulations . 456 13.3 Relationship with Risk Analysis. 456 13.3.1 Suitable Risk Analysis. 457 13.3.2 Use of Event Trees . 459 13.3.3 Use of Consequence Models . 460 13.3.4 Sensitivity to Changes in Active Safety Systems . 462 13.4 Approach to Risk Based Design of Topside Systems . 463 13.4.1 Basis for Approach . 463 13.4.2 Fundamentals of Proposed Approach. 464 13.4.3 Overview of Sensitivities. 465 13.4.4 What Should be the Target Protection Level. 466 13.5 Risk Based Design of Structural and Passive Safety Systems . 467 13.6 Practical Considerations. 467 13.6.1 Design Against Fire Loads . 467 13.6.2 Design Against Explosion Loads. 472 13.6.3 Design Against Collision Impacts . 473 13.6.4 Design Against Dropped Load Impact . 474 13.7 Safety Integrity Levels. 474