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Tel: (+44) 01492 879813 Mob: (+44) 07984 [email protected] 1
Linking task analysis with other process safety activities
Andy Brazier
Working in silos
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QRA
HAZOP
Human factors
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Risk profile
Hazard detail
Engineered Human
Hierarchy Task or activity
1. Instrument2. Alarm3. Trip4. Mechanical
Task analysis
1. HMI2. Deviation response3. Emergency4. Generic competence5. One-off risk assessment6. Automated
Prioritise according to risk of MAHQRA, HAZID
Identify deviations leading to MAHHAZOP, PHR
ALARP
HSE Roadmap
Barriers
Bowtie?
HAZOP and human factors
Safeguards with human componentMonitoring and controlAlarm responseTraining or procedure???
Safeguard maintenanceTasks considered as potential causes of deviationRecommendations.
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Issues with HAZOP and human factors
Not a systematic study of human factors Human factors principles not always applied (correctly)HAZOP is already demanding without adding human factorsBut creating good links between HAZOP and human factors could be very beneficial.
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Use HAZOP to structure task analysis
HAZOP nodesFocus on deviations that can result in Major Accident hazards (MAH)Use causes of deviations to identify tasksConsistent reference to causes and consequences.
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Identifying tasks Planned deviations - pressure
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Pre
ssur
e
Time
Start-up Normal Optimise Shutdown
Unplanned deviations - pressure
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Pre
ssur
e
Time
Start-up Controlled excursion
Failure
HazardUn-controlled excursion
Safety critical task analysis
What does ‘safety critical’ mean?What is a task?What about non-tasks?Prioritise to get the maximum benefit from the effort put in
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Principles to apply
Area where MAH identified = safety criticalSafety Critical Task (SCT)
There is a clear start and finishThere are discrete stepsA change of status occurs
Safety Critical Activity (SCA) where the critical aspects are:
Timing (when to perform the task)Tools and equipment to be usedInformation presentationDecision making
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Examples of SCT
Node start-up and shutdownStarting main items of equipment
Stopping same equipment often simpler
Remove, calibrate and replace relief valve or bursting diskLeak or pressure test.
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Examples of SCA & how to address
Control/optimise process Human Machine Interfaces (EEMUA 191/201)
Emergency responseEmergency planning/staffing assessment
Routine maintenance/inspection Planning and schedulingCompetence of personnel, permit to work
One-off tasks (e.g. temporary repair)Risk assessment and management of change.
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SCT or SCA depends on circumstance
Changing operating modeManual stop or tripCheck/calibrate transmitterFunction test tripMaintain process equipment
Contractor management
Prepare plant for maintenanceNormal shutdown?
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Conclusions
Linking human factors with other process safety activities has great benefits
Linking all process safety activities should be the aim
Differentiating SCT and SCA helps clarify the way forwardNeeds to be continuous and iterative
Changing the approach to human factors is not the only requirementProcess safety studies need to be modified to provide better date for human factors studies.
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