3. 3
Risk profile
Hazard detail
Engineered Human
Hierarchy Task or activity
1. Instrument
2. Alarm
3. Trip
4. Mechanical
Task
analysis
1. HMI
2. Deviation response
3. Emergency
4. Generic competence
5. One-off risk assessment
6. Automated
Prioritise according to risk of MAH
QRA, HAZID
Identify deviations leading to MAH
HAZOP, PHR
ALARP
HSE Roadmap
Barriers
Bowtie?
4. HAZOP and human factors
Safeguards with human component
Monitoring and control
Alarm response
Training or procedure???
Safeguard maintenance
Tasks considered as potential causes of
deviation
Recommendations.
4
5. 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 factors
But creating good links between HAZOP and
human factors could be very beneficial.
5
6. Use HAZOP to structure task analysis
HAZOP nodes
Focus on deviations that can result in Major
Accident hazards (MAH)
Use causes of deviations to identify tasks
Consistent reference to causes and
consequences.
6
9. 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
9
10. Principles to apply
Area where MAH identified = safety critical
Safety Critical Task (SCT)
There is a clear start and finish
There are discrete steps
A change of status occurs
Safety Critical Activity (SCA) where the critical
aspects are:
Timing (when to perform the task)
Tools and equipment to be used
Information presentation
Decision making 10
11. Examples of SCT
Node start-up and shutdown
Starting main items of equipment
Stopping same equipment often simpler
Remove, calibrate and replace relief valve or
bursting disk
Leak or pressure test.
11
12. Examples of SCA & how to address
Control/optimise process
Human Machine Interfaces (EEMUA 191/201)
Emergency response
Emergency planning/staffing assessment
Routine maintenance/inspection
Planning and scheduling
Competence of personnel, permit to work
One-off tasks (e.g. temporary repair)
Risk assessment and management of change.
12
13. SCT or SCA depends on circumstance
Changing operating mode
Manual stop or trip
Check/calibrate transmitter
Function test trip
Maintain process equipment
Contractor management
Prepare plant for maintenance
Normal shutdown?
13
14. 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 forward
Needs to be continuous and iterative
Changing the approach to human factors is not the
only requirement
Process safety studies need to be modified to provide
better date for human factors studies.
14