41
What Makes a Task Safety Critical?
“ main site hazards” ( i.e. MAHs). For their second step, identification of safety critical tasks, they recommend looking into documentation which specifically addresses
those hazards. Safety critical tasks ( and operational barrier elements) can be identified as either causes or safeguards in safety studies such as hazard identification
( HAZID)/ hazard and operability ( HAZOP), LOPA and QRA and also as part of
other documents such as operating and emergency procedures, safety strategies and
philosophies, as well as technical specifications and requirements.
It should be noted, however, that EIs guideline does not apply the term “ barrier
function” or the Type A, B and C categorization directly as part of their safety critical task analysis method. Instead, this is partly addressed implicitly through how
they define safety critical tasks as tasks where human factors ( HF) can contribute to
MAHs in positive or negative ways, including:
• Initiating events;
• Prevention and detection;
• Control and mitigation, and;
• Emergency response.
However, despite this definition, the examples provided in the guideline suggest that
safety critical tasks are analysed bottom-up according to their operational goals ( e.g.
“ unit start-ups”) instead of a top-down approach based on the safety critical tasks
( i.e. operational barrier element) role in performing barrier functions ( e.g. maintain
containment during work on equipment with pressurized hydrocarbons). As such, the
approach developed for identification of operational barrier elements was inspired by
EIs guidance, but still adopted with the modifications necessary to better align with
the framework and definitions of barrier management.
WHAT MAKES A TASK SAFETY CRITICAL?
The next step of the process ( Step 2) – and the core topic of this c hapter – involves
screening the operational barrier elements to determine their level of criticality.
Guidance provided by Health and Safety Executive UK and EI was again reviewed
for inspiration regarding method development. The former contains a comprehensive
approach which involves rating the criticality of offshore production tasks or well
operations based on scoring the answers to a set of pre-defined questions. Task criticality is ranked as high, medium/ high, medium, medium/ low or low based on which
intervals the diagnostic score falls within. The same approach was used by the developers to risk rank the generic task inventories published as part of the guidance note.
As it turned out, when attempts were made to apply the method for rating the criticality of operational barrier elements, several challenges emerged ( see Table 3.4).
While the questions used to diagnose criticality appear relevant, to some degree,
the way they are phrased makes them more suitable for normal production activities
and less for operational barrier elements. This also reflects the “ generic tasks” listed
in the guidance note for which they have been used to rank criticality. Another challenge was that the scoring system was not calibrated to differentiate between operational barrier elements with higher and lower criticality. This was apparent by how
What Makes a Task Safety Critical?
“ main site hazards” ( i.e. MAHs). For their second step, identification of safety critical tasks, they recommend looking into documentation which specifically addresses
those hazards. Safety critical tasks ( and operational barrier elements) can be identified as either causes or safeguards in safety studies such as hazard identification
( HAZID)/ hazard and operability ( HAZOP), LOPA and QRA and also as part of
other documents such as operating and emergency procedures, safety strategies and
philosophies, as well as technical specifications and requirements.
It should be noted, however, that EIs guideline does not apply the term “ barrier
function” or the Type A, B and C categorization directly as part of their safety critical task analysis method. Instead, this is partly addressed implicitly through how
they define safety critical tasks as tasks where human factors ( HF) can contribute to
MAHs in positive or negative ways, including:
• Initiating events;
• Prevention and detection;
• Control and mitigation, and;
• Emergency response.
However, despite this definition, the examples provided in the guideline suggest that
safety critical tasks are analysed bottom-up according to their operational goals ( e.g.
“ unit start-ups”) instead of a top-down approach based on the safety critical tasks
( i.e. operational barrier element) role in performing barrier functions ( e.g. maintain
containment during work on equipment with pressurized hydrocarbons). As such, the
approach developed for identification of operational barrier elements was inspired by
EIs guidance, but still adopted with the modifications necessary to better align with
the framework and definitions of barrier management.
WHAT MAKES A TASK SAFETY CRITICAL?
The next step of the process ( Step 2) – and the core topic of this c hapter – involves
screening the operational barrier elements to determine their level of criticality.
Guidance provided by Health and Safety Executive UK and EI was again reviewed
for inspiration regarding method development. The former contains a comprehensive
approach which involves rating the criticality of offshore production tasks or well
operations based on scoring the answers to a set of pre-defined questions. Task criticality is ranked as high, medium/ high, medium, medium/ low or low based on which
intervals the diagnostic score falls within. The same approach was used by the developers to risk rank the generic task inventories published as part of the guidance note.
As it turned out, when attempts were made to apply the method for rating the criticality of operational barrier elements, several challenges emerged ( see Table 3.4).
While the questions used to diagnose criticality appear relevant, to some degree,
the way they are phrased makes them more suitable for normal production activities
and less for operational barrier elements. This also reflects the “ generic tasks” listed
in the guidance note for which they have been used to rank criticality. Another challenge was that the scoring system was not calibrated to differentiate between operational barrier elements with higher and lower criticality. This was apparent by how