50
Sensemaking in Safety Critical and Complex Situations
CONCLUSIVE SUMMARY
This chapter summarizes the experiences from developing and applying a tool for
ranking the criticality of operational barrier elements. Operational barrier elements
are safety critical tasks required to realize ( i.e. perform) barrier functions implemented to prevent, control or mitigate hazardous conditions and events with potential
of causing major accidents. The rationale for using such a tool stems from the need to
identify and select which operational barrier elements to prioritize in further analysis
and follow-up activities as part of HF engineering or during operations.
Although several tools are available in freely accessible guidelines, attempts to apply
these tools to operational barrier elements revealed that they were suboptimal for such
use. They either proved to be too complex or targeted at specific systems and operations,
or overly simplified and coarse in how they ranked criticality. While acknowledging that
task criticality is a complex phenomenon, efforts were put into developing a tool which
was as user friendly as possible, but without compromising on the ability to accurately
distinguish more and less critical operational barrier elements. Definitions of what characterizes safety critical tasks were therefore developed and further transformed into a
“ roadmap” for determining criticality for operational barrier elements.
The presented tool ( i.e. roadmap) is qualitative and intended to be flexible in its
use to allow for expert judgement. Numerical scoring is not required and documenting the justification behind the criticality ranking is considered irrelevant, perhaps
with the exception for highly critical operational barrier elements which may require
substantial resources as part of further work. Experience from practical applications of the tool ( Ludvigsen et al., 2018) shows that it is successful at distinguishing
between operational barrier elements with high, medium and low criticality in what
is considered a sensible distribution. While the tool should also be applicable to other
types of safety critical tasks than operational barrier elements, adjustments may have
to be done for it to be suitable for tasks with risk of introducing latent failures into
the system, so called Type A actions. However, an argument is made about how
approaches such as safety critical task analysis ( or similar processes) may not be the
most useful for managing such risks. It is instead encouraged to integrate HF principles and methods into other types of safety studies and risk analysis, such as HAZOP,
LOPA and FMECA. Such techniques are intended for complete reviews of systems
and can identify issues related to safety critical tasks with minor additional efforts.
This will allow for time consuming and to some degree overlapping HF analyses to
be skipped, and resources can instead be spent on implementation of measures targeted at improving design, procedures, training and other factors influencing human
performance. As such, international standards such as IEC 61882 and IEC 60812
( among others) should be examined to check whether they could provide guidance on
how to address HF issues as an integrated part of the safety study.
REFERENCES
Bridges, W. ( 2011). LOPA and Human Reliability – Human Errors and Human IPLs ( Updated).
Prepared for Presentation at American Institute of Chemical Engineers 2011 Spring
Meeting 7th Global Congress on Process Safety Chicago, Illinois March 13–16, 2011.
Sensemaking in Safety Critical and Complex Situations
CONCLUSIVE SUMMARY
This chapter summarizes the experiences from developing and applying a tool for
ranking the criticality of operational barrier elements. Operational barrier elements
are safety critical tasks required to realize ( i.e. perform) barrier functions implemented to prevent, control or mitigate hazardous conditions and events with potential
of causing major accidents. The rationale for using such a tool stems from the need to
identify and select which operational barrier elements to prioritize in further analysis
and follow-up activities as part of HF engineering or during operations.
Although several tools are available in freely accessible guidelines, attempts to apply
these tools to operational barrier elements revealed that they were suboptimal for such
use. They either proved to be too complex or targeted at specific systems and operations,
or overly simplified and coarse in how they ranked criticality. While acknowledging that
task criticality is a complex phenomenon, efforts were put into developing a tool which
was as user friendly as possible, but without compromising on the ability to accurately
distinguish more and less critical operational barrier elements. Definitions of what characterizes safety critical tasks were therefore developed and further transformed into a
“ roadmap” for determining criticality for operational barrier elements.
The presented tool ( i.e. roadmap) is qualitative and intended to be flexible in its
use to allow for expert judgement. Numerical scoring is not required and documenting the justification behind the criticality ranking is considered irrelevant, perhaps
with the exception for highly critical operational barrier elements which may require
substantial resources as part of further work. Experience from practical applications of the tool ( Ludvigsen et al., 2018) shows that it is successful at distinguishing
between operational barrier elements with high, medium and low criticality in what
is considered a sensible distribution. While the tool should also be applicable to other
types of safety critical tasks than operational barrier elements, adjustments may have
to be done for it to be suitable for tasks with risk of introducing latent failures into
the system, so called Type A actions. However, an argument is made about how
approaches such as safety critical task analysis ( or similar processes) may not be the
most useful for managing such risks. It is instead encouraged to integrate HF principles and methods into other types of safety studies and risk analysis, such as HAZOP,
LOPA and FMECA. Such techniques are intended for complete reviews of systems
and can identify issues related to safety critical tasks with minor additional efforts.
This will allow for time consuming and to some degree overlapping HF analyses to
be skipped, and resources can instead be spent on implementation of measures targeted at improving design, procedures, training and other factors influencing human
performance. As such, international standards such as IEC 61882 and IEC 60812
( among others) should be examined to check whether they could provide guidance on
how to address HF issues as an integrated part of the safety study.
REFERENCES
Bridges, W. ( 2011). LOPA and Human Reliability – Human Errors and Human IPLs ( Updated).
Prepared for Presentation at American Institute of Chemical Engineers 2011 Spring
Meeting 7th Global Congress on Process Safety Chicago, Illinois March 13–16, 2011.