Procedural drift
When a plant is first built, operating procedures are written to allow the plant to be operated as intended. The initial procedures always contain a few errors and are generally marked up for correction during the commissioning period.
Almost as soon as the procedures are completed, they begin to be out of date. The plant is modified slightly, the company works hard during the first years to increase output and operators ‘improve’ procedures to make work easier. A classic example is a change in a procedure when an operator is required to access a valve that is inaccessible or requires a long climb.
Even with very well-regulated procedures, there will be changes. Change in raw material quality or change in product specifications forces change in operating parameters and sometimes requires change in procedures too.
Written procedures may or may not be updated for these reasons, and procedural drift may occur, where the actual procedure differs from the written procedure.
Procedural drift becomes insidious if they improve production rate or improve convenience but at the same time push the plant to the limit of the operating envelope.
Accidents with this kind of effect are not common in accident reports, but struggling with control is a periodic problem in some plants. Many incidents arise because new phenomena which were not considered in the original design occur or develop with time.
Written procedures may or may not be updated for these reasons, and procedural drift may occur, where the actual procedure differs from the written procedure.
Procedural drift becomes insidious if they improve production rate or improve convenience but at the same time push the plant to the limit of the operating envelope.
Accidents with this kind of effect are not common in accident reports, but struggling with control is a periodic problem in some plants. Many incidents arise because new phenomena which were not considered in the original design occur or develop with time.
Reducing procedural error
Apart from checking the completeness of the procedures, checking using the UK HSE Recommendation for Operating procedure is a very good idea.
However, to capture most mistakes, a workshop is recommended to be carried out which includes operators, and following HAZOP practice in which everyone has access to a set of plant drawings and specific guidewords are used.
However, to capture most mistakes, a workshop is recommended to be carried out which includes operators, and following HAZOP practice in which everyone has access to a set of plant drawings and specific guidewords are used.
A good check list for writing procedures is given in following books:
Human Error in Process Plant Design and Operations: A Practitioner’s Guide by Robert J. Taylor and
Writing Operating Procedures For Process Plants by Sutton, Ian S.
Human Error in Process Plant Design and Operations: A Practitioner’s Guide by Robert J. Taylor and
Writing Operating Procedures For Process Plants by Sutton, Ian S.
REFERENCES
1. J. Robert Taylor Human Error in Process Plant Design and Operations
1. J. Robert Taylor Human Error in Process Plant Design and Operations
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