PT Notes
PHA for Phases of Operation in the Process Lifecycle
PT Notes is a series of topical technical notes provided periodically by Primatech for your benefit. Please feel free to provide feedback.
Processes experience various phases or modes of operation during their lifecycle, such as startup, normal operation, and shutdown. Hazard scenarios may occur in any of these phases. The characteristics of many of these phases of operation can differ considerably from normal operation. Consequently, their hazard scenarios may be different. Therefore, it is essential that process hazard analysis (PHA) studies address all phases of operation that a process may experience. Unfortunately, current PHA practices often provide an inadequate treatment of phases of operation other than normal, or simply ignore them.
Other phases of operation may be more hazardous than normal operation for various reasons. Operators are often less familiar with them as some of these operations are conducted infrequently and equipment is used less frequently. Thus, operators are more prone to making errors. Furthermore, phases of operation other than normal are often non-steady state with greater potential for something to go wrong.
Ignoring hazard scenarios that may occur in different phases of operation cannot be justified as the risks of a process would be underestimated, possibly very significantly. PHA studies should address phases of operation for a process before a phase is experienced by the process so that an opportunity is provided to determine if risk reduction is needed before the risks are experienced.
There are no technical reasons why PHA cannot be performed equally well on all phases of operation. The obstacle is the additional time that is required beyond the consideration of normal operation but, given the record of accidents that occur in other process phases, particularly startup, the exclusion of other process phases from the scope of PHA, or the inadequate treatment of these other phases, cannot be justified. PHA studies should provide an appropriate treatment of all significant process phases.
For more information, you can contact Primatech or consult the article:
Process Hazard Analysis for Phases of Operation in the Process Life Cycle, by Paul Baybutt, Process Safety Progress, Volume 31, Issue 3, Pages 279–281, September 2012.
http://onlinelibrary.wiley.com/doi/10.1002/prs.11506/abstract
