Bryan,
Here are some observations related to Bayer PHA effectiveness, as mentioned in the CSB report.
The Chem Safety Board Incident Investigation Report for the Bayer incident was very critical regarding the quality / effectiveness of the PHA study. Please take a look over the attached extract from the report and keep these items in mind when you lead your next PHA. Although the Chem Safety Board has no regulatory authority, in many instances they represent the perspective of OSHA regarding what is considered recognized and generally accepted good engineering practices.
It is easy to look back after a disaster and identify what could have been done better to prevent or mitigate the event. It is much harder during a PHA study to decide what is an appropriate level of detail and what is an appropriate degree of reliability of a particular safeguard or set of safeguards. According to the Chem Safety Board;
1. The PHA team failed to validate critical assumptions (page 53).
2. The PHA team failed to make any recommendations regarding management of changes to computer controls (bottom of page 54).
3. The PHA team apparently failed to adequately incorporate and/or use known Process Safety Information (page 55). According to the CSB the team decided high methomyl concentration was not a safety concern, only an operational issue. Apparently the design information stated that the pressure relief system was incapable of preventing a catastrophic failure if the methomyl concentration was too high. This fact was either ignored by the PHA team or the team did not properly address this potential process hazard.
4. The PHA team did not properly identify and address human factors (page 56).
5. The PHA team should have, but did not conduct a procedure-based HAZOP for this batch operation & startup. ( J Philley comment – this is a decision each PHA team needs to make based on the complexity and severity of consequences for batch operations. Critical procedure steps need to be carefully considered.)
I do not have the full information, but I do not think I agree or understand the comment on page 53 that the PHA team poorly executed because they did not spend sufficient time. The team apparently met for 12 days, 6 hours/day. If these was consecutive days, then perhaps I can understand the team not executing properly due to fatigue. However if the days were not consecutive, then I do not understand the comment that insufficient time was devoted to the study. The report does not discuss the scope and boundary limits of the study. The team did 37 nodes in 12 days, which is about average. The team may not have set the scope of the review properly, but the report does not discuss this issue.
Jack Philley
Process Safety Specialist
Baker Hughes
(281) 275-7262
Integrity, Teamwork, Performance, Learning