Monday, October 31, 2022

Reader Comment – Fail Open Valves

A long-time reader, and former CSB insider, Rosearray posted a comment to my blog post about the publication of the CSB report on the PES fire and explosions. He was kind enough to post my discussion to the AIChE Engage Discussion Central (not a site to which I have direct access), and he noted that it received an interesting comment (Rosearray quoted it in his comment here). The comment from a PE addressed my suggestion that the control valves for the HF deluge system should have been designed to ‘fail open’. He noted (in part) that:

“The preference for making the deluge valves fail open may seem obvious when viewed through the lens of one particular scenario. But one must also consider the consequences in other circumstances, such as during normal operation in cold weather. If the deluge valve failed open for any reason, the entire area could be coated in a thick layer of ice, and that may also create conditions adverse to process and personal safety.”

And he is absolutely correct. That is one of the reasons that process safety reviews of any sort always (hopefully anyway) include more than one person, with multiple backgrounds. This way, problems with a ‘perfectly good’ solution can be identified and corrected before someone has to figure out how to chip ice away from a manual valve that just has to be closed right now.

Needless to say, I recommend that readers interested in process safety read the entire comment.

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