I'm doing some reading on the TMI incident.

There were human factors at play, but a critical pilot operated relief valve was also faulted. I've seen this noted in many reports (Rogovin report) as well as all over the net and unfortunately also Wikipedia which everyone references.

What I don't find is what exactly was the mechanical fault of this particular valve. As it turns out there were other failures in plants of similar design in the same valve/gate valve (from different manufacturers).

I've done what scouring I can do to find out. What do you know about it? As valve designers, it seems like this is the kind of 'learning from history' is a good thing.

About a year ago I spoke with someone at Ferris engineering on the matter of failing PORV's. He himself said that the PORV sales have descresed rapidly over the past decade. They are useful in some applications, but I would much rather have a mechanically controlled relief valve than one that uses system pressure.

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