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RE: Actuation and Interlocks of Valves



How about interlocking PSV MOVs with vent valves? For our new coker, the Licensor is recommending an interlock that will prevent closing PSV Mov’s before opening the vent valves right after closing to blodown, when drum is quenched and ready for drain; the expected drum pressure at that point is about 10 times lower than PSV set point.
In your experience, is there any other reason for this, than jsut drum safety protection?
and, how about the potential for backing H2S from blowdown header? wouldn’t it be a lesser risk blocking PSVs first.
I appreciate your feedback,  

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