One of my co-workers asked me about the requirement for a PSV for fire relief case of the shell side of a heat exchanger. We currently do not have a PSV on the shell. The shell has a mixture of 97% isobutane and the remainder other C3-C5's. The tube contains a glycol mix and runs at the lower pressure. I haven't sized PSV's recently - years ago at a previous employer the policy was to only consider fire case on the shell side for exchangers if they had a significant volume of liquid (reboilers etc.). My co-worker could not find anything specifically in API-520/521 that mentioned the liquid volume of the exchanger being a factor in whether a fire case PSV is required. Does anyone know what the current standards are for whether a PSV is required for fire case on an exchanger shell?

trishk,

Welcome...

I would invite you to read the following posts. You may get some ideas / answer to your question.

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API 521 / ISO 23251, Jan 2007 section 4.3.14, 5.15, 5.16 and 5.19 may provides answer to your question.

JoeWong