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[ayan_dg]

What is the difference between an ERV (Emergency relief valve) and a PSV ?

[Art Montemayor]

Ayan:

An emergency relief valve is a term normally used for a device used on an atmospheric storage tank (API 650 type). This device is used as a means of¨"last resort" - in other words, it is intended to work by opening wide open and saving the tank in the event a catastrophic over-pressure should occur and the normal relief devices are over-whelmed. This would constitute an "emergency" and that is the name given to the device. Physically, the device usually is nothing more than a weighed, blind flange set on top of a large flanged nozzle. The blind flange can be hinged or, when the user is a cheap skate, it can simply be chained to the base flanged nozzle. These precautions are taken in order to avoid having a heavy piece of steel flying through the air during an emergency discharge.

I am not going to define a PSV because that is something you should be familiar with and you can easily research or look it up on the internet.

I hope this explanation has helped you out.