Pressure relief valves and pressure regulators - what's the difference?

[EllieWest83]

What is the difference between a pressure reducing valve and a pressure relief valve? pressure-reducing/regulating/ relief/release - There are so many different options available!

I read this article on Fluid Controls that did a really good job of explaining pressure regulators, but I am a bit lost on the difference between regulators and relief valves.

 

[btrueblood]

A relief valve is intended to stay closed and sealed until a limit pressure is exceeded, at which point it opens fully. It may not re-close (some boiler safety relief valves operate this way, as do burst discs and similar) or may re-close only at a substantially lower pressure than the opening pressure (perhaps 80% of the opening pressure).

A pressure regulator will be designed to open and close in a very narrow band of pressure, and may or may not really shut off tightly. How narrow that regulation band is, and how repeatable the band is across a flow rate range depends a lot on the design of the regulator...and money.

 

[handleman]

Additionally, a regulator limits the pressure on its downstream side by only allowing fluid to pass until the set pressure is reached. The fluid that passes through the regulator is intended to be used by the process. A pressure relief valve controls the pressure upstream from it by dumping excess pressure to the atmosphere/return/drain/whatever, often as mentioned by btrueblood without resetting.

There are some processes (usually liquid) that use back-pressure regulators to maintain the desired pressure upstream in the processing system. They are more similar to pressure relief valves, but they dump excess pressure in a much more controlled manner into the return.

 

[KarenBurton]

Does anyone have any preferred valve suppliers for this type of situation?

There's just so much variety and there's distributors then brands etc - Im looking at doing a placement with BM Engineering next year anad wondereded if anyone had any experience with them and their products??

 

[fel3]

YT has some video animations of control valve operation, which might help. Search for "control valve animation". Some control valve manufacturers have these animations on their websites. I am most familiar Cla-Val (

https://www.cla-val.com/).

Cla-Val also has diagrams that show how the valves are plumbed and how they can be used in a system.

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