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Air Compressor Pressure Relief Valve Sizing

Air Compressor Pressure Relief Valve Sizing

Air Compressor Pressure Relief Valve Sizing

(OP)
Hi All,

I've been asked to review the safety relief valve capacities on an existing Ingersoll Rand (IR) air compressor and size a PRV on the air receiver. The information I received from IR has a rated output of 58 ACFM and the max pressure is 250 psi. The pressure safety valves supplied by IR compressor are rated for 172 SCFM @ 65 psi on the first stage and 267 SCFM @ 325 psi on the second stage. Shouldn't the second stage relief valve be set at 250 psig? IR was unable to provide the output in SCFM so I did the conversion to SCFM using 250psi for p and I get about 1,024 SCFM which is far greater than the relieving capacity of the IR supplied relief valves on the compressor. Have I done my conversion from ACFM to SCFM incorrectly? Do safety relief valves need to relieve the full capacity of the compressor? Is there other information I should be IR for to do the conversion to SCFM?

Thanks in advance.

RE: Air Compressor Pressure Relief Valve Sizing

It's rare to see a relief valve set at exactly the max operating pressure so the pressure looks OK, but the flow is over 1000scfm.

But what type of compressor do you have?

What is the rated flow at 325psi?

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Also: If you get a response it's polite to respond to it.

RE: Air Compressor Pressure Relief Valve Sizing

(OP)
Thanks for the reply LittleInch. It’s an Ingersoll Rand H15TX20, 20HP, 2 stage air compressor. Unfortunately, after several calls with IR, the only flow information I can get from them is 58ACFM. I asked if there was a pressure associated with that but, all they could tell me was the max operating pressure is 250. Any thoughts?

RE: Air Compressor Pressure Relief Valve Sizing

Ah ok - two stage Piston type large shop air compressor.

This from IR website states 15TE20 is 72 cfm @ 90 psig. Now on your sheet that relates to the lower pressure unit.

The higher pressure H unit runs slower (900 rpm) and 58 acfm. Now the indication is that this is also at 90 psig.

The 250psi seems to relate to the maximum pressure, but the acfm @90psi will be the same, so about 415 SCFM.

Add the two relief valves together and you get 430.

Makes sense to me...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Air Compressor Pressure Relief Valve Sizing

(OP)
Thanks again for the reply. I follow your logic and I think that’s what I’m going to have to use. It would be nice if IR could confirm but, as The Rolling Stones song goes, “you can’t always get what you want”.

RE: Air Compressor Pressure Relief Valve Sizing

I think it's hidden in plain sight, but agree, they don't always know themselves sometimes..

This was the link which didn't copy for some reason https://www.ingersollrand.com/en-us/air-compressor...

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