75 PSI pressure valve popping on cross line?

by David
(Cleveland, Ohio)

PRV hidden, not on list!

PRV hidden, not on list!

Speedaire 7.5 hp upright compressor has a 150 psi tank mounted PRV that is ok.
By the head, there is another PRV that is 1/8 npt and 75 psi rated. I have to keep the compressor set at a lowly 70 psi to keep that valve from popping.

I had the compressor running at 110 psi for the last 6 months with no problems. All of a sudden in the last two weeks I have had to keep adjusting the pressure down lower and lower to keep it from popping while I figure out the problem.

Do I have a head problem? Or do I just have a bad PRV? Or am I missing something elsewhere?





Bill says...

From the look of your diagram, the "cross-over" line you refer to is the one that runs over to the pressure switch.

The PRV senses the pressure in the system, and is set to "blow off" at a certain pressure, if the pressure in your system approaches what is deemed unsafe.

I've never hear of a PRV set to go off at 75 PSI. That doesn't make sense if it's purpose is to prevent over-pressurization, and the system pressure is 125 PSI.

If you could identify in the diagram the number of the PRV, maybe I could help identify the problem more closely.

However, if the PRV is letting to at 75 PSI now, and it didn't when you had the system pressure at 110 PSI, why? I can't that it would be anything but the PRV, yet I don't have a lot of experience with one of them failing, unless after it lets go, it isn't closing properly and then requires less pressure to open again. Here's more info.

Cheers, and thanks for writing in.

Bill




Comments for
75 PSI pressure valve popping on cross line?

Click here to add your own comments

Aug 26, 2011
 help
by: Michael

What do you suggest I do?

Will taking apart head and valve plate assembly out and clean/replacing those part remedy the problem?

Thanks in advance!

------------------

As per an earlier post... "What is happening is a failure of the high pressure valve allowing the doubled air pressure back into the primary which pops the safety each stroke causing it to flutter. You need to get a high pressure rebuild kit for the reed valves."

Still sounds like good advice.
Aug 26, 2011
 my problem also.
by: Michael

I think is also my problem.
The PRV at the start of the intercooler is popping on and off until tank gets max psi at 175.

Can I just replace the PRV with a cap?
or just use it as is? since the compressor is still doing what it's suppose to?

Thank you!

____________________

I would never, ever, cap or replace a PRV with a non-pressure relieving valve. Ever!
Dec 24, 2009
 Safety popoff on low pressure feed line 2 stage compressor
by: Anonymous

What you have is a two stage compressor.

There is a safety pop-off valve between the high and low cylinders. The low pressure cylinder pushes air around 60 psi into the high pressure cylinder which doubles the output pressure.

What is happening is a failure of the high pressure valve allowing the doubled air pressure back into the primary which pops the safety each stroke causing it to flutter. You need to get a high pressure rebuild kit for the reed valves.
_____________

Sounds like good advice to me. Thanks very much.

B.

Click here to add your own comments

Join in and write your own page! It's easy to do. How?
Simply click here to return to Compressor PRV Valve Opens