PRV opening prematurely on 919.176920

by Manuel Reyes
(Orange, CA USA)

Older Sears compressor

Older Sears compressor

Older Sears compressor
Close up of PRV and Switch
Label close up showing CFM info.

Trying to use older Sears compressor that has been sitting idle for at least 20 years.

It's a 2 HP / 12 Gallon portable unit.
The Mfg. plate spot welded on tank says 125 psi at 350 degrees, DeVilbiss Co. 1986.

Sears Decal on tank reads – Max 100 psi Model No. 919.176920

Slight oil film on tank, and switch handle doesn't turn on or off the compressor. Plug it in to run and unplug it to stop. Not too convenient or sounding too safe.

Main problem is that the PRV opens up at 80 psi. Thought PRV was faulty so bought a new
125 psi PRV and it still opens up at 80 psi.Can't build up higher working pressure with PRV
blasting out air.

Could use some help here. How do I / we fix this problem. Need air to finish a project.

Appreciate any assistance you can give me.

Comments for PRV opening prematurely on 919.176920

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Jul 31, 2016
by: Doug in

Another thought -

If you open the regulator all the way (just to where it loosens up...) the regulator gauge might give you another way to check the tank gage.

Jul 30, 2016
PRV opening prematurely
by: Manuel Reyesl

I never clicked on the link for your comments. So after 1 month I'll try to address the solutions both of you recommended.
To repeat myself...the 125 psi PRV is new from Graingers. Could that much oil be in the air that would make it pop off prematurely?
Thanks for your comments.

Jun 27, 2016
by: Doug in

You probably should put another gauge on it, too.

From the sound of it, I'm fairly certain it's reading on the low side by 20PSI or so.

Even if I'm wrong, it's worth a look/check.

Jun 26, 2016
PRV opens
by: Bill

Very odd about the PRV, particularly when you got a new one.

I suspect a high level of oil is being pumped into the air, and that's lubricating the PRV innards so that the PRV cracks way too early. That or you've got another bum PRV.

Drain the tank thoroughly.

Try rinsing the PRV in solvent and after letting it dry, reinstall it and see if the cracking pressure rises. If it does, it certainly suggests lots of compressor oil in the air.

Since the cut out pressure of the compressor is 100 PSI, I'd be happier of the PRV had a cracking pressure of 115 PSI rather than 125 PSI if one was available.

As to "Plug it in to run and unplug it to stop", if the tank pressure is low, plugging it in to start emulates the ON/OFF switch. If the tank pressure exceeds the 100 PSI cut out setting however, you likely have a bum pressure switch, and that I wouldn't mess with.

After dealing with the PRV and pressure switch, replacing the ON/OFF switch should be fairly straightforward. Good luck.

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