Sears compressor 12 yr old blows pressure relief valve.

by Ferdi
(Houston, TX.)

My Sears compressor cutting-off pressure is not working.


Also when trying to inflate the tires of my SUV it isn't doing anything even though good air flow is coming from the inflating adapter.

The tank pressure gage is set up for 120 CFM. It goes up to 140 or more and then the safety valve kicks off and the tank is depleted to 80 cfm.

The out-pressure valve is set for 100 PSI which should be enough for my tires and for my compact wrench to operate but also I'm not getting enough power out of it.

What could be wrong? Does the air hose diameter have anything to do with it? I'm using the original which I believe is a 1/4 or 5/8 rubber hose with a nylon sleeve.

Thanks for the help.






Comments for Sears compressor 12 yr old blows pressure relief valve.

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Apr 15, 2008
Problem with pressure on a Sears Compressor
by: Bill - Publisher

Ferdi...sorry to take so long getting back to you. I posted a response to your question a while ago, but I guess it got lost in the internet ether and didn't get to the site.

In any case....your question asks a bunch more.

"The tank pressure gage is set up for 120 CFM. It goes up to 140 or more and then the safety valve kicks off and the tank is depleted to 80 cfm."

Ferdi, get a new pressure switch. The PRV is a safety backup. Your pressure switch is supposed to shut the compressor off when it reaches the high set point. Don't rely on the PRV.

"...when trying to inflate the tires of my SUV it isn't doing anything even though good air flow is coming from the inflating adapter." If your compressor has up to 140 PSI coming out of it, that pressure should blow your tire up to 30-35 PSI no problem.


"The out-pressure valve is set for 100 PSI which should be enough for my tires and for my compact wrench to operate but also I'm not getting enough power out of it." The out pressure valve you speak of is the pressure regulator and if it's set for 100 PSI, then that's what should be coming down the line to your tire. If the tire won't inflate, and air is coming out of the tire fill valve on the end of the air line, then your regulator is fried. It may be showing 100 PSI, but you aren't getting it. Put a fitting on the end of your air line, with an air gage to see what the pressure is at the end of the line. It should be almost the same as what's showing on your gage at the regulator.

As to the hose size, even if through a needle sized hose, 100 PSI flowing into your tire would eventually blow it up. So, if after a minute or so you aren't seeing your tire inflate then either the backpressure inside the tire is preventing any more air to get into it (your regulator is pooched) or the valve on the tire itself is broken and not letting air into the tire.

Now, when it comes to impact wrenches, you need much higher flow at the recommended pressure. That's where you want to use an air line with a higher flow, to get more air to your tool faster. Check here for into on PRV's, Regulators, and Air Lines.

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Speedaire comrpessor PRV source

by David

I have a Speedaire compressor, Model # 3Z124C and the spring loaded pressure relief has gone out and needs replacing. I am looking for the part and price. If you could give me any information I would appreciate it.






Bill answers...

Hello David, and thank you for visiting my website and for writing in.

Check out the Speedaire page linked from the Nav bar to help for your closest supplier of Speedaire parts.

Or, check out the Repairs page to see if there's a local repair shop that can help you.

I would think that PRV's are pretty basic. As long as the cracking pressure for two different units is close, and the plumbing fits, I would suspect you can use any PRV from any compressor store.

Cheers,

Bill

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Blowing off valve

by Mark

I have a 5Z630 air compressor and the pop off valve that is located on the center cylinder blows off continually while running. My question is: What causes this and how would I repair it? ( I have changed safety valve already )






Bill says...

Howdy Mark.

You have a multi-piston compressor, and I suspect that the compressed air flows from piston to piston, increasing pressure as it goes, and then flows from the last cylinder into your tank.

That being the case, there must be a check valve between pistons to ensure that the higher pressure doesn't flow back towards the low pressure piston.

If that check valve has failed, then the higher back pressure could blow the PRV.

Cheers,

Bill

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Relief valve on discharge line

by Dave Giles
(TN)

What is the purpose of the relief valve on the discharge cross over line on a 2 cylinder compressor? Thanks

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Apr 15, 2008
Relief Valve on Discharge Line
by: Bill - Publisher

Dave, a two cylinder compressor is often a two stage compressor.

The air gets preliminary compression in the first cylinder, and then that already compressed air gets further compressed in the second cylinder as it sends air into the receiver.

Since PRV's are used in many places to ensure that over-pressurization and catastrophic failure of a pressure vessel can't occur, the engineer that designed your compressor decided that the cross over line was where one was needed in that compressor's design.

Can't think of any other reason.

Cheers,

Bill

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