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Compressor part??
- Thread starter 4lug39
- Start date
Jbullfrog
ALLIANCE MEMBER
check with devilbiss, they are the OEM for most compressors.
http://www.devap.com/
http://www.devap.com/
clueless
Well-known member
what i see is the pipe out of the tank to a t,on the right is a safety valve,designed to blow off at possibly 150 psi to prtotect the tank,left is the gauge,on top is the cut in/off switch,that lets it cut in at a certain pressure,out at a certain pressure.
MAD
Well-known member
Is this a check valve or an unloader valve? Where do I get a replacement ____ valve? Mine went south this week. I couldn't get the camera to focus.
James
I believe the correct term for what is pictured is an Air compressor pressure switch. The unloader is the part of the pressure switch assembly that bleeds air (through the small tubing) from pump cylinder(s) when the switch shuts off the pump motor. The unloader allows the pump to start the next cycle with no pressure on it for a softer start.
Your pressure switch looks similar to mine which is a Square D Pumptrol FHG series Pressure switch available from Grainger. The part # on mine is on the plastic cover. If you have the cover that may help you match the correct one for your compressor. Your switch looks like it may have an adjustment for the pressure differential as well as the cut off pressure.
The pressure release valve (out of focus picture) for the unloader is available as well from Grainger if it is a Square D pressure switch.
If the problem is that tank pressure is leaking from the unloader pressure release valve, the problem could be a bad check valve between the pump and the tank.
Link to compressor pressure switches from Grainger:
http://www.grainger.com/Grainger/wwg/productIndex.shtml?originalValue=Compressor+Pressure+Switch&L2=Air+Compressor&operator=prodIndexRefinementSearch&L1=Pressure+Switches%2C
Last edited:
Major Ramifications
Well-known member
Why do you need a new one? Is it leaking when the compressor is running?
If it is leaking air when the compressor is shut off, then the problem is with the check valve farther upstream.
If it is leaking air when the compressor is shut off, then the problem is with the check valve farther upstream.
MXtras
Well-known member
The pressure relief valve relieves pressure and is there to protect the tank from explosion. It's the thingy with the ring on it. If replaced, the CFM of the replacement releif valve must match or exceed the original (which should be MORE than the CFM potential of the pump).
The check valve allows air into the tank from the pump, but not out. It's located where the line from the pump goes into the tank and most will have the connection for the unloader line. When the check valve goes bad, it will cause the unloader to constantly hiss and it can also make your the compressor either start really slowly or not start at all.
The unloader is a mechanical relief valve that is actuated by the pressure switch. When the pressure switch "sees" the set pressure, it flips the motor off and mechanically releases the pressure in the pipe between the pump and the tank by depressing the plunger on the unloader. This gives the motor a fair shake at firing up to full RPM without much of a load. If the head pressure was not released, the motor would not be able to spin the pump - too much resistance from the already pressurized pump.
Scott
The check valve allows air into the tank from the pump, but not out. It's located where the line from the pump goes into the tank and most will have the connection for the unloader line. When the check valve goes bad, it will cause the unloader to constantly hiss and it can also make your the compressor either start really slowly or not start at all.
The unloader is a mechanical relief valve that is actuated by the pressure switch. When the pressure switch "sees" the set pressure, it flips the motor off and mechanically releases the pressure in the pipe between the pump and the tank by depressing the plunger on the unloader. This gives the motor a fair shake at firing up to full RPM without much of a load. If the head pressure was not released, the motor would not be able to spin the pump - too much resistance from the already pressurized pump.
Scott
Steve in Mi
Well-known member
The cut-in/cut-out pressure switch should be available at most any auto parts store, ACE hardware and Tractor Farm Supply. Critical is making certain a replacement meets or exceeds the amperage of your motor unless you have a magnetic starter in which case about any will do as the starter coil draw is very small.