Compressor Not Sustaining Pressure.

[Bob Williams]

Hello people.

I have a Sip AS 3HP/50 compressor.

Whilst recently spraying a panel (large door), it would barely do three quarters until the main gauge dropped to 50psi and consequently the trap gauge was hardly pushing 35-40psi - NOT ideal!

I know it's not a huge compressor, but it's always been capable of such work, in fact it used to cope with a whole vehicle (with care). So obviously, as nothing else in the set-up has changed, a fault has occurred.

The head gaskets seemed OK, as do the reeds and pistons/rings/bores. Any ideas on the cut-off valve? Could that be the cause of the symptoms?

Anyway - any advice most welcome.

Bye for now.

 

[the snooper]

did you clean the reeds and the seats just to make sure they work correctly ? have you also checked the non return valve from the receiver the only other thing is wear I suppose and leaks from joints, is the delivery pipe copper ? check it for cracks

 

[Rig Pig]

Has it got an unloader valve?

 

[mfletch]

Air cleaner dirty??

 

[rtbcomp]

Can you feel air escaping from around the pressure switch?

 

[gordon stephenson]

Is it one of the compressors that uses a wobble "piston" and just has a nylon/teflon seal, just like a bike pump?

 

[Robotstar5]

Is the receiver full of water?

 

[Bob Williams]

Thanks for all your replies. Life got in the way and I've only just managed to get back to the forum!

We didn't look at the non-return valve and after a bit of research I see they can suffer with carbon build up, so I'll strip it down and take a look. The reeds are a little dirty so maybe they could be the cause - we'll clean them carefully before assembly

There didn't appear to be any leaks, but it was hard to tell when running because of the fan. At rest all was fine, so at least the non-return valve was closing OK - whether it's opening fully is another matter.

I assume an "unloader valve" is different to the pressure switch?

No, the Pressure Switch is not leaking and the filters AOK.

No, it's not a wobble piston - it's a twin with rings.

The receiver is drained every Saturday or more frequently even, so no, it's not full of water.

HUGE UPDATE THOUGH. Having personally looked at the gaskets (someone else stripped it down), there is damage to one of them that would certainly cause a leak around one of the bolts (although when it was running I couldn't feel it - I wished I'd done a soapy water test before it was eagerly stripped down!).

All being well, I'll look at the non-return valve tomorrow and then order the gaskets and valve parts (if necessary) and if things aren't going well - I'll be back.

Thanks again all, bye for now.

 

[Rig Pig]

Whilst it's in bits measure the bores to check how round they really are. The unloader is the dump valve that drops the outlet pressure from the pump on startup to ease the load on the motor.