Brunell Engineering

Apologies if this is a stupid question!
I have been refurbishing a SIP compressor. It came to me basically as a tank with a compressor and motor mounted on it. Through SIP I have acquired and replaced the pressure switch, the outlet regulator, the pressure relief valve and the drain tap.
It is has a 50 litre tank and is a belt driven type. Amongst the parts I have replaced is the pressure switch (brand new from SIP). This has two pressure connections. Both direct to the tank. There were two pipes sticking up (of the right dimension!) that seemed to fit, so I used those
I am assuming that the two form the "high" and "low" pressure switches. Switching off at >120psi and turning back on

Was the compressor already plumbed direct to the tank? Your new switch evidently includes an unloading valve, which opens at the same time as the contacts, to allow the motor to start against minimal pressure. I'm guessing that one of the switch air connections should go to the pump, and the other to the tank. I can't remember how mine is done (not SIP), but if you're stuck I can check it out later in the day.
HTH
Cheers Tim

Isn't the unloader output to lift the compressor valves while it is still running, like truck air brake compressors do? The larger compressor sets run continuously, just opening the valves allows the pump to turn over while not supplying any air.
Normally the compressor switch on smaller units simply turns off the supply to the motor.
Might be worth checking with SIP as they bought in parts from all over.
Peter
-- Peter & Rita Forbes Email Address: snipped-for-privacy@easynet.co.uk Web Pages for Engine Preservation:

I've just checked how mine is set up. The compressor pump feeds into the tank via a non-return valve block, which has a small side connection (maybe 3/16" OD) going to the unloader valve on the pressure switch. There's a second tank connection which connects to a block which holds the safety valve and the pressure switch . The (Danfoss) switch has a main pressure connection which is perhaps 3/4" BSP, and the unloader valve has a much smaller fitting with a coule of vent holes, which connects to the small pipe from the non-return valve.
I used to have a big diesel driven compressor which did unload by diverting the compressor output - since you can't realistically switch the engine off every time the tank comes up to pressure - though it did reduce the engine speed at the same time.
HTH
Tim

Where did you buy the pressure switch from, I need a new one for my SIP compressor. I rang SIP but they will only sell through agents and the local "agents" they gave me the number of were no good (didn't deal in spares). Is there anyone online who sells SIP spares? The stupid thing is that SIP are only five minutes down the road, but they won't sell me anything!
Regards
Kevin

Machine Mart do one. part # 000320100 £18.74 inc VAT. -- Regards,
John Stevenson Nottingham, England.

Good thinking!
It turns out it was the "three piece"! unloading/relief valve (it should have been one piece!)
I'll get a new one ordered from SIP in the morning.
Cheers
Peter

Kevin,
This is the first time I have dealt with SIP. Their technical people gave me the spares numbers and the details of my local dealer (in my case Trowbridge Power Tools). I passed the part numbers onto my dealers, they ordered the parts and I collected them.
If you get really stuck, I can get the parts through my dealer and send them on to you.
Cheers
Peter