50 Litre Air compressor problem

[dalejg]

I have a Valley 50 litre 3hp compressor and it runs up to max which is 120 psi, this is when the safety valve cuts in and releases the pressure.

I picked the air compressor up second hand.

Been trying to find some information on what pressure it is meant to charge to before cutting out. But the lable is missing on the side.

Are these type of compressors fitted with a electric cut out?

Thanks
Dale

 

[the snooper]

it should have a cut out similar to the one below

 

[dalejg]

Yeah it has one of those fitted.

Do you know what pressure they normally cut out at?

 

[Gary900r]

Direct drive are normally max 8bar

 

[dalejg]

Been doing alot of reading from this site and i have found that they do tend to cut in about 120 psi and cut back in at 90 psi.

Thing is when it hit 120 psi the safety valve on the side by the T section opened.

So something must be wrong with the electric cut out or it is adjusted to high as it should cut in before the safety valve.

Does anyone know which screw adjusts the electric cut out?

 

[Gary900r]

Silver hex on top of the switch adjusts cut out pressure should be a + and - signs on the top near the hex.
Should be markings on the safety valve showing its operating pressure.

 

[wyn]

If the safety valve is the bit circled in the pic below it looks like it is adjustable.

 

[eil]

Your safety release valve looks like an adjustable type from your pic, looks like someone has been doing some twiddling with things.
Wyn quicker than me there

 

[brightspark]

if its suposed to cutout at 120 and blow off valve is set at the same pressure. slighly increase the pressure of safety valve by about 5psi and see if it cuts out before blowing off. it might have a tired spring in it if it does its sorted if not some ajustment will have 2 be made on pressure switch

 

[Robotstar5]

I would rather lower the cut off pressure on the switch rather than mess with the SAFETY valve - name says it all!

 

[brightspark]

I would rather lower the cut off pressure on the switch rather than mess with the SAFETY valve - name says it all!

its better to up the safety valve by ONLY 5PSI when pressure switch is suposed to cut out at 120 AND THE SAFETy IS CUTTING OUT AT SAME PRESSURE if u alter the settings on the pressure switch u have to alter the differential as well

 

[eil]

Unless its a fixed diff type, more than likely someone has been trying to squeeze more psi out of it by adjusting the switch.

 

[Gary900r]

Adjust pressure switch to decrease pressure to check if the pressure switch is faulty.
If the pressure switch works strip the safety valve some of the ones on these machines have a rubber seal. This seal can harden and cause the safety valve to open early. If the valve has a seal and its ok rebuild the safety valve. Tighten the safety valve hex to increase pressure on the spring. Run the compressor upto 120psi and adjust the pressure switch to shut off the compressor. When to compressor is off undo the safety valve adjuster until it operates(do it slowly you should hear a slight hiss as you get close to the pressure in the tank). After it has operated redo the hex by one turn. Run and test compressor to check pressure valve operates without the safety valve operating.

 

[rtbcomp]

Before you fiddle with anything, does it stop and hiss if you operate the red knob? If not the pressure is suspect.

 

[dalejg]

Got another problem with it now!!

When the compressor runs it stops by itself, it sounds like the compressor itself is sticking, as it trys to kick back in all the time but never fully restarts. It sometimes restarts when you unplug it and plug it back in.

If you turn the motor over by hand using the fan it feels abit stiff.

I think it might need a strip down.

 

[rtbcomp]

When it stops does it give a brief hiss?

Also have you tried this Before you fiddle with anything, does it stop and hiss if you operate the red knob? If not the pressure is suspect

 

[dalejg]

It does give a slight hiss as it stops.

The motor then pulses trying to restart.

 

[rtbcomp]

Does the motor try to restart as soon as it stops or does it wait until the pressure has dropped by about 30 psi?

 

[dalejg]

The motor trys to restart straight away then pauses for a couple of seconds then pulses again. It continues to do this for a while before i pul the plug as it cannot be good for the motor.

This happens from 20 psi to 100 psi. The pressure does not seem to affect when it is going to suddenly stop.

There does not seem to be any drop in pressure as there is no leaks on the system.

 

[rtbcomp]

It sounds to me like the pressure switch is faulty, what happens when you try to stop it by using the red knob?