compressor problems

[pondy]

hello, i got a fiac rd3150 comprsssor, its about 7 years old, around 150-250 litre, its been sitting around a few years and got it as a project as it didnt have a motor, got a new motor etc and set it all up tonight, it will run fine but will not show an presure on the gauge, there is air leaking slightly from the valve on the metal pipe between the pump and the tank and there is another small valve on the bottom of the main on and off switch, it has a plastic push fit pipe going from it into the tank, this has a small drilling inside, air is leaking worst here, have removed there and the valve moves fine, the pine apears fine to

what should i look for, re stipped and clean again, could the pump turning the wrong way cause issues? it does build up some preasure but gauge dont move. could a sticking valve on the pump line cause this

need some help as i dont know anything about these things
sam

 

[the snooper]

after you run the compressor does it have any pressure in the tank could it be a faulty guage

 

[pondy]

there is some preasure when i open the valve on the front, not enough to show on the gauge, because its leaking from these valves

 

[rtbcomp]

If air is leaking from the relief valve under the switch and you don't get any pressure then it'll be the valve itself.

Some relief valves have delayed closing, i.e. it doesn't close until you get about 20 psi in the tank.

Try disconnecting the plastic pipe and blocking it off to see if you get pressure in the tank.

 

[pondy]

its leaking from both valves, i removed the pipe and held my finger over the end and it made no difference. i removed the valve between the pump and the tank and found a load of black stuff in there, not able to strip it down as its all sealed, i put it in the parts cleaner then blowed with compressed air, not fitted yet but will do later tonight

 

[eil]

Sounds like your check valve/ non return valve is faulty, thats the one fitted on the tank with the pipe running from it up to the compressor and the little pipe running to the pressure switch.

 

[pondy]

fitted and now working fine, takes a little time to build preasure up because the one on the control panel seals,

not sure what preasure thi will run up to, it went to 120psi, i shut it down as the new pulley on my motor is a little to big for my vee belt, slips now and again and getting very hot
sam

 

[pondy]

what preasure should i be running this at, in the control unit there are two bolts with springs under them, guessing this is the adjustment, can any one explain how to set them, can i change them when its running?

 

[rtbcomp]

Does the switch look like this

If so you need to adjust the two pressure nuts at the same time, keeping equal amounts of thread above the nuts.

The hysteresis adjustment sets the difference between switching on and off.

I guess 100 psi would be OK. If the pullies are getting hot you need to tighten the belt.

It is normal to adjust the switch with pressure in the tank, I personally prefer to adjust with power off and isolated at the mains!

 

[pondy]

spoke to the guy that had it before, said it should cut out at 150psi, i havnt got it that hi yet. the belt slips as the belt is to small for the pulley, have one on order

the switch is simular, the springs etc are the same, then the rest is coverd in plastic.

when adjusting the springs, how do i know when its correct, i was planning to run about 135 psi, then it comes back on at 115?

 

[rtbcomp]

The plastic contact housing has been removed on the one in the photo.

When you've got the correct belt, run it until it stops and check the pressure. If it's not high enough tighten both nuts a couple of turns each. Let air out of the tank until it restarts and check the new cutout pressure.

If the pressure is too high slacken both screws a bit.

Next check the hysteresis. Note the cutoff pressure and release pressure until it restarts, note this pressure. The hysteresis is the difference.

I think tightening the hysteresis screw increases the pressure difference. At the same time it may also increase the cut off pressure, so you'll have to reset that again.

It's normal to have hysteresis set to about 30psi.

 

[pondy]

thanks, were is the hysteresis screw

 

[rtbcomp]

It's pointed out in that pic I posted, but yours may not have one, some are pre-set.

Look to see if there are other screws, pressure is usually marked with a + or - and hysteresis with a triangle.

 

[pondy]

o sorry my mistake
sam

 

[pondy]

right, got a new belt with is alot better, no more slipping and it builds up preasure faster, it gets to 130psi then it cuts out, air then leaks from the valve on the bottom of the control unit untill the preausre drops to around 90psi then it stops leaking and the motor cuts back in, i have not touched the other screw just the 2 large ones with the springs, should the other adjustment cause this

may not be related, since i have started moving this compressor around the baked on carbon etc has come off some and it keeping the valve on the side of the pump open a little so i have a small leak, this is fixed by pushing the valve open with a small screw driver to dislodge it
sam

 

[rtbcomp]

........ air then leaks from the valve on the bottom of the control unit untill the preausre drops to around 90psi then it stops leaking and the motor cuts back in..........sam

This is classic faulty non-return valve on the tank where the thick pipe from the pump connects.

 

[pondy]

i sorted the leak at the valve in the pipe between the pump and the tank when the motor is running, its the short brass valve on the bottom of the control unit is (box with adjustment is and main on and off switch), leaks when the motor cuts out, this valve has a thin plastic push fit pipe which goes to the tank also

what the cure, and if need be, who can supply this valve
sam

 

[rtbcomp]

I know the one you mean.

The pipe that goes to that valve should connect to a small hole on the non-return valve, which in turn is the same as the delivery pipe I mentioned above.

That valve is opened when the motor stops which gives the characteristic short hiss.

If it is hissing all the time the air must be coming from the pipe connected to it, which means (if it is connected properly) that it must be finding its way passed the non return valve.

 

[eil]

Drain the tank and unscrew the cap nut and clean the inside of the valve housing and check if there is a hole or tear in the black diaphragm pictured above.

 

[pondy]

the valve thats leaking dont look much like that. both of mine cannot be stripped, im sure its got dirt in there as it held preasure last week