Dumb newbie needs help with a compressor

[funstuie]

So I have been after a compressor for a while thinking it would be a handy thing to have a around when working on my vw beetle.

I found won on ebay and won it at what I thought was a great deal. Went to collect it from the guy and he seemed genuine and he worked as an industrial compressor (refridgeration etc) engineer. He said he had recently serviced the compressor and fitted a new motor.

I have not had much chance to use it since I collected it as my wife has been working weekends and I have had to look after my son.

So tonight I started it up to see what the deal was and it doesn't seem to be working correct.

When I turn it on the motor starts and the tank starts filling up then after a couple of minutes it just dumps the air out through the pipes near the switch. I don't have any instructions or any tools to test it with, all I have is a lenght of hose and a paint gun.

It's an Air Master 15/50 and I can't find much info on the net about it.

Anyone have any idea what I need to do to get it setup properly.

Here are all the details from the little plaques on the side:

AirMaster Compressor
Model: Popular 15/50
M.W.P. : 150 psi
OIL: SAE30

Clarke Motor
Type: 9OLB/2
V: 230
HP: 3.0
KW: 2.2
Hz: 50
RPM: 2700
PH: 1
A: 14.5 (probably shouldn't be running it off a 13amp socket?)

Switch: 12bar, 175 psi

Help?

Here are some photos so you get the idea:

 

[JayRS4]

Does it actually build pressure before it "dumps" it. You might find it`s just the safety vavle popping as it reaches full pressure. I`m assuming after it dumps the motor shuts off right?

 

[funstuie]

It builds up to about 100 psi before it "dumps". It dumps the air and then the motor starts up again and builds up the presure again.

 

[rtbcomp]

Sounds like the non-return valve on the tank, where the pipe from the pump goes.

When pressure builds up and the switch trips off it operates a small valve in the switch to drain the air from the pipe between pump and tank.

If the tank non-return valve doesn't close air will drain from the tank through the switch valve.

 

[scarecrow]

It could be the pressure release valve on the cut out switch is faulty when the motor cuts out you will hear hissing noise that is a release valve releasing the pressure off the pistons in the pump so when it started up again it's not under pressure you will probably have to replace the old switch

 

[funstuie]

Sounds like the non-return valve on the tank, where the pipe from the pump goes.

When pressure builds up and the switch trips off it operates a small valve in the switch to drain the air from the pipe between pump and tank.

If the tank non-return valve doesn't close air will drain from the tank through the switch valve.

Thanks for taking the time to answer but I don't understand any of that (well I understand a little). What should I be looking for?

 

[funstuie]

It could be the pressure release valve on the cut out switch is faulty when the motor cuts out you will hear hissing noise that is a release valve releasing the pressure off the pistons in the pump so when it started up again it's not under pressure you will probably have to replace the old switch

The switch is new (I still have the old one which the seller gave me). One thing air was coming from the psi gauge until I tightened it up.

 

[rtbcomp]

It's not the valve in the switch.

If the valve on the switch fails open it will hiss all the time, but the NRV on the tank will prevent the tank from draining.

If it fails closed it will not hiss at all.

You're looking at a new non-return valve on the tank. It's the bit the thick pipe from the pump (edit) fits into. Machine Mart, Thorite and so on sell them. Make sure the tank is empty before trying to unscrew it!

 

[scarecrow]

It's not the valve in the switch.

If the valve on the switch fails open it will hiss all the time, but the NRV on the tank will prevent the tank from draining.

If it fails closed it will not hiss at all.

You're looking at a new non-return valve on the tank. It's the bit the thick pipe from the pump (edit) fits into. Machine Mart, Thorite and so on sell them. Make sure the tank is empty before trying to unscrew it!

You probably right rtbcomp it's hard to tell from the photos but the switch looks to be mounted on the pipe from the pump so the nonreturn valve should be between the switch and the pump

If you mix some washing-up liquid and water and wet joints with it if they are leaking you will see bubbles

 

[rtbcomp]

I think the black "pipe" between the pump & switch is the mains cable.

The output fromm the pump is that fat copper pipe you can just see connected to the bottom of the aftercooler.

The air will be coming out of the dump valve in the switch, not from a joint. You should be able to feel it with your hand.

 

[funstuie]

Hi thanks for taking time to answer.

When it dumps the air does seem to be coming from somewhere in the switch and I can feel it.

One more question. On this photo:

I only noticed the circled lever when I was putting it away. What is that for?

Also is this a good compressor or is it crap?

 

[rtbcomp]

It looks like a ball valve, simply to cut the air off.

The original photo looks a bit odd to me. The pump and tank seem out of proportion, and I've had a quick look at the Airmaster range on MM's website and nothing matches exactly.

The pump and motor look newer than the tank. That being the case if you can sort the non-return valve out you could have a little beauty there.

 

[rtbcomp]

Thinking about the non-return valve, it may have a large nut on the back of it, opposite to where the pipe enters. If you take this nut off (empty tank, watch out for the spring!) you may be able to clean the gubbins in the valve to get it working.

 

[funstuie]

I had a goal again this evening. When I turn it on it starts to build up pressure and I can use the paint gun (filled with water), when it gets to about 100 psi it dumps the air and drops to about 10psi and starts again.

I have taken the cover off the switch and this is what I get:

Is that nut on top the valve? It has +/- on either side.

Had a good look tonight and the motor is new and the switch are new. The pump looks older. None of the connections are tight through, air is seeping out from everywhere.

 

[shenion]

The check valve is on the left side of the picture with the copper pipe and small black tubing coming out. That is the nut referred to.

The nut on the switch set the cutoff pressure that the motor will turn off.

 

[rtbcomp]

Yes, as Shenion says, the nut is on top of the check (non-return) valve, slightly different layout to mine.

The device sticking out to the left is a safety valve, just check that the air isn't coming out of that.

I'm a bit suprised it drops as low as 10 psi before switching on again. Are there 2 adjusting screws in the switch? The one marked +/- sets the cut-off pressure, there may be another one marked with a triangle or "delta" this sets the difference between switching off and on again (hysteresis).

Check the non-return valve first though, you may just have two problems.

 

[shenion]

I'm a bit suprised it drops as low as 10 psi before switching on again. Are there 2 adjusting screws in the switch? The one marked +/- sets the cut-off pressure, there may be another one marked with a triangle or "delta" this sets the difference between switching off and on again (hysteresis).

Could be the pressure of all that air leaking past the check valve through the dump valve is keeping the pressure switch from turning back on.

See what the check valve looks like inside. May just need cleaning. If, not they are fairly common over here. Just make sure you get one with the same fitting, seem to be 3 different outlet sizes here.

Also, my 2 compressors had two different types. One was just a single fitting (dump valve runs to separate port on the head of the compressor,) the other had the fitting for the dump valve line.

 

[rtbcomp]

Could be the pressure of all that air leaking past the check valve through the dump valve is keeping the pressure switch from turning back on.

The switch turning off opens the dump valve, the air rushing through will try to close it, so I would have thought the back-force would attempt to close the switch, thus causing the motor to start earlier? I doubt whether the forces involved would affect the switch.

In any event, sort the check-valve out, no point in looking for a hypothetical problem before fixing the real one.

 

[funstuie]

I got it working, everything just needed to be tightened up. It no longer dumps the air.

The problem now is I have no idea how to work it.

Does anyone know where I could get a manual for it?

Under the cover for the switch there is a little bolt with + - on either side. What is this for?

On the top of the outlet (where I hook up the hose) there is a knob, does this do anything?

Also there is a gauge on both the switch and outlet both displaying psi. Why is there two?

 

[gavuk]

the pressure of the tank controlled approx by the motor starting and stopping , is set by the +/- control,one gauge shows tank pressure,gauge nearest wires,othr gauge with valve circled is the line pressure,this is adjustable by the large knob on top,normally have to lift up or push down to change pressure ,don't force it as there are other types of locking used on some machines, you would normally turn line pressure down to paint spray ,,maybe 20-60 psi ,instead of tank pressure of 100psi+