Compressor Screaming! Help!!

[olmasters]

Hi all,

Ive not posted here in years, but am a frequent lurker. Ive recently purchased a second hand compressor from ebay which looked like a great spec/price for my needs.

http://www.ebay.co.uk/itm/compressor-/251713530665?ssPageName=ADME:B:EOIBSA:GB:1120

I got it delivered on a pallet and have just fired it up on its 16a plug, but via an adapter cable with a 13a plug on. Anoyingly it only reaches around 30psi before the whole thing beings screaching (this sounds like the cylinder not the pump). Unless i manually stop it, the thermal cutout trips.

Ive only experienced this before when using a friends compressor, only to find out at the time that it had no oil in it. Upon refilling, this cured the problem.

I did notice my new second hand compressor had been overfilled slightly with oil therefore drained the excess (this did look pretty fresh, if not new), however im still getting the same problem. I dont want to carry on running it at the moment in case i damage it.

Im wondering whether the compressor has been run dry, this has caused the rings/cylinder walls to be damaged, producing higher levels of friction under load which then cause the motor to trip?

Please someone tell me otherwise, i really hope this doenst need rebuilding!!


Many thanks,
Ollie

 

[olmasters]

Just a quick brain fart before i head to bed. I believe this compressor was used by the previous owner as part of a sprayshop install. If there was ever a drier fitted between the cylinder and tank, after being removed for sale, could the flexi pipe and check valve for the compressor have been reattached the wrong way round when reverting back to the original setup? This could cause some explination for the thermal cutout tripping. This is probably wishful thinking though.

To test this theory, providing i drain the tank beforehand, would it be safe to remove the flexi between the compressor cylinder and tank, then run it?

Ollie

 

[olmasters]

One final one! I was told that the seller had this compressor directly connected to a 16a breaker. When prepping it for sale and attaching the 16a plug, could it have been wired the wrong way round, causing the motor to spin the wrong way, and therefore cause the pump to have to pump against the one way valves to allow air to enter the tank?

Sorry for the naievity, im pretty new to all this, ive got a few air tools but in the past have just borrowed compressors from friends.


Thanks for your help in advance,

Ollie

 

[MattF]

Is there a rotation direction arrow on the flywheel? Also, stating the obvious I know, but you have checked it's not just something basic like a slipping belt causing the screeching?

 

[Spark plug]

Start with basic checks air filter, motor direction, take the guard and belt off make sure everything turns ok buy hand..

 

[rtbcomp]

If it's single phase connecting the mains the wrong way won't change the direction of rotation. It's still worth checking though just in case the motor's been changed or someone's been fiddling.

+1 for belt tension - I moved my Clarke compressor and the motor wasn't tightened down enough and the belt slackened off.

 

[normspanners]

I would run it with the valve open ie not pressuring then listen to it run, connecting the pipe the wrong way round will make no difference, if it was pumping against a one way valve the air would go nowhere so would not put any air in the tank.
A loud squealing sounds like belt

the thermal cutout trips.

which ? the one on the motor connection box. ie overcurrent protection , or the one in the motor ie do you reset it or does it reset itself.

 

[rtbcomp]

If you think the NRV is back to front, post a photo of it, we'll soon be able to tell, it looks OK from the Ebay photo.

 

[octo0072000]

sounds like belt slip
try removing belts first then see if the motor runs ok
while belts off turn the pump by hand see if it turn over ok not locking etc
sometimes old belts will slip even if tight you can buy belt dressing or try a bit of talcum powder on them

 

[Wallace]

The outlet pipe from the head down to the NRV and tank is normally copper or alloy and looks like it's been changed for a rubber hydraulic hose, might be worth checking it's still flexible and has not gone hard letting parts break off inside. I would take that hose off first, check the condition and that you can see through it then run the compressor with the hose off and see if it starts screaming. What model number is it?

 

[olmasters]

Hi All,

Many thanks for your help, I've had a busy day tinkering around with the compressor today.

First off, I ensured that both the motor and cylinder were free to move - which they were. I also checked the tension, which was similar to the alternator belt on my car - I assumed this was about right. I also removed the pipe between the cylinder and tank, ensuring it was clean and allowed free movement of air. Likewise, I opened the tank outlet and ensured that the passage of air from the inlet to the outlet was fine too. Just out of interest, is the part that enters the tank in the right of this picture the check valve?

I then went on to check the direction of rotation which matched the arrow on the cylinder pulley.

I did notice that when looking at the oil sight glass I couldn't see any air, so drained the oil down to the correct level via the drain plug. The oil that came out was clean and didn't contain any contaminants, it looks like someone was just a bit overkill on filling it. The oil did look pretty thick though - what grade is recommended just out of interest?

After this, I fired it up and the horrible squealing stopped.. Result!!

The comp was still cutting out at around 4 bar though via the current overload protector to the right of the capacitor. This is meant to cut out at 20A, so i really hope this isnt the cause of the issue!!

I dont have a 16a supply, so popped it on my 32a, just to be sure it could be provided with sufficient power, rather than starve it on a 13a. The motor didnt feel hot to the touch, even after me testing it for half an hour of pumping.

When opening up this box of tricks on top of the motor, the capacitor didnt look to be the original one, because it doesnt really sit quote right in the space. If this is an incorrect aftermarket one, could this cause the current overload protector to trip? To confirm whether or not this tripping was infact my issue, I joined the two wires going to it together as a temporary measure and the comp reached 10 bar nicely without the motor appearing hot to the touch, and no cut outs in the process. I'm going to buy a clamp meter tomorrow to double check the current flow anyhow just for peace of mind.

In the mean time, does anyone know that this female pcl is for, it does leak a small amount of air out (i'm assuming it is behind a leaky check valve) do you think someone has in the past used this to daisy chain another compressor to feed this one? I'd like to replace it with a plug if its not needed.


Thanks again for all your help!!

Ollie

 

[normspanners]

IMO the over current trips do get tired if they have been used a few times, for this reason i have spares ready in stock for mine, but they usually go on re-startup when there is pressure in the system and when the compressor is cold to help mine I have put a longer feed pipe, so that the pipe takes a longer time to build up to tank pressure. But also they can trip because of thick cold oil, again mine struggles when temp drops to near freezing, I have to drain all air out and let it run up from empty. When this happens I usually change oil for new thin oil. It sounds to me that you are suffering from afew of these things try again tommorrow when it is cold.
Also if your voltage is lower ie supply not as it should be ie low mains 210v etc or running off an extension, the start up kick is not as strong therefore it draws more amps and can trip the overcurrent switch.That pcl coupling would not be used to connect another tank because it is the wrong way it is male and would allow the air to escape, if it leaks from it slightly I think is maybe screwed into the bleed off from the feed pipe, that port is meant to open to atmosphere so that when the compressor builds up to pressure and switches off it empties the feed pipe to help with restart, if it is that unloader port then that means the NRV /check valve is prob leaking then there will be tank pressure on the back of the compressor outlet valves as soon as it tries to restart, because the feed pipe is full of tank pressure.

 

[rtbcomp]

That brass thing on the tank is the check valve and it's fitted correctly.

...That pcl coupling would not be used to connect another tank because it is the wrong way it is male and would allow the air to escape, if it leaks from it slightly I think is maybe screwed into the bleed off from the feed pipe, that port is meant to open to atmosphere so that when the compressor builds up to pressure and switches off it empties the feed pipe to help with restart, if it is that unloader port then that means the NRV /check valve is prob leaking then there will be tank pressure on the back of the compressor outlet valves as soon as it tries to restart, because the feed pipe is full of tank pressure.

That PCL connector is connected directly to the tank, the bleed from the unloading valve comes from the valve itself. The safety valve, gauge and PCL connector are all connected together, you have a 3 port pressure switch. Do you get a stream of air from that PCL connector? It may have been used to connect to another compressor via a standard airline, which is why it's a male connector. Normally that port has a blanking plug in it on the larger compressors.

The correct grade of oil should be indicated on the rating plate attached to the tank or pump. My Clarke uses SAE30. You can get it from Machine Mart or you could use a straight SAE30 non-detergent engine oil, the correct level is to the top of the sight glass, the red dot indicated the minimum level.

The valve on the side of the aftercooler remains open until pressure has built up in the delivery pipe (from pump to tank), this gives the motor chance to spin up to speed before coming under load. It also prevents a slight leak from the NRV building pressure up in the delivery pipe. If the NRV is leaking badly enough to cause this valve to close prematurely then you need to fix/change the check valve.

 

[normspanners]

That PCL connector is connected directly to the tank,

If it were connected directly to tank then the compressor would not build up any pressure, anybody with half a brain would use a female pcl for that application, then use a double male adapter to enable a standard air hose to Siamese two compressors, though that does look like a 3port valve I have seen the bleed from the unloader valve threaded 1/4 bsp so that a silencer or a line can be fitted to stop the sudden hiss of the unloader.

it does leak a small amount of air out (i'm assuming it is behind a leaky check valve)

it seems a little suspect that, that is there in my mind

 

[rtbcomp]

If it were connected directly to tank then the compressor would not build up any pressure, anybody with half a brain would use a female pcl for that application, then use a double male adapter to enable a standard air hose to Siamese two compressors, though that does look like a 3port valve I have seen the bleed from the unloader valve threaded 1/4 bsp so that a silencer or a line can be fitted to stop the sudden hiss of the unloader..........

My thoughts exactly - I made a gender changer from a couple of PCL males. I suppose if it's a permanent installation though that would be OK.

 

[olmasters]

Hi Guys,

Many thanks for all your advice, I'll be going home for Christmas at the end of next week so will give the compressor a more thorough look over then while I'm back. I've ordered bits to do the following:

Change oil for correct grade
Replace NRV
Replace current overload protector
Replace female PCL with blank/air silencer (depending whether the pressure switch blows off using this port)

Hopefully I'll be able to get it running as intended, ready for some spannering on my mgb. here it is if your interested:

Thanks again,
Ollie

 

[captain-destructo]

hi there
its a clarke compressor yes? why not have a wander into machine mart and see if they have one in stock, then you can see if its piped up the same and see what is supposed to be fitted where the pcl fitting is etc.

you never know the fitter might be in a good mood and give you some tips!!

 

[olmasters]

Many thanks for all the advice, I've finally got round to replacing the thermal cutout, and its now working exactly as it should do, even in the cold weather.

I did order a fresh nrv, although went to fit, realizing I'd bought one too small - doh! Ah well, a project for another day.

Cheers again,
Ollie

 

[rtbcomp]

Thanks for letting us know.