howden compressor oil problem

[riknik]

hey all am new here just found this site on the net, am having a problem with a mk6 204 howden, its the standard pumped oil compressor on top of the oil sep, was wanting a bit of advice before i open it, the compressor has been rebuilt 3 months ago and was running sweet, then the compressor stoped on lp because it would not unload, the guys on site changed the vickers valve so now unloads and loads ok, but when the compressor is run it struggles like its part loaded and the oil pressure drops rapidly, when the oil pump is run by its self the oil pressure stays at 2 bar but when the compressor starts the pressure drops after about 30 seconds to nothing, it has a new oil pump and regulating valve, filters and oil, i was thinking maybe the nut on the back of the slide valve may have come off as to explain why its hard to start but the oil pressure problem i not sure? any advice would be great cheers

[Andy]

Hello Riknik:)

if the piston has fell off the slide you would loose your oil pressure there.

I would pull it down and check it.

Kind Regards Andy D

[riknik]

cheers andy for ya advice,

[josef]

Hi, excuse my spelling.
I believe that you kontoloval coil and the entire valve Vickers, there are many problem.
Check the oil pipe-dirt.
When the oil control, there are many ways to release pressure, as in the picture, "O" ring and seal.
Many does not work with Howden, but the same problem years ago, dirt in the valve Vickers, the new "O" ring and the OK.

[RANGER1]

It sounds like you have a few problems .
Is full unload micro switch or linear load sensor calibrated to 0 % for start up ?
Is new oil pump same as old one and running at same speed ?
Maybe set oil pessure regulator at a higher pressure until you get it going , then adjust to normal .
You also said installed a new regulator , do you mean oil pressure reg or oil injection into rotors ? Rotor oil injection regulating valve would normally be restricted to a few turns open ( depending on valve brand etc ) to control discharge temp .
Oil pressure will drop on start up if there is not enough oil supply due to pressure difference across suction end main bearings . This causes higher oil flow requirments during and after start up , which is normal .

[Gerben]

Hi Riknik,

I think this an SES unit, or Refricomp?
The Vickers valve can easily be used on a Howden package. If there is oil pressure drop, it can not be caused by a broken valve: the holes are far to small to cause pressure drop.
I had the same problem years ago with a Mk5, it's similar, except taper shaft and shaft seal.
At that time the problem was also that the pressure dropped after 30 seconds. The cause was a too large oil flow into the compressor. I'll explain: when a WRV204 Mk5 or Mk6 is running between 40 and 50% load, the oil injection hole in the slide moves exactly in front of the hole in the compressor casing. Oil goes in very easy, without restictions. That means that if there is just enough oilpressure, it goes to 40%, suddenly a pressure drop and the compressor shuts down. What I did at that particular job was build in an orifice with 5mm hole and put it in the oil injection line. But a regulating valve would be better (I didn't have one at that time....).
And according to Andy, if the piston comes of, it is not possible the get the compressor back to minimum capacity, but if you start the compressor it will immediately run to 100% (and you will hear a bang!!!), but you will still keep enough oil pressure, i'm sure.
It more sounds like an oil pump that is very ill..........

[Tycho]

Hi Riknik,

I think this an SES unit, or Refricomp?
The Vickers valve can easily be used on a Howden package. If there is oil pressure drop, it can not be caused by a broken valve: the holes are far to small to cause pressure drop.
I had the same problem years ago with a Mk5, it's similar, except taper shaft and shaft seal.
At that time the problem was also that the pressure dropped after 30 seconds. The cause was a too large oil flow into the compressor. I'll explain: when a WRV204 Mk5 or Mk6 is running between 40 and 50% load, the oil injection hole in the slide moves exactly in front of the hole in the compressor casing. Oil goes in very easy, without restictions. That means that if there is just enough oilpressure, it goes to 40%, suddenly a pressure drop and the compressor shuts down. What I did at that particular job was build in an orifice with 5mm hole and put it in the oil injection line. But a regulating valve would be better (I didn't have one at that time....).
And according to Andy, if the piston comes of, it is not possible the get the compressor back to minimum capacity, but if you start the compressor it will immediately run to 100% (and you will hear a bang!!!), but you will still keep enough oil pressure, i'm sure.
It more sounds like an oil pump that is very ill..........

I agree with this, only, if the piston does not unload, you should also notice that the compressor is very heavy to start (Pulling a lot more amps during startup than it should).

also one thing I have noticed is that the overflow valve on old SES units tend to stick in the open position, even if you tighten the spring down as far as it will go it's not possible to get a good oil pressure.

This is the bad valve:
http://img142.imageshack.us/img142/3518/2704200910821.jpg

they have starte3d using a new kind of valve now, I don't remember what it is, but it is a kind of PM valve with a CVP, and instead of keeping a 2 bar pressure on the oil line, it gives you a 2 bar difference between the separator and the oil line

[riknik]

hey thanks for ya help i opened it up and the nu on the back of the slide valve came off is why was hard to start and losing oil pressure

[Gerben]

Hello Riknik,

Good that you solved your problem.

Was it the nut on the piston (discharge side) or the nut that holds the shaft in the valve (suction side)?

Gerben