Air bubbles in the oil........

[Namreg 58]

Hi Craig,

Thanks for that handy bit of info. Means that I have a spare set of valves ready to install should the need arise and that I can then repair broken ones again at my leisure.


Heinz

 

[widget]

Thanks Namreg, will spend some time looking.

Well, an update and not all happy to be honest.

Part arrived thursday afternoon, as I was flying back to SA on friday evening, we quickly installed the valve and started up, machine sounded fine and the oil pressure which had fluctuated before is rock steady at 6 mega pascals.

Then, at around 120 bar the bubbles (froth) in the oil sight glass start again.

SO, we stripped out the piston and liner again thinking it was faulty and replaced with another, still frothing, checked the valves suction and discharge, seem fine, start up, machine sounds fine oil pressure steady, 120 bar oil froths.

Stripped oil pressure regulator, replaced o-rings all looks fine, bled the oil pump, rechecked - oil froths.

Now, we are left with limited options, -

1)Can the check valve on the final seperator cause this, we thought if the check valve is faulty,it mat allow air back into the oil return line?? - it may be a long shot, but can it be a cause.?

2)As only the final (fourth) stage is under oil pressure, can a fault on another, say the third stage, cause this. What could it be.?

Something we noticed now is that when we turn the machine off, the oil pressure only drops to about 2 mega pascals not to zero, like the other machine, one of the technicians here dosnt seem to think this is an issue.?

Something else we noticed was just before the oil starts to froth, there appears to be an audible "click" like a valve opening or closing, until we hear that click there is no frothing, so somewhere its connected.

Okay chaps, put your thinking caps on, wednesday I am flying back - gotta have some answers.!!

 

[Namreg 58]

Hi Widget,

I think Craig was on the right track re. the ball and seat on the oil pressure regulator. It is quite possible that either or both the ball and the seat have irregular wear which is causing the problem. The troubleshooting guide in your manual says to clean and readjust oil pressure regulator, so if it still persists, I would be looking for worn parts.

If you have access to a stethoscope, try to determine where the click is coming from. If not , a piece of 1/4 inch flexible tubing with a screw stuck up the probe end will do the same job.

Heinz

 

[pescador775]

If I could look at a diagram of the oil circuit or conduct some simple tests I might be able to offer something definitive. At this point, all that comes to mind is broken rings in the third stage.

 

[Namreg 58]

The oil that passes through the sight glass is the excess oil on its way back to the sump, so the aeration must be passing through the ball valve. The only place this air can be supplied from is through the orifice in the 4th stage that the oil is injected to lubricate that stage and the con rods.

My other guess is that maybe the spring loses tension through heat fatigue as the oil heats up. Got me intrigued as to the final outcome of this.

 

[widget]

Would a photo help?, I can ask the technician to send one and I can post it here Pescador, BAUER KOMPRESSOREN Group - BAUER COMPRESSORS also has some technical documents under the SERVICE AND SUPPORT section on the K14 unit - I have been looking at and trying to figure it out, it but its not coming to me at all.

I agree with you Namreg, its mysterious for sure, but as you rightly say the only place this air can come from is the oil orifice in the 4 th stage where oil is injected into the cylinder at pressure to lube the floating piston, - as the oil in the sight glass is returning to the sump, could it be sucking air through the ball in the oil regulator which is causing the airation?? Surely as the pressure is quite high it would blow oil out, not suck air in?

So far I (in my limited understanding) cant see it been wear in the piston and liner as its doing it with two various pistons, the valves both suction and discharge are new, oil level is fine,oil pressure is good and not fluctuating (rock steady at 6 mega pascals)
everything is torqued correctly, the unit reaches 300bar pressure with no issues,- its just that the oil in the sight glass is airating heavily.

Can there be a check valve issue on the final seperator here, dosnt seem likely?

Is this ball from the regulator often a cause of issues, I looked at it and it appeared fine, but thats just with the eye, do I need to inspect it under a magnifying glass.?

 

[pescador775]

The pneumatic check is not an issue. However, an oil check might. Such is included in the parts list for the three stage Capitano if I translated it right (oelkontrollvershraubung). It's probably the same as yours being part of the regulator, and that component on your compressor appears to be OK as I heard it. The sight glass is in line with the check valve and the oil return line which feeds a lower stage(?). On three stage compressors this line feeds the second stage. In my imagination, I tried to picture what stage or stages this line would service in a 4 stage machine and if air could blow back through the return line. That was the thought behind the speculation on the 3rd stage rings. It seemed very queer that the oil bubbles consistently initiated at a discharge pressure of about 1700 psi.

I don't know if a bad oil pump could generate air bubbles but that seems kind of low on the list since pressure is good.

Another thought, make sure the O rings on the 4th stg piston sleeve are good. One wonders why the piston froze up and if a lack of oil could have affected a lower stage, eg, if the return line delivers oil to any lower stage as in the Capitano.

 

[Namreg 58]

Would it be possible to change over the whole oil regulator assembly from the other K14 compressor to see if that makes any difference ? Process of elimination may be the way to go.

Heinz

 

[Namreg 58]

Pescador, the oil in the return line simply flows back into the sump. I am leaning more toward a damaged ball seat in the regulator, as the trouble shooting guide states to "clean valve and readjust oil pressure regulator" if sight glass exhibits air bubbles. This of course implies foreign matter gumming up the works, however it could also be a faulty component....curious?

Heinz

 

[CraigAClark]

If the seat in the oil regulator has overlapping impressions, it will allow air back flow.

Craig