Oil Differential

[PLEH2EREH]

Howden twin screw compressor with lube oil pump(s).... when system load increases (capacity slide "say 65% to 90% and discharge pressure increases of course) however the oil pressure maintains a constant pressure which creates a lower lube oil dp. (R-134A) The (adjusted) oil pressure regulator which is located downstream (oil seperator>>oil pump>>oil filter>>oil reg>>manifold...seems to be operating correctly so I'm leaning towards the oil pump itself. Shouldn't the oil pressure at least somewhat follow the discharge pressure rise? The compressor drive is constant and yes the filter/strainer/water cooled condenser are clean.. tks

[RANGER1]

PLEH2ERH,

Are you saying compressor & oil pressure are OK, but when it gets to 65-95% load problem occurs?

Oil pressure should be 30psi or 2 bar above discharge.

Assume you have clean oil filters & enough oil in oil seperator.

Can you advise us of all pressures & oil/discharge temp!

Does the oil in oil seperator sight glass foam up at any stage?

As differential pressure across machine increases ,compressor will consume or need more oil.

Can you set oil pressure higher, short term to see if compressor will continue to run.
If it can't maybe oil pump is worn, so try you stated spare.

[Magoo]

Hi
added to what RANGER 1 has said, the oil regulation valve may require a service kit. The oil diff pressure should follow the increase in discharge pressure and maintain minimum 2 bar gauge 35 psig. Howden oil pumps are growly/noisy on a good day, oil temp should be after cooler in region of + 45'c supply to compressor.

[PLEH2EREH]

1st. Tks. Plenty of oil in seperator; yes, 30+ psi above discharge but not a constant ( not a "H" compressor); no oil foaming (or at least visible from sight glasses in seperator), oil pump is Haight gpm, ..... compresor uses liquid injection for oil cooling. I'm sure there is a simple answer why, rather it's the op regulator or the pump itself (or both), but it would seem that if once the regulator is set (rather its at 20% slide capacity or 50 %) that no matter what the discharge pressure is, the differential should follow. No liquid floodback (suction accum)..

[Magoo]

Hi PLEH
Possibly the pre strainer between separator and the oil pump suction, if there is one fitted, or even the actual oil filter after the pump. Generally the oil diff safetys and gauges are after the filters and from the injection/ supply header at compressor.
May not be related but had a problem on an older 204, that at high load percentage had oil pressure issues and creaping unloaded, the seal on the slide and oil injection tube was warn/passing.

[PLEH2EREH]

Strainer before each pump; recently inspected and cleaned;ok. Compressor inspected {Howden Rep} as well;ok. both oil filters replaced (filters clean and assemblies clean); coalescer elements in seperator inspected;ok. oil return line from seperator plate operational; yes. Only using two oil supplies two the compressor bearings.... I'll try to provided more info when I have time. Oh yes, Oil is Vilter B-68, oil pump is a 40 gpm pump, And the oil sample lab results came back a ok!