Causes of High oil consumption

Dear Friends
After replacement of Piston rings I am facing the problem of high oil consumption in Sabroe SMC 108 L ammonia compressor and also there is foaming of oil. Please let me know the possible causes.

Did you consider that oil foaming could cause large oil consumption?
I would first look at the cause of the oil foaming.
Nico.

Hi Ahmed
If your oil is foaming are you getting liquid back to the compressor? Does the oil foaming occur after the compressor has been off for a while? Are there other compressors connected to the same discharge line?
You need to supply a lot more information otherwise it is very hard to help solve the problem.
Regards
Paul

Hi Ahmed

I would recommend that you check your oil return lines back to the compressor?, are you getting high oil carry over? Did you check liners for ovality wear? have your ring gaps been lined up during assembly? Does that unit have thermo syphon oil cooler? Have you contaminated oil?

What was condition like before service?

Lots to check! :D

Hi Ahmed

If the oil is foaming, at firstyou must to solve this problem.
The liquid can coming by de suction line or by the discharge line.
If this liquid is returning by the suction line, the oil will foaming during operation of the equipment even after several hours of operation. The region below the cylinder cover will be cold.

Attachment 10055

In this case the problem is in your instalation. You need to check the liquid separator and lines.

If the liquid is returning by the discharge line, the oil will foaming during the start of equipament and with the cold discharge line. In this case, the check valve must be in top of discharge line, near of discharge header (there should be a long line verticar after the check valve).
In this case you dont need to change the instalation. Just barely maintain closed the valve of oil return to separator for 15 minutes. Do a test and then put a timer on the oil return solenoid valve.

Attachment 10056

Check the orifice, the correct is 0,6 mm. If this orifice is bigger than 0,6mm the compressor will warm, the oil viscosity will decrease and the oil is gone.

Dear Sir,
there is no any abnormal noise of liquid pumping.Oil is foaming little while first hour of operation starts but foaming of oil increases after some hours of operation i.e 5 to 6 hours. there is a compressor connected to the same discharge line.

Dear Friend,
Oil foaming during first 5 to 6 hours of operation is little but after that the foaming increases.there is no abnormal noise of liquid back or any cold area near cylinder.There is float type oil return valve from separator.I think the compressor is getting hot ( crank case).

I would say any prolonged oil foaming is very suspect. Sometimes it will foam if compressor loads & suction pressure drops.
Can you measure sump or oil temperature in sump of compressor as well as discharge temperature.
Also compressor operating pressures as well as oil pressure.
A leaking or passing oil seperator oil return float can cause oil carry over by heating oil in sump as well as carrying oil up into cylinder liner area through sump equalization port.
Close oil return & see how much oil it uses, more or less oil.

Was the compressor using oil before piston ring change?

Hi Ahmed,

what kind of oil and cylinders cooling are you using. Water or thermopump?

with thermopump, at low capacity, you can get liquid back to the crankcase through the oil separator.
with water cooling, if the difference between water temperature and condensing temperature is very high, you can also get condensation in the cylinder covers which are unloaded.

Hi .
did you hone out cylinder bores and de-glaze them so the new rings could bed in properly. if not the new piston rings will by pass and create turbulance in sump and compressor will carry over oil.