View Full Version : Gram Hubkolbenverdichter HC 8125

Thomas 1978
24-06-2012, 08:55 PM
Hello i have a problem with a GRAM HC8125 Compressor.
The compressor looses his oil after 2-3 hours of operation.
It is an ammonia compressor. I have checked the compressor twice and could not find the failure.

Can anybody help me?

T0: 0C

TC: 38C

Oil Pressure: 3,0bar

Thomas 1978
24-06-2012, 08:56 PM
Has anybody manuals for GRAM Compressors?

24-06-2012, 09:26 PM
Hi Thomas.
You could have several conditions causing your issue.
Without more info I am guessing.
Maybe you have worn pistons and rings or worn cylinders?
Or possibly the oil return line from the oil separator to the crankcase is blocked?
Maybe the oil return line solenoid is faulty or even it's timer?
Or its filter is blocked?
The KP77 thermostat controlling the solenoid could be faulty?
Alternately you could be pulling liquid refrigerant back which is washing out the oil?
Is the crankcase heater working by the way?

These are just a few quick thoughts and not finite!
My initial thoughts would be excessive wear or mechanical failure within the compressor.
How quick do the suction and Discharge pressures equalise upon compressor shutdown?

Thomas 1978
25-06-2012, 06:16 AM
Hello Grizzly,
Thank you for your answer. The pistons and the rings are looking good. There is no liquid refrigerant. The oil return line and the thermostat and,the solenoid valve are ok.
The gaskets under the zylinders I have changed. The gaskets from the capacity regulation cylinders I have also changed. I have no more idea. Do you have manuals from this compressor?

25-06-2012, 08:57 AM
Hi Thomas.

I have sent you some info that will help.

I don't normally send out info to new posters as I like to see posters contribute as well as take out.

However I was reminded recently how harsh that can be. When desperately in need of info!

Do you know the service history of this compressor, only things can look good and still be worn.

I cannot think of anything else that would create that much oil loss so quickly.
You did not reply about the pressures balancing out across the comp yet!

Good luck Grizzly

Thomas 1978
25-06-2012, 06:59 PM
Hello Grizzly,

thanks for your answer.
The pressure balances out very slowly so i dont think that i have a problem with the discharge valves.

The Discharge gas temperature is normal. Between 90 - 115C.

When the compressor run with base load (25%) i have vibrations on this compressor. (Bearings??)

On two cylinders i have seen deep scratches. How much oil can the compressor loose when the Piston rings or the oil scraper rings are defect?
They looks good.

Please Help i have no more idea.

25-06-2012, 07:07 PM
On two cylinders i have seen deep scratches

Worn liners will transfer oil at an incredible rate.
When liners and or rings/ pistons become worn they become very efficient oil pumps.
I don't know what spares are still available but I think they are still supported by Johnson Controls Parts division.
At least I would hone the liners change the piston rings and check all else for wear.

You are correct that from what you say there does not appear to be a valve issue.
However they are not the prime cause of high oil carry over.
Wear in the cylinders is!

Given the rate of carry over you describe I would bet you have excessive wear.

Cheers Grizzly.

25-06-2012, 09:49 PM
Thomas ,
Was there something that led to the oil usage like maintenance, has it been ok inthe past?

Scored cylinder liners will not help so should be rectified of course, maybe there is a broken suction valve!
This will also cause excess oil carry over.

Sump pessurization from excess gas entering sump, from oil return can also be a big issue.

Check float or regualting valve, even close for awhile to monitor.
Have seen a Sabroe SMC100 use 20 litres of oil a day because of this.

Have also seen piston oil scraper rings installed upside down, so double check if you think its possible.

Heads should be cool with enough water flow for general healthy operation.