View Full Version : Oil carry over

07-08-2012, 03:54 PM
Gentlemen, A newly commissioned refrigeration plant , 10 nos HOWDEN screw compressors, 6 of them high stage 4 of them low stage cascade system, motor capaciy 630 kw HS and 200 kw LS, While compressor operating full capacity of HS compressor (above 70%) OIL carry over from oil seperator... one ltr per a minute..

Refregerant R22

Please advice, appreciate it

08-08-2012, 01:37 AM
Is just one of them doing it, or all? High or low stage?
Is the plant operating within its design parameters?
If it started immediately I would think the oil separator filters might not been installed properly.

08-08-2012, 02:59 AM
Possible HS compressors are over injecting oil, HS suction oversaturated and combined slide load rate too fast. And as NH3LVR suggested filters missing in separator.

09-08-2012, 01:25 PM
Hi, NH3LVR, THANKS FOR YOUR COMMENTS, All HS are loosing oil very fast , one ltr /Hr. and while running 50% load oil not loosing. coalescers filter seems good , if it is damaged or not installed properly, it may happened even 50% running .
Compressor Howden WRVI 255/193.

Pla advise,


Joseph PUTEN

09-08-2012, 04:10 PM
What are the suction, intermediate and discharge pressures?

10-08-2012, 04:40 PM
Try to lower intermediate pressure. Go to 2.5 bar and then to 2.0 bar. Monitor operation and let us know how it goes. Your oil separators might be under sized. Lowering intermediate pressure will reduce mass flow and might improve oil carry over. Did you talk to Howden?

11-08-2012, 02:35 PM
Hello Sir, Thanks for your comments, But if pressure drops up to 2.0 bar , intermediate temp wil be 14.5 deg C,
That wil be effected of secondary refrigerant temp (Glyco)

your comments will be validated


Joseph PUTEN

11-08-2012, 09:52 PM
For machines this size on R22 would expect at least 4 to 6 coalescers 225 dia x 1000mm.
What do you have & what does contractor/supplier have to say?

Do you know sealing design on end of filter ie "0" ring on ID or on end of filter?

12-08-2012, 12:13 AM
I beleive that the HS compressors are loading too fast, above 50% slide, the volumetric change and swept volume change is huge and separator velocities are huge, slow and easy load rates, system driven not load demand driven.

12-08-2012, 08:43 PM
I agree with ranger what coalescors are installed, also how are you measuring your 1L/Hr ? what is the discharge pressure and plant room temp? also why on earth is the system this size on R22? locate the designer and give him a kick from me.

13-08-2012, 02:32 AM
Hi Lync
Do the HS compressors have economiser lines fitted and if so do they have check valves installed?

13-08-2012, 04:13 PM
Hi, all ...

I agree with ranger what coalescors are installed, also how are you measuring your 1L/Hr ? what is the discharge pressure and plant room temp? also why on earth is the system this size on R22? locate the designer and give him a kick from me.

... a big kick from me too :mad:

what is the reason .... probably, those units are custom made, quite cheap, without proper coalescer elements both in size and quality, installed maybe, without O-rings and not tightened, for sure undersized oil separators, because until 70% capacity without oil carryover .... what about oil recovery line installed and open or not? ... it is not easy to guess what went wrong .... let's wait for OP to put some more light on this ...

Best regards, Josip :)

22-09-2012, 09:57 AM
First, how come that a system like this running with R22?
Second, what kind of oil separator do we talk about?
Third, probably the oil separator is calculated wrong and is to small for your system.
You have to send me all technical information and a system drawing before it possible to give you an good advice.


22-09-2012, 05:59 PM

Is there solenoid valves in oil injection lines?

I had problem once with bitzer compressors losing too much oil, reason to this was leaking oil injection valve on standby comp and it blows all oil from separator through the compressor to the suction line and ended to pump separator (no check valve on suction, only discharge) when both comps was running there was no problems. And this was nh3 system

03-10-2012, 11:45 AM
Hi Lync

Why not install seconday oil separator in series. Are the evaporators flooded design or dry expansion?

Are the primary oil separators horizontal or vertical?

In horizontal oil separators there are chances of higher oil carry over in case the oil charging is excessive.

In case of vertical oil separators there should be enough space (Vertical separation space) in the oil separator for primary separation because of the change in direction, deflection, etc.

20-10-2012, 01:53 AM
What is the condensing pressure when the oil is being lost. I bet it is low enough that the CFM at the discharge is over loading the separator elements. Try raising the discharge pressure and see if this helps.