View Full Version : Sab 89 oil sludge

30-04-2016, 05:08 PM
We are using several Ammonia screw compressors SAB 89 in our plant facing with some problems in the oil system.
After around 35000 hours running, there is some oil sludge and carbonated oil in the oil separator sump and oil cooler, because of unavailable space, cleaning is too hard and sticky carbon on the wall seems difficult removing.(used oil is SHELL CLAVIUS S2-FR A 68) ,also I found out thick burnt particle around the heater element. I would like to know your recommendation about this issue.
Also there is a question about relationship between amount of differential oil pressure and the capacity of oil cooling system.
The other compressor works with conditions that shown in the attachment, I found foamy oil in the sight glass, while running compressor, it is not normal. I would be very grateful if you help me to find out the problem.

30-04-2016, 07:07 PM
I am slightly confused as to how long you intend to keep this compressor running for!
Basically the MAJOR Service interval for these compresors is =
With a operational condensing pressure of up to 18 bar it is 30,000 run hrs.
With a condensing pressure of 18 - 26 bar it is 20,000 run hrs.
You have a oil temp issue I assume and how well does your oil cooling system work.
I.e. What is your normal oil running temp?
Carbonised oil is a classic sign of oil breakdown and overheating.

When did you last change the oil and filters?
Foaming could mean Liquid refrigerant in your sump?
Honest answer get a Sabroe trained engineer to have a look at it.

30-04-2016, 11:42 PM
Sorry no attachments to look at, you might have to type in or try again.
The Shell oil is mineral oil which is probably not the best oil for these compressors.
The ones I work on are all Mobil synthetic & very clean systems, as oil filters are a ridiculous price for genuine.

1/ Consider oil analysis of current oil
2/ make sure oil heater controls at about 45deg C & is only on when compressor is off.
3/ Also oil heater is always submerged in oil, or it will burn the oil.
4/ All compressor conditions suction,discharge oil pressures & temperatures.
5/ Oil filter usually has high differential alarm & trip points, are they set correctly & working.
Maximum I think 1,6 bar or 2 bar
6/ Air in system also can cause issues with oil breakdown, so does system have air purger &/or low refrigerant level in liquid receiver?
7/ Does other machine have similar problem?