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Oil color problem

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Quote Originally Posted by Glenn Moore View Post
Hi khaled
2 questions
1) How old is the system .?
2) Has there been any new work on the system i.e. Pipe work ,brazing etc ?
Having carried out many warranty strip downs on compressors and also investigated many system problems ,some of the following may help you find the cause of your oil problem.

With the change from the old ***** gases to the new gases such as R404A,R134A, R407C etc meant also changing the type of lubricant from mineral oil to Polyoester oil.
Due to these "new" refrigerants having different operating pressure/temperature relationships from the old ones many compressor manufacturers use POE lubes with "additives" to enhance their lubricating qualities to overcome the various extra stresses compressors have to cope with.
These additives take some time to attach and bed themselves into the granular structure of the bearing surfaces and wearing parts of the compressor.
Unfortunately these "good" additives can be stripped from the POE oil by the desiccant in some driers before they can be adsorbed into the bearing surfaces into the machine. This leaves the oil somewhat less able to lubricate the machine safely.
It seems a combination of events can create this oil discolouring problem and severe bearing wear.
Such issues include:-
Poor installation practises i.e. Lack of ofn during brazing of the pipe work, use of to much brazing flux material, leaving the compressor open to atmosphere for long periods ( POE oil is highly hydroscopic ) adsorbs moisture.
Poor evacuation
Poor commissioning of the system ( poor condensing pressure control , poor superheat( expansion valve ) control
Most service filter driers have a combination desiccant type made from silica gel, molecular sieve and activated oxides in various percentages as deemed relevant for the job in hand.
Silica gel and molecular sieve are good moisture adsorbents whereas activated oxides are good for acid adsorbtion.
With a new plant there is No acid present as its a by product of the refrigerant,oil heat,electrical arcing etc and this comes after many run hours , so why have a drier that can absorb acid when there is none.
So in a new system you fit a filter drier to dry the system down to a level that the initial evacuation process cannot achieve. The best drier to do this will have a pure 100% molecular sieve desiccant .
By fitting this type of drier the additives are left intact to do their important task of protecting the machine.
Driers with silica gel and active oxides can and do absorb these additives ,so after the system has been operating for some time these multi desiccant driers can then be used as the additives will have been ingrained into the bearings etc and some weak acids will now be present in the system where the activated oxides desiccant comes into play.
POE oil and these new gases tend to clean the system by scouring flux and system debris back to the compressor sump.
So if any of the above issues occur and the oil has been degraded then the oil starts to discolour as metallic bearing particles slowly sludge to produce a grinding paste like material in the compressor sump

So fit some pure molecualar sieve driers and replace with fresh oil and sort out the liquid flooding problem and the problem should go away
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