Dear all

 I am facing to increasing TAN number for bitzer bse 170 (poe oil)after 2 month   charging new oil with 0.02 TAN increase to 0.2. Lab oil analysis shows high copper wear element . All other parameters were ok. Refrigerant is R134a.pls share your idea .

Best regards 

Original Post

acidity/basicity - for chlorinated refrigerants like Freon or R-22, we recommend running a test for Total Acid Number (TAN). For ammonia-based systems we recommend running a test for Total Base Number (TBN). TAN can affect the miscibility of the lubricant in the refrigerant.

https://forums.noria.com/topic...trifgual-chiller-oil

https://www.tranehk.com/files/...THD_IOM__AUG2018.pdf page 105

Copper is not a good sign, normally there is a coating protecting the copper, once you find copper bearings are worn

Dave

@aziz58
Thanks for uploading the lab report. I am not familiar with this format but assume that the items with the asterisks (*) are the results the lab is showing concern about. If you have real concerns then contact the oil supplier or the compressor supplier. These results are not bad, but you need to pay attention to some aspects.

I think the The Total Acid Number is OK.  It may reflect contamination from any remaining oil from the previous charge, as well as current operating conditions.  Do you have any manufacturer's guidelines for used oil analysis results?

Iron (Fe) will come from the moving parts of the compressor as a wear result and 90 ppm is certainly higher than expected. I would expect single figures normally. This number reflects particle sizes up to about 8 or 10 micron.

PQ (PQ Index). Reflects large iron particles (>20 micron, say) and is used to assess more aggressive wear. The number is an index based on the relative strength of an induced magnetic field in the large particles (the number does not reflect particle size but the amount that is present). Typical results are <10. A PQ of 20 is not normally a number to get excited about. I guess it has been marked as an alert to be aware of it in association with the Fe result.

On balance of the Fe and PQ results I would say there is some increased level of wear occurring but it is not aggressive. Keep an eye on these results and establish a trend with extra samples of this oil charge or comparing results with previous samples. Results 21 through to 23 are about the proportions of different size ranges in the particles. The compressor manufacturer can give you guidelines to what is normal.

Copper (Cu) is as Rotating Guy comments. It can also come from an oil-cooler core that has lost its passivation coating. Typical values are <10 ppm. If it is part of a bearing shell then any associated lead (still normal at 1.8) and tin will eventually show.

Water and TAN.
TAN typically increases through the formation of weak organic acids, aided by the presence of water and the oil's operating temperature. Copper increases this reaction.

NOTE Gross Water Content by Crackle Test. A negative result by Crackle means that the water level is too low to be detected by the test, but there will be some water. Crackle is estimated by to be positive at levels >500 ppm.

I note that the TAN result has not been highlighted and would infer that the laboratory database does not see this as a problem. Published new values for this oil are given as 0.01. 0.02 would be an acceptable variation.

The viscosity has dropped some 9% from new value (170cSt) and should not go below 10% of new value. Check with the oil supplier if this is typical behaviour for this grade.

Take care.

Add Reply

Post
×
×
×
×