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We just performed a oil analysis test on the centrifugal chillers oil (Carrier P/N PP49-5). The result are as followed:

chiller no. 1
copper : 126 mg/kg
Lead : 6.73 mg/kg
Tin : 0.21 mg/kg
aluminium : 0.68 mg/kg
iron : 2.31 mg/kg
zinc : 257 mg/kg
acid number : 0.38
kinematic viscosity 40 deg C : 16.3 cSt
Flush point : 10 degC
water by distillation : 0.05 % vol

Anyone know what was the maximum metal content in chiller compressor
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water content is high. (100 ppm)
Copper content is way high (10 ppm)
Zinc is usually not in chiller oils (as a additive) - probably abnormal
Acid number (TAN?) is high.
Visk is strange (probably caused by NH3 or similar gas in the oil during analysis)

(Our recommended limits) Note: Not all oil analysis labs can do the correct analysis for cooling compressors / chillers.

- refrig guy, any comments?
PT, you need to do a few things differently before you can fully evalute the condition of your oil. You may want to contact Carrier to see if they have more information for you to study. You may be better off sending the oil to a lab that truly specializes in refrigeration systems so you can get good advice while you are learning. Evaluating these oils by standards built for other systems is a bad practice.

Based on the viscosity of the sample you did not remove the refrigerant prior to analysis. The nominal viscosity is 64 cSt at 100 degrees F., and rarely drops to the extent you have measured. The moisture analysis by distillation likely picked up loss of refrigerant rather than loss of water. The proper way to measure moisture is with Karl Fisher titration.

I assume you measured 'flash' point, and got a result of 10 degrees C? This makes no sense as the base oil has a flash point much higher than this, and unless you are running a hydrocarbon refrigerant, there should be nothing in the system to lower the flash to this value. If you are using hydrocarbons, then you need to remove the excess refrigerant prior to analysis.

Your metals analysis results are fine, but you are missing some metals that are diagnostic for this Carrier compressor. Silver is used as a tracer layer in the bearings and should be measured.

The lead result looks like it doesn't belong with the rest of the metals results. It is still well within the normal range, but based on the level of iron and tin it seems like an outlier.

The copper (and sometimes magnesium as well) is a result of the additive package in the oil solubilizing copper from the heat exchangers, and your result is normal. Sulfur, zinc, phosphorous and calcium are from the oil additives.

The acid number of the oil suggests the oil is near the end of its life as fresh oil is normally above 1.
refrig guy.

When is Zink used as a additive in oils of this type? I though it wasnt used because of evt. chemical reactions with the cooling medium leaking into the oil.

Do you have any literature or recommandations on where to get hold of some about cooling compressors and oil analysis? You seem to know a lot on this issue.
We run analysis for one of the worlds largest cooling compressor companies (in scandinavia, Netherlands and New Zealand) and have from the manufactorer only condemning limits. I would like to have some deeper knowlege.

mr hughes
The Carrier internally geared centrifugal compressors (17 Series) use a hydraulic oil in the compressor, essentially the same as Mobil DTE heavy medium. They need the antiwear additive package to protect the gears. This is one of the few compressor models that use this type of additive package, but there are a lot of these compressors installed across the globe. Oil test results for these systems get flagged incorrectly by test labs all the time.

I am not aware of any public information on refrigeration oil testing limits. The ASHRAE 2002 Refrigeration handbook chapters on lubricants, system chemistry, and contamination control have some basic information on the fluids used in the refrigeration system.

I learned my craft by working for a lubricant and refrigerant manufacturer where I was responsible for helping the system and compressor OEMs transition away from CFCs into the replacement refrigerants and lubricants. I worked with OEMs doing life testing and field trials on systems and analyzing the fluids and components coming out of the testing. Many of the limits used in the industry are based on these type of test results, as well as historical field failures and system chemisty knowledge of the particular fluids.

Your moisture limit of 100 ppm is too general for me, but may be acceptable if you restrict it to HCFC and HFC refrigerant systems. My limits are based on the particular refrigerant / lubricant combination, compressor type, and application temperature. For the system PT described, I would use a 35 ppm limit for moisture because the CFC-11 refrigerant in the system is relatively unstable around moisture and will lead to strong acid formation.

Organizations like ASHRAE and RSES are where the people plugged into the refrigeration industry gather, and only two lubricant test labs regularly participate. There are a couple of other test labs who know one manufacturer's systems well because they do a lot of work directly for them (likely the case with your lab), but none of them have a broad background with multiple manufacturer's systems. Some customers have developed the expertise to interpret the test results on their own, but if something out of the ordinary comes up they are usually lost because they don't know the system chemistry well enough.

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