moisture content/acid number on compressor oil analysis

[MedicineEng]

Hi All:

Recently we performed our chillers and heat pumps oil analysis to decide if oil replacement was warranted.
When we received the reports from the equipment manufacturers there were a couple of values that were kind of strange to me:

Chillers manufacturer oil replacement levels are: 50 ppm water content and/or 0.15 acid number (as mgKOH/g)
Heat Pumps manufacturer oil replacement levels are: 1000ppm water content and 0.35 acid number (as mgKOH/g)

I was expecting closer parameters between both equipment and I have the suspicion that chiller manufacturer wants to make some quick money with the oil replacement works...
Anybody came across something like that and what would be the reason for similar equipment to have such discrepancy on the oil replacement levels.

Thanks a lot.

 

[pierreick]

Hi,
Better to ask a third party to perform the analysis if you have some doubt about the manufacturer .
My 2 cents
Pierre

 

[EnergyProfessional]

What did the manufacturer say when you asked them?

I bet it has to do with the material and tolerances used and required in each device. They could use different refrigerant, seals, oil etc. I assume the chiller is much larger device than a heat pump (well, a chiller, or any refrigeration device is a heatpump). The heatpump design also could be older or newer, or made by a different manufacturer. Maybe the chiller manufacturer just put their name on the heatpump, like Trane cooperates with Mitsubishi on selling their VRF etc.

 

[moideen]

I did an oil test for carrier 30XA screw chiller with a reputed firm in the local industry. The report shows the limit of water content is OK when lower than 150 ppm. The water content then it shows 74 ppm in the test result, and lab says it is OK.

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

 

[engineering_investigator]

Hi MedicineEng,

I would recommend contacting the people that did your tests and make sure that you understand what their results are telling you. Aside from from the results, 1000 ppm of moisture sounds awful high to me. Has your heat pump experienced a refrigerant leak and had to be recharged? Perhaps the system wasn't evacuated as well as it should have been and the filter drier is saturated. Has a compressor been replaced or other component been replaced that would have necessitated the evacuation and recharging of the system? Instead of evacuation, was the system purged? Purging the system might not have been adequate to remove moisture in a system that was open to atmosphere for more than a few minutes. In any case, the moisture in the system will have to dealt with as it will eventually cause problems.

 

[MedicineEng]

All:
Thanks for your feedback.

engineering investigator: 1000ppm is the limit on the heat pump report as recommended to have the compressor oil replaced, not the current moisture content on our heat pumps' oil.
Apologies if that wasn't clear on my original post.

It seems that it all goes back to the type of compressor, refrigerant, oil and service of each equipment.
I might have been comparing oranges to apples and making inferences that are not exactly correct.
I was just surprised for the difference between alarm levels when compared equipment one to another...

 

[TugboatEng]

What types of bearings do the units use? Rolling element bearings are more sensitive to water content than journal bearings. Babbited journal bearing tolerate but don't prefer high base numbers. A roller bearing compressor vs plain bearing heat pump would align with your original post.