Inconsistant KF Water from R134A

[rttech]

We have been getting varied results from performing KF Water on samples from two Refrigeration Turbine Type Compressors.
These two compressors are running Castrol Icematic 68 with the gas being R134a, Tetrafluoroethane (CF3CH2F) from the family of HFC refrigerants.

KF Water performed on other machines appear correct and as expected with the difficulty only appearing with these two compressors.

We have split samples between the two labs and gathered results from other samples processed from the two compressors at the same labs.

As we can see from the results tabulated in the chart both Labs have low and elevated results, note when we split samples with dry bottles we received dissimilar results.
Note how when the lab manager double checked the results on the 18th of November that the individual lab process’s delivered similar results as expected.

As you would understand these two compressors are a sealed system operating at approximately 100 PSI and there should be no opportunity for environmental contaminates to gain entry and we have been monitoring these compressors by microscope for 6-7 years and at present the two compressors appear to be running in a normal wear mode at a low rate of wear with a low level fine hard particle abrasive wear debris evident but no indication of oil gelling or water damaged lubricant agglomerations in the samples.

The only variable we can think of is if the R134a, Tetrafluoroethane (CF3CH2F) refrigerant is affecting the titration process and the amount of gas remaining in the sample is the variable as the sample temperature and length of time standing would change the amount of residual gas remaining.

We need to figure why we are getting the varied results as when we go over 100 ppm water a $10,000 system dry out and oil change is recommended for the compressor and at present we have invested > 8 hours of R&T lab time, 6 hours of site time and > $500 of KF Water analysis and have no results that we are confident in enough to hand onto our customer.


Thanks for your assistance with this.


Best Regards





Rob S

[mad fridgie]

Firstly you say you have tested other compressors, where these on R134a?
You have indicated that these are the only ones on R134a.
The oil is an ester type, and thus is hygroscopic by nature.
I suspect that you maybe allowing air to mix with oil "a" when removing, then "b" at the lab (the varing results may depend upon the weather and the room conditions at each lab (water vapour pressure)

[Brian_UK]

I would suspect your method of gathering the samples.

There is no consistency with the results. Readings going low and then high, moisture, if present in the system has no means of escape so should remain steady or increase, if leakage present.

How are you taken the oil samples?

[constantine]

And what is KF water analysis? please explain and help
thank you.

[Brian_UK]

And what is KF water analysis? please explain and help
thank you.

Reading the supplied pdf file and searching the internet brings up this....

http://en.wikipedia.org/wiki/Karl_Fischer_%28chemist%29