Refrigerant oil analysis

[mbreward]

Hi Chaps

Technical assistance required for a British Refrigeration Engineer a little out of his depth

We have 2 copeland scroll compressors on a chiller unit & would like to know if they have been damaged by moisture ingress.

An oil analysis was carried out but I need help in interpreting the results

Can anyone help?

MACHINERY DESCRIPTION Compressor
DATE SAMPLED 4/20/2010
OIL GRADE / MAKE Emkarate Synthetic Polyolester RL32H

TEST METHOD MEASUREMENT RESULT
Kin. Visc. @ 40°C ASTM D445 mm2/s 27.8
Kin. Visc. @ 40°C after degassing ASTM D445 mm2/s 29.46
Water Content ASTM D95 %m/m 0
Total Acid Number ASTM D974 mg KOH/g 0.09
Strong Acid Number ASTM D974 mg KOH/g 0
Total Acid Number with respect to Zinc Calculated mg KOH/g <0.01

TEST PARTICLE COUNT
METHOD PORE BLOCKAGE ISO 4406
MEASUREMENT PARTICLES / 1ml OIL


ELEMENTS IN PPM
Wear Metals Contaminants Additives
Iron 1
Copper 0
Lead 0
Chromium 0
Aluminium 58
Molybdenum 0
Tin 0
Nickel 0
Silicon 5
Sodium 0
Lithium 0
Calcium 0
Barium 0
Magnesium 0
Zinc 0
Phosphorus 1
Boron 1
Potassium 0

COMMENTS
The oil condition is good.
Aluminium wear is high but remaining levels are acceptable.
There is no visible wear debris.

This is on production equipment so reliability is important but I don't want to fork out £2000 per compressor on the off-chance that they are damaged.

Mark Breward

[james10]

What makes you think the compressors are damaged the Oil analysis seems fine. moisture in the system can give you carbon deposits on the scrolls have you had water ingrees in to the chiller if so a good long triple vac should sort it out.

[Gingerair]

Hi Mark

Why do you think you have moisture in your system ?
Is the lab that did your analysis familiar with refrigeration oils & systems ?

Normally the lab should be able to explain any results & advise accordingly.
All other lab results i've seen have given moisture content in ppm, which is normally advised to be less than 50ppm in a refrigeration system. Not sure if the scale that your lab uses would be this accurate. It gives water content as 0, it may be expected to see some level in a used system.
Have been advised before that the TAN (Total Acid Number) for new oil is around 0.04 to 0.05..
If no one else on the forum can help may be the oil or compressor manufacturers could give you some guidelines.
Sometimes a high silicon level can be an indication that moisture saturated desiccant has started to break-up.

Otherwise you could buy some new oil of the type you have & send some away for analysis. The results could then be used as a reference.
Regular testing can show trends in oil & gas contamination before they get to dangerous levels.

You could always just change the oil, although this may be pointless if any contamination in the system is not cleaned up..

[icecube51]

make a regular change of filter/dryers.
as long as the drawn Amps are in accepteble range, you don't have to worry. otherwise you can always call on a elektric engineer who has an strong megger or oscilloscoop to test the windings on damage.

Ice

[mbreward]

Thank you all for your help, I sent the oil analysis to the compressor manufacturer & got the following reply:

Based on our interpretation of the report. The quantity of aluminum present on the oil sample is high.

On the internal parts of the scroll model the motor and the oldham coupling are mostly built with this material. The function of the oldham coupling is to allow the rotational motion of the rotor/shaft assembly to be changed into a precise orbiting motion. Mostly the factors that can cause such problem for the coupling is when the compressor accumulates large quantity of liquid.

The life span of the compressor may already be shortened if the oldham coupling is damaged. For this reason we can not commit if the compressor should still be used afterwards.

Any comments would be appreciated

Mark

[james10]

Mostly the factors that can cause such problem for the coupling is when the compressor accumulates large quantity of liquid.
By quantities of liquid they mean refrigerant as it does not compress in a liquid state this can seriously damage scrolls, personally i would recommision the system and see how it runs if the comps are damaged then replace them

[icecube51]

Yep, could not agrey more. but wat was, or is the couse, that the comps are liquid succing?
beware when yore going to replace them, and the problem still exists.

Ice

[Gingerair]

+1, sounds like you're getting liquid back to the compressor. Just need to identify the reasons why now..

[icecube51]

Dirty evap? fans broken on evap? ore overcharge, when its not enough cool, just ad some more...(LOL)

Ice

[Gingerair]

Hi Mark

Did you also check with the lab that did your analysis about the value they gave for the water content ?
Not sure if the scale they've used is for water content per % mass.. It's needs to be acurate down to parts per million, ppm..

[sterl]

Not much to the analysis other than the aluminum. They did employ essentially Mineral Oil test and of course, this is a syntheitc....So anything on the strong acid no side represents a breakdown of the refrigerant, not carbonic acids as per water+ mineral oil +Temperature woudl make.

Aluminum and Copeland's input both ineresting: barring the coupling and certain motor parts, and presuming the motor is the only source for particulate aluminum and not the evaporator coils or similar: appears the a liquid incident has overloaded the couping; whcih nominally means the scrolls have passed some aluminum fragments. The coupling is portion of the motor bearing arrangement so reduced life of the compressor unit is to be expected.



And if this thing contains synthetic lube, TAN should be near-0 because mixing some of the new lubes with water doesn't make acidity...But