Acid in Oil

[Metz]

How long does it take to develop acid in oil? We had a compressor fail within 20 minutes of startup on initial installation, and compressor supplier said it was due to acid in the oil. System went off on LRA, inspection showed the windings to still be good. We pulled a good vacuum and had a drier in the line. I wonder what is the time frame for acid to form?

 

[MintJulep]

I would think longer than 20 minutes.

What is the compressor supplier basing his statement on? You said supplier, not manufacturer. Was this a new compressor, or a rebuild?

How did you inspect the windings? High amps suggests a short phase-to-phase, or to ground, or an actual locked rotor.

If there actually is insulation damage, overheating seems more likely than acid given the short time. Did you actually have refrigerant flow? What was the suction condition?

Have you done an acid test yet? Many kits available, or take a sample and pour it in the supplier's eye. If he screams in pain, you've got acid.

 

[Metz]

I quoted from the response we recieved from the compressor supplier, who said "Tests performed showed the mmotor windings were within tolerances, no breakdown of winding insulation and no shorts or opens existed with the windings. The valves were also disassembeled and inspected, no discrepancies were found."

Acid test were performed via kits (Sporlan AK-1)and they showed acid in the oil (i.e. yellow in color).

They even went so far as to say they removed the piston and the cyclinder was found to ahve aluminum plated on the surface, which they claim is another indication of acidic oil in the system. They further clainm an increased level of acid in the oil degrades the oil enough to cause a malfunction of the piston and shaft.

I have a hard time believing all that can happen in 20 minutes. I am convinced in my mind that the problem was a mechanical one with the compressor, but have no data to refute their claim. The end user, and I, believe the supplier should provide another compressor at no cost. I was hoping someone had done some more definative work on the acid in oil.

Thanks

 

[MintJulep]

Was this a new system, or a new compressor in an old system?

I have never heard of aluminum plating. Copper plating yes, but not aluminum.

Assuming that the pistons are aluminum, indications of aluminum on the cylinder bore seems more like a lack of lubrication. This would be more consistant with high amps as a result of a siezed compressor.

Does the oil pump work in either direction of rotation? If not, was the rotation correct?

Possibly suction flooding?

 

[Metz]

Brand new system! Complete with hot gas bypass. All obvious parts were working. Rotation was correct. No oil pump because it is a pot compressor. I agreed with a seized compressor.

Question: If you "cook" the oil due to lack of lubrication, will it break down with an acid component?

 

[MintJulep]

My recollection is that acid is formed by the break-down of refrigerant in the presence of water and heat.

The acid then tends to collect in the oil.

IF you don't already have one, get a copy of Carrier's publication GTC2-101A "Why Compressors Fail"