General properties of refrigeration compressor oils

Refrigeration compressor oils not only have to lubricate the moving compressor parts, but (according to individual design and circuit) also seal the compression chamber and valves as well as dissipate heat. In order to ensure oil circulation and return from the system as well as to avoid lack of oil, the oil must be sufficiently soluble in the refrigerant (exception: R717 - ammonia, see Technical Information AT-640): Phase separation can lead to malfunctions e.g. in the evaporator, receiver and heat exchanger. Another important parameter is the viscosity over the whole temperature range: In the compressor, the oil must be adequately viscous, while still flowing sufficiently in the cold part of the system. In addition, the oil should be age-resistant, thermally and chemically stable.

Oil with high water content may damage compressor and refrigeration system!

Oil with high water content may damage compressor and refrigeration system!

Avoid air intake into the system and oil containers.

Use only originally sealed oil containers. Opened oil containers should be closed tightly and their content be used up as quickly as possible.

For used oils: Observe the warning values on water content.

Water in the refrigerating circuit can lead to corrosion and to freezing of the expansion valve. It adversely affects lubricity and stability of the oils. With some refrigerants (e.g. CO2) or oils (e.g. ester oils), water also reacts by forming acids – the acid in turn corrodes metal surfaces, and the water cannot be removed anymore by evacuation. Special care is necessary with polyalkylene glycol oils (PAG), polyvinyl ether oils (PVE) and polyolester oils (POE): They are strongly hygroscopic, i.e. they withdraw water from ambient air. This dissolves in the oil and can therefore not be recognised visually.