OIL SYSTEM:

The primary function of the oil in a refrigeration compressor is to lubricate the bearings and other rubbing surfaces. It is also required to (i) seal the clearance spaces between the discharge and suction side of the compressor (ii) act as a coolant, removing the friction heat from rubbing surfaces, (iii) actuate capacity control mechanism and (iv) dampen the noise generated by the compressor.

Refrigeration oils should possess the following properties :-

1)                    Good chemical stability. There should be no chemical reaction with the refrigerant or materials in the system.

2)                    Good thermal stability. They should not form hard carbon deposits at hot spots in the compressor.

3)                    Low viscosity. This is the ability of an oil to maintain good lubrication properties at high temperature and good fluidity at low temperature i.e. to provide a good lubricating film at all times.

4)         Low wax content. Particularly important in the case of CFC and HCFC plants, operating at low evaporating temperature, as separation of wax particles from the refrigerant -
oil mixture may cause problem by blocking expansion and regulating valves.

5)                    Low Pour Point and floe point. Ability of the oil to remain in a fluid state at the plants lowest evaporating temperature.

6)                    Moisture free and anti foam characteristics. Any moisture added with oil may cause corrosion or would form ice and choke expansion valve.

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