2200M4JE-HO-iS2-N_2014.04.
Chapter 4
Operation of Compressor and Unit
Screw Compressor i-series
4.1 Lubricant (Refrigerant Oil)
4-1
Chapter 4 Operation of Compressor and Unit
4.1
Lubricant (Refrigerant Oil)
Lubrication management is very significant to keep the compressor in a good operating condition.
Take the following notes when managing lubricant.
4.1.1 Precautions for Selecting the Lubricant
Selection of the lubrication oil should depend on the type of the refrigerant, the type of the
evaporator used with the compressor, and the conditions under which the compressor is
operated. Also to be considered when selecting lubrication oil are the properties of the oil that
include not only the viscosity but also such characteristics as solubility in refrigerant,
separability from refrigerant, low temperature fluidity, high temperature thermal stability, etc.
We therefore recommend to contact our sales offices or MAYEKAWA representative for choice
of a specified brand for your system.
Lubrication oil used for compressors must have a viscosity appropriate for lubricating the
bearings and other components in the compressors. The viscosity to be considered in this
case should be the viscosity the oil shows at the oil inlet of the compressor. The viscosity of
lubrication oil significantly changes depending on the type of the refrigerant used in
combination with the oil. If the refrigerant dissolves in the oil (or the oil and refrigerant are
inter-soluble), the viscosity of the oil drops to a level remarkably below the level required for
operation of the compressor under some operating conditions. On the contrary, if the
refrigerant does not dissolve in the oil (or the oil and refrigerant are non-inter-soluble), the
viscosity may become too high when the supply oil temperature is low. For this reason, the
lubricant must be selected such that it is supplied to the compressor with an appropriate
viscosity (kinematic viscosity of 13 - 40 mm
2
/s) in the operating state.
The circulation of the lubricant for the entire system must be considered. After lubricating and
cooling each part of the compressor, the lubricant is discharged with refrigerant gas. Most of
the oil which is discharged from this compressor is trapped by the oil separator and is cycled
to the compressor. A small quantity of refrigerant oil goes to the condenser and the evaporator.
The lubricant is required to have sufficient fluidity and stability inside parts with different
temperatures.
Be careful since polyolester synthetic oil (POE) cannot be used with ammonia
refrigerant.
