REFRIGERATION DIVISION
V SERIES
SCREW COMPRESSOR HANDLING MANUAL
Supersedes all previous version. This information is for reference use only and subject to change without notice
Revision 2 (June 05,2000) Page 58 of 61
Compressor Oil
The quality of lubricating oil significantly affects the performance and life of the compressor. Important
requirements of refrigeration system lubricating oil include suitable viscosity over a wide temperature
range, low fluidity and high flash point.
Taking the above-mentioned characteristics of lubricating oil into consideration, oil used should satisfy
the following requirements:
1) Proper viscosity should be maintained within the potential working temperature range.
2) Low fluidity should be maintained at low temperature.
3) The oil should be chemically stable, with no corrosion effect on metal and no effects on system
parts made of rubber.
4) The oil should not experience wax separation at low temperature.
5) The oil should not generate sludge or carbon under high temperature conditions.
6) The oil should be free from moisture and foreign matter.
7) The oil should be able to provide the necessary lubricating effect for a long period of time.
Selection of Compressor Oil
a) First, consider the lubrication requirements of the compressor. Obviously, oil of proper
viscosity must be supplied to the moving parts at all times.
b) Next, consider oil circulation throughout the system. Contradictory factors such as high oil
viscosity in the evaporator and low oil viscosity in the compressor must be reconciled.
c) When using Halocarbon refrigerant, even though the proper initial viscosity was secured, a
considerable change in viscosity is inevitable because under certain operating conditions the
refrigerant will dissolve in the oil. For this ISO-VG46 (JIS K2211) grade oil is recommended.
Changing Compressor Oil Brands
When changing from a brand of oil normally used to a new brand, unexpected problems may
be encountered due to incompatibility of the old and new oils when they are mixed. Exercise
care when changing oil brands.
a) If the new oil is produced by a different manufacturer, consult with both makers to determine if
the change will cause any problem.
b) Changing the viscosity grade of the same maker’s oil is acceptable, e.g., SUNISO 4GS Æ
SUNISO 5GS.
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