Oil in Refrigerant Circuits

5.1 INTRODUCTION

The primary purpose of the oil is for compressor lubrication; also sealing and cooling for oil-injected types. The oil specified by the compressor manufac­turer should be used whenever possible. Various mineral and synthetic types of lubricant are available and Figure 5.1 gives some indication as to their suit­ability with refrigerant type. A blank indicates that the oil type is generally unsuited. It is necessary to emphasize that the oil types shown each represent a family of products, which can be blended to give the required viscosity, and it is necessary to use an appropriate grade or product within the family. For exam­ple, polyolester (POE) oils are shown as suitable for hydrocarbons, but a higher viscosity grade will generally be required for hydrocarbons when compared

Refrigerant type

Traditional mineral oil (MO)

Alkyl­

Benzine

(AB)

MO + AB

Poly­Polyolester Polyalphaolefin alkalene-

(POE) glycol (PAG)

CFCs and HCFCs

S

Y

K)

K)

HCFC blends

K)

S

K)

HFCs and HFC blends

K)

K)

Hydrocarbons

K)

K)

K)

Ammonia

K)

K)

K)

CO2

K)

K)

✓ Good suitability ( ) Applicable with limitations

66 Figure 5.1 Lubricant types

With that used for HFCs. Moreover, specific additive packages to enhance lubricity or to act as inhibitors may be present in branded products, and this is why the compressor manufacturer should be consulted with regards to chan­ging the specified oil for a particular compressor.

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