ACR Journal

CMYK / .ai CMYK / .ai CMYK / .ai acrjournal.uk 23 SERVICE AND MAINTENANCE Miscibility with the refrigerant so that it returns to the compressor and does not get stuck in the evaporators, impacting the cooling capacity. All these properties can have an influence over oil return to the compressor; therefore, it is critical that high quality and fit for purpose oil is always used. Today’s commonly used types of oils can be defined as below: Hydro treated mineral oils (HTMO): Refrigeration equipment using ammonia often requires a specific type of oil to ensure correct operation. Mineral oils: Mixtures of virtually wax- free hydrocarbons used for the lubrication of refrigeration compressors, selected for their excellent fluidity at low temperatures. This kind of lubricant was particularly suited for use with CFC, HCFC refrigerants and is still used with ammonia. Alkyl benzene oils: have enhanced thermal and chemical stability and superior miscibility with hydrochlorofluorocarbons (HCFCs) allowing use at low temperatures. Alkyl benzene oils are not generally recommended for use with HFCs. They are compatible with all traditional mineral oils which they can replace where the system malfunctions with the original lubricant, but it should be noted any mixture of oils may detract from the performance properties of the oil. Very low pour and floc points help to prevent harmful wax precipitation that can block expansion valves and heat transfer surfaces. Polyol ester synthetic oils (POE): are the most common type of synthetic oil that can be used with HFC refrigerants and are intended for use in all refrigeration and air conditioning applications. Poly alkylene glycol oils (PAG): have a high viscosity index and thermal stability. PAG oils have a benefit in that they can lock in moisture to prevent it being an issue in a refrigeration system. They are extremely stable within the harsh environments of R-744 systems. PAG based lubricants are suitable for use with most commonly used refrigerants including ammonia and carbon dioxide. Poly-alpha-olefin oils (PAO): can be described as ‘synthetic mineral oils’ because of their identical structure to traditional mineral oils, the only difference being that they are manufactured from monomers such as ethylene. PAO oils can be used in refrigeration systems working in extreme conditions that are beyond the capabilities of many conventional mineral oils, thanks to their low pour points and excellent chemical and thermal stability. They have low miscibility with refrigerants and are compatible for use with carbon dioxide and ammonia. PAO oils are fully miscible with most conventional mineral refrigeration oils, but it should be noted any mixture of oils may detract from the performance properties of the PAO. Summary As an industry, we can help to improve energy efficiency with careful thought and planning on new equipment and employ some good practices relating to service and maintenance. It is our responsibility as individuals and as a collective industry to ensure we act in line with the legislation and take actions that support the movement towards improving energy efficiency. Here at Climalife we have a wide range of refrigeration oils available from all the major brands and can offer a range of packaging size options. We can help advise you on the suitability of an oil to meet your system requirements. For information regarding this article, please contact: Mel Summers, marketing manager, Climalife UK Tel: +44 117 980 2520 Email: msummers@climalife.dehon.com