COMPRESSOR TECHNOL OGY i s understandable.

It takes good maintenance to operate an industrial refrigeration system efficiently, and oil is an immensely important part of this maintenance. Interruption of service or reduced system capacity can result in significant loss o f production or products in storage. With the growing trend towards natural refrigerants (ammonia, CO2, and HCs) and the gradual replacement of HFCs with low global warming potential HFOs, the availability and accessibility of high-performance lubricants to meet

environmental requirements has never been more i mportant than it is today. As with upkeep of motor vehicles, it is recommended to carry out an oil change at regular service intervals.


M odern high speed ammonia compressors require a high quality lubricant and should ensure the f ollowing qualities are met:

 High film strength for sealing between male and female rotors and between rotor tips and compressor barrel.

 Ability to cool the compressor.

 Sufficient lubrication to reduce wear on reciprocating compressors and maintain

adequate viscosity at discharge temperatures for lubrication and sealing on screw c ompressors.

Large refrigerant systems using ammonia (non- or low-miscible with HCs) as a refrigerant are equipped with oil separators, so it is desirable to use a lubricant that is quite immiscible with the r efrigerant fluid, and has low vapour pressure to avoid or minimise oil carry-over in the circuit. The harsh chemical environment of an ammonia refrigeration system requires an oil that must l ubricate, cool and seal.

Carbon dioxide arbon dioxide

Although either miscible or immiscible oils can be used in CO 2 systems with traditional refrigeration compressors, it is recommended that miscible POE oils (polyolester) are used. This is because in refrigeration systems with immiscible oil such as POA (polyalphaolefin), the oil management s ystem is not simple. Oil filtration requirements a re high, and the separation of oil from CO 2 is complicated by the fact that the oil is less dense than CO

In comparison, in CO 2.

2 refrigeration systems with miscible POE oil, oil management system

requirements are simple. The only challenge in POE systems is the stability of POE oil, as it has a high affinity for water, meaning a ‘clean’ system is required for successful operation.

F ailure to keep the oil in good condition will lead to changes in its properties and can lead to an increase in energy consumption, greater wear and reduced compressor life. Unlike with refrigerant, records are not often kept of the grade of oil used in a system. Sometimes the name may be unfamiliar, or the oil used as the i nitial fill may not be readily available in the UK market. This makes it increasingly important to keep accurate and up-to-date records stating oil types, or, alternatively, consult an expert for advice. The manufacturer of the compressor will always specify the oil type and viscosity for their e quipment.

Choosing the wrong type of oil or even the incorrect viscosity for a specific type of compressor could cause problems and prove a great expense. This is why consulting a technical specialist such as Climalife – which stocks a wide range of lubricants and has extensive knowledge a nd experience of selecting the right oil for the right system and conditions – can be extremely useful.

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