Polyol Ester Oil (POE)

All mechanical refrigeration systems now being manufactured for freeze dryer use are based on HFC refrigerants such as R507. The use of a Polyol Ester synthetic oil is the rule in R507 refrigeration systems. This oil has superior lubricating ability over the mineral oils commonly used in older CFC refrigerant systems.

1. Only POE oil should be used in a R507 system. However, not all POE oils are the same. There are a variety of POE oil types and grades and it is important to know which POE oil is in the system being serviced. Mixing incompatible POE oils may create problems and lead to compressor failure.

2. All POE oils are highly hydroscopic, they absorb moisture quickly and hold the moisture they absorb. Once absorbed, the moisture cannot be removed through system evacuation even at a vacuum pressure as low as 500 microns (millitorr). A contaminated system must be drained, flushed, and refilled.

3. It is important to prevent moisture from getting in the oil in the first place. The general recommendations for handling POE oil are to keep it in a metal container, transfer it with an oil pump, and keep the container sealed except when absolutely necessary.

4. Polyol Ester oils are good solvents. When upgrading a system from a CFC refrigerant such as R502 to a HFC refrigerant such as R507, the POE oil will readily remove any trace amounts of the mineral oil they are replacing. However, this also means seal, gasket, and electrical potting compounds must be carefully reviewed for compatability before adding the new oil.

5. POE oils are irritating to the skin and a real concern if they come in contact with your eyes. Hand and eye protection are essential when working with this oil. Be sure to read and follow the manufacturer's safety and handling advisories and the MSDS warnings and guidelines for the specific oil being used.