Chapter 4 Compressor and Package Unit Operation
UD-series Screw Compressor 4.1 Lubricating Oil (Refrigerant Oil)
4-4
Within ±10 % from that of fresh oil
(e) Degree of contamination
Degree of contamination measured by mass method (Millipore value)
shall be 15 mg/100 mL or less
Note 1: Synthetic oils (compatible with ammonia) are so highly hygroscopic that they can absorb
moisture at the time of sampling. In addition, the ammonia content they have absorbed may
be detected as the water content at the time of the analysis, making it difficult to precisely
measure the water content. Thus, use the criterion value only as a reference.
4.1.5 Lubricating Oil Replacement Timing
After Starting the Initial Operation
As the oil can easily be contaminated and degraded relatively quickly during the initial operation due to
scales and deposits remaining in piping and vessels, be sure to sample and analyze the oil after 500
hours of operation.
If it is found as a result of the analysis that the criteria given in Tables 4-3 to 4-5 are not satisfied, the oil
must be replaced.
During Normal Operation
Lubricating oils will degrade gradually as the system is operated over time.
The rate of degradation depends on the operating condition, type of oil and amount of foreign matters
and moisture contained in the oil. The lubricating oil must be sampled and analyzed every six months. If
it is found as a result of the analysis that the control criteria given in Tables 4-3 to 4-5 are not satisfied,
the oil must be replaced.
If the oil filters are frequently clogged or the oil color quickly becomes darker and unclear, replace the
oil after removing the cause of the problem.
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