Maintenance & Repair; Exchanging The Refrigerant; Replacing A Compressor; Lubrication And Oil Removal - Emerson Copeland 4MTL-05 Application Manuallines

6 Maintenance & repair
6.1

Exchanging the refrigerant

4MTL* and 4MSL* compressors are released for use with CO
CO with any other refrigerant is not allowed.
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In the event that the refrigerant needs replacing, the CO
can be blown off into the environment. Ensure that no oil is blown off (use a filter drier). It is essential
to ensure a good ventilation or evacuation of the CO
6.2

Replacing a compressor

CAUTION
Inadequate lubrication! Bearing destruction! Exchange the accumulator
after replacing a compressor with a burned-out motor. The accumulator oil
return orifice or screen may be plugged with debris or may become plugged.
This will result in starvation of oil to the new compressor and a second failure.
In the case of a motor burnout, the majority of contaminated oil will be removed with the compressor.
The rest of the oil is cleaned through the use of suction and liquid line filter driers. A 100 % activated
alumina suction line filter drier is recommended but must be removed after 72 hours. It is highly
recommended that the suction accumulator be replaced if the system contains one. This is
because the accumulator oil-return orifice or screen may be plugged with debris or may become
plugged shortly after a compressor failure. This will result in starvation of oil to the replacement
compressor and a second failure. When a single compressor or tandem is exchanged in the field, it
is possible that a major portion of the oil may still be in the system. While this may not affect the
reliability of the replacement compressor, the extra oil will add to rotor drag and increase power
usage.
6.3

Lubrication and oil removal

CAUTION
Chemical reaction! Compressor destruction! Do not mix up ester oils with
mineral oil and/or alkyl benzene.
The compressor is supplied with an initial oil charge. The standard oil charge for use with R744
refrigerant is a polyolester (POE) lubricant Emkarate RL 68 HB.
One disadvantage of POE is that it is far more hygroscopic than mineral oil (see Figure 39). Only
brief exposure to ambient air is needed for POE to absorb sufficient moisture to make it unacceptable
for use in a refrigeration system. Since POE holds moisture more readily than mineral oil it is more
difficult to remove it through the use of vacuum. Compressors supplied by Emerson contain oil with
low moisture content, and it may rise during the system assembling process. Therefore it is
recommended that a properly sized filter-drier is installed in all POE systems. This will maintain the
moisture level in the oil to less than 50 ppm. If oil is charged into a system, it is recommended to use
POE with moisture content no higher than 50 ppm.
Figure 39: Absorption of moisture in ester oil in comparison to mineral oil in ppm by weight at 25 °C and 50 % relative
humidity (h=hours)
The diagram in Figure 39 compares the hygroscopic characteristics of POE oil with mineral oil
(moisture absorption in ppm at 25 °C and 50 % relative humidity). If the moisture content of the oil in
AGL_Stream_ST_4MTL_4MSL_E_Rev01
refrigerant only. The replacement of
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charge does not need to be recovered and
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refrigerant to avoid a risk of suffocation.
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