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If the moisture content of the oil in a ref rigeration system reaches unacceptably high levels, corrosion
and copper plating may occur. The system should be evacuated down to 0.3 mbar or lower. If there
is uncertainty as to the moisture content in the system, an oil sample should be t aken and tested for
moisture. Sight glass/moisture indicators currently available can be used, however, the moisture
indicator will just show the moisture contents of the refrigerant. The actual moisture level of the PAG
or POE oil would be higher than the sight glass indicates. This is due to the high hygroscopicity of
the PAG or POE oil. To determine the actual moisture content of the lubricant, samples have to be
taken f rom the system and analysed.
POE/PAG
Figure 26: Absorption of moisture in ester oil in comparison to mineral oil in ppm by weight at 25 °C and 50 % relative
humidity (h=hours)
6.7
Oil additives
Although Emerson cannot comment on any specific product, f rom our own testing and past
experience, we do not recommend the use of any additives to reduce compressor bearing losses or
f or any other purpose. Furthermore, the long-term chemical stability of any additive in the presence
of ref rigerant, low and high temperatures, and materials commonly found in ref rigeration systems is
complex and difficult to evaluate without rigorously controlled chemical laboratory testing. The use
of additives without adequate testing may result in malfunction or premature f ailure of components
in the system and, in specific cases, in voiding the warranty on the component.
AGL_HP_VS_YHV_RG_RT_EN_Rev00
37
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