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Centrifugal Chillers
D-EIMWC00804-14EN
to R-134a. Some mineral oils contain wear inhibitors which react with iron and can
result in a high iron content in the lubricating oil.
Tin
The source of tin may be from bearings.
Zinc
There is no zinc used in the bearings on Daikin chillers. The source, if any may be from
additives in some mineral oils.
Lead
The source of lead in Daikin centrifugal chillers is the thread sealant compounds used
during chiller assembly. The presence of lead in the lubricating oil in Daikin chillers
does not indicate bearing wear.
Silicon
Silicon can originate from residual particles of silicon left from the manufacturing
process, filter drier material, dirt or anti-foam additives from residual mineral oil which
may be present in machines that have been converted to R-134a.
Moisture
Moisture in the form of dissolved water can be present in lubricating oil to varying
degrees. Some polyolester oils may contain up to 50 parts per million (ppm) of water
from new unopened containers. Other sources of water may be the refrigerant (new
refrigerant may contain up to 10 ppm water), leaking evaporator condenser tubes or oil
coolers, or moisture introduced by the addition of either contaminated oil or refrigerant
or improperly handled oil.
Liquid R-134a has the ability to retain up to 1400 ppm of water in solution at 100
degrees F. With 225 ppm of water dissolved in liquid R-134a, free water would not be
released until the liquid temperature reached -22 degrees F. Liquid R-134a can hold
approximately 470 ppm at 15 degrees F (an evaporator temperature which could be
encountered in ice applications). Since free water is what causes acid production,
moisture levels should not be of a concern until they approach the free water release
point.
A better indicator of a condition which should be of concern is the TAN (Total Acid
Number). A TAN below 0.09 requires no immediate action. TANs above 0.09 require
certain actions. In the absence of a high TAN reading and a regular loss of refrigerant
oil (which may indicate a heat transfer surface leak) a high moisture content in an oil
wear analysis is probably due to handling or contamination of the oil sample. It should
be noted that air (and moisture) can penetrate plastic containers. Metal or glass
containers with gasket in the top will slow moisture entry.
In conclusion, a single element of an oil analysis should not be used as the basis to
estimate the overall internal condition of a Daikin chiller. The characteristics of the
lubricants and refrigerants, and knowledge of the interaction of wear materials in the
chiller must be considered when interpreting a wear metal analysis. Periodic oil analysis
performed by a reputable laboratory and used in conjunction with compressor vibration
analysis and operating log review can be helpful tools in estimating the internal
condition of a Daikin chiller.
Normal Sample Intervals
Daikin recommends that an oil analysis be performed annually. Professional judgment
must be exercised under unusual circumstances, for example, it might be desirable to
