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operating history of the equipment. A single oil sample is not sufficient to estimate the condition of the chiller. Oil analysis
is only useful if employed to establish wear trends over time. Changing lubricating oil and filter prior to when its needed will
reduce the effectiveness of oil analysis as a tool in determining machinery condition.
The following metallic elements or contaminates and their possible sources will typically be identified in an oil wear analysis.
Aluminum
Typical sources of aluminum are bearings, impellers, seals or casting material. An increase in aluminum content in the
lubricating oil may be an indication of bearing, impeller or other wear. A corresponding increase in other wear metals may
also accompany an increase in aluminum content.
Copper
The source of copper can be the evaporator or condenser tubes, copper tubing used in the lubrication and motor c ooling
systems or residual copper from the manufacturing process. The presence of copper may be accompanied by a high TAN
(total acid number) and high moisture content. High copper contents may also result from residual mineral oil in machines
which have been converted to R-134a, R-513A and R-1234ze. Some mineral oils contained wear inhibitors which react
with copper and result in high copper content in lubricating oil.
Iron
Iron in the lubricating oil can originate from compressor castings, oil pump components, shells, tube sheets, tube supports,
shaft material and rolling element bearings. High iron content may also result from residual mineral oil in machines which
have been converted to R-134a, R-513A and R-1234ze. 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, R-513A
and R-1234ze.
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 whic h 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.
Daikin recommends that an oil analysis be performed annually. Professional judgment must be exercised under unusual
circumstances, for example, it might be desirable to sample the lubricating oil shortly after a unit has been pl aced back into
operation after it has been opened for service, as recommended from previous sample results or after a failure. The
presence of residual materials from a failure should be taken into consideration in subsequent analysis. While the unit is
in operation, the sample should be taken from a stream of refrigerant oil, not in a low spot / quiet area.
