Hi Alex,

Her is a piece from an article which might help as the oil is emersed in the refrigerant it should be a straight forward case of completing the sample what i would say though is placing it in a ultrasonic bath with lid off to remove gas pockets trapped in the oil before sampling is crucial as there can still be micro pockets of gas which cant be seen.

Analyzing compressor lubricant is an important part of maintaining and restoring a
refrigeration/air-conditioning system's health. A refrigeration oil's viscosity, color, acidity,
moisture and elemental content are parameters that may signal potential problems when they
deviate from their normal state. As lubricating oil circulates throughout a refrigeration/AC
system, it tends to pick up indicators of a machine's internal conditions. Thus, a properly
performed oil analysis can reveal developing problems within a chiller or refrigeration/AC
system. Spectrochemical Analysis, Water Analysis, Total Acid Number, and Viscosity are the
tests most commonly performed in a laboratory analysis of refrigeration oil.
• Spectrochemical Analysis identifies the type and concentration of wear metals such
as iron, aluminum, lead, copper, tin, zinc, etc. within the oil. When the concentrations of
the various metals used in the construction of the refrigeration machine is known, any
increase in these concentrations is an indicator of wear or corrosion of an internal
machine component.
• Water Analysis determines the amount of water present in the oil. Taken by itself, the
presence of water in the oil may/may not indicate a problem as most new hermetic
compressor oils contain a measurable quantity of water before being installed into the
compressor. Changes in water content over time also may/may not indicate a problem
as the water may migrate to different areas of the machine during varying load
conditions.
• Total Acid Number (TAN) measures of the acidity of the oil. A high TAN value
indicates moisture contamination or an abnormally high operating temperature in the
refrigeration system. TAN results may not be meaningful on some older paraffin based
oils with rust and oxidation inhibitor and extreme pressure packages used in hermetic
centrifugal chillers with R-11 and R-12 and with internal gears.
• Viscosity determination verifies that the correct oil is being used in the refrigerant
system and that the oil is still serviceable.

What you can do
Visually inspect the oil on small reciprocating compressors for contamination and analyze the oil
on-site with an oil acidity test kit to determine its usability. On centrifugal, screw, and large
reciprocating water chillers, perform a laboratory oil sample analysis to determine that the oil is
still serviceable and if critical problems such as wear, corrosion, water leaks, or abnormal
operating temperatures require further investigation and action. A typical hermetic centrifugal
chiller (in good condition, used for normal comfort cooling) may operate with the same oil
charge for two or three operating seasons before any of the analysis parameters are found to
be outside the acceptable operating range.

Because of budget constraints, laboratory oil analysis is usually performed only after the oil has
been in use for at least one operating season. A common assumption is that oil, when new, has
specific initial values for analysis parameters. A frequent misconception is that these initial
values are zero. In reality, the analysis parameters of new oil can be higher than many samples
of used oil. To avoid misleading results, when performing the oil change take a new oil sample
as a benchmark against future analyses. Deviation from established trends would then indicate
a possible chiller operational or conditional problem.
Prevent poor oil conditions by using proper oil and filters for equipment and frequently
inspecting the refrigeration system to ensure that there are no operational/conditional problems
that would contribute to oil degradation. Frequent oil analyses will confirm the absence of such
Building Technologies

Cheers Sean