An oil analysis report contains results on as many as 40 different parameters that each have acceptable ranges identified. The type of oil, its formulation, how it should be maintained, and the operating conditions all are considered when evaluating an oil sample and setting acceptable ranges. Also considering the type of equipment and the operating environment is just as important.
An acceptable oil analysis program should consist of these basic components; standard processes for the establishment of normal ranges, along with the identification of limits and a reliable system for recognizing failure modes. Most labs offer comments and recommendations in the form of flags that are patterned after green, yellow and red traffic lights. Yellow and red flagged parameters indicate that a threshold has been passed and further action is required on the part of the end user; green flagged information indicates an item is within range, and is archived for trending. Some parameters, such as particle counts, only have upper limits. Other parameters, such as oxidative stability, only have lower limits. Parameters such as viscosity, that measure stability, have both upper and lower limits. There is not a universal approach for setting alarm limits. Also, some parameters and stats on the lab report are not critical to that specific piece of equipment, so not every oil analysis parameter needs an alarm limit.
Because oil analysis is as much expertise as formulae and there are so many considerations involved, most labs do not publish limit information. The issue for end-users is who sets the range and who to believe—formulator, OEM, lab, industry, association such as ASTM—and why.
There are four traditional absolute methods for determining oil analysis ranges and flagging limits.
These methods are:
Consider working with your Technical Advisor and a Lab to help determine any changes to flagging limits for the end-user.