Setting ISO Cleanliness Targets

Part of a lubrication program involves establishing ISO cleanliness targets, whether for new lubricants, or for in-service machines. The two primary difficulties of setting these targets arise from finding a reputable data source and trying to find an exact fit. A seemingly smaller concern, but one with greater ramifications, is defining the difference between a target and a limit.

A target is defined as a desired value, whereas a limit is defined as a value that prompts a form of action to be taken. Original Equipment Manufacturers (OEMs) may provide either, so it is important to make the distinction before committing to using any OEM values.

For example, a speed limit is truly a limit, not a target, even though it is treated is as such. If a highway has an imposed speed limit of 55 mph, it is within the law to issue a ticket for travelling at a speed of 56 mph, though this is rare. Experience would say than speeds of up to 60 mph won’t result in a ticket, but 65 mph or higher certainly could. In this metaphor, the OEM limit becomes a target, and the actual limit somewhat higher.

For lubricated machines monitored by oil analysis, interpreting a limit as a target will void any warranty, therefore targets are generally set at least two codes lower than the limit. Conversely, limits should be set at least two codes higher than a target. The difference between the target and limit provides some latitude to ensure that no action is required when the cleanliness is on target, and accounts for the precision and bias of the test (results may vary by up to one code).

Cleanliness targets are not set generically according to machine type (e.g. compressor, pump), but rather to the most sensitive component within the system (e.g. type of bearing or valve), the system pressure (higher pressures require cleaner fluid), type of fluid (e.g. mineral oil or water glycol) and operating conditions (e.g. criticality, ease of repair, dirty environment). Given so many variables, it's apparent why OEM cleanliness targets may not always be available, but also that one target may not necessarily apply to all machines of the same type.

It should be noted that new oil generally has a cleanliness of 20/19/16 (give or take a code) regardless of packaging (bulk, tote, drum or pail), and that most in-service targets will be decidedly lower. Therefore, without prefiltration of new oils, nor without decent lubricant handling, any top-up or fluid change will result is a marked increase in the particle count, potentially surpassing a limit. The best solution is to prefilter the new fluid to at least the target cleanliness level, avoiding taxing the system’s filtration with the new fluid.

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About Eurofins TestOil

With more than 30 years of experience in the oil analysis industry, Eurofins TestOil focuses exclusively on assisting industrial facilities with reducing maintenance costs and avoiding unexpected downtime through oil and fuel analysis program implementation. As industry experts in diagnosing oil-related issues in equipment such as turbines, hydraulics, gearboxes, pumps, compressors and diesel generators, Eurofins TestOil provides customers with same-day turnaround on routine oil analysis testing.  For more information on partnering with Eurofins TestOil on oil analysis programs or training opportunities visit https://testoil.com. Contact: Al Yates 216-251-2510; sales@testoil.com. 

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