MRO Magazine

Fluid cleanliness test predicts your system’s health


September 14, 2001
By PEM Magazine

A trend that’s finally coming of age in the maintenance department involves using oil analysis techniques to determine the health of a hydraulic system. Like a blood sample, a good analysis offers in-depth information on what is going on in your system and is a great indicator of the things you often don’t see until it’s too late. In addition, like a blood sample, misunderstanding the facts or misinterpretations can be very costly.

By removing damaging contamination, it’s possible to eliminate up to 80 percent of hydraulic problems. To do this however, the maintenance professional must first determine the level of contamination in a system through an oil analysis. Once this is established, findings can be compared to manufacturer’s specifications.

This is where a good quality oil analysis is required. The challenge is often deciding what to do once the analysis is returned. You’re in the majority if you were to ask yourself the question: "what do I do when I get the results of the analysis?" Sadly, the answer for most is: "file it". More often than not, the results are put in a drawer or thrown it in a pile somewhere. This is usually due to an uncertainty of what to do with the results.

Oil samples are incredibly effective maintenance tool. When used properly, they act as a lifeline to prevent system breakdowns. The key is knowing what to look for and how to use it. Although all components in oil samples are important and say something about your system, there are two key factors to look for in the results that are the most important.


The first is the ISO particle count. This is a measurement of the amount of particles in a system often indicated by a two or three digit code. Eg: ISO 16/13 or ISO 16/13/10. These three numbers typically refer to levels of particle sized 2 micron, 5 micron and 15 micron respectively. In December, 1999 the ISO altered the the fluid cleanliness code; the digits now represent 4 micron, 6 micron and 14 micron.

Don’t let this confuse you however; a high-quality oil sample should also indicate the total amount of contamination particles in each of those sizes. This is exactly what the ISO standard reflects. Each of the three numbers refers to the amount of particles of a particular size present in the oil. In other words, if your sample is 16/13/10, the 16 refers to the 2 micron (old measurement) or 4 micron (new measurement). The 13 represents 5 micron (old) or 6 micron (new) and the 10 refers to 15 micron (old) or 14 micron (new). You would then look up 16, 13, and 10 on an ISO chart which would tell you the amount of particles of that particular size in your sample. It makes it much easier when the lab results already show a total particle amount. If your lab does not do this now, ask them to.

What is a good count then? Check the manufacturers’ specifications as an indication. You would be doing well if your oil is kept at a range around ISO16/13. This will keep you system running very well, reduce your breakdowns by as much as 65 percent and make your oil last longer.

The second key issue is the TAN or Total Acid Number. This number reflects the acidity of the oil and the fluid’s general condition. You want this number to be below 1 using the standard test. Once your oil exceeds 1 the oil should be disposed of.

It is very important that a company have a good lubrication program in place. If you are not sure how to do this, contact a consultant who specialises in lubrication programs and oil analysis and you could end up saving thousands of dollars.

Webster is with Triple R America Ltd., Toronto, Ontario. He can be reached at (416) 413-9202 or by e-mail at