ILMA Compoundings - January 2020 - 22

Following the Trends

The key to successful and truly useful oil analysis is to first
establish a baseline and then periodically pull samples for
analysis to track the trends. "Oil analysis is all about establishing what is normal and waiting for it not to be normal,"
said Evan Zabawski, senior technical advisor for Test Oil and
editor of Tribology & Lubrication Technology, the publication
of the Society of Tribologists and Lubrication Engineers.
Steffen Bots, technical advisor with LubeServe, emphasized that to achieve a true understanding of the current
state of the lubricant and the equipment involved, "it is
very important that the machine and sample information
are complete. Without an idea about the equipment, used
lubricant, operating conditions and operating hours, the
wear situation can hardly be evaluated."
Unfortunately, there are no standard limits or recommended tolerances to offer guidance when it comes to wear
metals. "A static limit can be skewed by volume or run time,"
Zabawski explained. "Instead, we want to focus on trends.
Establishing a trend will be more powerful than waiting for
a certain threshold to be crossed. That's because the limits, or
absolute values, on wear metals really depend on the sump
size, how many hours you're going to run and other factors."
Zabawski noted that standard trend analysis starts with
a minimum of three samples and becomes significant with
seven to nine samples. "A lot of sampling occurs monthly or
quarterly," he said. "On large-volume systems, it may occur

JANUARY 2020

| COMPOUNDINGS | ILMA.ORG

semi-annually or even annually. However, some people do
an increased rate of sample-taking at first. Maybe they will
take monthly samples for the first six months to establish
baseline information and then switch to quarterly sampling.
We don't rely on that shorter interval to establish a trend as
much as to establish the baseline."
Added Leistikow, "It's critical to be consistent in the
timing of when the samples are pulled as well as how samples are pulled. If either of those two things changes, it will
skew the tracked trends, which can negatively impact the
interpretation of the results.
"It's important to note that all of the tests in oil analysis
- viscosity, wear metal, contaminants and so on - are
done in conjunction with one another. Each contributes to
the complete understanding of what is happening within a
given piece of equipment," he said. "To state a few examples,
wear metal analysis can tell us, based on the type of wear -
copper, aluminum, etc. - which parts are starting to see a
wear mode. Contaminants can tell us what needs to change
in order to prevent future issues. Additive metals can tell you
what state the fluid is still in.
"If you see iron in the wear metals analysis," Leistikow
continued, "there's a potential that some sort of protection
is failing in machine gears/cylinders. If all other metrics are
in good quality, you know something is going on. Metals
analysis can point to potential areas to investigate as well as
potential root causes."
Bots agreed, noting, "When it comes to the used-oil
analysis data from the laboratory, [wear metals] analysis
is the most important tool to measure and detect wear. It
shows the amount of elements present in the used oil that
potentially have been picked up from the parts the lubricant
contacts. An important one is iron, as many machinery
elements contain iron alloys. The alloy components - like
chromium or molybdenum detected by the analysis - help
to identify the specific machinery element where the wear is
coming from.
"The root cause for the increased amount of wear metals
needs to be identified," Bots added. "When the cause is
clear, corresponding maintenance is required in order to
solve the problem and determine whether the oil can remain
in the machine or not."
"With oil analysis, you're trying to predict failure by using
empirical evidence, tests that all point in a certain direction," Holloway summarized. "The more tests you can run,
the more information you'll have regarding what's going on
with that asset. Just be aware that you can get bogged down
with the data."
The solution for some manufacturers is to turn to an
outside laboratory for oil analysis and maintenance.

http://www.ILMA.ORG

ILMA Compoundings - January 2020

Table of Contents for the Digital Edition of ILMA Compoundings - January 2020