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Bewildering Oil Analysis Results
Doug McBride, Reliability T.E.A.M. Leader, Temple Inland
After reading the readers challenge, I have a couple
of things that come to mind in relation to the problem
of unexplained elevated particle counts.
The first thing that should be done when investigating
the anomaly would be to verify that the particle counter
was operating correctly and within calibration. This can
be done with calibration fluids that can be purchased
that have a known particle count, however these fluids
can be costly, but are worth the expense to insure accuracy.
After the particle counter has been verified for accuracy
I would then want to take a look at the testing procedure
itself, I would like to observe the lab technician running
samples. There could be a possibility that the correct
procedure isin't being followed correctly.
Generally speaking it is preferabler to run the samples
as soon as possible following extraction from a machine,
however this usually is not the case, as the samples tend
to sit around for a day or two depending upon whether
the samples are run in house or sent out to an independant
lab.
In order to get an accurate representation of the oil
circulating within the machine it is generally accepted
practice to agitate the samples before testing is started.
With this said, it is fair to assume that agitation induces
air into the samples. This air must be removed before
laser particle counter testing is done. Entrained air
when left in oil will be seen by the laser particle counter
as particles.
I would suspect that after sample agitation the proper
procedure for removing the entrained air had been skipped
or improperly done. The process for removing entrained
air within oil samples can be accomplished by several
different methods depending upon the equipment utilized.
One method for degassing an oil sample is acomplished
using a small ultrasonic jewelry bath cleaner, the oil
is placed in the bath for an appropriate amount of time
and the ultrasonic frequencies transmitted by the cleaner,
coalesce the entrained air into larger bubbles allowing
them to escape the sample.
The other method for removing entrained air is by vacuum
degassing, where the sample has a vacuum drawn on it,
thereby drawing air out of the oil. The sample must be
degassed before laser particle counting can be done, otherwise
air bubbles will be seen as particles by the counter.
In order to get to the root cause of the problem of elevated
particle counts, I would suggest the lab be the first
place to start.
I would recommend a re-test of all of the samples and
insure proper procedures were followed. It might be a
possability that two different lab technicians ran the
test on the oil samples, or one of the technicians was
new or in training and had not been informed of, or understood
the degassing procedure fully.
If after re-testing the results are the same, I might
then want to look at the sampling procedure itself, is
there a possability that a new shipment of bottles has
arrived that could have been contaminated with particulates
that aren't silicon based, the bottles could be contaminated
with wood dust, plastic fines from manufacturing, or a
host of other contaminants that would not reflect in the
original report as silicon. You might want to send a representative
sample of the bottles to an independant lab to test for
particulate contamination to eliminate the bottles as
the culprit.
Given the information supplied and the lack of any corrolation
to any element other than an abnormally high particle
count my first suspicion would be a flawed testing procedure
and the presence of air within the first set of oil samples.
With this information, it sould help resolve the problem
and effectivly eliminate the elevated particle counts.
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responses to this Readers Challenge.
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