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Bewildering Oil Analysis Results
Daryl Kelly, Condition Monitoring Engineer, Xstrata Coal
Particle counts can still be influenced by matter even
though spectrometric analysis hasn't given a positive
indication of such. Additives out of solution or products
of oxidation could influence particle counts. Moisture
levels could also still influence particle counts due
to the point of saturation for this particular oil. Remember
that is possible for some turbine oils to become saturated
at around 50ppm water at 20 deg C.
If the laser particle counts can be relied on and particles
are actually present then further checks should be performed
to establish this. I would suggest running 100ml of the
sample through a 1.2 micron patch membrane and viewing
particles under an optical microscope. Concentrations
of solid particles can be counted or at least checked
against an optical comparator to gauge if cleanliness
level does indeed correlate with laser particle count
results. Look for discolouration of patch membrane caused
by insolubles filtered out from the oil. I find by just
looking that further information is gained to unlock the
truth.
Check for signs of oil degradation. Has RBOT been performed?
Has KF or KF "oven" method been used to determine
absorbed moisture content and at what temperature was
this tested at? Can a moisture percentage saturation curve
be obtained for this oil?
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