Challenge: Bewildering Oil Analysis Results
A number of return line bearing samples have
been taken from a steam turbine and you are puzzled
and concerned by some of the oil analysis results.
Your main concern is the large number of samples
that show elevated particle counts. It’s
been recommended that maintenance personnel check
the seals, breathers, etc. However, this leads
you straight to the silicon count, which is, for
the most part, zero. Therefore, the increase cannot
be attributed to the ingress of normal dust or
dirt. Neither does there seem to be any increase
in any telltale wear metals or contaminants in
the elemental analysis.
You are aware that particles large enough to
contribute to the particle count may not directly
affect the elemental analysis; however, it seems
that an increase in particulate contamination
with no supporting evidence from the elemental
analysis may be spurious. What else could the
particles be? Water levels in the samples are
low, ranging from 30 ppm to 40 ppm (no interference
on laser counts).
What steps can be taken to determine the root
cause of the elevated particle counts?
Submit your answer
before Tuesday, September 14, 2004. Lube-Tips
editors will choose the best answer and the $100
recipient will be announced next week.
If you have a reducer that is water-cooled and
the water temperature is too cold, it could condense
and put water in the oil. If you notice water on
the floor, or on the cooling water lines entering
the gear reducer or the gear reducer sweating, you
probably have water in the gear reducer. I have
encountered this problem twice. Both reducers were
critical equipment. When you find this problem,
first increase the temperature until the water lines
quit sweating. Second, perform oil analysis on the
reducer and check for water. If this issue isn't
corrected, it could be catastrophic. (Submitted
by Hack Hensley, Predictive Maintenance, Mitsubishi
Polyester Film, LLC. Thanks Hack!)
Detecting Oil Oxidation
Test your knowledge and prepare for ICML lubrication and oil analysis certification.
When an oil oxidizes, what are two changes that
can be detected by oil analysis?
& A: Achieving Oil Change Objectives
that the ISO cleanliness level doesn't change much
after changing the oil in my gearboxes. Shouldn't
the oil be cleaner after the change?"
Most gearboxes are drained on a quarterly, semi-annual
or annual basis - usually to eliminate contaminants.
Typically, five percent or more of the old lube is
left in the gearbox. If the oil is not drained shortly
after shutdown, the sludge and contaminants will accumulate
in the bottom of the sump and remain with the residual
oil. When the box is refilled with lubricant and restarted,
the contaminant is resuspended, and the oil change
fails to achieve its objectives. Also, the new oil
may not be clean if it is not prefiltered.
1. Drain the
oil within 15 minutes of shutdown and prefilter the
2. Instead of
draining the oil, periodically filter the oil with
a portable filtration cart while the machine is operating.
Sample and analyze the oil periodically to determine
if it needs to be changed. This strategy will reduce
your overall cost of maintenance and extend the life
of the gearbox, and requires little upfront investment.
3. Install full
time filtration on the gearbox and sample and analyze
the oil periodically to determine if it needs to be
changed. This strategy will also reduce your overall
maintenance cost and extend the life of the gearbox,
but requires some upfront investment.
1 helps, but alternatives No. 2 and No. 3 are the
best. Most scheduled oil changes can be eliminated
with the one-two punch of filtration and oil analysis.
This strategy reduces lubricant and labor costs -
and the fact that your gearboxes will last longer
is a major bonus. Plus, the maintenance of the fluid
can typically be performed during run-time, shrinking
the task list during scheduled outages.
Troyer, Noria Corporation