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In this issue:
1. Torque Converter /
Transmissions - Failure Indicators
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Torque Converter /
Transmissions - Failure Indicators
One of the goals of a well
run oil analysis program will be to allow a component to remain in service for
as long as possible - to use up all of it's service
life. There is significant financial
advantage to doing this. Condition
measurements (oil analysis) are taken to try to determine the end point as
accurately as possible. This example
concerns torque converter / transmission assemblies using common oil only.
As the component nears the
end of it's service life, there are several factors to
watch for in oil analysis trends:
- particle
counts in various size ranges
- component-specific
indicators (metallurgy)
Aluminum/Aluminium
This metal is generally
present in torque converter impeller blades.
When results show a rise in aluminum with a minimal rise in copper or
iron and a rise in large particle percentages, the failure is most likely the
torque converter and not the transmission.
However, if a transmission is operated in this condition, it can be
affected detrimentally.
Copper
If a rise in copper is seen,
it can indicate wear out in clutch discs, thrust plates or bushings in the
transmission or pump. If the pump is
failing, a rise in pump casing material (iron or aluminum) will quickly
accompany the rise in copper. If the
transmission is failing, copper and silicon (clutch discs) will generally
increase quickly, with a greater silicon increase.
Large Particles
An increase in the ratio of
large particles to small particles is a very good sign that a component is
entering an advanced stage of wear out.
Not all labs report the percent or ratios of particles in different size
ranges so check what your lab reports.
Particle counters can be set to output the numbers in a variety of
formats so it may be a simple change for your lab to give you these figures if
they do not. If any particles at all are
present in the 25-50 micron size range, failure may occur within 1 - 14 days. As the particle counts do not differentiate
between particles of different materials, it is prudent to carry out other
checks to confirm the source of particles.
If a particular metal is rising quicker than another, it may be the
cause of the rise in large particle counts. Two good practical confirming
checks are: 1. Pull
the suction screens for inspection (if present). 2. Cut open the filters
for inspection.
If particles are present in
the 25-50 micron size range, they will generally be visible on screens and
filter material. Copper will show as
shiny yellow particles (unless heated severely). Aluminum will show as shiny silver
particles. Iron will be a darker gray
color and can be verified with a magnet.
The naked eye can see particles above about 40 microns.
It is premature to change
out a component at the first sign of trouble in the oil analysis results
without some confirming checks. This
will almost certainly lower the success of the oil analysis program. Practical checks such as these involve the
mechanics in the decision making process and help take the economic risk out of
component change-out decisions.
*** Note: Many more factors
are involved than presented here. This
discussion is presented as a starter guide only to interpreting oil analysis
results in a multi-component system with common oil. Consult your OEM if unsure of component
metallurgy.
Many
thanks to Charlie Pearcy, Dingo's Western Region
Project Manager for this Interpretation Tip. Charlie brings 13 years of Mine Maintenance
experience to Dingo customers in the west.
Best Regards,
Andy Ling and the Dingo Team
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