| Today's
Tip: Modifying Sight Glass Improves Visibility |
On equipment with vented oil tube sight glasses,
it is sometimes hard to determine the oil level.
This may be due to poor lighting or a dusty environment.
On the next inspection of the equipment, try removing
the tube and glass. Clean the inside of the tube
with a degreaser, then color the inside with a
white or bright color marker that is compatible
with your oil. A felt-tip white metal marking
stick works great because it allows you to get
inside the tube channel. This has worked well
on several machines at our facility. Equipment
oil levels will be easier to detect with the lighter
background. (Submitted by Spencer Anderson, PDM
Tech., TLNA A.E. Staley. Thanks. Spencer!)
Each tip published will earn the sender $100.
Submit
your tip.
From the book "Fluid Contamination
Control".
The amount of water that a given fluid will absorb
depends upon its base stock, viscosity, additive
package, and temperature. The amount of water that
can dissolve in a fluid is termed its saturation
level. The saturation level for a hydraulic fluid
is 200-300 ppm while for a lubricating oil it is
around 500-600 ppm. Oil is cloudy when it is above
its saturation level. The saturation level for a
synthetic fluid is generally much higher than for
a mineral base fluid.
More
information about the book "Fluid Contamination
Control"
| Lube-Trivia:
Understanding Beta Ratios |
Test your knowledge and prepare for ICML lubrication and oil analysis certification.
QUESTION:
What would a beta ratio of 75 mean for a 10-micron
filter?
Get
the answer.
| Q
& A: Advice for Oil Sampling |
"We have a
600 liter sump that supplies 150 liters per minute
to eight turbine bearings from one reservoir. The
oil flows from the reservoir by a single pump and
filter, then separates to the eight bearings. We take
the oil samples from the return lines before they
join for the return to the reservoir. None of the
samples show much wear. On the last sampling when
there was a sign of bearing failure, the sample for
that bearing showed only 4 ppm iron, 2 ppm tin, 1
ppm aluminum, 2 ppm silicon, 2 ppm sodium, 2 ppm magnesium,
and everything else 0. Viscosity was 66.7 on Regal
68 at 1,000 hours (6,200 on the unit). Why would samples
not show that there is a problem?"
The answer to your question can likely be summed up
in one word - dilution! Assuming, as you state, that
you are sampling on the return lines from each bearing,
the reason for the low wear metal levels is likely
due to the comparatively high oil volume in the return
lines. In oil analysis, wear debris is measured in
parts-per-million. So when you state "2 ppm tin" what
we are actually saying is "2 mg of tin for every kilogram
of oil".
So the same amount
of wear debris, distributed in a large volume of oil
such as a circulating turbine, will generate a much
lower ppm than the same amount of wear in a small
wet sump system where the volume of oil is typically
much smaller.
To minimize the
effects, try to ensure the sample is taken as close
to the bearings as possible. Also ensure that the
sampling method is precisely controlled with the same
method, used every time including flushing volumes.
You might also need to tighten your alarms considerably
to the extent where "normal" really means 0 ppm of
tin (and other key elements), and any slight increase,
even just 1 to 2 ppm is consider "cautionary".
Other possible
causes of the low wear metals limits could be a failure
mechanism which really doesn't generate significant
amounts of wear debris, or one that creates larger
sized particles (in excess of 5 microns) which do
not show up in conventional elemental spectroscopy
techniques. However, given the nature of this application,
dilution is the most likely scenario.
Mark
Barnes, Noria Corporation
