For the past three years, your company has successfully been using on-site oil analysis. Currently, as many as 500 samples per quarter are analyzed in the on-site
lab.
Over the past week, condition-based maintenance personnel have noticed that the particle count results seem to be backward, i.e., more particles are showing up after the in-line filter than before the filter.
Initially, it was suspected that the unusual particle counts were due to a labeling mix-up, confusion on the direction of oil flow through the filter, a damaged filter or background contamination. Your
plan initially is to resample. If the results are the same, you will change the filters and then sample again.
What other steps could help identify the root cause
of the abnormal particle counts?
Submit your answer at http://www.noria.com/challenge.asp before Tuesday, July 13, 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 going into 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!)
From the book "The Practical
Handbook of Machinery Lubrication"
An absolute rating indicates the size above which no particle of any size will pass. It does not specify the size of the smallest opening in the media, so
that a filter rated at 10 micrometers absolute will do little to reduce silt particles measuring less than 10 micrometers. Also, these filters will be ineffective every time the bypass valve opens (regardless
of their absolute rating) whenever they are used in full-flow applications.
| Q & A: High Oil Temperatures Are Not Always Bad |
"I have learned that high temperature
encourages additive depletion and base stock oxidation in bearing oils. We are a paper mill and have been told by the paper machine supplier that our main lube oil reservoir should be maintained at 180 degrees
F. Why are these high temperatures recommended, considering the harm it can cause?"
You are correct, high operating temperatures encourage additive and base oil failure. The widely used rule
of thumb is that for every 18 degrees F increase in temperature, the life of the oil is cut in half. Still, it is common for high temperatures to be recommended in paper mill applications.
Reasons include better water-shedding ability, lower foaming tendency, better air release, improved particle settling rate, better drain back flows, and more rapid vaporization of water. However,
most of the benefits from increased temperatures can be sufficiently achieved at, say, 140 degrees F.
At this lower temperature, viscosity will be higher and therefore you might want to revisit
the viscosity grade selection. Lower viscosity oils, in general, are more resistant to oxidation and thermal failure. It is good advice to discuss a proposed temperature and/or viscosity change with your machine and oil
suppliers.
