Check Gear Reducers for Condensation

Readers 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 at http://www.noria.com/challenge.asp 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!)

Q & A: Achieving Oil Change Objectives

"I notice 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.

Consider the following alternatives:

1. Drain the oil within 15 minutes of shutdown and prefilter the new oil.

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.

Alternative No. 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.

Drew Troyer, Noria Corporation