ALS Tribology eSource
December 22, 2011

Are You Letting Sump Size Get in the Way of Your Oil Analysis Program?
by Ambrose Hughey
Business Manager, Northwest

When I am visiting a client’s work site, I too often hear, “Oh we don’t sample that unit because it has a small sump. We just change the oil.” Unfortunately, there seems to be the common misconception that if the sump capacity is not large then there isn’t a need to test that particular unit, but this is not always the case.  

Oil analysis is much more comprehensive than just monitoring the condition of the lubricant itself. While the determination of the lubricant’s condition is a chief function of oil analysis, so is checking for abnormal machine wear and monitoring levels of contaminants being ingressed. Monitoring wear metals from the oil wetted components aids in scheduling maintenance based upon condition, before an unexpected failure occurs.  Likewise, ingressed contamination can often wreak havoc on a system. Knowing that the contamination is being ingressed through a sampling program allows you to take measures to remove the contamination and prevent further ingression from occurring, thus maximizing the equipment’s reliability. To put it simply, we don’t just test the oil, but we test what is in the oil as well.

With that said, how do we determine which units should be tested? Below is a list of chief factors to help determine which units and/or components you should sample and how often.

  • Criticality – How critical to your process is the unit/component? For instance, if this unit goes down then half the plant shuts down- SAMPLE, SAMPLE, SAMPLE… As criticality of the equipment increases, your sampling interval decreases.
  • Ease of Maintenance – Are there any extraneous factors for maintenance and repair of the equipment? If the replacement for a particular gearbox takes 6 weeks to import from Europe, then an oil analysis program would help complement other maintenance activities.
  • Duty cycle – The harder we operate a piece of machinery, the greater the need to monitor it. Consider shortened sampling intervals for severe duty cycles.
  • Environment – Dirty environments pose a much higher probability that the equipment could be ingressing contamination. Extreme environments may call for the need to sample and/or reduce the sampling interval.
  • Age – Age related failures generally occur at an early age due to misalignments or errors in manufacturing and then later down the road as equipment begins to reach the end of its normal life. An increased sampling interval may make sense during these two stages.

At times, small oil reservoirs can contribute to a heavier duty cycle of the lubricant through a loss of lubricant sump time. The time that the lubricant is allowed to spend in the sump can be crucial for allowing key activities to occur such as air release, settling of contaminants, water separation, and cooling time. Therefore, with the possible reduction in these activities, the burden placed on the lubricant may be greater in some small sumps.

So the next time you are deciding what equipment to put on the sampling schedule, please don’t let sump size get in the way of your oil analysis program.

 

 

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