When to Replace Bulk Oils

Mohammad Naseer Uddin, Petroleum Development Oman
Tags: oil changes

During a recent discussion with a friend who works in a large power generation plant, he told me about his annual shutdown activities, including the turbine oil replacement conducted on one of the power turbines. I asked him about the criteria for oil replacement but didn’t like his answer.

He said they had spent more than $250,000 on bulk oil replacements during the past 12 months. In reviewing the previous oil analysis reports, I was not surprised to see that all of those oils didn't require replacement and could have been returned to a healthy state with the proper mitigation action. If he had only talked with me a few weeks earlier, it might have been a different story.

Oil Replacement Strategies

There are two main strategies for bulk oil replacement: time/cycle-based and condition-based. Lots of companies still have decision-makers with a stone-age mentality who follow the time/cycle-based replacement strategy. This results in oil being replaced too early or too late.

Of course, both of these conditions are undesirable. Unnecessarily replacing oil not only is a waste of money, but it also may lead to the introduction of other failure modes due to human intervention. Replacing oil too late puts the asset at risk of a lubrication-related failure, thereby resulting in poor reliability and production losses.

Many organizations use a condition-based oil replacement strategy, thinking it is the correct approach, but this is a myth. Having reviewed numerous cases from across the globe, I have discovered that the majority of these companies underestimate the power of oil analysis and spend little effort in developing the right maintenance strategy for their lubricants.

10 Common Mistakes

Following are 10 of the most common mistakes organizations make with their oil analysis program:

1. Lack of basic lubrication knowledge and training among decision-makers, leading to incorrect interpretation of oil analysis reports.

2. Wrong test slates that are incapable of detecting the oil’s health or condition.

3. Oil analysis reports arriving too late from the laboratory.

4. Poor oil sampling practices (wrong method and/or location).

5. Receiving only numbers/figures from the oil analysis lab without any remarks, which often results in no interpretation and reports filed away with no action taken.

6. Lack of information (oil life, type/brand, machine application, top-up rate, etc.) sent to the lab for proper interpretation.

7. Too few/irrelevant oil analysis tests conducted by the in-house lab, resulting in improper actions.

8. Lab analysts with no knowledge of the basics of lubrication and tribology or with no previous oil analysis experience who are asked to conduct critical analysis.

9. Cross-contamination of oil samples in the lab during analysis, leading to inaccurate results.

10. Oil that easily could have been cleaned with the proper tools and methods being discarded because condition monitoring suggested the oil be changed.

Replacement as a Last Resort

Due to ignorance and a lack of knowledge, every day companies throw away millions of gallons of oil that could be brought back to a perfectly healthy state with little effort. Therefore, ensure that the individuals who interpret your oil analysis reports have up-to-date knowledge of all the available technologies that can be used to recover an oil's physical and chemical properties, as new methods can now restore certain properties which previously were considered irreversible.

Oil replacement should always be the last resort, as it is the most expensive option for bulk reservoirs. Replace bulk oil in the reservoir only when you can't cost effectively recover all the essential specifications as recommended by the equipment manufacturer.

Business as usual will not work for companies seeking to be competitive in the marketplace. It’s time for dedicated efforts to establish a proper oil analysis program for improved machine performance.

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