Increasing Reliability through Oil Analysis
Author: Ray Garvey, Tribology Solutions Product Manager
Emerson Process Management / CSI
Industrial maintenance departments are in search of improved reliability. This means they want increased Mean Time Between Failures (MTBF) and when failures do occur, they want plenty of advance notice. The way to increase MTBF is to find and eliminate root causes of failure. This is proactive maintenance. The way to gain advanced notice of upcoming machine failures is to monitor failure signatures. This is predictive maintenance.
IS OIL ANALYSIS PROACTIVE OR PREDICTIVE?
Industrial oil analysis is both a proactive and a predictive. The operational life of most industrial machinery is directly related to the contamination and chemistry of the lubricants. Water and dust are two common contaminants that drastically increase wear rates and shorten machine life. Degraded oil, wrong oil, and inadequate lubrication are also significant contributors to early failures.
By monitoring, reporting, and recommending the correction of contamination problems, oil analysis is possibly the most valuable proactive condition monitoring technology available for improving plant reliability.
In addition to being proactive oil analysis can effectively forecast the impending catastrophic failure of mechanical and electrical systems through which the oil flows. In the same way as a doctor analyzes blood to discern internal problems of the human body, maintenance professionals can use wear debris analysis (WDA) to discern impending problems in equipment. These four categories represent the bulk of the abnormal wear for industrial machines: abrasive wear, adhesive wear, fatigue wear, and corrosive wear.
- Abrasive wear particles are normally indicative of excess dirt or other hard particles in the oil that are cutting away at the load bearing surfaces.
- Adhesive wear particles reveal problems with lubricant starvation as a result of either low viscosity, high load, high temperature, slow speed, or inadequate lubricant delivery.
- Fatigue wear particles are often associated with mechanical problems such as improper assembly, improper fit, misalignment, imbalance, or other condition.
- Corrosive wear particles are the result of corrosive fluids such as water or process materials contacting metal surfaces.
Armed with facts about dust contamination, water contamination, oil chemistry, and detailed wear debris analysis, the maintenance professional knows about lubricant related problems, their severity and appropriate corrective actions.
WHAT ARE THE BENEFITS?
The benefits of doing oil analysis have been well documented. Numerous case histories and cost savings examples have been published "Case Histories and Cost Savings Using In-Shop Oil Analysis." Most people quickly understand the value of oil analysis and most industrial plants are doing some amount of oil analysis. However only a few plants are experiencing the measurable benefits of extended machine life and predicted failure through their oil analysis program.
It is very common for industrial plants to leave responsibility for oil analysis to their oil supplier. A medium size paper mill typically spends $300,000 per year on lubricants. With this much money on the line, it is not difficult to negotiate "free" oil analysis from the lubricant supplier. I have talked to dozens who use free oil analysis, and none could tell me about case histories, few new of any cost savings, and most just felt like they had the requirement to do oil analysis covered.
There are many ways to get a false sense of security about oil analysis and one of them is to think you are covered because your lubricant supplier takes care of everything. General Motors Linden Truck and Bus Plant found out the hard way that this does not work. Eddie Bohn and Frank D'Arcio, reported that two years earlier, GM Linden was relying on their "free" oil analysis when a critical gearbox failed costing them 27 hours of production down-time. Supplier provided oil analysis had just been done giving a clean bill of health to the offending gearbox. Unfortunately the "free" oil analysis did not include tests for particle counting or wear debris analysis so it missed the impending failure.
In another incident, Eddie Bohn reports that his "free" oil analysis from two different labs totally missed severe contamination of a robotic laser turntable lube system. In this case the oil system was loaded with spherical iron particles of welding slag that had gotten in through a missing inspection plate. On-site oil analysis caught this problem that two labs missed. The labs could have found the problem just as well as on-site testing had they been paid to do the right tests, but they were not.
Off-site lab oil analysis and on-site minilab oil analysis are both capable of finding root causes and predicting wear related failures so long as good samples are collected and correct testing is done.
Many plants send out ten to twenty samples a month and consider they have an acceptable oil analysis program. Once again, this is a false sense of security. There is no way that an industrial plant maintenance department can adequately monitor the condition of lubricated machinery with so few samples.
Whether your plant is a paper mill, automobile assembly plant, chemical plant, steel mill, food processing plant, or a power plant, you will find plenty of need for oil analysis. Each of these diverse plants require hundreds of oil-lubricated machines including gearboxes, pumps, motors, engines, hydraulics, processing machines, rolls, fans, turbines, and compressors. In general you will find a need to analyze 100 to 200 samples per month at most industrial plants. For an integrated steel mill or large mining operation it will take 1000 or more samples per month to do the same.
WHO IS GOING TO DO THE OIL ANALYSIS?
An important question to answer about on-site oil analysis is, "Who is going to do the oil analysis?" Many industrial plants are faced with downsizing and out-sourcing for maintenance activities. Some predictive maintenance teams that formerly had 4 to 6 people have been cut in half. How can these plants possibly increase the numbers of oil samples collected from 10 per month to more than 100 per month? How can they begin doing the oil analysis on-site as well?
The single most important ingredient to a successful tribology program is the champion behind it. One individual must take the lead toward continuous improvement. The industrial plant that is only collecting 10 or 20 samples per month is missing many problems that cost far more labor (and other expenses) than it would take to collect the missing samples. It only takes about one week a month to collect and test 100 samples. The payoff in both labor and cost savings is far greater than the time spent doing this work. The key to success is the in-house champion with a vision for improvement.
Which department should perform on-site oil analysis? The reliability team in the maintenance department is first choice. A good alternative is to add oil analysis to the technical services department who already do lab analysis for environment and process monitoring. Third choice is to hire an outside contractor to collect the samples and perform on-site oil analysis. In any of these situations, the essential criterion is that the findings from oil analysis must impact equipment maintenance. Oil analysis without corresponding corrective actions is obviously the wrong thing to do.
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Revised: Thursday, 08-Oct-2015 11:54:03 AEDT