Implementation and training costs are extremely low compared to the hundreds of thousands of dollars that will be saved by predicting when problems may occur and then effectively planning and scheduling machine repairs.
Overcoming corporate or plant culture is another obstacle to the proper application of condition monitoring techniques like oil analysis. We’ve all heard the comment; “We’ve been doing our maintenance this way for 30 years. Why should we apply oil analysis (or any other predictive maintenance technology) now?”
Some plants have vibration analysis programs that are very sophisticated, yet oil analysis is barely, if ever, used. Many plant personnel are not aware that oil analysis is actually more effective than vibration analysis in condition monitoring of equipment such as reciprocating machinery, slow-speed rotating equipment and hydraulic systems. But oil analysis should not be limited to this equipment, since oil analysis ‘sees’ the machine’s condition from a totally new perspective — if the right testing program is designed for the appropriate machines.
The following suggestions will help you to establish an effective program.
Know the critical equipment and its lubrication requirements. It is true that many technicians and engineers know very little about the lubrication requirements of much of their machinery, other than to change oil and filters at the scheduled PM interval.
These personnel must become familiar with lubricant specifications, the temperature and environmental conditions that might af fect the machine’s lubrication system, and they must also familiarize themselves with the metallurgical makeup of the appropriate equipment.
Research the specifications on your critical equipment as they apply to oil analysis wear limits, suggested alarm levels and contamination limits. For example, most hydraulic equipment manufacturers publish ISO cleanliness code contamination limit specifications for their equipment. Plant personnel must become familiar with these specifications and learn how to compare them with the oil analysis results.
Understand the lubricants in your plant. Have your lubricant supplier carry out a complete and thorough lubricant survey for all of the equipment in the plant. There is usually no charge for this service and if you pay attention, you will learn a great deal about the lubricants specified.
Obtain a current set of specification data sheets or a product information book from your supplier. This information will provide the basis for comparing oil analysis test results with the appropriate specifications provided by the oil supplier. Study these materials, understand the specifications and what each represents and share this information with everyone in the plant who may be involved in greasing machinery, changing or topping off oils, or taking oil samples.
Send samples of all new oil types to a laboratory for analysis (based on the tests that you have selected for each critical machine). The results of these new oil samples will establish a baseline for trending each oil type.
Understand oil analysis testing. Become familiar with each of the techniques that are selected for the appropriate machines on your oil analysis program. Visit the lab of your choice and familiarize yourself with the techniques used. Above all, insist that the laboratory carry out the selected tests based on ASTM (American Society for Testing Materials) test methods. This way, you will be confident that oil analysis test results from the lab can be effectively compared with the specifications listed in the product information book that was provided to you by your lubricant supplier.
Learn to correctly interpret the oil analysis results, look for anomalies and changes in the trended data and record the limits of wear and contamination, based on your plant and machine conditions.
In other words, do not immediately react to a set of data which may be higher than that suggested by your equipment manufacturer or by the laboratory. Keep this important point in mind: It is not a set of high numbers that is important. It is a dramatic increase or change in a set of oil analysis report numbers that is important. There may not be a potential problem if the results are within the trend, even though the trend itself is higher than that indicated by the equipment manufacturer.
Train personnel to sample oil carefully using approved methods. These methods can include the use of devices such as handheld suction guns or permanently mounted sampling valves installed on the appropriate machines. Remember that oil samples are to be taken while the machine is running (if possible) or immediately after it has been shut down. Samples should also be taken from the same location each time and obtained on a regularly scheduled basis (i. e. every 500 hours).
Following these simple guidelines consistently will ensure that used oil samples will be representative of the lubricant in the machine and will provide the best chance of repeatable results.
Carefully maintain complete records. Include the operating hours for each selected machine. Statistical trending cannot be effectively established if oil samples are taken at random operating periods, or if the sampling schedule is too long, such as every two months or more. Whenever possible, install hour meters or tachometers on every critical machine assigned to the oil analysis program.
Also keep a careful record of the amount of oil that is added between oil samples. Large quantities of top-up oil can dilute the wear or contamination levels, resulting in a potential problem being overlooked.
Establish baseline trends by sampling each machine at least three times at the same interval. Once a baseline trend has been established, a decision may be made regarding the sampling frequency for each piece of machinery. Be careful to factor in machine criticality so that you obtain the biggest bang for your oil analysis buck. If a potential problem does arise, the sampling frequency can be increased.
The application of oil analysis, together with other predictive maintenance technologies to accurately provide information on critical equipment problems, will make it impossible for the plant manager to say “no” to a shutdown when the results confirm that a catastrophic failure is about to occur.
Lloyd (Tex) Leugner is an Alberta-based specialist in maintenance and lubrication problems, author, and an award-winning contributor to this magazine. References used for this article include: The Practical Handbook of Machinery Lubrication, 3rd Edition, L. Leugner; Lubricant Properties, Analysis & Testing, J. Denis, J. Briant, J. C. Hipeaux; and Reliability Centered Maintenance, 2nd Edition, John Moubray.
Many plant personnel are not aware that oil a
nalysis is actually more effective than vibration analysis …