Don't let your PdM get derailed by unintended consequences

Do not allow unintended consequences to degrade the program's value

The general perception of predictive maintenance is that it's a maintenance tool that uses vibration, infrared and lube analysis data to prevent catastrophic equipment failures and unplanned production downtime. Because of this perception, predictive programs are established with the singular mission of breakdown prevention without even a thought about the effect these programs have on the overall picture. While many such programs have resulted in verifiable and measurable reductions in unscheduled downtime, they've increased overall maintenance cost substantially and decreased overall plant performance.

Several factors contribute to the negative results of traditional predictive maintenance programs. The fundamental reason that most programs fail to achieve a marked improvement in overall plant performance resides in the breakdown mentality that continues to dominate the philosophy in many plants. They've failed to perceive the benefits a predictive maintenance program can provide and haven't recognized the negative effect this limited application generates. These plants fail to understand that high breakdown rates, as well as maintenance cost, are the visible symptom of a more serious problem in design, purchasing, production or management that can't be resolved simply by preventing catastrophic failure of critical machinery.

Another factor that limits traditional programs is the improper use of diagnostic and analysis techniques. In most cases, existing programs don't utilize the real power that vibration, thermography, tribology and the other plant evaluation techniques can provide. To some extent, this is the result of seeking simple answers to the extremely complex problems that limit our ability to compete in the world market.

Test your program
Some guidelines offer an evaluation of a program's effectiveness.

The first step in determining predictive maintenance effectiveness is to evaluate the change in the maintenance labor and material cost resulting from having a predictive maintenance program. In the majority of plants we evaluated during the past few years, both categories have shown marked increases. In one plant, the annual bill for rolling-element bearings increased from $2.4 million to $14.1 million. Obviously, the labor required to install the bearings also increased. If incremental cost increases substantially, the program isn't working.
The second evaluation concerns the effect of predictive maintenance tasks on the availability or productive capacity of critical plant systems. In too many cases, these activities substantially increase the downtime scheduled for preventive or corrective maintenance. The predictive maintenance program, in effect, converts unscheduled downtime into scheduled downtime. Because most plants consider scheduled downtime a cost of doing business, the incremental loss of capacity isn't considered a negative.

Finally, evaluate any recommendations the predictive program generates. If the vibration program predominantly reports bad bearings, misalignment, imbalance or mechanical looseness, it's probably not providing real benefit. These defects are merely symptoms of underlying problems that must be corrected. Simply replacing bearings, or attempting to correct misalignment, imbalance and looseness without correcting the reason these abnormalities exist only increases cost and reduces total plant throughput. The same is true of thermography programs that find only loose connections, faulty fuses and other simple electrical problems. The same is true of tribology problems that identify dirty or contaminated lube oil. These kinds of results simply don't generate the reliability and life cycle cost improvements needed to justify the program cost.

Implementing and maintaining an effective predictive maintenance program requires great effort, but the potential benefit is also great. Done properly, predictive maintenance, as part of a life cycle asset-management program, can reduce limitations, including breakdowns. At the same time, these programs provide reliability needed for increases in throughput, revenue and profitability.

Such predictive maintenance transforms the maintenance operation from an expensive support function to a full member of the profit-generating team. Don't expect an easy, quick fix. Like anything of value, a certain amount of effort is required to gain positive results. If you're diligent about it, you can establish a total plant predictive maintenance program that provides maximum benefits. 

Contributing Editor R. Keith Mobley is principal consultant at Life Cycle Engineering in Charleston, S.C. E-mail him at

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