By Jim Fitch
Diagnetics Publications
Plainly stated, the burgeoning cost of maintenance is a serious business problem. According to DuPont, “maintenance is the largest single controllable expenditure in a plant: in many companies it often exceeds annual net profit.” One major U.S. automotive manufacturer has a maintenance staff of between 15,000 and 18,000, all plants combined. They say “85% to 90% is crisis work” (breakdown).
While preventive maintenance, when well implemented, has been shown to produce savings in excess of 25 percent, beyond that its benefit quickly approaches a point of diminishing return. According to a Forbes Magazine study, one out of every three dollars spent on preventive maintenance is wasted. A major overhaul facility reports that “60 percent of hydraulic pumps sent in for rebuild had nothing wrong with them.” These inefficiencies are the result of maintenance performed in accordance with a schedule (guess work) as opposed to the machine’s true condition and need.
Most recently, predictive maintenance (also known as condition monitoring) has been leading the way to additional savings over preventive maintenance. The use of real time or portable instruments such as vibration monitors, thermography, ferrography, etc. has been effective at recognizing the symptoms of impending machine failure. The major benefit is the availability of an earlier warning, from a few hours to a few days, which reduces the number of breakdown “catastrophic” failures. Predictive maintenance is usually implemented concurrently with preventive maintenance and targets both the warning signs of impending failure and the recognition of small failures that begin the chain reaction that leads to big failures (i.e., damage control).