Predictive maintenance

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Predictive maintenance (PdM) techniques help determine the condition of in-service equipment in order to predict when maintenance should be performed. This approach offers cost savings over routine or time-based preventive maintenance because tasks are performed only when warranted.

[edit] Overview

PdM or condition based maintenance attempts to evaluate the condition of equipment by performing periodic or continuous (on-line) equipment monitoring. The ultimate goal of PdM is to perform maintenance “just in time”, before the equipment fails in service. This is in contrast to time and/or operation count based maintenance where a piece of equipment gets maintained whether it needs it or not. Time based maintenance is labor intensive, ineffective in identifying problems that develop between scheduled inspections and is not cost effective.

Most PdM inspections are performed while equipment is in service, thereby minimizing disruption of normal system operations. Adoption of PdM in the maintenance of equipment can result in substantial cost savings and higher system reliability.

Reliability centered maintenance or RCM emphasizes the use of predictive maintenance (PdM) techniques in addition to traditional preventive measures.

[edit] Technologies

PdM technologies used to evaluate equipment condition can include infrared, acoustic (partial discharge and airborne ultrasonic), corona detection, vibration analysis, sound level measurements, oil analysis and other specific online tests. Vibration analysis is most productive on high speed rotating equipment and can be the most expensive part of a PdM program to get up and running. Acoustical analysis can be done on a sonic or ultrasonic level. Sonic monitoring equipment is less expensive but it also has less uses than ultrasonic technologies. Sonic technology is useful only on mechanical equipment while ultrasonic equipment can detect electrical problems and it is more flexible and reliable in detecting mechanical problems. Oil analysis is a long term program that, where relevant, eventually can be more predictive than any of the other technologies. It will take years for a plant's oil program to reach this level of sophistication and effectiveness. Infrared monitoring and analysis has the widest range of application from high to low speed equipment and it can be effective for spotting both mechanical and electrical failures. Some consider it to be currently the most cost effective technology.