Preventive Maintenance (PvM)
Preventive maintenance is a reliability based maintenance management tool used to identify, and monitor equipment or system condition and the failure modes of that equipment or systems prior to fault or failure. It can be divided into two subgroups:
- planned maintenance and
- condition-based maintenance.
The main difference of these subgroups is the determination of maintenance time, or determination of the moment when maintenance should be performed.
While preventive maintenance is generally considered to be worthwhile, there are risks such as equipment failure or human error involved when performing preventive maintenance, just as in any maintenance operation.
Preventive maintenance used for the scheduled overhaul or replacement of parts provides two of the three proactive failure management policies available to the maintenance engineer. The methods of determining what Preventive failure management policies should be applied are typically based on OEM recommendations; requirements of codes of practice, current legislation and regulation within a jurisdiction; expert opinion and recommendations; and the maintenance techniques already in place for similar equipment.
The most important aspect of any preventative maintenance management system is to measure and track the relevant parameter values of critical equipment and the performance indicators.
In a nutshell:
- Preventive maintenance is conducted to keep equipment working and/or extend the life of the equipment.
- Corrective maintenance is conducted to get equipment working again following a failure.
Difference Between Preventive and Predictive Maintenance
Predictive maintenance tends to include direct measurement of the equipment parameters and condition. Example, an infrared picture of a circuit board to determine hot spots while Preventive Maintenance includes the evaluation of particles in suspension in a lubricant, sound and vibration analysis of a machine.
An individual bought an incandescent light bulb. The manufacturing company mentioned that the life span of the bulb is 3 years. Just before the 3 years, the individual decided to replace the bulb with a new one. This is called preventive maintenance.
- On the other hand, the individual has the opportunity to observe the bulb operation daily. After two years, the bulb starts flickering. The individual predicts at that time that the bulb is going to fail very soon and decides to change it for a new one. This is called predictive maintenance.
- The individual ignores the flickering bulb and only goes out to buy another replacement light bulb when the current one fails. This is called corrective maintenance.
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