Predictive Maintenance (PdM)

Definition - What does Predictive Maintenance (PdM) mean?

Predictive maintenance (PdM) as a maintenance approach that involves testing and monitoring machines in order to predict machine failures. It refers to maintenance based on the actual condition of a component.

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

The main premise of this maintenance is to allow convenient scheduling of corrective maintenance, and to prevent unexpected equipment failures. Other potential advantages include:

  • Increased equipment lifespan
  • Increased plant safety
  • Fewer accidents with negative environmental impact
  • Optimized spare parts handling

Corrosionpedia explains Predictive Maintenance (PdM)

Predictive maintenance includes activities involving continuous or periodic monitoring and diagnosis in order to forecast component degradations so that as-needed, planned maintenance can be performed prior to equipment failure. This approach uses principles of statistical process control to determine at what point in the future maintenance activities will be appropriate. An example of predictive maintenance would be a pump bearing replacement, after wear-out was indicated as a result of an oil analysis.

It attempts to evaluate the condition of equipment by performing periodic or continuous (online) equipment condition monitoring. The ultimate goal of PdM is to perform maintenance at a scheduled point in time when the maintenance activity is most cost-effective and before the equipment loses performance within a threshold. Adoption of PdM can result in substantial cost savings and higher system reliability.

Maintenance is not performed according to fixed preventive schedules but rather when certain changes in characteristics are noted. Corrosion sensors supplying diagnostic information on the condition of a system or component play an important role in this maintenance strategy. A useful analogy can be made with automobile oil changes. Changing the oil every 3000 miles to prolong engine life, irrespective of whether the oil change is really needed or not, is a preventive maintenance strategy.

In determining equipment condition, predictive maintenance utilizes nondestructive testing technologies such as:

  • Infrared
  • Acoustic (partial discharge and airborne ultrasonic)
  • Corona detection
  • Vibration analysis
  • Sound level measurements
  • Oil analysis
  • Other specific online tests

The purpose of these tools is to find defects not possibly found through previously available inspections methods, specifically while the machine is in normal operation.

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