Preventive vs Predictive Maintenance

Both preventive maintenance and predictive maintenance are designed to increase the reliability of assets and reduce the amount of reactivity to failures.

With each maintenance type, work orders are scheduled well in advance of when maintenance is actually performed, making them both a form of scheduled maintenance. The main difference between the two is that preventive maintenance is scheduled at regular intervals while predictive maintenance is scheduled as needed (based on asset conditions).

Because predictive maintenance is performed only when needed, it reduces labor and material costs. However, implementing a predictive maintenance program requires a substantial amount of money, training, and resources up front. These costs are often acceptable to organizations that have already successfully implemented a preventive maintenance program.

Differences between preventive and predictive maintenance

Preventive maintenancePredictive maintenance
Definition Preventive maintenance (PM) is work that is scheduled based on calendar time, asset runtime, or some other period of time. Predictive maintenance (PdM) is work that is scheduled as-needed based on real time conditions of assets.
Workflow
TriggerTimeCondition
CostLowMedium/High
Cost Savings12% to 18% [1]25% to 30% [1]
Resources Needed
  • Maintenance software for scheduling
  • Maintenance scheduler (for larger organizations)
  • Condition monitoring software
  • Condition monitoring tools and sensors
  • PdM training
Pros
  • Better than reactive maintenance
  • Relatively easy to implement
  • Maintenance is performed as needed
  • Reduces maximum amount of downtime
Cons
  • Risk of over-maintaining (e.g. over-lubrication can damage asset)
  • Labor intensive (not performed as needed)
  • Expensive technology needs purchased
  • Time-intensive to implement correctly
Use CaseAn organization wants to decrease unplanned downtime and emergency maintenance but does not have a large maintenance budget. As a solution, they implement a PM program for select assets. Work orders are scheduled for inspections, lubrication, filter replacements, and parts replacements based on recommendations from OEMs.An organization has assets with slow-speed bearings that frequently fail. Preventive maintenance is already in place but the organization suspects that assets are being over-greased. To perform maintenance with more precision, they use ultrasound analysis (good for slow-speed bearings). Now, work orders for greasing are only scheduled when certain ultrasound measurements are reached.

[1] Types of Maintenance Programs by the Department of Energy, O&M Best Practices Guide, Release 3.0