Preventive maintenance is the discipline of doing maintenance before something breaks. Instead of waiting for a pump to fail, the team services it on a regular cadence (every 90 days, every 500 operating hours, etc.) so that the failure never happens — or at least happens far less often.
The opposite is reactive maintenance: fixing things only after they break. Most teams have a mix of both. The goal of a mature operation is to shift the ratio toward preventive work, because planned work is faster, cheaper, and safer than emergency repairs.
Common PM triggers
- Time-based: every 7 days, every month, every year.
- Usage-based: every 500 operating hours, every 10,000 cycles, every 50,000 km.
- Condition-based: when a sensor reading crosses a threshold (vibration, temperature, oil quality).
What a PM program looks like in practice
For each asset, the team defines:
- Which PMs apply (lubrication, calibration, inspection, parts replacement).
- The cadence for each one.
- The procedure to follow during the PM.
- The parts that may be needed.
A CMMS then generates work orders automatically when each PM comes due, and the team executes them as planned work — not as emergencies.
How PM compliance is measured
The most common metric is PM compliance rate: the percentage of scheduled PMs completed on time. A healthy program runs at 90%+ compliance. Teams that drop below 70% typically see breakdown rates and emergency costs climb sharply.