The Definition of Preventive Maintenance

Definition of Preventive Maintenance

Preventive maintenance (PM) is scheduled, proactive maintenance performed on equipment and systems to prevent breakdowns, malfunctions and safety hazards before they occur, rather than repairing equipment only after it fails. PM tasks include inspections, lubrication, adjustments, cleaning, testing and replacing parts at set intervals based on time, operating hours, cycles or condition.

Preventive maintenance is a core part of both equipment reliability and hazard prevention. Many serious incidents trace back to defective equipment or safety devices, such as brakes, guards, interlocks, alarms and relief valves, that were overdue for maintenance.

Key Facts About Preventive Maintenance

• Maintenance strategies range from reactive (run to failure) to preventive, condition-based and predictive.
• Safety-critical equipment, such as fire protection, gas detectors, emergency stops and relief devices, should have the highest PM priority.
• Maintenance work itself is high risk and usually requires lockout/tagout and often a permit to work.
• Several OSHA standards require equipment to be inspected and maintained in safe condition, including those for powered industrial trucks, cranes and fire extinguishers.
• Under PSM, mechanical integrity programs require written inspection and testing procedures for critical process equipment.

Example of Preventive Maintenance

Replacing the belts on a conveyor system on a fixed quarterly schedule, rather than waiting for one to snap, is preventive maintenance. It avoids unplanned downtime and the injury risk of a sudden mechanical failure, and it lets maintenance crews do the work under planned lockout instead of in a rush to restart the line.

How to Build a Preventive Maintenance Program

1. Create an equipment inventory and rank assets by safety and production criticality.
2. Set PM tasks and intervals from manufacturer recommendations, regulations and failure history.
3. Schedule work orders in a maintenance or EHS system and assign owners.
4. Use pre-use inspections to catch defects between scheduled PMs.
5. Track completion, overdue tasks and failures, and adjust intervals based on the data.

Related Terms

• Pre-Use Inspection
• Defective Equipment
• Non-Destructive Testing (NDT)
• Lockout/Tagout (LOTO)
• Inspection (Workplace Inspection)

Preventive Maintenance Frequently Asked Questions

How is preventive maintenance different from reactive maintenance?

Reactive maintenance addresses equipment only after it fails, which can seem cheaper in the short term but is riskier and more disruptive. Preventive maintenance follows a planned schedule based on time, usage or condition to catch issues before they cause failure or injury.

What safety hazards does poor maintenance commonly create?

Neglected maintenance is linked to equipment malfunction, electrical faults, brake and steering failures, failed guards and interlocks, fluid leaks, fires and structural degradation.

Who typically develops a preventive maintenance schedule?

Maintenance or reliability engineers usually develop schedules based on manufacturer recommendations, equipment criticality, failure history and regulatory requirements. EHS teams should help prioritize safety-critical equipment.

What is condition-based maintenance and how does it relate to preventive maintenance?

Condition-based maintenance uses data such as vibration, temperature or oil analysis to trigger maintenance based on the equipment's actual condition rather than a fixed interval. It is an advanced form of preventive maintenance that can catch problems a calendar schedule might miss.

How does preventive maintenance connect to OSHA compliance?

Several OSHA standards, including those for machine guarding, powered industrial trucks, cranes and process safety, effectively require equipment to be maintained in safe operating condition. Documented PM records are often the evidence employers use to show compliance during an inspection.

What metrics show whether a PM program is working?

Common metrics include PM completion rate, overdue safety-critical PMs, mean time between failures, the ratio of planned to unplanned work and incidents linked to equipment failure.