Preventive maintenance (PM) is any planned maintenance work performed on equipment before a failure occurs. Unlike reactive maintenance — where teams respond to breakdowns after they happen — PM follows a schedule based on time, usage, or manufacturer specifications. The goal is to prevent failures, extend asset life, and keep production running without costly unplanned interruptions.
For asset-intensive operations, the difference between a disciplined PM program and a reactive one is measurable in dollars. A single unplanned failure on a crusher, compressor, or centrifugal pump can cost more in lost production than months of scheduled maintenance work.
Why Preventive Maintenance Matters
Most equipment does not fail randomly. It fails because wear accumulates, lubricants degrade, components fatigue, and inspection intervals get missed. Preventive maintenance interrupts that progression before a failure event occurs.
The business case is straightforward: planned downtime is controllable, unplanned downtime is not. A two-hour scheduled PM window costs a fixed amount in labor and parts. An unplanned bearing seizure on the same asset can cost 10 to 20 times that figure once you account for emergency labor, expedited parts, production loss, and secondary damage.
The 10 Percent Rule of Preventive Maintenance is one of the most practical benchmarks in reliability management: if emergency or unplanned work exceeds 10 percent of your total maintenance hours, your PM program is not catching failures early enough.
How It Works in Practice
A PM program defines what work gets done, on which assets, at what interval, and by whom.
Asset Identification and Criticality Ranking
Not all equipment warrants the same PM investment. Assets that directly impact production, safety, or regulatory compliance receive more frequent PM attention. A criticality ranking process evaluates failure consequence and failure likelihood to drive this prioritization. See: Asset Criticality Ranking (ACR).
PM Task Development
Each asset gets a defined task list: inspections, lubrication points, filter changes, torque checks, alignment verification, fluid sampling. These tasks are built from OEM recommendations, maintenance history, and field experience. In operations where tribal knowledge runs deep, standardizing this into documented PM tasks is itself a reliability improvement.
Scheduling and Compliance Tracking
PM schedules are built on time intervals (weekly, monthly, quarterly, annually) or usage triggers (operating hours, production cycles, mileage). A CMMS executes and tracks this schedule, generates work orders, and records completion. Preventive Maintenance Compliance (PMC) — the percentage of PMs completed on time — is the primary metric for measuring program health.
Execution and Documentation
Technicians complete PM tasks in the field and record findings: oil conditions, vibration readings, unusual wear patterns, abnormal temperatures. This documentation feeds back into reliability analysis and drives interval adjustments over time.
Preventive Maintenance by Industry
Manufacturing: PM schedules are built around production windows — planned shutdowns, shift changes, or low-demand periods. TPM (Total Productive Maintenance) frameworks extend PM responsibility to operators, making equipment care a shared function rather than a maintenance department task exclusively.
Mining: Haul trucks, crushers, and conveyor systems operate in extreme conditions with high wear rates. PM intervals are often usage-based rather than calendar-based — a haul truck running 20 hours per day reaches component replacement milestones faster than calendar scheduling accounts for. Lubrication tasks represent a disproportionate share of PM activity in mining.
Oil and Gas: Rotating equipment — compressors, pumps, turbines — runs in remote locations where emergency maintenance is logistically difficult and costly. Regulatory compliance requirements define minimum inspection frequencies.
Crane and Rigging: Wire rope inspections, hydraulic system checks, and load-bearing component examinations are PM tasks with direct safety implications. PM compliance here is a regulatory and liability requirement, not just a reliability question.
Common PM Program Failures
Interval errors: PM intervals set from OEM recommendations without adjustment for actual operating conditions. An asset running in high-contamination or high-load conditions degrades faster than a standard interval accounts for.
Incomplete task execution: Technicians skip steps under time pressure or lack clear documentation of what each task requires. Standardized digital work orders with step-by-step instructions close this gap.
No feedback loop: PM programs that never adjust based on failure history are not learning. When an asset fails between scheduled PMs, the program should trigger an interval review — not just an emergency repair.
Reactive creep: Organizations allow PM schedules to slip during high production periods, trading short-term output for accelerating wear. The 10 Percent Rule exists specifically to identify when this pattern has taken hold.
Preventive vs. Other Maintenance Strategies
- Corrective maintenance: Repair after failure. Appropriate for non-critical, easily replaceable assets. See: Corrective Maintenance.
- Preventive maintenance: Scheduled work before failure. The foundation of most reliability programs.
- Condition-based maintenance: Maintenance triggered by equipment condition data. See: Condition-Based Maintenance (CBM).
- Predictive maintenance: Uses sensor data and analytics to forecast failure timing. See: Predictive Maintenance (PdM).
Frequently Asked Questions
What is the difference between preventive and predictive maintenance?
Preventive maintenance follows a fixed schedule based on time or usage intervals regardless of equipment condition. Predictive maintenance uses real-time sensor data — vibration analysis, oil analysis, thermal imaging — to trigger maintenance only when condition data indicates a failure is approaching. Preventive maintenance is the standard foundation for most reliability programs; predictive maintenance is layered on top for high-criticality assets where early failure detection justifies the monitoring investment.
How do you build a preventive maintenance schedule?
Start by identifying all maintainable assets and ranking them by criticality — failure consequence multiplied by failure likelihood. For each asset, define PM tasks from OEM recommendations and maintenance history, assign intervals (time-based or usage-based), and load them into a CMMS to generate and track work orders. Review compliance monthly and adjust intervals based on actual failure data.
What is a good preventive maintenance compliance rate?
Most reliability programs target 90 percent or higher PM compliance — meaning 90 percent of scheduled PMs are completed on time. Below 85 percent, the program is not providing enough protection against unplanned failures. Compliance below 75 percent typically indicates a scheduling, resource, or prioritization problem that needs to be addressed before interval optimization makes any difference.
What is the 10 Percent Rule in preventive maintenance?
The 10 Percent Rule states that emergency and unplanned maintenance work should not exceed 10 percent of total maintenance hours. If it does, the PM program is not catching failures early enough and reactive work is consuming resources that should be going toward planned maintenance.
Related Terms
- Preventive Maintenance Compliance (PMC)
- Condition-Based Maintenance (CBM)
- Predictive Maintenance (PdM)
- Mean Time Between Failures (MTBF)
- Asset Criticality Ranking (ACR)
- Maintenance SOP
Strengthen Your PM Program With Redlist
See how Redlist helps industrial maintenance teams build, schedule, and track preventive maintenance programs — without the spreadsheets and missed PMs that reactive programs depend on.
