Preventive maintenance

What is preventive maintenance?

Preventive maintenance (or preventative maintenance) is regularly and routinely performed on physical assets to reduce the chances of equipment failure and unplanned machine downtime. Effective preventive maintenance is planned and scheduled based on real-time data insights, often using software like a CMMS (opens in new tab). A preventive maintenance task is performed while the equipment is offline or in lockout-tagout to prevent safety hazards and unexpected breakdowns. A preventive maintenance strategy is a commonly used approach that falls between reactive maintenance (opens in new tab) (or run-to-failure), corrective maintenance and predictive maintenance (opens in new tab).

O'Brien (1997) defines preventive maintenance as a program strategy intended to arrest light deterioration, retard progressive failures, and reduce the need for routine maintenance and service activities. In practice, it's a blend of people, processes, and systems working to extend asset life and maintain operational readiness.

Joel Levitt (2011) refines this definition even further through the P3 Model, classifying preventive tasks into three strategic functions:

• Preventive failure: Tasks that remove the causes of deterioration (e.g., cleaning and sealing)
• Postpone failure: Tasks that delay degradation (e.g., lubrication and tightening)
• Predict failure: Tasks that identify conditions before breakdowns (e.g., inspection and analysis)

PM is not a single activity, but it's a composite system designed to manage the probability of failure through a mix of proactive measures.

Modern programs also recognize overlap with other strategies like condition-based maintenance (CBM) and predictive maintenance (PdM). In fact, most mature operations integrate all three approaches into a hybrid reliability framework that continuously evolves with data.

Build your preventive maintenance schedule with this template (opens in new tab)

Why you need a preventive maintenance schedule

A PM schedule is the backbone of operational stability. It dictates when, how, and why work gets done. More importantly, it prevents maintenance for maintenance's sake.

According to Levitt (2011), every task in a PM program must meet four criteria:

• It serves a clear purpose
• It's cost-effective
• It avoids duplication
• It directly targets a known or probable failure mode

When schedules are built without this rigor, teams fall into what Levitt calls iatrogenic maintenance, which is work that causes more harm than good. This happens when tasks are added or repeated too frequently without data justification, leading to unnecessary downtime or early component wear.

To optimize scheduling:

• Group assets by class to build shared failure data
• Assigned frequencies based on service environment and criticality
• Validate all PM frequencies annually based on reliability results

Use this template to build your own preventive maintenance schedule (opens in new tab)

Types of preventive maintenance

There are many different types of PM, and each is triggered by different maintenance challenges. Below is a table that details the different PM types, their triggers, the data required for each maintenance task, and the primary goal of each PM type.

Maintenance type	Trigger (What starts the work?)	Data needed	Primary goal
Time-based (TBM)	A set time (e.g., every 6 months)	Calendar	Prevent failure based on assumed lifespan
Usage-based (UBM)	A usage meter (e.g., every 5,000 hours)	Meter readings	Prevent failure based on actual use
Condition-based (CBM)	A sensor alert (e.g., temperature threshold)	Real-time data	Identifying a trend that we can act on before it becomes a problem
Predictive (PdM)	A forecast (e.g., a failure is likely in 2 weeks)	Historical and sensor data	Act just before predicted failure
Prescriptive (RxM)	AI recommendation (e.g., Reduce load; repair on Tuesday)	AI and business data	Optimize the operational response

Each tier on the table builds on the last, transforming maintenance from reactive to predictive intelligence.

The business case for preventive maintenance

Reactive maintenance creates a trap of constant firefighting and can kill team morale, making it difficult to create a culture with maintenance as a pillar. As Levitt (2011) describes, breakdowns lead to emergency work, which consumes labour and spares budgets. It leaves no time for PM tasks and as compliance drops, failure rates risk, restarting the cycle.

Breaking the loop requires a shift from crisis response to controlled planning, a cultural and procedural change reinforced by scheduling, measurement, and management support.

The economics: The PM cost curve

Preventive maintenance is an investment that pays for itself. O'Brien (1997) illustrates this relationship in the PM cost curve (Figure 1) for pavement, showing that $1 spent on preventive care saves $4-$5 in deferred failure or rehabilitation costs.

Key cost saving effects of preventive maintenance include:

• Extended equipment lifespan
• Reduces costly repairs and overtime
• Fewer production interruptions
• Improved safety and compliance metrics
• Eliminates the need to stockpile costly spare parts
• Reduces scrap production caused by machine restarts after crashes
• Detects hidden issues like friction or clogs that increase energy consumption
• Provides maintenance documentation to protect against lawsuits and insurance claims
• Prevents blame-shifting between production and maintenance teams
• Defers major capital expenses by delaying the need for new equipment

A well-designed PM program targets a net cost reduction by aligning labor, inventory, and scheduling to minimize unplanned failures while avoiding unnecessary over-maintenance.

See our maintenance ROI calculator (opens in new tab)

Four dimensions of a successful PM program

Levitt (2011) outlines four essential dimensions for long-term PM success:

1. Technical: The quality and accuracy of PM task design.
2. Administrative: The scheduling, work order, and record keeping system.
3. Economic: Cost analysis and resource optimization.
4. Cultural: Leadership commitment and frontline buy-in.

An imbalance in any of these areas will weaken the program's effectiveness over time.

How failures actually behave and why PM intervals matter

Failures don't always follow the same curve. While some assets degrade gradually, others fail randomly. Understanding these patterns is central to effective scheduling.

The six classic failure patterns are shown in the bathtub curve model illustrate that:

• Only 11% of failures are age-related
• 89% occur randomly or due to external factors (Levitt, 2011, p. 133)

Preventive maintenance shifts these curves by detecting issues earlier and reducing the slope of degradation. Using P-F curves, teams can calculate inspection intervals that intercept failure before the point of functional loss (MTBF improvement).

How to implement a preventive maintenance (PM) program

Based on Gross (2015) and Levitt (2011), the following six-step framework provides a practical roadmap for establishing or upgrading a PM system:

Step 1: Establish scheduling

Before any task writing, set up a structured scheduling system. Gross (2015) calls this the “cornerstone of total productive work.” Whether using a CMMS or a manual folder system (1–31 for monthly cycles), consistent scheduling breaks the reactive cycle and builds accountability.

A practical tip: It's a good idea to build your schedule with a technician with experience or using a manual. Best is a mixture of experience and data to build.

Step 2: Create your equipment lists

You can't maintain what you don't know you have. Create a master equipment list divided by logical facility zones. Each asset should have a unique identifier, description, and operational context.

Step 3: Write PM task lists

This is the core of your program. For each critical asset:

• Define the task action (inspection, clean, lubricate, and replace)
• Define the interval (daily, weekly, and monthly)
• Document in clear, technician-friendly work orders

Each task should correspond to a known failure mode and be validated through review.

Step 4: Development equipment manuals

Centralize all vendor manuals, drawings, and parts lists, digitally if possible. Easy access to documentation eliminates guesswork and improves first-time fix rates.

Step 5: Set up inventory management

PM cannot function without parts. Implement a managed inventory system for high-turnover consumables (e.g., filters, belts, and lubricants). Tag critical spares to assets and forecast usage based on PM frequency.

Step 6: Maintain and improve the system

A PM program is never static. Use completed work orders and failure data to refine task frequencies and eliminate redundant work. If an asset fails despite scheduled PM, use that feedback to correct your program. This is the foundation of PM optimization.

A practical tip: PM optimization (PMO) can lead to better PMs, and savings. Pick a section of your facility twice a year and see how those PMs are helping your performance. Or choose the production room with the most downtime to see how you can correct it.

Practical examples of PM tasks

Hathaway (2018) provides practical, component-level examples illustrating how PM tasks translate across systems:

• Engines: Inspect air filters, check turbo seals, change oil, and flush cooling systems.
• Fuel systems: Drain water traps, replace filters, and clean strainers.
• Power train and hydraulics: Adjust clutches, check hydraulic fluid, and inspect hoses.
• Electrical and safety: Clean battery terminals, inspect plugs, and verify lockout/tagout compliance.

These examples underscore the importance of standardization, documentation, and safety integration in task design.

Optimizing your preventive maintenance strategy

Modern reliability programs use technology like vibration analysis, oil sampling, and thermography to move from guessing when a failure will happen to actually knowing when it's going to happen.

Levitt (2011) identifies three frameworks for mature programs:

• Total production maintenance (TPM) - Operators perform daily care tasks to increase ownership.
• Reliability-centered maintenance (RCM) - Systematic analysis of critical failure modes to assign optimal maintenance strategies.
• PM optimization (PMO) - Data-driven refinement of PM content and frequency to maximize ROI.

Shifting the culture: From maintenance first to reliability first

O'Brien (1997) argues that PM is the first pillar of a maintenance first philosophy, one that safeguards the organizations' capital assets through structured care and continuous improvement. Gross (2015) reinforces that a PM program is not a one-time project; it's a permanent shift from reactive to proactive control.

When implemented strategically, preventive maintenance becomes more than an engineering function. It transforms into a deeper business strategy that aligns asset performance with organizational goals. A reliability-first culture integrates data-driven decision-making, predictive technologies, and cross functional collaboration to ensure that maintenance is not just about fixing equipment, but about maximizing uptime, reducing risk, and creating sustainable value.

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