Preventive Maintenance: The Complete Guide

What is preventive maintenance and how does it work?

At its core, preventive maintenance replaces guesswork with a system. Every asset gets a maintenance plan that specifies what needs to be done, when it needs to happen and who is responsible. A fleet truck might get an oil change every 10,000 km. A rooftop air handling unit might get a filter swap every 90 days. A conveyor belt might get a tension check every 500 operating hours. The trigger varies, but the principle is the same: intervene before wear becomes failure.

PM programmes generally use three types of triggers. Time-based triggers schedule work on a fixed calendar, such as quarterly or annually. Usage-based triggers tie work to meter readings like kilometres, engine hours or production cycles. Condition-based triggers use inspection findings or sensor readings to flag when a component has degraded past a threshold. Most organisations blend all three, choosing the trigger type that best fits each asset and failure mode.

The workflow is consistent. A work order is generated automatically or manually when a trigger fires. A technician receives the assignment, follows a checklist, records findings and closes the order. Parts consumed are logged, labour hours are captured and the next service date is calculated. Over time, this cycle builds a complete service history for every asset, which is essential for warranty claims, compliance audits and replacement planning.

Preventive vs reactive maintenance: costs and trade-offs

Reactive maintenance, sometimes called breakdown or run-to-failure maintenance, means fixing things only after they stop working. It is the default mode for organisations without a structured maintenance programme, and it is expensive. When a critical asset fails unexpectedly, the costs stack up fast: emergency call-out fees, expedited freight for parts, overtime wages, idle operators waiting on repairs and downstream production delays. Industry benchmarks from the US Department of Energy put reactive maintenance costs at two to five times higher than equivalent planned work.

Preventive maintenance does not eliminate reactive work entirely. Equipment will still fail between scheduled services, especially during the early phase of a PM programme when optimal intervals have not yet been dialled in. The goal is to shift the ratio. A mature maintenance operation typically targets 80 percent planned work and 20 percent reactive. Organisations just starting out might sit at 40/60 or worse.

The financial case for PM extends beyond direct repair costs. Unplanned downtime affects revenue, customer commitments and safety. A single hydraulic hose failure on an excavator can idle an entire earthmoving crew for a shift. A compressor failure in a food processing plant can spoil an entire batch. These knock-on costs rarely appear in maintenance budgets, but they dwarf the price of the hose or compressor. Tracking total cost of downtime, not just repair cost, is what builds the business case for investing in a preventive programme.

Building a preventive maintenance schedule

The biggest mistake organisations make is trying to schedule preventive maintenance for everything at once. That approach overwhelms technicians, creates a backlog and erodes trust in the programme before it delivers results. A better path is to prioritise. Rank each asset by criticality, considering the impact of its failure on safety, production, compliance and cost. Focus the first wave of PM schedules on assets in the top tier.

For each asset, define the maintenance tasks, their frequency and the estimated labour time. Manufacturer manuals are the starting point for intervals, but they should be adjusted based on your operating environment. A truck running dusty haul roads needs air filter changes more often than one on sealed highways. A pump handling abrasive slurry wears faster than one pumping clean water. Use your own failure history and inspection data to refine intervals over the first 6 to 12 months.

Scheduling also means levelling the workload across the week and month. If 30 assets all have quarterly services due in January, spreading them across weeks prevents a spike that technicians cannot absorb. Tools like MapTrack automate this levelling by distributing work orders evenly and alerting supervisors when capacity is at risk. The schedule should also account for seasonal demand. Mining and construction operations often push non-critical PM to quieter periods to maximise equipment availability during peak production.

Document every schedule in writing, even if you use software to manage it. A printed or exported PM calendar gives supervisors a clear view of upcoming work, helps with parts ordering and provides evidence for compliance audits. Review the schedule quarterly for the first year, then annually once intervals stabilise.

Preventive maintenance checklists and SOPs

Checklists exist to remove variation. When three different technicians service the same compressor, the outcome should be identical. A well-written checklist specifies each task in plain language, includes pass/fail criteria where applicable and prompts the technician to record measurements like belt tension, oil level or vibration readings. It should also list the parts and consumables needed so technicians arrive prepared rather than making trips back to the storeroom.

Good checklists share a few traits. They are organised in the order a technician would physically work through the asset, not in an arbitrary list. They distinguish between inspection items (look, listen, measure) and action items (replace, adjust, lubricate). They include a sign-off field and a timestamp. And they fit on one or two pages, because a 10-page checklist for a routine service will be skimmed, not followed.

SOPs sit above checklists and cover the broader context. They define lockout/tagout requirements before starting work, personal protective equipment, environmental controls such as oil spill containment, quality checks after the service is complete and what to do when a defect is found that exceeds the scope of the scheduled service. SOPs also specify competency requirements, ensuring that only qualified personnel perform safety-critical maintenance on assets like cranes, pressure vessels or electrical switchgear.

Measuring PM programme effectiveness with KPIs

PM compliance rate measures the percentage of scheduled work orders completed on time. It is the single most telling indicator of programme health. If compliance is below 80 percent, the programme has a resourcing or discipline problem that needs to be addressed before any other metric will improve. Common causes of low compliance include unrealistic scheduling, parts shortages, competing priorities from reactive work and poor supervisor follow-up.

The planned vs unplanned ratio shows whether the PM programme is actually shifting the maintenance mix. Track the number and cost of planned work orders against unplanned ones each month. A healthy trend shows the unplanned share declining over 6 to 12 months as the PM programme catches failure modes earlier. If the ratio stays flat, the intervals or task lists may need revision.

MTBF and MTTR are asset-level metrics. Mean time between failures measures reliability: how long, on average, an asset runs before its next breakdown. As PM takes effect, MTBF should increase. Mean time to repair measures maintainability: how quickly a technician can restore an asset to service. PM improves MTTR indirectly by ensuring parts are on hand and technicians are familiar with the asset from regular servicing.

Maintenance cost as a percentage of replacement asset value (RAV) provides a financial benchmark. Industry norms range from 2 to 5 percent depending on asset type, with heavy mobile equipment trending higher and building systems trending lower. If your ratio is climbing year on year despite a mature PM programme, it may signal that assets are approaching end of life and replacement planning should begin.

Common preventive maintenance mistakes

Over-maintenance wastes money and labour. Changing oil every 250 hours on an engine rated for 500-hour intervals does not make the engine last longer; it just doubles consumable costs and takes a technician away from work that actually matters. This happens when organisations copy manufacturer recommendations without considering their specific duty cycle, or when they apply the most conservative interval across the entire fleet regardless of operating conditions.

Under-maintenance is the opposite failure, and it is more dangerous. It typically affects assets that are hard to access, located at remote sites or perceived as less important. A backup generator that only runs during power outages still needs regular fuel system, battery and coolant checks. A safety shower in a chemical plant still needs flow testing. These assets are low-use but high-consequence, and they are the ones most likely to slip through the cracks in a PM schedule.

Failing to review and adjust the programme is the subtlest mistake. A PM schedule built in year one should not look the same in year three. Failure data, technician feedback and changing operating conditions should drive continuous refinement. If a particular task has never found a defect in 24 consecutive inspections, the interval may be too short, or the task itself may be unnecessary. Conversely, if a failure mode keeps recurring between scheduled services, the interval needs tightening or the task list needs expanding. Treat the PM programme as a living document, not a laminated poster on the workshop wall.

How software automates preventive maintenance

The core function of PM software is automated scheduling. When an asset hits a time, usage or condition trigger, the system generates a work order, assigns it to the right technician and notifies them via mobile app or email. This eliminates the supervisor who manually checks a spreadsheet every Monday to see what is due. It also prevents the most common cause of missed services: nobody remembered.

Beyond scheduling, PM software centralises asset data. Every service record, inspection finding, parts replacement and cost entry lives in one place, searchable by asset, location, technician or date range. This makes compliance audits straightforward, because the evidence already exists in the system rather than in a filing cabinet or a technician’s notebook. It also supports warranty claims, because you can prove that manufacturer-required services were completed on time.

Platforms like MapTrack go further by combining preventive maintenance with asset tracking, so the system knows not just what is due but where the asset is. If a mobile generator is due for a 500-hour service but has been transferred to a different site, the work order routes to the technician at that site automatically. This integration between tracking and maintenance closes a gap that standalone CMMS tools leave open, particularly for organisations with distributed or mobile asset fleets.

Preventive maintenance for vehicles, equipment and facilities

Vehicle preventive maintenance is the most familiar form of PM because most people have experienced scheduled car servicing. Fleet vehicles follow a similar pattern at larger scale: oil and filter changes, brake inspections, tyre rotations, fluid top-ups and safety checks at fixed kilometre or time intervals. The complexity increases with specialised vehicles like refrigerated trucks, which add compressor and temperature system checks, or concrete agitators, which require drum and chute cleaning schedules.

Heavy equipment and plant maintenance is driven by engine hours or production cycles rather than distance. A 250-hour service on an excavator typically covers engine oil, hydraulic filters and a walk-around inspection. A 1,000-hour service adds hydraulic oil sampling, undercarriage measurement and electrical system checks. A 2,000-hour service might include major component inspections like swing bearing clearance or final drive oil changes. The stakes are high because heavy equipment downtime costs $500 to $2,000 per hour in lost productivity on most construction and mining sites.

Facilities and building maintenance is calendar-based and covers a broad range of systems. HVAC units need seasonal filter changes and refrigerant checks. Fire suppression systems require monthly visual inspections and annual functional testing. Electrical switchboards need thermographic surveys. Roofing, guttering and stormwater systems need pre-wet-season inspections. The challenge with facilities PM is the sheer number of assets spread across a building or campus, which makes a centralised tracking system essential for keeping nothing overlooked.