Introduction: Moving From Firefighting to Anticipation
A Preventive Maintenance Plan (PMP) is the full set of planned, anticipatory actions designed to reduce the probability of equipment failure. In many organisations, however, the PMP remains wishful thinking: disorganised interventions, unexpected breakdowns that bring operations to a halt, and maintenance teams permanently stuck in reactive mode.
Why do so many PMPs fail? Because they lack methodological structure, because critical assets are never properly prioritised and, above all, because there is no central tool capable of managing that complexity.
The promise of an effective PMP is simple but demanding: devote at least 80 to 85% of maintenance time to planned work rather than to putting out fires. That shift delivers three major benefits: a higher MTBF (Mean Time Between Failures), stronger operational reliability and a sharp reduction in corrective maintenance costs.
This guide sets out a method in 4 structuring steps, driven by a CMMS (Computerised Maintenance Management System) that turns your approach to preventive maintenance into a coherent, measurable and scalable system.
The 4 steps of an effective PMP:
- Asset inventory and criticality (ABC classification)
- Defining tasks and frequencies (calendar-based versus condition-based)
- Planning and scheduling (CMMS optimisation)
- Review and adjustment (KPI tracking)
Step 1: Asset Inventory and Criticality (A/B/C Classification)
The fatal mistake: maintaining everything the same way
The first rule of an effective PMP is counter-intuitive: do not maintain everything with the same intensity. Not every item of equipment has the same impact on your operation when it fails. Spending as much energy on an accommodation fan as on the main propulsion train wastes resources and condemns your PMP to inefficiency.
The ABC classification method: prioritising intelligently
The ABC classification applies the Pareto principle (80/20) to maintenance. It splits your equipment into three categories according to criticality:
Category A (Critical): 15-20% of equipment, 80% of the consequences
These assets are your operational bottlenecks, your safety-critical equipment, or those whose failure causes major financial or regulatory losses. Examples: main engine and its auxiliaries, steering gear, main air compressors, emergency generator.
→ Recommended strategy: condition-based or predictive maintenance (continuous sensor monitoring, lube oil analysis, thermography).
Category B (Important): 30% of equipment, 15% of the impact
Equipment with a moderate impact on operations or safety, but which still needs regular attention. Examples: secondary transfer pumps, circulation pumps, standard HVAC systems.
→ Recommended strategy: calendar-based maintenance or simplified condition monitoring.
Category C (Secondary): 50-55% of equipment, 5% of the impact
Redundant or easily replaceable equipment, or items whose failure does not significantly affect operations. Examples: lighting in non-critical spaces, small handling equipment.
→ Recommended strategy: corrective maintenance (run to failure) or light calendar-based routines.
The decisive role of the CMMS in Step 1
Your CMMS is the single centralised register in which every asset is recorded with its technical data sheet, its ABC classification and its potential impacts (safety, environment, operations, cost). This structured database prevents duplicates, keeps the full history of each item of equipment and, most importantly, allows you to justify your maintenance strategy with objective data.
Step 2: Defining Tasks and Frequencies (The Two Types of PMP)
Once your assets are classified, the challenge is to determine precisely what to do (the nature of the work) and when to do it (the frequency). Your PMP will be built around two complementary approaches.
Calendar-based maintenance: the schedule as the driver
Definition: work carried out at fixed intervals, either calendar-based (every 6 months, every year) or usage-based (every 500 running hours, every 10,000 cycles).
When to use it
- For Category B equipment where wear is predictable
- To meet regulatory obligations (mandatory periodic surveys, maker warranty conditions)
- For low-complexity routine tasks (lubrication, visual checks, tightening)
Practical example: annual renewal of a compressor's air filters, oil change on a reduction gear every 2,000 running hours.
Condition-based maintenance: monitor, then act at the right moment
Definition: work triggered by the actual condition of the equipment, revealed by continuous or periodic monitoring (vibration analysis, infrared thermography, lube oil analysis, electrical current measurement and so on).
When to use it
- Mainly for Category A assets where every failure is expensive
- When early warning signals can be detected before the equipment breaks down
- To optimise cost: you intervene only when it is genuinely needed, neither too early (waste) nor too late (failure)
Practical example: renewing the bearings of an electric motor only once vibration analysis detects the abnormal frequencies typical of a developing defect.
The decisive role of the CMMS in Step 2
The CMMS holds your detailed task sheets: operating procedures, estimated durations, required competencies, special tools and spare parts lists (BOM - Bill of Materials). It also handles the automatic triggering of work orders:
- For calendar-based maintenance: triggered by counters (running hours, distance) or by calendar due dates
- For condition-based maintenance: triggered by alert thresholds when a monitored parameter crosses a predefined limit
This automation removes oversights and guarantees that no critical task slips through the net.
Step 3: Planning and Scheduling (Optimising the CMMS Calendar)
Defining tasks and frequencies is not enough: those intentions still have to be turned into concrete action, taking account of the real constraints of your organisation.
The art of scheduling work orders
Scheduling means organising maintenance work in time and space while optimising three dimensions:
Grouping by location and by trade
Concentrating jobs by area (engine room, deck, a given space) or by trade (electricians, mechanics, automation technicians) cuts unproductive movement and maximises effective wrench time.
Resource management
- People: technician availability, specific competencies, workload
- Materials: availability of spare parts in the CMMS inventory, special tools, lifting gear
- Operational: equipment availability windows (planned shutdowns, quiet periods, port calls)
Dynamic prioritisation
Not every work order carries the same urgency. Your schedule must distinguish between:
- Critical jobs on Category A assets (absolute priority)
- Calendar-based maintenance on Category B assets (some flexibility possible)
- Category C jobs (deferrable if necessary)
The decisive role of the CMMS in Step 3
The CMMS calendar gives you a real-time overview of all planned work. Its key capabilities:
- Graphical visualisation of workload by team and by period
- Automatic alerts when a critical work order is at risk of running past its due date
- Dynamic adjustment: drag and drop jobs when the unexpected happens
- Integration with inventory management: automatic check that the parts are on board before a work order is scheduled
- Full traceability: every scheduling decision is documented and defensible
Without a CMMS, scheduling relies on scattered spreadsheets, emails and the memory of a few key people - a guaranteed recipe for chaos as soon as complexity increases.
Step 4: Review and Adjustment (Performance KPIs)
A PMP is never set in stone. Operational excellence demands continuous improvement based on objective performance indicators.
The essential KPIs for your PMP
1. Planned maintenance percentage (PMP rate)
Formula:
PMP rate = (planned preventive maintenance hours / total maintenance hours) × 100
Recommended target: ≥ 85%
This ratio measures how much of your maintenance time goes into anticipation rather than reaction. A rate below 70% means you are still firefighting. If your rate stalls or falls back, question your scheduling and your ABC classification again.
2. MTBF (Mean Time Between Failures)
Definition: the average time elapsed between two failures of a repairable item of equipment.
Formula:
MTBF = total operating time / number of failures
Interpretation: an effective PMP should increase the MTBF of your critical assets. If MTBF falls despite your PMP, there are two likely explanations:
- Your intervals are too long (tighten them)
- Your tasks do not address the right failure modes (revise your procedures)
3. Preventive versus corrective maintenance cost
Objective: preventive work should account for roughly 20 to 30% of the total maintenance budget, but that increase must go hand in hand with a sharp fall in corrective costs (breakdowns, operational downtime, emergency interventions).
The winning equation: every extra euro invested in preventive maintenance should save three to five euros in corrective work and lost operating time.
The decisive role of the CMMS in Step 4
The CMMS calculates and displays these KPIs in real time through customisable dashboards. That immediate visibility allows maintenance managers to:
- Spot drift instantly (falling MTBF, dropping PMP rate)
- Take corrective decisions based on data rather than intuition
- Justify investment in preventive maintenance to senior management with figures that cannot be argued with
- Fine-tune PMP frequencies at a granular level (by item of equipment, by family)
Without a CMMS, calculating these indicators by hand is time-consuming, error-prone and always retrospective - you end up steering by looking in the rear-view mirror.
Asset Classification Table (A/B/C)
| Category | % of assets (approx.) | % of impact (approx.) | Recommended strategy |
|---|---|---|---|
| A (Critical) | 15-20% | 80% | Condition-based / predictive |
| B (Important) | 30% | 15% | Calendar-based / condition-based |
| C (Secondary) | 50-55% | 5% | Corrective (run to failure) |
Panel: Glossary of Key Acronyms
PMP (Preventive Maintenance Plan): the structured set of anticipatory jobs planned to reduce failures.
CMMS (Computerised Maintenance Management System): centralised software used to manage, trace and optimise maintenance activity.
WO (Work Order): the document that triggers a maintenance job, generated automatically or manually in the CMMS.
MTBF (Mean Time Between Failures): the average time between two consecutive failures of a repairable item of equipment. A key reliability indicator.
PMP rate: the percentage of maintenance time devoted to planned work (target: ≥ 85%).
Calendar-based maintenance: preventive work carried out at fixed intervals (by date or by usage).
Condition-based maintenance: preventive work triggered by the actual condition of the equipment (monitoring).
Conclusion: From Theory to Action
The success of a Preventive Maintenance Plan does not rest on the complexity of its procedures, but on methodological discipline and the ability to measure continuously. The four steps set out in this guide give your approach its structure, but it is the CMMS that turns it into a living, adaptable and high-performing system.
Moving from 60% to 85% planned maintenance is not wishful thinking: it is the result of a rigorous ABC classification, well-targeted tasks, optimised scheduling and management by KPI. That cultural shift - leaving firefighting behind to embrace anticipation - is the only route to lasting operational reliability.
Start your transformation today
🎯 Immediate start-up checklist:
- List your 20 most critical items of equipment (your future Category A assets)
- Identify, for each one, the most expensive failure mode
- Define a first pilot condition-based maintenance task
- Measure your current PMP rate (your starting point)
- Set yourself a target of improving it by 10 points over 6 months
Effective preventive maintenance is no longer optional in a competitive operating environment - it is a condition of survival. Your CMMS is ready to help you get there. Are you?
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