There is no single best strategy
Every plant has to decide, whether deliberately or by default, how it will deal with equipment that wears out. The main options are to repair things when they break, to service them on a schedule, to service them when measurements show a problem is developing, or to work out for each asset which of those makes sense. These are usually called reactive, preventive, predictive and reliability-centered maintenance.
A common mistake is to treat them as rival camps and pick one for the whole site. In practice, a small cooling fan and a main process pump have very different consequences when they stop, so they deserve different treatment. The useful question is not “which strategy is best” but “which strategy fits this asset, given what its failure would cost.”
Reactive maintenance
Reactive maintenance, also called run-to-failure, means the equipment is used until it stops, then repaired or replaced. It sounds careless, but it is a legitimate choice for some assets.
It tends to make sense when:
- the failure is not a safety risk,
- the item is cheap or easy to replace,
- a spare is on hand or quickly available,
- a stoppage does not halt production or damage other equipment.
Think of a simple lamp or a low-cost, easily swapped component on a non-critical line. Spending time inspecting such items may cost more than letting them fail.
The weakness is obvious. Unplanned failures tend to happen at inconvenient times, repairs are rushed, parts may not be in stock, and a failed component can sometimes damage whatever it was attached to. Relying on this approach for important machinery usually leads to a cycle of emergencies.
Preventive maintenance
Preventive maintenance means doing work at set intervals, based on calendar time or on usage such as running hours or cycles, regardless of the exact condition of the equipment. Typical work includes lubrication, filter changes, belt checks, cleaning and inspections. The specific work items are covered in more detail in our look at preventive maintenance tasks.
The strength of this approach is predictability: work can be planned, parts ordered ahead and labor scheduled around production. Its weakness is that the schedule is only an approximation. Some parts are replaced while still healthy, and some fail between visits because the interval did not match how they actually wear. Intervals also work best for parts whose wear is fairly related to age or use, and less well for failures that appear at random.
Manufacturer manuals are the usual starting point for intervals. Experience with the specific machine, its duty and its environment then lets a team adjust them over time.
Predictive maintenance
Predictive maintenance, often called condition-based maintenance, bases the timing of work on the measured state of the equipment. Instead of replacing a bearing every so many months, the team watches for signs that it is deteriorating and acts when the evidence says it is time.
Common condition monitoring techniques include vibration measurement, temperature checks, oil analysis, ultrasonic listening and electrical measurements. Some are done by a person on a route with a handheld instrument; others use permanently installed sensors. Vibration analysis is a typical example for rotating machinery, because many mechanical faults change the vibration pattern before they cause a breakdown.
The advantage is that work can happen when it is needed, ideally with enough warning to plan it. The costs are instruments, training, and the discipline to act on the readings. It is also not suited to every failure: some faults develop too quickly to catch, and some assets are not worth the monitoring effort. A predictive maintenance program works best when it targets equipment where early warning is both possible and valuable.
Reliability-centered maintenance
Reliability-centered maintenance, or RCM, is less a separate technique than a structured way of choosing among the others. For each asset, a team asks what the equipment is supposed to do, how it can fail, what happens when it does, and which task, if any, would reasonably prevent or catch that failure. The answer may be a scheduled task, a condition check, a design change, or a decision to run to failure.
This connects closely to failure mode analysis, which lists the ways an asset can fail and ranks their consequences. A full RCM study takes real time and skilled people, so many plants apply it only to their most important systems, or use a simplified version.
Choosing a mix per asset
A practical way to build the mix is to work through the equipment in stages.
- List the assets you actually maintain. Many plants start from an equipment register.
- Rank them by consequence. Asset criticality ranking looks at safety, production impact, environmental risk, repair cost and how easily the item can be replaced.
- Match the strategy to the ranking. The most critical items usually justify closer attention, such as condition monitoring plus planned tasks. Mid-range items often suit scheduled preventive work. Low-consequence items may be left to run to failure.
- Consider how the asset fails. Age-related wear responds well to scheduled work, while failures that give gradual warning suit condition checks. Failures that give no warning and are not related to age may be better handled by redundancy or spares.
- Check the resources. A strategy that the team cannot staff, schedule or document will not hold up, however good it looks on paper.
Spares are part of the picture. Even a well-run program will see occasional failures, so critical spares for the most important machines can turn a long outage into a short one.
Reviewing the results
A mix is not permanent. Breakdown records, repair histories and maintenance metrics such as time between failures and time to repair show whether the chosen approach is working. Repeated failures of the same kind call for root cause analysis rather than another quick repair. Over time, a team might loosen intervals on items that never fail, tighten them where they do, and move an asset to a different strategy as its condition or role changes.
Keeping simple, accurate records makes this review possible. Maintenance software can help, but even a well-kept paper log is better than relying on memory.
A note on safety
Whatever the strategy, work on industrial equipment carries real hazards. Follow the manufacturer’s manuals, use lockout and tagout style procedures to keep machines from starting during service, rely on trained and qualified personnel, and comply with local regulations. This article is general information, not engineering advice for a specific machine.