Preventive vs Predictive vs Corrective Maintenance: Differences

Preventive, predictive and corrective maintenance: what they are

Corrective maintenance acts after the equipment fails; preventive maintenance intervenes at fixed time or usage intervals, before failure; predictive maintenance intervenes when measured condition (vibration, temperature, oil) shows failure is approaching. The right choice depends on downtime cost, risk, and whether the failure gives warning signs.

There is no single "best" type. A mature plant uses all three, each on the right assets.

Visual map of the three maintenance types

The map compares the three types and shows the cost versus availability curve, using the numbers from this article's example.

The three types side by side

There are also detective maintenance (testing hidden functions, such as a protection system) and improvement (modifying the asset to remove the cause). EN 13306 sets the European terminology for maintenance.

Example: yearly cost of each strategy

Illustrative example with simple numbers. A press runs 6,000 hours per year and each hour of downtime costs $1,500 in lost output. Each failure repair costs $2,000 in parts and labor.

Availability = (6,000 − hours down) ÷ 6,000

Corrective: (6,000 − 48) ÷ 6,000 = 99.2%. MTBF and MTTR give the same result: MTBF = 6,000 ÷ 6 = 1,000 h; MTTR = 8 h; 1,000 ÷ (1,000 + 8) = 99.2%.

Preventive saves $38,000 (45%) against corrective, and predictive saves $41,500 (49%). The gap between the two is small because monitoring cost eats part of the gain: predictive really pays off only when the asset is critical and downtime is expensive.

Cost versus availability curve

The more you invest in prevention, the higher availability climbs and the lower failure cost falls. But maintenance cost rises too. The sum of both forms a U-shaped curve, and the minimum total cost sits at an intermediate point. Going past it spends more on maintenance than it saves on breakdowns. That point differs for every machine, so define the strategy per asset, not for the whole plant.

How to choose the strategy for each asset

1. List the assets and rank criticality. Use the impact of a stop on safety, quality, output and cost. A Pareto chart of downtime hours shows where to focus.
2. Analyze failure modes. With FMEA, see how each asset fails and whether it gives warning.
3. Random failure with no wear pattern? Calendar-based preventive wastes effort; prefer inspection or predictive.
4. Predictable wear and cheap to replace? Preventive.
5. Expensive failure with a measurable sign? Predictive.
6. Cheap, redundant, no risk? Planned run-to-failure.
7. Review with data. Track MTBF, MTTR and cost per asset and adjust.

This logic of deciding by criticality and failure mode is the basis of reliability-centered maintenance (RCM), described by John Moubray.

How this fits into TPM

In TPM, preventive and predictive work are pillars of planned maintenance, while the operator handles the basics in autonomous maintenance: cleaning, lubricating, tightening and inspecting. The gain shows in OEE, because stops and minor stops cut availability. When a failure happens anyway, use the 5 Whys to stop it from repeating.

Common mistakes and limits

• Too much preventive work. Replacing good parts on a calendar wastes money and can introduce post-maintenance failures.
• Predictive with no action. Measuring and ignoring the alert is cost without return.
• Predictive on everything. Sensors on cheap assets do not pay back.
• A plan that is never reviewed. Intervals must be tuned with failure history.
• Ignoring failures with no warning. Some failures (sudden electrical faults, for example) show no prior symptom; predictive cannot protect against them.
• The example numbers. They are illustrative; use your real downtime and repair costs.

Frequently asked questions

What is the difference between preventive and predictive maintenance?

Preventive is done by time or usage regardless of condition; predictive is done when condition monitoring says it is needed.

Which is cheapest?

It depends on the asset. Corrective has no plan cost but tends to cost more in downtime; in the example it came to $84,000 versus $46,000 and $42,500.

Is corrective maintenance always bad?

No. It is the rational choice for cheap, redundant items with no safety risk.

What does predictive maintenance monitor?

Conditions such as vibration, temperature, oil analysis, ultrasound and thermography, depending on the asset.

How do I know the strategy works?

Through MTBF, MTTR, availability, maintenance cost per asset and hours of unplanned downtime.

Can preventive and predictive coexist?

Yes, and that is normal: preventive on predictable-wear items and predictive on critical assets.

About the author

Vagner Soares

Lean Manufacturing & Behavioral Management Specialist

Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.

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