There are only two true categories of maintenance:

• Corrective Maintenance (CM)
• Preventive Maintenance (PM)

Maintenance is not the same thing to everyone. Operations staff, maintenance staff, and reliability engineers have long struggled to arrive at a common understanding. Unfortunately, the public domain is flooded with misleading terms and flawed definitions.

At ETEQ, we cut through the noise. We bust myths, clarify concepts, and bring precision to the language of maintenance.

Misused and Misleading Terms

One of the most abused terms is “Breakdown Maintenance.”

• A breakdown is an event, not a category.
• You cannot “plan” a breakdown—it simply happens.

What people often mean is a run-to-failure strategy, which is only valid for equipment that is:

• Non-critical
• Easily available
• Quickly replaceable
• Low cost

Very few rotating machines meet all these criteria. The correct term remains Corrective Maintenance (CM)—repairs or replacements that restore equipment to its functional state.

Reactive Maintenance

• Not a category – just an adjective.
• Describes CM done after an unexpected breakdown.
• The category remains CM.

Corrective Maintenance (CM)

CM requires dedicated funds for:

• Materials and spares
• Repairs : Refurbishment of Components where feasible
• Skilled manpower
• Logistics and planning
• Disassembly, reassembly, and start-up support

Budgeting for CM must be done separately and explicitly.

Preventive Maintenance (PM)

The second valid category is Preventive Maintenance (PM). Do not confuse this with the PM module in ERP systems—that is software, not maintenance.

PM involves scheduled activities designed to keep equipment healthy and avoid breakdowns:

• Inspections (Time-based Maintenance, TBM)
• Servicing (User-based Maintenance, UBM)
• Calibration (UBM)
• Functionality checks/testing (Condition-based Maintenance, CBM)
• Health measurement & parameter correlation (CBM)
• Analysis & detection of faults (Predictive Maintenance, PdM)
• Alignment (UBM or CBM)
• Performance monitoring (Metrics-based Maintenance, MBM)

All these are subsets of PM. Each requires separate funds for tools, instruments, and manpower—distinct from CM budgets.

Proactive Maintenance

• Not a category – just an adjective.
• Describes CM done before the breakdown can happen based on one or more PM findings.
• The category remains CM.

Linking PM and CM to KPIs

A powerful KPI emerges when you track the trigger for CM:

• Breakdown
• PM-TBM
• PM-UBM
• PM-CBM
• PM-PdM

By categorizing CM events by their trigger, you gain deep insight into how your maintenance strategy is performing. Monthly tracking reveals whether breakdowns dominate or whether preventive actions are successfully reducing failures.

The Temptation of New Terms

Some invent terms like Opportunity Maintenance (OM):

“The motor was down, so we repaired the pump in parallel.”

Parallel work is fine—but hiding it under OM cheats your KPI. Every maintenance event must be counted. Use opportunities wisely, but call it what it is: Corrective Maintenance.

Holistic Strategies

Beyond CM and PM, you will encounter terms like:

• Risk-Based Maintenance (RBM)
• Reliability-Centred Maintenance (RCM)
• Total Productive Maintenance (TPM)

These are not categories but strategies—frameworks to ensure maintenance is efficient, structured, cost-effective, reliable, and safe.

No single strategy is universally superior. Plants must select what fits their needs. For most, a condition-based asset management strategy is more than sufficient.

Final Word

Breakdowns are events, not categories. Reactive and proactive are adjectives, not independent terms. The only valid categories are:

• Corrective Maintenance (CM)
• Preventive Maintenance (PM)

Everything else is either a subset or a strategy. Clarity in terminology leads to clarity in execution—and that is the foundation of world-class maintenance.