When to Replace Time-Based PMs with Condition-Based Work

Facility Maintenance
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The Big Question

At what point does a calendar-based PM stop adding value?

Time-based PMs are easy to schedule and defend, but they aren’t always the most effective—especially for assets that fail based on condition, not time.

Time-Based PMs Work Best When:

  • The asset has predictable wear intervals

  • Failure risk increases steadily over time

  • The task itself prevents failure (e.g., lubrication, filter changes)

  • Regulatory or compliance requirements mandate fixed intervals

Examples:

  • Fire/life safety inspections

  • Code-driven testing

  • Simple mechanical wear items

These PMs should usually stay time-based.

Signs It’s Time to Move to Condition-Based Work

If you see one or more of these, a review is warranted:

  • Failures occurring shortly after PMs

  • PMs repeatedly marked “no issues found”

  • Wide variation in asset usage or loading

  • High PM labor hours with low failure reduction

  • MTBF not improving despite high PM compliance

When PMs aren’t influencing failure behavior, the calendar is the wrong trigger.

Assets That Benefit Most from Condition-Based Maintenance

  • Rotating equipment (motors, pumps, fans)

  • Compressors and air systems

  • HVAC critical components

  • Electrical systems with thermal risk

  • Assets operating under variable loads

These fail based on stress, heat, vibration, and contamination—not dates.

What Condition-Based Work Looks Like in Practice

Instead of “every 90 days,” triggers become:

  • Vibration trending out of baseline

  • Temperature exceeding thresholds

  • Pressure or flow deviations

  • Electrical current anomalies

  • Runtime or load-based indicators

The work order is created because the asset changed, not because the date arrived.

The Hybrid Model (Most Facilities Land Here)

Very few facilities go fully condition-based.

A common and effective approach:

  • Keep light, low-effort inspections time-based

  • Trigger corrective or detailed work condition-based

  • Use condition checks as part of existing PMs

  • Reduce PM frequency once trends are established

This balances risk, labor, and reliability.

Mistakes to Avoid

  • Eliminating PMs without historical data

  • Switching critical assets without proven baselines

  • Collecting data without acting on it

  • Over-instrumenting low-risk assets

Condition-based maintenance fails when it becomes “data for data’s sake.”

Field Reality Check

  • PM compliance ≠ reliability

  • Condition-based work shifts effort from volume to precision

  • Fewer work orders doesn’t mean less control—it often means better control

  • Technicians’ observations are often the first “sensor”

Discussion

  • Which assets in your facility still rely on PM dates but shouldn’t?

  • Have you successfully reduced PM frequency using condition data?

  • What data do you trust most—sensor readings or technician feedback?

  • What’s holding your facility back from condition-based work?