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Building an Effective Maintenance Schedule: PM vs PdM vs Reactive
2025-03-25Vallejo Reliability Group

Building an Effective Maintenance Schedule: PM vs PdM vs Reactive

PMStrategyPlanning

The Three Maintenance Strategies

1. Reactive Maintenance

"Fix it when it breaks"

  • Equipment fails unexpectedly
  • Emergency repairs at premium cost
  • High downtime
  • Typical cost: $100–$500 per repair hour

When to use: Non-critical assets, items with low failure impact

2. Preventive Maintenance (PM)

"Replace it before it fails"

  • Fixed schedule based on time or running hours
  • Example: "Oil change every 500 hours" or "Filter replacement quarterly"
  • Planned downtime
  • Typical cost: $20–$80 per maintenance hour

When to use: Assets with predictable wear patterns (oil, filters, belts)

3. Predictive Maintenance (PdM)

"Monitor it and fix only when needed"

  • Condition-based monitoring
  • Example: "Replace pump bearing when vibration exceeds 0.5 inches/sec"
  • Maintenance only when indicators suggest failure is near
  • Typical cost: $50–$150 per hour + monitoring equipment

When to use: High-value, critical assets with expensive emergency repairs

Cost Comparison Over 5 Years

Assuming a critical pump, failure cost = $15,000:

| Strategy | PM Cost | PdM Cost | Emergency Repairs | Total | Downtime Hours | |---|---|---|---|---|---| | Reactive | $0 | $0 | $45,000 (3 failures) | $45,000 | 60 | | Preventive | $3,000 | $0 | $15,000 (1 failure) | $18,000 | 20 | | Predictive | $2,000 | $4,000 | $0 | $6,000 | 5 |

Designing Your Maintenance Mix

Critical Assets (Top 20% that drive 80% of value)

→ Use Predictive Maintenance

Standard Assets

→ Use Preventive Maintenance with basic PM tasks

Non-Critical Assets

→ Use Reactive Maintenance only

5-Step Implementation Plan

  1. Classify your equipment — Which tier (critical, standard, non-critical)?
  2. Define PM tasks — Oil changes, filter replacements, inspections
  3. Set schedules — Based on manufacturer recommendations and historical data
  4. Implement PdM on critical assets — Start with vibration analysis or oil analysis
  5. Track metrics — MTBF, MTTR, cost per failure, downtime

💰 A well-balanced maintenance program (70% PM + 20% PdM + 10% reactive) typically costs 30–40% less than reactive-only maintenance.