Operations and Maintenance: Work Management, Maintenance Strategy, and Reliability Metrics
The Operations and Maintenance domain tests whether you can run the asset base to deliver promised service levels at an accepted cost and risk. Expect work management, maintenance strategy selection, criticality, and program-health metrics.
Work management is the backbone
Requests follow a defined path: request, approval and prioritization, dispatch, execution, closeout with failure coding, then analysis. The CMMS is the system of record: bad asset registers or work history make every downstream metric wrong. Closeout codes - what failed, why, what was done - turn history into maintenance intelligence.
Select strategy by criticality
- Run-to-failure: only for non-critical, low-cost, easily replaced assets.
- Preventive: time- or usage-based, set from manufacturer guidance plus failure history.
- Predictive/condition-based: vibration, thermography, oil analysis, ultrasound; needs baseline data and skilled interpretation.
- Corrective: repair after detected degradation but before functional failure.
Metrics that hold up
MTBF = operating time ÷ failures. MTTR = repair time ÷ repairs. Availability = MTBF ÷ (MTBF + MTTR). PM compliance = PM tasks completed on schedule ÷ tasks due. Backlog is measured in labor-hours and weeks of work; a rising backlog signals under-resourcing, weak PM design, or both.
Worked example
A chilled-water pump runs 4,000 hours between failures and averages 8 hours to repair. Availability = 4,000 ÷ 4,008 = 99.80%. Condition monitoring cuts repair time to 5 hours: 4,000 ÷ 4,005 = 99.88%. Small on paper, but for a pump serving a data hall that fraction is hours of avoided downtime.
Traps
Confusing MTBF with MTTR; applying one PM frequency to every asset; hitting PM compliance by count while doing the wrong tasks; over-maintaining non-critical assets; closing work orders without failure codes, so the data never improves.