Equipment Reliability
What this domain tests
Equipment reliability tests how failure is understood and prevented: RCM, FMEA, criticality, failure patterns, condition-based maintenance, root cause analysis, and asset tactics. The exam rewards failure-mode thinking rather than generic maintenance activity.
Core rules and concepts
- RCM follows SAE JA1011 logic: functions, functional failures, failure modes, failure effects, failure consequences, and applicable, effective tasks.
- FMEA is a bottom-up risk tool using severity, occurrence, and detection. RCM is top-down and consequence-driven.
- Criticality ranking sets effort. Consequence includes safety, environment, production, quality, and cost.
- The P-F interval is the time between potential failure detection and functional failure. The inspection interval must be shorter than the P-F interval-commonly one-half or less-to leave time to act.
- Weibull shape helps choose tactics: β < 1 suggests infant mortality, β ≈ 1 random failure, β > 1 wear-out. The bathtub curve is not universal.
- RCFA addresses causes, not symptoms. Correct the physical, human, and latent system causes.
Worked example
A bearing shows a measurable vibration increase about 30 days before functional failure. The planner proposes a 30-day vibration route. The reasoning: a task interval equal to the P-F interval gives no warning time and will miss failures. At half the P-F interval, 15 days, there are roughly two opportunities to detect the defect before failure. If the consequence is safety-critical or the P-F interval is variable, shorten further or select a different task. The task must also be applicable: it detects the specific bearing defect and is worth doing given the consequence.
Traps that cost marks
Assuming every asset follows a bathtub curve. Using MTBF alone without failure distribution. Applying PM to a failure mode that has no measurable deterioration. Giving all equipment the same criticality. Choosing a task that cannot detect the failure mode. Fixing the operator instead of the system cause in RCFA.
Exam tip
For a task-selection question, first identify the failure mode and consequence. Then test whether the proposed task is applicable and effective; if not, consider redesign, failure finding, or run-to-failure.