Maintenance, repair, and operations Study Guide

📖 Core Concepts Maintenance – Any functional check, service, repair, or replacement that keeps equipment, infrastructure, or utilities operating at designed capacity. MRO (Maintenance, Repair, Overhaul) – Umbrella term covering all three activities: maintaining, repairing, and overhauling equipment/systems. Maintainability – The ease with which an item can be retained in or restored to a functional state under defined conditions, using prescribed procedures and resources. Basic Maintenance Types – Preventive, corrective, and reinforcement (the latter is seldom examined; focus on the first two). Preventive Maintenance (PM) – Routine, scheduled actions (inspections, oil changes, overhauls) to stop failures before they start. Planned Maintenance – A subset of PM that is scheduled by date, operating hours, or distance; also called scheduled or planned preventive maintenance. Predictive Maintenance (PdM) – Uses sensor data + trend analysis to predict when a component will fail, performing work only when needed. Condition‑Based Maintenance (CBM) – Maintenance triggered by real‑time condition indicators (vibration, temperature, pressure) that show degradation or imminent failure. Corrective Maintenance – Repair after a breakdown; usually the most costly and disruptive. Related Strategies – Reliability‑Centered Maintenance (RCM), Total Productive Maintenance (TPM), Value‑Driven Maintenance, Active Redundancy, Design for Repair, Intelligent Maintenance Systems, Operational Availability. --- 📌 Must Remember PM Goal: Move equipment from one planned service to the next without fatigue‑related, temperature‑related, or wear‑related failures. CBM Advantage: Performs only the right maintenance → lower spare‑part cost, less downtime, reduced labor. PdM vs CBM: PdM predicts future failure; CBM reacts to current condition thresholds. Corrective Cost: Highest among all types; includes collateral damage, revenue loss, and longer downtime. Maintainability Definition: Ability to restore function under stated use conditions using prescribed procedures/resources. Operational Availability = (Actual Uptime) / (Predicted Uptime). Intelligent Maintenance System: Collects machine data → supports maintenance decisions (often the technology backbone for PdM/CBM). --- 🔄 Key Processes Preventive Maintenance Cycle Set schedule (date / hrs / distance) → Perform inspection/servicing → Record condition → Update maintenance log → Reset timer. Predictive Maintenance Workflow Install sensors → Continuously collect data → Store in Historian → Apply analytics/trend analysis → Generate health index → Trigger work order when index crosses predictive threshold. Condition‑Based Maintenance Steps Define critical condition parameters → Install real‑time monitors → Set alarm limits → When limit exceeded → Diagnose → Execute targeted maintenance → Verify post‑maintenance condition. Corrective Maintenance Process Failure occurs → Fault reporting → Diagnose root cause → Order parts/repair crew → Perform repair → Test and return to service → Update failure database. --- 🔍 Key Comparisons Preventive vs Corrective Preventive: Planned, cost‑predictable, aims to avoid failure. Corrective: Unplanned, usually expensive, reacts after failure. Planned vs Predictive Planned: Fixed schedule regardless of actual equipment health. Predictive: Schedule driven by data‑based failure forecasts. Predictive vs Condition‑Based Predictive: Uses trends to forecast future failure (e.g., vibration growth curve). Condition‑Based: Acts when a current measurement exceeds a threshold. Reliability‑Centered Maintenance vs Total Productive Maintenance RCM: Maintenance plan derived from reliability analysis of each asset. TPM: Broad cultural program that embeds maintenance into daily production activities. --- ⚠️ Common Misunderstandings “Predictive eliminates all maintenance.” – PdM still requires periodic inspections and sensor calibrations. “CBM is always cheaper than PM.” – High upfront instrumentation cost and uneven cost distribution can offset savings. “Planned = Preventive.” – Planned is the scheduling method; preventive is the type of work performed. “Higher reliability means no maintenance.” – Even highly reliable assets need periodic checks to sustain reliability. --- 🧠 Mental Models / Intuition Health‑Check Analogy: Think of equipment like a human body—preventive = annual physical, predictive = blood‑test trends, condition‑based = symptom‑driven doctor visit. Ladder of Maintenance: 1️⃣ Condition‑Based (react only when sick) → 2️⃣ Predictive (watch trends) → 3️⃣ Preventive/Planned (regular check‑ups) → 4️⃣ Corrective (emergency surgery). Cost‑Benefit Curve: Upfront CBM/PdM investment → early‑life higher cost → later‑life lower total cost; the break‑even point is the “value‑driven” sweet spot. --- 🚩 Exceptions & Edge Cases CBM Initial Cost: Installation on legacy equipment may be prohibitive; sometimes a hybrid (partial CBM) is used. Uneven Cost Distribution: CBM can cause spikes in spending when many components simultaneously hit alarm thresholds. Sensor Failure: A false‑negative sensor can hide an impending failure—maintain sensor health as part of the program. --- 📍 When to Use Which Use Preventive when: Equipment has well‑known wear patterns (e.g., oil changes every 500 hrs). Downtime costs are moderate and schedule can be accommodated. Use Predictive when: High‑value assets with measurable degradation signatures. Sufficient data history exists for trend analysis. Use Condition‑Based when: Real‑time monitoring is affordable and critical (e.g., rotating equipment with vibration sensors). You need to prioritize limited maintenance resources. Use Corrective only as a last resort or for low‑criticality items where the cost of preventive outweighs failure impact. Choose RCM for complex systems where failure consequences differ widely among components. Choose TPM when organization seeks cultural integration of maintenance into daily production. --- 👀 Patterns to Recognize “Based on running hours or distance” → indicates planned or preventive maintenance. “Sensor data + trend analysis” → signals predictive maintenance. “Alarm threshold exceeded” → points to condition‑based maintenance. “After a breakdown” → describes corrective maintenance. “Design includes backup components” → refers to active redundancy. --- 🗂️ Exam Traps Distractor: “Predictive maintenance is the same as condition‑based.” Why wrong: PdM predicts future failure; CBM reacts to current condition. Distractor: “Planned maintenance always reduces cost compared to preventive.” Why wrong: Planned is a scheduling method; cost depends on the type of work (preventive vs corrective). Distractor: “Higher reliability automatically means less maintenance.” Why wrong: Reliability‑centered maintenance still schedules work to maintain reliability. Distractor: “CBM eliminates the need for any scheduled inspections.” Why wrong: Sensors need calibration; periodic inspections remain necessary. Distractor: “Corrective maintenance is the preferred strategy for high‑value equipment.” Why wrong: Corrective is the most expensive and risky for critical assets. ---