CMRP Preventive and Predictive Maintenance 2 — Questions and Answers
Question 1: What is the primary difference between preventive and predictive maintenance?
- They are the same
- Preventive follows fixed schedules; predictive uses condition monitoring data (Correct answer)
- Predictive is always more expensive
- Preventive requires more advanced technology
Correct answer: Preventive follows fixed schedules; predictive uses condition monitoring data
Preventive maintenance performs tasks at predetermined intervals; predictive maintenance monitors actual condition.
PM is effective for age-related failures but can lead to over- or under-maintenance. PdM uses vibration, oil analysis, thermography, and ultrasound to assess health and optimize timing.
Question 2: What role does motor current analysis play in predictive maintenance?
- Measures electricity for billing
- Detects electrical and mechanical faults by analyzing current waveform variations (Correct answer)
- Controls motor speed
- Determines horsepower rating
Correct answer: Detects electrical and mechanical faults by analyzing current waveform variations
Motor current signature analysis detects both electrical defects and mechanical problems by analyzing current patterns.
Broken rotor bars create specific frequency sidebands; stator faults alter current symmetry; mechanical faults modulate the current. MCSA can be done non-intrusively at the motor control center.
Question 3: What is the purpose of preventive maintenance optimization (PMO)?
- To add more PM tasks
- To evaluate existing PM tasks for relevance, effectiveness, and interval optimization (Correct answer)
- To convert all PM to corrective
- To reduce staffing
Correct answer: To evaluate existing PM tasks for relevance, effectiveness, and interval optimization
PMO reviews assess each PM task to determine if it is valid, effective, performed at the right interval, and cost-justified.
Typical PMO results: 20-30% of PM tasks can be eliminated or modified, resulting in cost savings and improved reliability focus. Common findings include duplicate tasks, overly frequent intervals, and tasks with no technical basis.
Question 4: What is the significance of the P-F curve in predictive maintenance design?
- The profit-and-loss forecast
- The progression from detectable potential failure to functional failure (Correct answer)
- Personnel-to-facility ratios
- PM completion rate tracking
Correct answer: The progression from detectable potential failure to functional failure
The P-F curve shows how condition degrades from first detectable change to functional failure.
Different technologies detect at different points: ultrasonic earliest, then vibration, thermography, and audible noise. Inspection intervals should be at most half the P-F interval.
Question 5: What is the role of a CMMS in supporting PM and PdM programs?
- Only tracks corrective work
- Automates PM scheduling, stores PdM data, manages work orders, and provides analytics (Correct answer)
- Only for financial reporting
- Replaces technicians
Correct answer: Automates PM scheduling, stores PdM data, manages work orders, and provides analytics
CMMS is essential for managing PM schedules, tracking PdM data, generating work orders, and maintaining equipment history.
For PM, CMMS auto-generates work orders based on time, meter readings, or conditions. For PdM, it records monitoring data, triggers work orders on alarms, and links monitoring data to equipment history.
Question 6: What is condition-based monitoring of electrical systems?
- Checking electricity bills
- Using technologies like insulation resistance testing and thermography to assess electrical health (Correct answer)
- Monitoring electricity prices
- Counting outlets
Correct answer: Using technologies like insulation resistance testing and thermography to assess electrical health
Electrical condition monitoring uses various techniques to assess the health of electrical components.
Techniques include insulation resistance testing, power quality analysis, thermography, partial discharge monitoring, transformer oil analysis, and surge testing. Electrical failures can progress rapidly once insulation is compromised.
CMRP Preventive and Predictive Maintenance 2
What is the primary difference between preventive and predictive maintenance?