Predictive & Preventive Maintenance Flashcards
7 cards from real MMC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Predictive & Preventive Maintenance flashcards as text
Acoustic emission (AE) testing differs from ultrasonic testing primarily because AE:
Answer: Detects stress waves generated by the material itself during active defect propagation
AE is a passive technique that listens for high-frequency stress waves emitted by growing cracks or active defects, unlike pulse-echo UT which generates and receives its own signal.
When calculating overall equipment effectiveness (OEE), which component is most directly improved by a strong preventive maintenance program?
Answer: Availability
PM reduces unplanned breakdowns, directly increasing availability (the ratio of planned operating time to actual uptime) within the OEE calculation.
A maintenance team discovers that 20% of their PM tasks account for 80% of PM labor hours. This observation is an application of:
Answer: Pareto principle
The Pareto principle (80/20 rule) states that a minority of items often accounts for the majority of the effect, helping prioritize PM optimization efforts.
In vibration analysis, a 'waterfall plot' (cascade plot) is used to:
Answer: Show vibration spectra collected at multiple time stamps to reveal developing frequency components
A waterfall plot stacks sequential vibration spectra in a 3-D view (frequency, amplitude, time), making it easy to see new frequency components emerging as a fault develops.
Which failure distribution is most commonly used to model wear-out failures in mechanical components?
Answer: Weibull distribution with shape parameter β > 1
A Weibull distribution with β > 1 models increasing failure rate over time, characteristic of wear-out mechanisms such as fatigue, erosion, and corrosion.
A predictive maintenance program finds that a centrifugal pump has elevated vibration at 2X running speed. The most likely cause is:
Answer: Mechanical looseness or misalignment
Strong 2X (twice running speed) vibration is a classic indicator of mechanical looseness or angular misalignment, which generates a second harmonic component.
The primary reason for documenting 'as-found' and 'as-left' conditions on PM work orders is to:
Answer: Build a historical record of equipment degradation rates to refine future PM intervals
As-found/as-left data captures the equipment's condition before and after maintenance, enabling analysis of degradation trends and optimization of PM task frequencies.