CMRT Predictive Maintenance Techniques 3 — Questions and Answers
Question 1: In lubricant oil analysis, a sharp increase in iron particle count combined with a high particle size distribution skewed toward larger particles most likely indicates:
- Normal run-in wear of new equipment
- Severe adhesive or abrasive wear in progress (Correct answer)
- Oxidation of the base oil
- Water contamination from a cooling system leak
Correct answer: Severe adhesive or abrasive wear in progress
Large iron particles in high concentration signal active, severe wear (adhesive or abrasive), which requires immediate investigation, unlike the fine particles typical of normal run-in.
Question 2: Infrared thermography on an indoor low-voltage switchgear panel is most effective at identifying which type of defect?
- Insulation degradation inside cable insulation
- Loose or corroded electrical connections causing resistive heating (Correct answer)
- Phase voltage imbalance in the utility supply
- Harmonic distortion from variable-frequency drives
Correct answer: Loose or corroded electrical connections causing resistive heating
Loose or corroded connections increase contact resistance; IR thermography detects the resulting heat signature before the connection fails, making it the primary electrical PdM tool for connection integrity.
Question 3: Airborne ultrasonic inspection is particularly useful for detecting which condition in compressed air systems?
- Internal pipe corrosion
- Pressure regulator setpoint drift
- Small leaks at fittings, valves, and hoses (Correct answer)
- Moisture contamination in the compressed air
Correct answer: Small leaks at fittings, valves, and hoses
Gas leaks through small orifices generate broadband turbulence with strong ultrasonic components; an ultrasonic detector can locate these leaks that are inaudible to the human ear.
Question 4: Ferrography (analytical ferrography) in oil analysis provides information that routine spectroscopy does NOT, specifically by:
- Measuring total acid number of the lubricant
- Allowing visual examination of wear particle morphology and size (Correct answer)
- Quantifying dissolved metal concentrations in parts per million
- Determining the base oil viscosity index
Correct answer: Allowing visual examination of wear particle morphology and size
Analytical ferrography separates and deposits wear particles on a substrate for microscopic examination, revealing particle shape, size, and surface features that identify the wear mechanism.
Question 5: During an infrared inspection of a steam trap, which thermal condition indicates a failed-open (blowing) steam trap?
- Trap body temperature equal to ambient
- Temperature drop of more than 100°F from inlet to outlet
- High inlet temperature with similar high outlet temperature (Correct answer)
- Cyclic temperature variation at the trap body
Correct answer: High inlet temperature with similar high outlet temperature
A failed-open trap continuously passes live steam, so the outlet pipe temperature approaches the inlet temperature instead of showing the expected temperature drop across a functioning trap.
Question 6: A lubricant's viscosity index (VI) is a measure of:
- The lubricant's resistance to oxidation at high temperatures
- How much the viscosity changes with temperature variations (Correct answer)
- The lubricant's film strength under extreme pressure
- The rate of additive depletion during service
Correct answer: How much the viscosity changes with temperature variations
Viscosity index quantifies the sensitivity of a lubricant's viscosity to temperature change; a high VI means viscosity changes little across a wide temperature range.
Question 7: When using contact ultrasound to inspect rolling element bearings, what does a loud, irregular crackling or 'frying' sound in the headset typically indicate?
- Normal lubrication of the bearing
- Early-stage bearing damage such as spalling or pitting (Correct answer)
- Shaft misalignment between coupled machines
- Belt slippage on a V-belt drive
Correct answer: Early-stage bearing damage such as spalling or pitting
Irregular crackling or frying sounds in ultrasonic bearing inspection are caused by stress waves generated when rolling elements strike defects such as spalls or pits on race surfaces.
CMRT Predictive Maintenance Techniques 3
In lubricant oil analysis, a sharp increase in iron particle count combined with a high particle size distribution skewed toward larger particles most likely indicates: