CPT Maintenance & Troubleshooting 3 — Questions and Answers
Question 1: A hydraulic system loses pressure gradually when the pump is stopped and valves are closed. This symptom indicates:
- A faulty pressure gauge
- Internal leakage past a relief valve or cylinder seals (Correct answer)
- Low hydraulic fluid viscosity
- An oversized hydraulic reservoir
Correct answer: Internal leakage past a relief valve or cylinder seals
Gradual pressure drop with pump off and valves closed points to internal leakage past worn seals or a leaking relief valve.
Question 2: What is the primary purpose of a lockout/tagout (LOTO) procedure before performing maintenance on machinery?
- To document the maintenance activity for records
- To prevent accidental energization that could injure workers (Correct answer)
- To protect equipment from unauthorized use
- To comply with ISO 9001 quality standards
Correct answer: To prevent accidental energization that could injure workers
LOTO procedures ensure all energy sources are isolated and locked before maintenance begins, preventing accidental startup or energy release.
Question 3: A three-phase motor fails to start and hums loudly. One likely cause is:
- Overvoltage on all three phases
- An open phase (single-phasing condition) (Correct answer)
- Excessive load inertia only
- Improper motor frame size
Correct answer: An open phase (single-phasing condition)
Single-phasing occurs when one of the three supply phases is lost, causing the motor to hum and fail to start because it cannot develop sufficient starting torque.
Question 4: Which type of bearing failure leaves a pattern of evenly spaced pits or fluting marks on the raceway?
- Fatigue spalling
- Electrical pitting from stray current (Correct answer)
- Brinelling from overload
- Corrosion from moisture contamination
Correct answer: Electrical pitting from stray current
Electrical pitting (fluting) creates regularly spaced groove marks on bearing raceways caused by stray electrical current passing through the bearing.
Question 5: A gear drive emits a high-pitched whine that changes pitch with speed. This symptom most likely indicates:
- Insufficient lubrication between gear teeth (Correct answer)
- A cracked gear tooth
- Misaligned coupling on the output shaft
- Bearing cage fracture
Correct answer: Insufficient lubrication between gear teeth
A high-pitched whine that tracks with speed in a gearbox is a classic sign of inadequate lubrication causing metal-to-metal contact between gear teeth.
Question 6: What does the acronym MTTR stand for in maintenance management?
- Maximum Time To Repair
- Mean Time To Repair (Correct answer)
- Minimum Turnaround Technician Rate
- Maintenance Tracking and Trend Report
Correct answer: Mean Time To Repair
MTTR (Mean Time To Repair) is a key maintenance metric representing the average time required to restore a failed component or system to operation.
Question 7: When using a vibration analyzer, a dominant frequency at 1× RPM (running speed) most commonly indicates:
- Misalignment
- Mass imbalance (Correct answer)
- Looseness
- Bearing defect frequency
Correct answer: Mass imbalance
A strong vibration peak at exactly 1× running speed is the classic signature of rotating mass imbalance.
CPT Maintenance & Troubleshooting 3
A hydraulic system loses pressure gradually when the pump is stopped and valves are closed.
This symptom indicates: