CET Maintenance, Inspection & Troubleshooting 3 — Questions and Answers
Question 1: A traction elevator's guide rails show excessive rust pitting. What is the PRIMARY concern with this condition?
- Increased guide shoe wear
- Impaired safety engagement and car ride quality (Correct answer)
- Electrical grounding issues
- Lubricant contamination of the pit
Correct answer: Impaired safety engagement and car ride quality
Pitted rails can prevent the safety device from gripping uniformly, compromising emergency stopping performance and causing rough car movement.
Question 2: What does a negative or reverse phase relay protect against in an elevator system?
- Overvoltage on the main line
- Incorrect motor rotation due to swapped power phases (Correct answer)
- Ground faults in the control panel
- Overloading of the hoisting motor
Correct answer: Incorrect motor rotation due to swapped power phases
A reverse phase relay detects incorrect phase sequence and prevents the motor from running in the wrong direction, which could cause the car to travel opposite the commanded direction.
Question 3: When performing a governor rope inspection, a technician finds broken wires in one strand. Per ASME A17.1, the rope must be replaced if broken wires exceed:
- 5% of the total wires in any rope lay (Correct answer)
- 2 broken wires per lay length in any strand
- 3 broken wires per strand across any 12-inch section
- 10 broken wires across all strands in one lay
Correct answer: 5% of the total wires in any rope lay
ASME A17.1 requires governor rope replacement when broken wires exceed the code-specified threshold, commonly 5% of total wires in one rope lay.
Question 4: An elevator's door operator motor runs but the doors do not move. The MOST likely cause is:
- Blown door operator fuse
- Broken or slipped door drive belt or chain (Correct answer)
- Faulty door close button
- Misadjusted door interlock
Correct answer: Broken or slipped door drive belt or chain
If the motor runs without moving the doors, the mechanical coupling (belt, chain, or coupler) between the motor and door mechanism has failed.
Question 5: A car position indicator shows the car at floor 4, but the car is physically between floors 3 and 4. This indicates a fault in the:
- Door interlock circuit
- Position reference system or selector (Correct answer)
- Motor encoder wiring
- Buffer compression switches
Correct answer: Position reference system or selector
A mismatch between displayed and actual position points to a fault in the position reference system, such as a missed vane, selector, or encoder pulse.
Question 6: During an annual inspection, the inspector asks for a 'buffer test' on an electric elevator. What speed must the car be traveling when it contacts the oil buffer?
- Contract speed
- 115% of contract speed (Correct answer)
- Rated speed plus 10 mph
- Governor tripping speed
Correct answer: 115% of contract speed
ASME A17.1 requires the buffer test to be performed with the car traveling at 115% of rated speed to verify proper buffer stroke and energy absorption.
Question 7: Which maintenance task helps prevent 'roping' wear patterns on traction sheaves?
- Regularly reversing rope lay direction
- Rotating ropes end-for-end at prescribed intervals (Correct answer)
- Applying extra lubricant to the sheave grooves
- Running the elevator at reduced speed daily
Correct answer: Rotating ropes end-for-end at prescribed intervals
Rotating ropes end-for-end distributes wear evenly along the rope length, extending rope life and preventing concentrated groove wear on the sheave.
CET Maintenance, Inspection & Troubleshooting 3
A traction elevator's guide rails show excessive rust pitting.
What is the PRIMARY concern with this condition?