NCCCO Maintenance and Troubleshooting 5 — Questions and Answers
Question 1: What is the correct procedure when a crane's engine oil pressure warning light illuminates during operation?
- Stop the crane immediately and shut down the engine (Correct answer)
- Reduce load and monitor pressure for 10 minutes
- Add oil while the engine is running
- Continue to the nearest safe parking spot before shutting down
Correct answer: Stop the crane immediately and shut down the engine
A low oil pressure warning indicates potential imminent engine damage; immediate shutdown prevents catastrophic failure.
Question 2: When testing the anti-two-block (ATB) device, which result confirms the device is functioning correctly?
- Hoist motion stops before the block contacts the boom head (Correct answer)
- An audible alarm sounds only after block contact
- The hoist slows down but does not stop
- The load is automatically lowered when triggered
Correct answer: Hoist motion stops before the block contacts the boom head
A properly functioning ATB device must stop hoist-up motion before the block reaches the boom head sheaves.
Question 3: A crawler crane's track tension is too loose. What operational hazard does this create?
- Track can derail or de-track during travel or slewing (Correct answer)
- Increased ground bearing pressure
- Reduced maximum load capacity
- Higher fuel consumption only
Correct answer: Track can derail or de-track during travel or slewing
Loose track tension allows the track to jump off the rollers and sprockets, causing a de-tracking event that can tip the crane.
Question 4: What does excessive heat on a crane's hydraulic return line filter indicate?
- A clogged filter element restricting flow (Correct answer)
- Normal system warm-up
- Low ambient temperature
- Correct system pressure
Correct answer: A clogged filter element restricting flow
A blocked return filter causes fluid to back up and heat to build as pressure drop across the clogged element increases.
Question 5: A technician finds corrosion pitting on the inner surface of a wire rope. What caused this condition?
- Internal moisture ingress from inadequate lubrication (Correct answer)
- Overloading causing metal fatigue
- Excessive sheave diameter
- High-cycle bending over a small radius sheave
Correct answer: Internal moisture ingress from inadequate lubrication
Internal corrosion pitting results from moisture penetrating the rope's core when internal lubrication is absent or depleted.
Question 6: During a pre-shift inspection, the operator notices the boom hoist holding brake releases but the boom does not lower. What is the most likely cause?
- A seized or sticking boom hoist motor control valve (Correct answer)
- Low hydraulic fluid level
- Excessive boom angle
- Incorrect counterweight configuration
Correct answer: A seized or sticking boom hoist motor control valve
A stuck boom hoist control valve prevents fluid flow to the motor even when the brake is released, stopping boom movement.
Question 7: What is the purpose of performing a rated load test after major structural repairs on a crane?
- To verify the repaired structure can safely handle the rated capacity before returning to service (Correct answer)
- To satisfy insurance documentation only
- To recalibrate the load moment indicator
- To check hydraulic pressure settings
Correct answer: To verify the repaired structure can safely handle the rated capacity before returning to service
A rated load test after structural repair confirms the repair restored full structural integrity before the crane is returned to service.
NCCCO Maintenance and Troubleshooting 5
What is the correct procedure when a crane's engine oil pressure warning light illuminates during operation?