NCCCO Mechanical Systems & Maintenance Practices 4 — Questions and Answers
Question 1: When inspecting wire rope, what is the maximum number of randomly distributed broken wires allowed in one rope lay length before the rope must be removed from service?
- 4 broken wires
- 6 broken wires
- 12 broken wires (Correct answer)
- 18 broken wires
Correct answer: 12 broken wires
ASME B30.2 specifies that 12 randomly distributed broken wires in one rope lay length is the threshold requiring wire rope removal from service.
Question 2: A crane's load line sheave shows a groove that is too narrow for the wire rope. What is the primary hazard of operating in this condition?
- Increased fleet angle
- Pinching and accelerated wire rope wear (Correct answer)
- Reduced hoist drum capacity
- Overloading of the boom tip
Correct answer: Pinching and accelerated wire rope wear
A sheave groove too narrow for the rope causes the rope to ride on its sides, pinching it and accelerating wear and fatigue failure.
Question 3: What does a crane's anti-two-block (ATB) device do when activated?
- Stops the swing motion
- Cuts power to the hoist and boom raise functions (Correct answer)
- Sounds an alarm only
- Releases the load brake automatically
Correct answer: Cuts power to the hoist and boom raise functions
When the ATB device activates because the hook block approaches the boom tip, it cuts power to hoist-up and boom-raise functions to prevent two-blocking.
Question 4: Which hydraulic system symptom most likely indicates internal bypass across a main control valve spool?
- Excessive pressure spikes during swing
- Slow or drifting cylinder movement under load (Correct answer)
- Frequent relief valve chatter
- Pump cavitation noise
Correct answer: Slow or drifting cylinder movement under load
Internal bypass across a control valve spool allows fluid to return to tank without doing work, causing cylinders to move slowly or drift under load.
Question 5: When should a crane operator lubricate the swing ring gear and pinion?
- Only during annual inspections
- Per the manufacturer's maintenance schedule and as conditions require (Correct answer)
- Only when grinding or squealing is heard
- Once every 500 operating hours regardless of manufacturer guidance
Correct answer: Per the manufacturer's maintenance schedule and as conditions require
Lubrication intervals must follow the manufacturer's maintenance schedule, with additional lubrication applied as environmental or operational conditions demand.
Question 6: A crane's load moment indicator (LMI) displays a warning at 90% of rated capacity. What is the operator's correct response?
- Ignore it if the load feels stable
- Stop operations and reassess the lift plan (Correct answer)
- Continue the lift but move more slowly
- Bypass the LMI and proceed
Correct answer: Stop operations and reassess the lift plan
An LMI warning at 90% of rated capacity means the operator must stop, reassess the lift plan, and ensure no rated capacity will be exceeded.
Question 7: What is the purpose of a crane's load brake (holding brake) in a hoist system?
- To slow the hoist drum during lowering operations
- To hold a suspended load stationary when the hoist is in neutral (Correct answer)
- To limit maximum hoist speed
- To prevent overloading the drum motor
Correct answer: To hold a suspended load stationary when the hoist is in neutral
The load brake (holding brake) automatically engages when the hoist control is in neutral, preventing the load from descending by gravity.
NCCCO Mechanical Systems & Maintenance Practices 4
When inspecting wire rope, what is the maximum number of randomly distributed broken wires allowed in one rope lay length before the rope must be removed from service?