NCCCO Mobile Crane Operator 4 5 — Questions and Answers
Question 1: What is 'side loading' of a crane boom, and why is it dangerous?
- Lifting a load from the crane's side quadrant, which is rated higher than front picks
- Applying a lateral force on the boom it is not designed to handle, risking structural collapse (Correct answer)
- Using a side-mounted winch for horizontal pulls
- Loading the counterweight on one side only
Correct answer: Applying a lateral force on the boom it is not designed to handle, risking structural collapse
Boom structures are designed primarily for vertical compression loads; lateral (side) forces can buckle or collapse the boom because it lacks adequate lateral strength.
Question 2: During a tandem (two-crane) lift, who is responsible for directing the overall operation?
- The operator of the larger crane
- A designated lift director who oversees both cranes and all personnel (Correct answer)
- OSHA on-site compliance officer
- The lead rigger of the rigging crew
Correct answer: A designated lift director who oversees both cranes and all personnel
OSHA 1926.1436 and best practices require a qualified lift director to coordinate all aspects of tandem crane lifts to ensure synchronized movement and load sharing.
Question 3: What does 'working radius' mean in crane terminology?
- The distance the crane can travel under load
- The horizontal distance from the crane's rotation axis to the center of the suspended load (Correct answer)
- The maximum boom extension length
- The turning radius of the crane carrier
Correct answer: The horizontal distance from the crane's rotation axis to the center of the suspended load
Working radius is the horizontal distance from the centerline of rotation to the plumb line of the hook, which determines which column of the load chart applies.
Question 4: A wire rope sling shows broken wires exceeding the discard criteria. The operator is instructed by the site foreman to use it anyway for a light pick. What should the operator do?
- Use it once since the load is light
- Refuse to use the defective sling and remove it from service (Correct answer)
- Use it with a 50% derating factor
- Wrap the sling with tape to secure broken wires
Correct answer: Refuse to use the defective sling and remove it from service
A sling meeting discard criteria must be immediately removed from service; no one, including supervisors, can authorize use of condemned rigging equipment.
Question 5: What is the purpose of cribbing and outrigger pads when setting up a mobile crane?
- To level the crane carrier during travel
- To distribute the outrigger load over a larger area and prevent ground sinkage (Correct answer)
- To insulate the crane from stray electrical currents
- To prevent the outrigger cylinders from retracting under load
Correct answer: To distribute the outrigger load over a larger area and prevent ground sinkage
Cribbing and pads spread the concentrated point load of each outrigger over a larger bearing area, reducing ground pressure and preventing settlement or tipping.
Question 6: Under OSHA 1926.1417, what is the operator required to do if they observe a defect that creates a safety hazard during a pre-shift inspection?
- Log it in the inspection record and monitor it during operation
- Remove the crane from service until the defect is corrected (Correct answer)
- Reduce the crane's rated capacity by 25% and continue
- Inform the rigging supervisor and proceed with non-critical lifts
Correct answer: Remove the crane from service until the defect is corrected
OSHA 1926.1417 requires the crane to be taken out of service whenever a defect creating a safety hazard is found, until the defect is corrected.
Question 7: What is the significance of the 'structural competence' rating on a mobile crane load chart versus the 'tipping' rating?
- They are the same value listed under different names
- The rated capacity is the lesser of the two — charts typically list the value that controls (Correct answer)
- Structural competence always exceeds tipping capacity at long radii
- Tipping capacity is used only for crawler cranes
Correct answer: The rated capacity is the lesser of the two — charts typically list the value that controls
The published rated capacity reflects the lesser of structural competence and tipping stability limits at each radius, ensuring both failure modes are accounted for.
NCCCO Mobile Crane Operator 4 5
What is 'side loading' of a crane boom, and why is it dangerous?