STSC Cranes, Derricks, Hoists, and Rigging Safety 4 — Questions and Answers
Question 1: When must a crane operator stop operations and contact a qualified person if the load line suddenly goes slack?
- Only if the load drops more than 6 inches
- Immediately, as slack line may indicate a structural failure or two-blocking (Correct answer)
- After completing the lift cycle to avoid disrupting operations
- Only when working near power lines
Correct answer: Immediately, as slack line may indicate a structural failure or two-blocking
A suddenly slack load line may signal two-blocking, a structural failure, or load contact with an obstruction, requiring immediate shutdown and inspection.
Question 2: What is the purpose of a 'anti-two-block' device on a crane?
- It prevents the crane from lifting loads over the rated capacity
- It automatically stops hoist motion before the hook block contacts the sheave (Correct answer)
- It locks the boom in place during high winds
- It disengages the swing brake when two people are operating simultaneously
Correct answer: It automatically stops hoist motion before the hook block contacts the sheave
Anti-two-block devices automatically cut power to the hoist when the hook block nears the boom tip sheave, preventing catastrophic two-blocking.
Question 3: Under OSHA 1926.1411, what action must be taken before using a synthetic web sling that has a melted or charred area?
- Apply a heat-resistant coating and reinspect
- Reduce the load rating by 50% and continue use
- Remove it from service immediately (Correct answer)
- Tag it for light-duty use only
Correct answer: Remove it from service immediately
Melted or charred areas on synthetic slings indicate heat damage that compromises structural integrity, requiring immediate removal from service.
Question 4: A rigger notices that a wire rope sling has a kink that was removed by straightening. What is the correct action?
- The sling may be reused if the kink is fully straightened
- Reduce the working load limit by 25% for that lift only
- Remove the sling from service; kinking permanently damages wire rope (Correct answer)
- Re-anneal the wire rope to restore ductility before reuse
Correct answer: Remove the sling from service; kinking permanently damages wire rope
Once kinked, wire rope strands are permanently deformed and weakened at that point, making the sling unsafe even after straightening.
Question 5: What minimum distance must a crane maintain from an unguarded energized power line rated at 50 kV under OSHA 1926.1408?
- 5 feet
- 10 feet (Correct answer)
- 15 feet
- 20 feet
Correct answer: 10 feet
OSHA 1926.1408 requires a minimum 10-foot clearance from power lines up to 50 kV when no encroachment plan is in place.
Question 6: When rigging a load with a basket hitch using a wire rope sling, what factor most significantly affects the sling's working load limit?
- The color coding of the sling tag
- The horizontal angle of the sling legs relative to the load (Correct answer)
- The number of wraps around the crane hook
- The ambient temperature at the jobsite
Correct answer: The horizontal angle of the sling legs relative to the load
As the sling angle decreases below 90°, the tension on each sling leg increases dramatically, reducing the effective working load limit.
Question 7: Who is authorized to give a 'stop' signal to a crane operator under OSHA 29 CFR 1926.1419?
- Only the designated signal person
- Only the lift director
- Any person who observes an unsafe condition (Correct answer)
- Only the site safety manager
Correct answer: Any person who observes an unsafe condition
OSHA 1926.1419 states that any worker who observes a dangerous condition may give a stop signal, and the operator must honor it immediately.
STSC Cranes, Derricks, Hoists, and Rigging Safety 4
When must a crane operator stop operations and contact a qualified person if the load line suddenly goes slack?