STSC Cranes, Derricks, Hoists, and Rigging Safety 5 — Questions and Answers
Question 1: What is the required action when a crane is to be used for a 'critical lift' as defined under OSHA 1926.1431?
- Use a more experienced operator with no other requirement
- Prepare and follow a written critical lift plan (Correct answer)
- Obtain written approval from OSHA before lifting
- Increase the load radius by 25% as a safety margin
Correct answer: Prepare and follow a written critical lift plan
OSHA 1926.1431 requires a written critical lift plan for lifts exceeding 75% of the crane's rated capacity or involving multiple cranes.
Question 2: A load is being rigged with a choker hitch. Compared to a straight (vertical) hitch with the same sling, how does the choker hitch affect the working load limit?
- It increases the WLL by distributing load over a larger sling surface
- It reduces the WLL because the choker creates a pinch point and angle loading (Correct answer)
- The WLL remains the same regardless of hitch type
- It doubles the WLL due to the wrap-around friction
Correct answer: It reduces the WLL because the choker creates a pinch point and angle loading
A choker hitch reduces the sling's rated capacity, typically to about 75-80% of straight-hitch WLL, due to stress concentration at the choke point.
Question 3: Under OSHA crane standards, what is the maximum wind speed at which a crane operator is typically allowed to continue operations with a rated load?
- There is no OSHA wind speed limit; the manufacturer's specifications govern (Correct answer)
- 25 mph for all cranes
- 35 mph for lattice boom cranes only
- 40 mph for mobile cranes under 100 tons
Correct answer: There is no OSHA wind speed limit; the manufacturer's specifications govern
OSHA defers to the crane manufacturer's load chart and operational specifications for wind speed limits rather than setting a universal mph threshold.
Question 4: What condition requires a wire rope to be removed from service per ASME B30.5 if found in any six-diameter length of the rope?
- 3 broken wires in any strand
- Six randomly distributed broken wires (Correct answer)
- One broken wire in the outer cover strand
- Any detectable rust on the outer wire surface
Correct answer: Six randomly distributed broken wires
ASME B30.5 requires removal from service if six or more randomly distributed broken wires are found in any six-rope-diameter length.
Question 5: When using a jib or luffer attachment on a crane, what additional concern must the rigger and operator account for in the load chart?
- The jib reduces the swing speed by 50%
- Load charts change with jib length and angle; a separate jib chart must be used (Correct answer)
- Jibs automatically double the rated capacity at long radii
- The main boom hoist must be locked out when the jib is in use
Correct answer: Load charts change with jib length and angle; a separate jib chart must be used
Jib attachments have separate rated capacity charts that account for the additional boom length, radius changes, and structural loading on the main boom.
Question 6: A tag line is used during crane lifts primarily to:
- Support part of the load weight to reduce hook load
- Control load rotation and prevent swinging without workers pulling the load directly (Correct answer)
- Connect the load to the headache ball for stability
- Serve as a secondary rigging attachment point if the primary sling fails
Correct answer: Control load rotation and prevent swinging without workers pulling the load directly
Tag lines allow workers to guide and stabilize a suspended load from a safe distance without standing in the path of a swinging load.
Question 7: Under OSHA 1926.1416, how frequently must a mobile crane's load-indicating device and boom angle indicator be inspected?
- Annually by the crane manufacturer only
- Monthly by a qualified inspector
- Daily before use by the operator (Correct answer)
- Every 90 days by a competent person
Correct answer: Daily before use by the operator
OSHA 1926.1416 requires operators to conduct a pre-shift inspection of safety devices including load indicators and boom angle indicators before each use.
STSC Cranes, Derricks, Hoists, and Rigging Safety 5
What is the required action when a crane is to be used for a 'critical lift' as defined under OSHA 1926.1431?