NCCCO Rigging Fundamentals and Hardware 1 — Questions and Answers
Question 1: What is the rated capacity of a wire rope sling used in a basket (U-wrap) configuration at an included angle of 120 degrees (60 degrees from vertical for each leg)?
- Approximately 1.73 times the single-leg vertical capacity (Correct answer)
- Reduced to 50% of the single-leg vertical capacity
- Equal to the single-leg vertical capacity regardless of angle
- Doubled because two legs share the load
Correct answer: Approximately 1.73 times the single-leg vertical capacity
At an included angle of 120 degrees (60 degrees from vertical per leg), the basket hitch capacity is approximately 1.73 times a single vertical leg due to the geometry. As the angle increases further, capacity decreases rapidly.
For a two-leg sling in a basket configuration, the capacity factor is based on the angle from vertical: at 0 degrees (vertical), factor = 2.0; at 30 degrees from vertical, factor = 1.73; at 45 degrees, factor = 1.41; at 60 degrees, factor = 1.0; at 90 degrees from vertical (horizontal), factor = 0. Wide angles (included angle over 120 degrees) reduce sling capacity significantly and create dangerous compressive forces on the load.
Question 2: A synthetic web sling is found to have a cut that has penetrated approximately 40% of the sling width. What is the correct action?
- Remove the sling from service immediately — any cut penetrating the sling body is a removal criterion per ASME B30.9 (Correct answer)
- Continue using it for lifts up to 60% of the rated capacity
- Tape the cut with load-rated splicing tape and re-tag the sling
- Use the sling in a choker configuration only
Correct answer: Remove the sling from service immediately — any cut penetrating the sling body is a removal criterion per ASME B30.9
ASME B30.9 requires removing synthetic web slings from service when cuts, tears, or abrasion remove material from the load-bearing webbing. Any cut penetrating the webbing warrants removal.
ASME B30.9-9.8.3 states that synthetic web slings must be removed from service for: cuts or punctures that penetrate the webbing, acid or caustic burns, melting or charring, holes or snags in the webbing that reduce effective cross-section, or any damage that causes doubt about integrity. A 40% cut is a severe structural reduction — the sling must be destroyed and replaced.
Question 3: When using a shackle in a rigging application, what is the correct orientation and securing method for the screw pin?
- The pin should be fully seated and moused (safety wired or taped) to prevent rotation and backing out under load (Correct answer)
- The pin should face downward so gravity keeps it seated
- The pin may face any direction as long as the shackle is rated for the load
- The pin should be replaced with a bolt of equal diameter for permanent use
Correct answer: The pin should be fully seated and moused (safety wired or taped) to prevent rotation and backing out under load
Rigging shackle screw pins must be fully tightened and moused with wire, tape, or a cotter pin to prevent the pin from backing out under repeated loading and unloading cycles.
Shackle screw pins are subject to rotation under dynamic loads, causing them to back out and release the load. ASME B30.26 and industry rigging standards require mousing (safety wiring through the pin's cross-drilled hole, or taping) to prevent unintended rotation. For permanent or recurring installations, bolt-type anchor shackles with nuts and cotter pins are preferred over screw-pin shackles.
Question 4: What information is required on a wire rope sling's identification tag per ASME B30.9?
- Manufacturer's name, rated capacity for each hitch type, and sling diameter or construction (Correct answer)
- Only the rated capacity in the choker configuration
- The purchase date and inspection log number
- The material grade and heat treatment code
Correct answer: Manufacturer's name, rated capacity for each hitch type, and sling diameter or construction
ASME B30.9 requires wire rope slings to be tagged with the manufacturer's name, sling rated capacity (for each configuration — vertical, choker, basket), and the sling's construction (diameter, classification).
Per ASME B30.9-9.3.1, all wire rope slings must be tagged with: (1) manufacturer's name or trademark, (2) rated load for single-leg vertical, choker, and basket hitches in appropriate configurations, and (3) sling material and construction type. Slings with missing or illegible tags must be removed from service until re-identified or replaced.
Question 5: A rigger is sizing a wire rope sling for a straight vertical (single-leg) lift of a 10,000-lb structural beam. Which factor is most critical in selecting the sling?
- The sling's rated capacity in the vertical hitch configuration must equal or exceed the total load weight (Correct answer)
- The sling color code matches the project specification
- The sling diameter is equal to the crane hook throat opening
- The sling length allows the load to be within 5 feet of the crane hook
Correct answer: The sling's rated capacity in the vertical hitch configuration must equal or exceed the total load weight
The fundamental sling selection criterion is that the sling's rated capacity in the configuration being used must meet or exceed the total load weight including all below-the-hook hardware.
Sling rated capacities differ by hitch type: vertical capacity is highest, choker is approximately 75% of vertical, and basket (at 0 degrees) is 200% of vertical. The rigger must know the configuration to be used, look up the rated capacity for that configuration from the tag or manufacturer's data, and ensure it exceeds the total load weight including shackles, hooks, and any other hardware.
Question 6: Under ASME B30.9, what is the minimum D/d ratio requirement for a wire rope sling passed around a pin or shackle?
- D/d ratio of at least 5:1, where D is the diameter of the pin/shackle and d is the wire rope diameter (Correct answer)
- D/d ratio of at least 1:1 — any size contact point is acceptable
- D/d ratio of at least 10:1 for loads over 10 tons only
- No ratio requirement as long as the shackle is rated for the load
Correct answer: D/d ratio of at least 5:1, where D is the diameter of the pin/shackle and d is the wire rope diameter
ASME B30.9 specifies that when a wire rope sling contacts a hook, pin, or other hardware, the D/d ratio should be at least 5:1 to avoid excessive bending stress and fatigue damage to the wire rope.
Wire rope loses strength rapidly when bent over a small radius. The D/d ratio compares the diameter of the object the rope bends over (D) to the rope's own diameter (d). A ratio below 5:1 causes internal wire fatigue and rapid degradation of rope capacity. For critical applications, ratios of 10:1 or more are recommended. Narrow shackle pins and hooks with small throat radii are common causes of premature rope failure.
NCCCO Rigging Fundamentals and Hardware 1
What is the rated capacity of a wire rope sling used in a basket (U-wrap) configuration at an included angle of 120 degrees (60 degrees from vertical for each leg)?