Rigging Techniques & Equipment Inspection Flashcards

A wire rope sling has a rated capacity of 10,000 lbs in a straight vertical hitch. When used in a basket hitch with a 30° horizontal angle from the load (60° from vertical), what is the maximum load the sling can safely lift?

Answer: 17,320 lbs

In a basket hitch, you double the vertical rated capacity (10,000 × 2 = 20,000 lbs), then apply the angle correction factor. At 60° from vertical (30° horizontal), the D/d angle factor is 0.866 (cos 60°). So 20,000 × 0.866 = 17,320 lbs. Many riggers mistakenly apply the angle factor to only one leg or skip it entirely when the angle appears mild.

During inspection of a 6×19 IWRC wire rope, a rigger finds 3 broken wires in one strand within one rope lay length, and 2 additional broken wires in an adjacent strand within the same lay length. What is the correct course of action per ASME B30.9?

Answer: Remove from service immediately — the total of 5 broken wires in one lay exceeds the 4-wire threshold for 6×19 rope

ASME B30.9 requires removal from service when 4 or more broken wires are found in one lay length of a 6×19 classification rope. The total here is 5 broken wires across adjacent strands within one lay length, which meets the removal criterion. Counting strands individually rather than totaling broken wires in one lay is a common and dangerous error.

A rigger is preparing to lift a load with a center of gravity that is NOT at the geometric center. The load is 12 feet long, weighing 8,000 lbs, and the CG is located 4 feet from one end. Using a two-leg bridle sling attached at each end, what approximate tension will the sling leg nearest the CG experience (assuming vertical sling legs)?

Answer: 5,333 lbs

When the CG is off-center, sling legs carry unequal loads. The leg nearest the CG carries more load. Using the principle of moments: the far leg (8 ft from CG) × its load = near leg (4 ft from CG) × its load, and both must total 8,000 lbs. Far leg = 8,000 × (4/12) = 2,667 lbs; near leg = 8,000 × (8/12) = 5,333 lbs. Riggers often mistakenly assume equal loads when CG is off-center.

Which of the following conditions would NOT be sufficient reason to remove an alloy steel chain sling from service per ASME B30.9?

Answer: Surface rust that has been cleaned off revealing no measurable section loss

Surface rust that can be cleaned off with no measurable section loss does not require removal from service — the chain's integrity is unaffected if no material has been lost. In contrast: any link twisted more than 1° from its original plane, wear exceeding 10% of link diameter, and any field heat treatment (which destroys the manufacturer's heat treatment and voids certification) are all mandatory removal criteria under ASME B30.9.

A rigger is using a mechanical advantage system (block and tackle) with a 4-part line to move a load horizontally. The system has a known efficiency of 85% due to sheave friction. If the load to be moved requires 6,000 lbs of horizontal force, what is the minimum pull force required on the hauling line?

Answer: 1,765 lbs

With a 4-part line (mechanical advantage of 4), the theoretical pull = 6,000 ÷ 4 = 1,500 lbs. However, because the system is only 85% efficient due to friction losses, you must divide by the efficiency factor: 1,500 ÷ 0.85 = 1,765 lbs. Many riggers calculate the theoretical MA without accounting for friction, which can lead to dangerously underestimating the required effort and overloading equipment.

A synthetic web sling marked with a yellow color code is being used in a choker hitch to lift a load with a sharp edge protected by corner padding. The sling's marked vertical hitch capacity is 9,000 lbs. The choker angle measures 100° (the sling back-wraps past 90°). What rated capacity applies?

Answer: 7,650 lbs — the 85% capacity factor applies when choker angle exceeds 90°

ASME B30.9 specifies that a choker hitch at 90° or less of choke angle carries 75% of vertical hitch capacity. However, when the choke angle exceeds 90° (the sling back-wraps beyond a right angle), the capacity increases to 85% of the vertical hitch rating. Therefore: 9,000 × 0.85 = 7,650 lbs. Corner padding addresses edge cutting — it does not restore or change the hitch-type capacity factor.