Rigging Fundamentals and Hardware Flashcards

A four-leg wire rope bridle sling is used to lift a load. During the lift, one leg goes slack because the load's center of gravity is offset. According to ASME B30.9, what is the rated load capacity that must be used when calculating the lift?

Answer: The combined capacity of only the two legs carrying the greatest tension

ASME B30.9 requires that when legs of a multi-leg sling may become slack due to load imbalance, the rated load must be based on the number of legs that can be assumed to share the load simultaneously. With a CoG offset causing one leg to go slack in a four-leg bridle, only two legs can be relied upon to share load — making the working capacity the sum of those two legs' rated loads adjusted for sling angle. Assuming three or four legs are sharing load when one is slack is a dangerous miscalculation.

A rigger inspects an alloy steel chain sling and finds a link with a measured wear of 11% of the original cross-sectional diameter at the bearing point. What is the correct action?

Answer: The sling must be removed from service immediately

ASME B30.9 sets the removal-from-service criterion for alloy steel chain slings at wear exceeding 10% of the original cross-sectional diameter at any point. At 11%, this chain has exceeded the limit and must be removed from service immediately — no capacity reduction or partial use is permitted. Individual links must never be replaced with field-sourced links; a damaged chain sling must be returned to the manufacturer or a qualified repair facility.

A rigger is using a screw-pin anchor shackle rated at 4.75 tons. The load is 4 tons and will be used in a sustained overhead lift lasting several hours with the shackle under continuous dynamic loading. Which statement is most accurate?

Answer: A bolt-type (round pin with cotter pin) shackle should be used instead of a screw-pin for this application

Screw-pin shackles are vulnerable to the pin unscrewing under dynamic, rotational, or sustained loads even when moused — mousing is a secondary precaution, not a substitute for proper hardware selection. ASME B30.26 and industry best practice specify that bolt-type (round-pin with nut and cotter pin) shackles should be used for sustained overhead lifts or applications with vibration, shock loading, or potential for rotation. Mousing a screw pin mitigates but does not eliminate the risk of the pin backing out in prolonged use.

A wire rope sling has an efficiency rating of 75% when used in a choker hitch. If the same wire rope (not the sling assembly) has a catalog breaking strength of 40,000 lbs and a design factor of 5:1, what is the maximum load the sling may handle in a choker hitch?

Answer: 6,000 lbs

First, calculate the wire rope's rated capacity: 40,000 ÷ 5 = 8,000 lbs vertical capacity. Then apply the choker hitch efficiency factor of 75%: 8,000 × 0.75 = 6,000 lbs. The 75% efficiency accounts for the stress concentration at the choke point reducing the rope's effective strength. No sling angle derating is applied here since the question asks about the choker efficiency factor specifically, not an off-vertical lift angle.

A rigger needs to connect a wire rope sling to a padeye where the shackle bow will experience a side load (out-of-plane loading). The shackle manufacturer's catalog states the WLL is for in-line loading only. What is the correct approach according to ASME B30.26?

Answer: Contact the shackle manufacturer for a derated WLL specific to the actual side-load angle

ASME B30.26 requires that shackles experiencing angular or side loading (out-of-plane loading on the bow or pin axis) must have their WLL established by the manufacturer for that specific loading condition. There is no universal blanket derating percentage in the standard — the correct action is to obtain manufacturer guidance or engineer-approved derated capacity for the actual load angle. Arbitrarily applying a 50% reduction or simply upsizing the shackle without addressing the root loading geometry is not compliant with ASME B30.26.

During pre-lift inspection of a below-the-hook lifting beam, a rigger notices that the beam's load test certification expired 13 months ago. The beam has no visible damage. Under ASME B30.20, what is the correct course of action before the lift proceeds?

Answer: The beam must be removed from service and inspected by a qualified engineer, with load testing only if the engineer deems it necessary

ASME B30.20 governs below-the-hook lifting devices. It requires periodic inspections by a qualified person, but does not mandate a specific re-certification or load test interval for standard service — that is determined by the manufacturer's instructions and the employer's inspection program. When a certification has lapsed, the device must be taken out of service for evaluation by a qualified person (often a structural engineer or the manufacturer), who then determines whether load testing is required based on condition, service history, and applicable standards. Visual inspection alone by the rigger does not satisfy this requirement, nor does a pre-use inspection substitute for a qualified engineer's evaluation of a device with a lapsed certification.