Rigging Fundamentals and Hardware Flashcards

A wire rope sling has a vertical rated capacity of 10,000 lbs. When rigged in a two-leg bridle at a 30° horizontal angle (60° from vertical), what is the approximate maximum load the sling assembly can safely lift?

Answer: 5,000 lbs

At a 30° horizontal angle (60° from vertical), the sling angle tension factor is approximately 0.5. Each leg carries MORE than half the load due to the acute angle, so the assembly capacity drops to 10,000 × 0.5 = 5,000 lbs. Rigging at acute horizontal angles severely penalizes capacity — this is a critical safety distinction. Many confuse horizontal vs. vertical angle references, which is why this scenario is frequently misanswered.

A hook latch is bent, sprung, and won't fully close, but a rigger argues the hook's throat opening is still within the manufacturer's dimensional tolerance. Under ASME B30.10 and OSHA 1926.1413, this hook must be:

Answer: Removed from service immediately regardless of throat dimension compliance

ASME B30.10 requires removal from service if the latch is damaged or doesn't seat properly — there is no exception for throat-dimension compliance. A latch that won't close creates an unguarded opening that allows load slippage. Field repair of hooks is not permitted; they must be inspected by a qualified person and repaired or replaced by the manufacturer or their authorized representative. The throat dimension is one of many criteria; a single disqualifying condition mandates removal.

When using a wire rope clip (U-bolt) to form an eye in a 1-inch diameter wire rope, the ASME B30.26 standard specifies the minimum number of clips and the minimum spacing between clips. Which combination is correct?

Answer: 5 clips, spaced 6 inches apart (6 rope diameters)

For 1-inch wire rope, ASME B30.26 and OSHA 1926.251 specify a minimum of 5 U-bolt clips, spaced no less than 6 times the rope diameter (6 × 1" = 6 inches) apart. Clip count and spacing are both critical — too few clips or insufficient spacing allows the dead end to slip under load. Always torque to manufacturer specs and re-torque after initial loading. Note that the U-bolt saddle must bear on the live (load-bearing) side, never the dead end.

A rigger is lifting an asymmetric load using a two-leg wire rope bridle sling. The load's center of gravity is NOT centered between the two lift points. Which consequence is most likely if the rigger uses equal-length sling legs without adjustment?

Answer: The shorter effective load path leg will carry a disproportionately higher tension, potentially exceeding its WLL

When a load's CG is off-center from the geometric midpoint, the leg closer to the CG (shorter load path in terms of moment arm) carries a proportionally greater share of the load. Equal physical sling lengths do NOT result in equal loading when the CG is offset. The leg on the CG side can be overloaded well beyond the rated capacity even though the total weight is within the hook's rating. A rigger must calculate the actual force in each leg using moment equations and verify each leg against its individual WLL.

A synthetic round sling marked 'EN 1492-2' has a color-coded violet jacket with a yellow core. When used in a basket hitch, the basket-hitch rated capacity on the tag is 26,000 lbs at 0° (vertical legs). A rigger needs to use it in a basket hitch with legs at 60° from vertical. What is the approximate adjusted capacity?

Answer: 22,516 lbs

The basket hitch capacity at 0° (vertical legs, 180° contact) is listed on the tag as 26,000 lbs. When the legs splay to 60° from vertical, a sling angle factor of cos(60°) = 0.5 is applied to EACH leg's tension. However, the basket still wraps the load, so the rated capacity is multiplied by the angle factor: 26,000 × cos(60°) = 26,000 × 0.866 = 22,516 lbs. Many riggers mistakenly use the 0° basket rating without applying the angle correction, or confuse the angle factor formula for single-leg vs. basket hitch configurations.

An alloy steel shackle is stamped '3/4 A' on the bow and has a WLL of 4.75 tons. During inspection, a rigger notices the screw pin has been replaced with a plain (non-alloy) carbon steel bolt of identical diameter. What is the correct action and reasoning?

Answer: Remove from service — the mismatched pin material voids the shackle's rated capacity and creates an unpredictable failure mode

The WLL of an alloy shackle is established as a system — body and pin together meet proof load and break strength requirements as a matched set. Substituting a carbon steel pin reduces the pin's yield and tensile strength significantly (alloy steel pins have roughly 2× the strength of plain carbon at equivalent diameter). This voids the manufacturer's rating, creates a pin that may yield or shear at a fraction of the intended load, and is prohibited under ASME B30.26. No downgrade provision exists for field-modified hardware — it must be removed from service and returned to the manufacturer.