Wire Rope With Broken Wires and a Questionable Splice
A 1-inch, 6x19 IWRC wire rope sling with a hand-tucked Flemish eye and a pressed sleeve is being used to lift 8,000 lb in a two-leg bridle at 45 degrees. During pre-use inspection a rigger counts 9 broken wires in one lay, distributed over about 2 inches, all in a section that runs over a shackle. There is also visible rust and a slight kink near the sleeve. The sling's tag is missing. The crew wants to 'just derate it' and finish the shift because the lift is only 8,000 lb and the sling is 1 inch.
1. Evaluate the sling against removal-from-service criteria and determine whether derating is a valid option.
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Derating is not a recognized remedy for a sling that meets removal criteria; the criteria are pass/fail. For a 6x19 rope sling, common removal thresholds include roughly 10 broken wires in one lay (or 5 in one strand) for running ropes, but sling criteria are stricter and the distribution matters: 9 broken wires concentrated in one lay and localized over a 2-inch section is effectively a severe local degradation even if a generic count is borderline. Additionally, visible rust indicates loss of area and fatigue, a kink indicates permanent deformation and possible core damage, and a missing tag means the sling's rated capacity and construction cannot be verified. A pressed sleeve with no identification cannot be assumed to have a valid termination efficiency.
Judgement: remove from service immediately. Do not derate. The combination of localized broken wires, corrosion, kink, and missing identification is disqualifying regardless of computed capacity. Replace with an identified sling of adequate rating and document the removal.
2. If a replacement 1-inch 6x19 IWRC sling with a proper termination is used, what is the tension per leg and what would you verify?
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Two-leg bridle at 45 degrees from horizontal: vertical share per leg is 4,000 lb. Leg tension = 4,000 / sin(45 deg) = 4,000 / 0.707 = 5,657 lb. If the angle is measured from vertical instead, the calculation changes; always confirm the reference. Assuming 45 degrees from horizontal, each leg sees about 5,660 lb.
Verify:
- Sling rated capacity for the configuration, including the angle factor and the termination efficiency (pressed sleeves typically develop a stated percentage of rope strength; use the manufacturer's rating, not a guess).
- Shackles and master link rated for 5,660 lb with the correct pin orientation and no side loading.
- Lug or lifting point capacity for the angled pull, including any horizontal component (4,000 lb per leg horizontally at 45 degrees).
- The rope's actual condition and identification; new sling must have a legible tag.
- Edge protection at the shackle contact and no sharp bends below the minimum D/d ratio.
Judgement: the number is simple; the discipline is confirming the angle reference, termination efficiency, and hardware ratings before the lift.