Wire Rope Sling Inspection Before a Critical Pick
A 2-inch, 6x37 IWRC wire rope sling with an eye on each end is scheduled to lift a 12,000 lb vessel. During inspection you find: (a) one broken outer wire in a valley between strands; (b) several broken wires at the end fitting; (c) a kink with a permanent bend near one eye; (d) heavy wear flattening the outer wires over a 6 in length; (e) a tag that is faded and unreadable. The sling is 12 years old and has no documented inspection history. The crew says the sling has been used for years and has never failed, and the lift is scheduled in one hour.
1. Apply removal criteria to each defect and decide whether the sling can be used.
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Defect-by-defect:
- (a) One broken outer wire in a valley: broken wires in valleys are hard to see and indicate fatigue; a single one is not automatically a removal, but it warrants counting broken wires over the affected length and comparing to the removal criteria for the rope construction and lay length.
- (b) Broken wires at the end fitting: broken wires at or near a fitting are a serious indicator of stress concentration; this alone is commonly a removal criterion.
- (c) Kink with a permanent bend: a kink or a bend that cannot be straightened is a removal criterion. The rope's strength and fatigue life are compromised.
- (d) Heavy wear flattening outer wires: significant abrasion and flattening reduce the metallic cross-section and are a removal criterion when wear is severe.
- (e) Faded, unreadable tag: without a legible tag the sling's rating cannot be verified, so it cannot be used for a planned lift.
Decision: Remove the sling from service. Multiple removal criteria are met, and the rating cannot be confirmed. Do not use it for the 12,000 lb vessel.
Note: A 2-inch 6x37 IWRC sling has a substantial vertical rating, so capacity is not the issue; condition and traceability are. The correct action is to tag it out and replace it.
2. The crew argues the sling has a long service history with no failures. How do you respond, and what is the correct disposition?
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Response: Past use without failure is not evidence of current capacity. Wire rope degrades progressively through fatigue, abrasion, and corrosion, and a sling that has been used for years is exactly the kind that accumulates broken wires and wear. The absence of a documented inspection history means you cannot know when the defects appeared or how fast they are progressing.
Disposition:
- Tag the sling out of service immediately, using a clear "Do Not Use" tag.
- Remove it from the lift area so it cannot be picked up by mistake.
- Record the defects and the removal criteria met.
- Notify the supervisor and arrange a replacement sling with a legible tag and documented rating.
- Delay the lift until a compliant sling is available and inspected.
Why this matters: A sling failure under a 12,000 lb load is a dropped load, which is a fatality risk. The cost of a one-hour delay is trivial compared with that risk. The crew's argument is a normalization-of-deviance trap and should be rejected.
3. Describe the inspection you would perform on the replacement sling before the lift and the documentation you would require.
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Inspection of the replacement sling:
- Verify the tag: legible, with the manufacturer, the rated capacity, the hitch type, and the serial number.
- Check the entire length for broken wires, especially at fittings and in valleys; count broken wires over the lay length against the removal criteria.
- Check for kinks, bird-caging, crushed or flattened areas, and heat damage.
- Check the eyes and fittings for cracks, wear, corrosion, and broken wires at the fitting.
- Check the D/d ratio at the choker or hook and confirm the hardware is compatible.
- Confirm the sling's rated capacity at the planned hitch and angle exceeds the calculated tension with margin.
Documentation:
- A legible tag and a certificate or record of the sling's rating.
- A record of this inspection with the date, the inspector, and the result.
- The lift plan showing the calculated tension and the sling selected.
- A periodic inspection schedule, with the frequency set by the employer based on use and conditions, and more frequent inspection for severe service.