Wire Rope and Hook Removal Criteria Before a Pour
A 5/8 in 6x25 FW IWRC wire rope on a 40-ton telescopic-boom crane's main hoist has logged 3,200 hours. During a pre-shift inspection the operator finds seven broken wires distributed around one lay length, including one break in a valley between strands. The rope shows light surface rust and two small pits, and a birdcage about 3 ft from the dead-end socket. The hook has a throat opening that measures 2.9 in against an original 2.5 in, and the safety latch is missing. The rope diameter measures 0.590 in against a nominal 0.625 in. The crane is needed for a concrete pour that starts in two hours, and the replacement rope is in the yard but swapping it will take four hours. The supervisor asks whether the crane can finish the pour and have the rope changed afterward.
1. Identify each inspection finding that requires removal from service under wire rope and hook criteria, and explain why.
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Several findings independently require removal. Seven broken wires in one lay exceeds the typical running-rope criterion of six randomly distributed broken wires in one lay, and the three-in-one-strand criterion may also apply if they cluster. The valley break is a fatigue indicator and supports removal. The birdcage is a permanent deformation and is a removal condition. The hook throat is 2.9 in versus 2.5 in, a 0.4 in or 16% increase, which exceeds the 15% throat-opening limit, and the missing latch alone makes the hook unserviceable. The 0.590 in diameter is 5.6% below the 0.625 in nominal; if the applicable criterion is 5%, that is also a removal. Any one of these is enough; the crane should be removed from service.
2. The supervisor wants to finish the pour and change the rope afterward. Write the operator's response, including what must happen before the crane is returned to service.
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The operator should refuse the lift and explain that the rope and hook have multiple removal criteria, not a cosmetic issue. The crane must be locked out and tagged, and the rope replaced before it is returned to service. The hook should be replaced or the latch and throat repaired only if the hook can be restored to within the manufacturer's limits; a hook with a 16% throat increase is normally replaced, not bent back. A qualified person should inspect the new rope and hook, verify the rope diameter and construction, and document the repair. Production pressure does not override the removal criteria. If the pour cannot wait, use another crane or change the schedule.
3. What additional information would you need to confirm the broken-wire removal threshold?
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Confirm the exact rope construction and the manufacturer's removal table, because broken-wire limits differ by rope type. Determine whether all seven broken wires are within one lay length and how many are in a single strand; a cluster is more serious than an even distribution. Confirm whether the valley break is counted separately and whether the rope is rotation-resistant. Check the diameter measurement method and reference diameter, because a 5% reduction criterion depends on the rope type and proper measurement. Review the rope's service history, sheave condition, and whether the birdcage indicates shock loading or mistreatment. The final decision should be made by a qualified person using the applicable standard, not by the operator alone.