Boom-Hoist Wire Rope Inspection Findings
During a pre-operational inspection, a 20 mm 6×37 IWRC boom-hoist wire rope is found to measure 18.9 mm at a low point. Over one 120 mm lay length, the inspector counts nine broken wires, four of them in a single strand. There is visible corrosion with pitting between the strands, and a birdcage deformation 1.5 m from the dead end. The rope has 3,800 operating hours. The manufacturer's removal criteria include: six or more broken wires in one lay, three or more broken wires in one strand in one lay, diameter reduction greater than 5%, and any birdcage, kink, or severe corrosion. The crane is scheduled for a critical lift tomorrow. The supervisor says, “Just run it and watch it; we will change it next week.”
1. Apply each removal criterion to the findings and state whether the rope is serviceable.
Read the worked answer
The rope fails multiple criteria. Nine broken wires in one lay > 6. Four broken wires in one strand > 3. Diameter reduction = (20.0 - 18.9)/20.0 = 5.5% > 5%. A birdcage is cause for immediate removal regardless of wire count. Corrosion pitting between strands further reduces strength and makes inspection unreliable. Any one of these is a removal criterion; together they make the rope unserviceable. Do not run it and watch it.
2. What are the risks of continuing to operate, and what immediate actions are required?
Read the worked answer
Continued use risks rope failure under the boom-hoist load, causing the boom to drop, the load to fall, and serious injury or death. A birdcage indicates a disturbed rope lay and possible core damage; diameter loss indicates core collapse or wear; broken wires concentrate stress. Immediate actions: stop the crane, lower and secure the load/boom if safe, lock out and tag out, remove the rope from service, barricade the area, notify supervision, and replace the rope. Inspect the sheaves, drum, and equalizer for wear or rope damage.
3. How should the inspection and replacement be documented, and what should be checked before returning to service?
Read the worked answer
Record the inspection date, hour meter, rope identification, nominal and measured diameter, lay length, broken-wire counts, corrosion and birdcage location, and photos in the crane log. Tag the removed rope and retain it for review. Record the replacement rope certificate, serial number, and installation date. Before return to service, check reeving, spooling, sheave grooves, rope guides, anti-two-block and limit switches, and run the rope in per the manufacturer. Re-inspect after the first few cycles and update the maintenance schedule.