Morning Pre-Use Inspection: Rope, Latch, and LMI Defects
At 06:40 after overnight rain, a 50 t crawler crane is due to lift a 2.8 t precast panel. The operator finds the 22 mm 6x19 IWRC boom-hoist rope has seven broken wires scattered in one lay, a tight kink 1.2 m from the dead end, and a worn hook latch that does not spring closed. The boom angle indicator reads 68° while a digital inclinometer on the boom foot reads 70°. The LMI powers up and shows no fault, but the anti-two-block alarm does not sound when the test weight is raised to the block. Track tension is slack on the left track, and there is fresh hydraulic oil under the swing motor. The supervisor says the panel must be flown before the 08:00 concrete pour and asks the operator to 'just watch the angle' and proceed. The load chart for the current 24 m boom and 10 m radius shows 6.4 t.
1. Which findings require the crane to be taken out of service before the lift? Explain the reasoning for each.
Read the worked answer
Stop the lift. The 2.8 t load is well below the 6.4 t chart value, so capacity does not rescue the defects.
- Boom-hoist rope: seven broken wires in one lay exceeds the common 6x19 running-rope removal threshold of six randomly distributed broken wires in one lay, or three in one strand in one lay. The kink is also a removal condition because it shows distorted rope geometry. Replace before use.
- Hook latch: a latch that will not close is a dropped-load hazard; the hook assembly must be repaired or replaced.
- Boom angle indicator vs inclinometer: a 2° error changes radius - at 24 m boom roughly 0.8 m - so the chart radius and LMI may be wrong. Recalibrate or repair.
- Anti-two-block: failure to alarm is a mandatory stop item; two-blocking can part the rope.
- Swing-motor leak and slack track: these indicate hydraulic and mechanical faults that affect swing control and stability; investigate and repair.
The crane is out of service. Tag it, secure the load, and do not start the concrete pour with this crane.
2. What must be done before the crane can return to service, and what records should prove it?
Read the worked answer
Return-to-service sequence:
- Lock out/tag out and remove the crane from the lift plan.
- Replace the boom-hoist rope per the manufacturer; inspect sheaves, drum, and dead-end connection. Replace or repair the hook and latch.
- Repair the swing-motor leak, check swing brake and gearbox oil, and adjust track tension to the manual.
- Recalibrate the boom angle indicator against a verified inclinometer and confirm LMI radius and angle readings at two or three boom positions.
- Repair and function-test the anti-two-block device on both hoists, including the test weight.
- Have a competent person inspect the repairs and complete a function test; if company or legal requirements call for a load test after structural or rope repair, perform it.
- Record the defects, parts replaced, calibration results, and sign-off in the crane logbook and inspection checklist.
Only a signed release by the competent person authorizes the lift. The pre-use checklist is not a substitute for the repair record.
3. The supervisor directs you to proceed. What is your response and what immediate controls do you apply?
Read the worked answer
Use stop-work authority. Tell the supervisor: 'The crane is defective; I will not lift until the competent person signs it off.' Then:
- Lower and secure the load, shut down, and tag the controls.
- Barricade the area and keep the crew out of the boom and load radius.
- Notify the site safety officer and crane owner; enter the defects in the logbook and defect report.
- Ask for a replacement crane or a revised schedule.
- Hold a toolbox talk on the reason for the stop.
If pressured, do not 'watch the angle' or bypass the anti-two-block. Document the instruction and your refusal. The operator's signature and the competent person's release are the only basis for restarting.