Pre-Use Inspection Findings and Fitness to Lift
A self-erecting crane has been on site for three months. During the weekly inspection the following are found: (a) the load moment indicator (LMI) displays a reading but the audible overload alarm does not sound when tested with the test function; (b) one of the four outrigger beams shows a 15 mm crack in the weld at the beam-to-chassis connection; (c) the hook block's safety catch is stiff but closes; (d) the wire rope has two broken wires in one lay length, against a manufacturer's discard criterion of six in one lay length; (e) the slew brake holds but there is slight creep when parked on a 1° slope. The crane is due to lift a 2.5 t load that afternoon, and the site is behind programme.
1. Categorise each finding and state whether the crane can be used that afternoon.
Read the worked answer
Assessment of each finding: (a) LMI alarm not sounding - the LMI is a safety device and its alarm is part of its function. A display without an alarm is not a functioning LMI. This is a defect that takes the crane out of service until repaired and re-tested. It cannot be worked around. (b) 15 mm crack in a structural weld on an outrigger beam - this is a structural defect in a primary load path. It is a stop-use item. The crane must be taken out of service, the crack assessed by a competent person, and a repair scheme agreed with the manufacturer or a qualified engineer. Continued use risks catastrophic failure of the outrigger under load. (c) Stiff but closing hook safety catch - a minor defect; it must be freed/lubricated and checked, but it does not by itself stop the lift provided it functions correctly. Record and rectify. (d) Two broken wires vs discard of six - within the manufacturer's discard criterion, so not a discard item on that count alone. Continue to monitor and record; check for other rope defects (corrosion, kinking, broken strands at terminations) which could change the assessment. (e) Slight creep on a 1° slope - the crane should be set up level; creep indicates the brake or set-up is not fully satisfactory. Investigate and level the crane before lifting.
Conclusion: the crane must NOT be used that afternoon. Findings (a) and (b) are both individually stop-use items. Programme pressure is not a justification.
2. The site manager asks whether the lift can go ahead if the LMI alarm is 'worked around' by the operator watching the display and the crack is 'monitored'. Respond.
Read the worked answer
No. Both proposals are unsafe and would breach the crane's safe system of work.
The LMI alarm exists because the operator cannot reliably watch a display while concentrating on the load, the signaler, and the surroundings. The alarm is the independent warning that capacity is being approached. 'Watching the display' removes the redundancy the device is designed to provide and relies on continuous human attention in a high-workload task - exactly the failure mode the alarm is there to catch. A defective safety device must be repaired and re-tested, not compensated for by procedure.
The crack is in a primary structural weld at the outrigger-to-chassis connection, which carries the highest reactions during lifting and climbing. 'Monitoring' a crack is not a control - cracks propagate under cyclic load, and the consequence of failure is collapse. It must be assessed and repaired by a competent person, with the repair method agreed by the manufacturer or a qualified structural engineer, and the crane re-inspected before return to service.
The correct response is to take the crane out of service, record the defects, notify the responsible person, and replan the lift - either with a different crane or after repair and re-inspection. The programme is secondary to the structural and functional integrity of the machine.