Daily Inspection, a Damaged Limit Switch and a Defect
During a pre-operational inspection, the operator finds that the hoist limit switch has a cracked housing and the lever does not return freely. The crane was used the previous day without apparent problem. The operator reports it to the site supervisor, who says the crane is needed for a two-hour concrete pour and that the switch 'probably still works'. The crane's manual lists the limit switch as a safety device that must be functional before use. The operator also notices that the load moment indicator shows a reading that does not change when the test load is applied, and the wire rope has two broken wires in one lay over a length of about 6 diameters. The pour is scheduled to start in 30 minutes, and the concrete trucks are already arriving.
1. Decide whether the crane can be used and justify the decision.
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The crane should not be used. The hoist limit switch is a safety device, and a cracked housing with a lever that does not return freely means it cannot be relied on to stop the hook at the upper limit. The manual requires it to be functional before use, and the supervisor's view that it 'probably still works' is not a basis for use. The load moment indicator not changing under test load means the overload protection may be faulty, which is a critical safety function. Two broken wires in one lay over 6 diameters is a defect that must be assessed against the retirement criteria; it may already require the rope to be replaced. The combination of a faulty limit switch, a suspect load moment indicator and rope damage means the crane is not in a safe condition. The concrete pour should be delayed or done by another method. The defects should be recorded, the crane isolated and tagged out, and a competent person engaged to repair and re-inspect it.
2. Describe the defect reporting and return-to-service process.
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The operator should record the defects in the crane's log or defect report, including what was found, when, and by whom. The crane should be isolated, locked out or tagged out so it cannot be started, and the supervisor and crane owner informed. A competent person should inspect the crane and specify the repairs: replace or repair the limit switch, test the load moment indicator, and assess the wire rope against the retirement criteria, replacing it if required. After repair, the safety devices should be function-tested, including the limit switch and the load moment indicator with a known test load. The wire rope should be inspected and the repair recorded. The crane should not return to service until the competent person signs it off and the operator completes a pre-operational inspection. The pour should be rescheduled or alternative lifting arranged, and the incident should be reviewed to see why the defects were not found earlier.