Archived report · 2 min read · Set in Wharf Street ·
Crane Load Test at Wharf Street
A load test on the Wharf Street dockside crane finds the hook holding a weight that is not on the lifting schedule, and the figure on the gauge matches the weight of a single adult, though the test rig is empty.
- filed: Filed after the annual lift inspection
- reference: DC/WS/22
Subject: dockside gantry crane, Wharf Street Quay, rated 10 tonnes safe working load.
1. The crane was installed in 1964 and last load-tested in 2021 at the rated load. It is inspected annually by the port authority's lifting engineer.
2. The test procedure requires the crane to lift a certified test weight of 12.5 tonnes, 125 per cent of rated load, to a height of one metre, and hold it for ten minutes. The weight is hung on a calibrated hook load cell and the readings recorded.
3. The test weight was rigged on the hook and lifted without incident. The load cell read 12.5 tonnes as expected. The hold period began at 10:00.
4. At 10:04 the load cell began to register a slow fall, to 11.2 tonnes, and then, without any change in the rigging, returned to 12.5 tonnes. At 10:07 it fell again, to 9.8 tonnes, and rose again. The pattern continued, at irregular intervals, until the end of the hold period.
5. The test weight had been removed from the hook at 10:02, following the first drop, on the advice of the lifting engineer. The hook was then left empty. The load cell continued to register fluctuating loads throughout the remaining period, between 58 and 74 kilograms.
6. Those readings are consistent with the mass of a single adult standing on the hook platform. No person was on the platform at any point during the test. The platform was inspected visually from the quay, and the surveyor found it to be empty.
7. Recommendation: the crane was taken out of service pending a review of the load-cell calibration. The cell has since been replaced and the recalibration returned a clean result.
8. Observation not explained by the survey: the log of the replacement calibration shows the old cell's final reading as 71 kilograms, and the engineer's note records that the figure is the surveyor's own weight, to within the nearest kilogram.