SWL plate dropped from crane block
- Safety Flash
- Published on 17 September 2025
- Generated on 17 December 2025
- IMCA SF 17/25
- 2 minute read
An “SWL” plate weighing 0.9kg fell from the auxiliary hook block and landed on the main deck of a newly purchased vessel.
What happened?
No one observed the plate fall so the height cannot be confirmed; potentially the plate fell 125 metres, due to the height of hook when the plate was last observed. The plate was redundant as there is a clearly painted SWL on the hook block.
The vessel had been handed over from the shipbuilder less than a year before the incident. The shipbuilder installed the SWL plate on hooks although this was not included in the hook block specification drawings.
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What was the cause?
- Previous internal dropped object inspections and daily crane pre-start checks, which include dropped object assessments, had not identified this hazard.
- The SWL plate was installed on the hook but was not included in hood block specifications.
- Galvanic corrosion: the use of dissimilar metals—stainless steel and aluminium—led to accelerated galvanic corrosion, which is believed to have caused the rivets to fail and the plate to detach.
Actions and lessons
- A check was made of all other SWL plates on all hooks and equipment that could pose a DROPS risk;
Fed back to shipbuilder and crane manufacturer to reduce the likelihood of a similar event occurring elsewhere. - A third-party DROPS inspection on the vessel was brought forward to a reasonable time when modifications were completed and after the handover of the vessel.
- Could there be other objects at height or elsewhere on the vessel that exist but are not in the specifications or in the General Arrangement drawings?
Related Safety Flashes
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IMCA SF 21/15
7 December 2015
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IMCA SF 34/16
29 November 2016
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IMCA SF 21/17
23 August 2017
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IMCA SF 20/18
10 September 2018
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IMCA SF 05/20
13 February 2020
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