Collapse of a crane onboard workboat Carol Anne results in fatality

The UK MAIB has issued report on the investigation of the collapse of a crane on board the workboat Carol Anne which resulted in one fatality.

Specifically, on 30April 2015, an Atlas lorry loader crane fitted on the workboat Carol Anne collapsed while being used to offload a net at a fish farm at Balure on Loch Spelve, Scotland. The crane fell onto the workboat’s skipper, who was declared deceased at the scene. The crane had been in operation since its installation 6½ weeks earlier. It was not overloaded when it failed.

According to the report, a number of factors contributed to the crane’s collapse including the following:

• No installation guidance was provided with the crane as none was required by the applicable regulations.
• The number and size of the lock nuts, bolts and washers supplied by Atlas (UK) to secure the crane to the vessel’s deck, and the torque to which they were tightened, were not in accordance with the crane manufacturer’s installation specifications.
• The lock nuts used were of inferior material grade to that indicated by their markings.
• The quality control and quality assurance procedures in place at Atlas (UK) did not prevent the use of an undersize mounting kit or the lower grade lock nuts.
• The thorough examination and testing of the crane following its installation did not identify the inadequacy of the crane’s mounting arrangement.

The failure was a result of three main factors:

1. no adjustment was made to the mounting arrangement to take account of the static mounting without stabilisers;
2. the use of an undersize mounting kit with smaller diameter studs, nuts and washers; and
3. the use of lower strength nuts on high strength studs.

The report also concluded that based on measurements and photographs taken at the accident site, the crane was working with the load at a radius of approximately 3.6m. It assessed that this was well within the envelope of acceptable working positions, assuming a load of 2.3 tonnes being carried at the time of the incident. Therefore, it was unlikely that the crane was overloaded at the time of the incident.

Further details may be found by reading UK MAIB report

Source: UK MAIB