Three bolts sheared on a lifting trunnion

What happened

After successful installation of a offshore renewables Transition Piece (TP), crew accessed the TP and discovered that the cover plate of the lifting trunnion had fallen off and was on the hatch cover of the TP with its three securing screws close by. The securing screws had sheared.  The cover plate weighed 44kg and fell approximately 0.5m from the lifting trunnion to the hatch cover. 

Further inspection followed and it was observed that there had been some damage to a survey beam and an antenna of GNSS positioning equipment. The damage caused to the antenna was fixed onboard. The survey lifting beam had to be replaced, but there was a spare onboard and a replacement beam was ordered.

What went wrong

It was considered that the method of verifying the suitability of the screws attaching the cover plate to the lifting trunnions was incorrect. It was assumed that the sideway forces experienced by the cover plate were exactly introduced in the centre of the lug cover. However, this was not case. This assumption resulted in the inadequate method of securing the cover plate to the lifting trunnion. 

What went right

• A permit to work was in use for the task, a toolbox talk was held where the Job hazard analysis was referenced and a Last-minute risk assessment was used.  The task plan was adhered to throughout the installation.

What were the causes

• The side forces experienced by the cover plate were greater than the screws could withstand; this could have been foreseen. Our member considers the root cause to be human error.

Actions

• Weld the cover plates to the lifting trunnions.

Members may wish to refer to:

• High potential near miss: tensioner pad dropped to under deck carousel
• Dropped Object – Steel deck plate falls from pipelay tower