What happened? A DMA* toppled over, trapping a diver on the seabed and causing an injury to his leg. The incident occurred whilst a diving support vessel (DSV) was working on preparation to install a closing spool. Three DMAs were being deployed to use static and mechanical hold backs attached to the spool. Two DMAs were deployed by the DSV. The third had been previously deployed and wet stored by a 3rd party vessel. The DSV had no involvement in the deployment to the seabed of this third Deadman anchor (DMA3), but upon arriving on site found it to be placed in the correct location and decided to use it rather than deploy the DMA identified on the approved dive plan.
Holdbacks were attached to DMA3 and as Diver 2 took up the slack in the rigging, it toppled over, trapping the diver on the seabed by his left leg. Diver 1 went to his assistance and helped free him.
Both divers made their way safely back to the bell and were recovered to surface. After decompression, diver 2 was flown ashore to hospital and was diagnosed with a fracture of the fibula and a torn ankle ligament. The diver has since made a full recovery and is expected to return to his normal work activities.
What were the causes?
- DMA3 that toppled over (blue DMA, right hand image) was different in weight and design from the one required in company procedures;
- DMA3 had a very narrow footprint and tall body with a high centre of gravity, making it unstable and unsuitable for rigging under tension and deploying in an upright position;
- The dive plan identified deployment of a 10te DMA (yellow DMA, left hand image). However, the team decided to use the one deployed by the 3rd party vessel;
- Whilst this was convenient, no check was made to ascertain whether or not it was fit for purpose;
- No management of change (MoC) process was initiated, and the risk of this DMA toppling was not identified.
Our member suggested that the following things went wrong:
- Existing procedures and risk assessments for the use of subsea DMAs were too generic;
- There was a ‘change’ which introduced an increased risk. However, the level of risk presented by the use of DMA3 was not adequately assessed and was perceived as being low;
- DMA3 was procured and sent offshore [by others] for another task. It was identified subsequently that DMA3 was in fact a crane counterweight and was not the most suitable piece of equipment for the task it was being used for;
- The lifting points on DMA3 were located on the top of the weight and it could only be deployed in the vertical position, offering a small footprint and high centre of gravity;
- The rigging arrangement placed the diver in close proximity to DMA3 during attachment, adjustment and detachment;
- There was a level of complacency within the offshore team – the hazards associated with the non-standard DMA3 were not immediately recognised and therefore not considered;
- The root cause identified was that the risk management process for the use of DMA3 was not effectively utilised and the work team risk perception on this occasion was poor.
Our member identified the following lessons learnt
There were a number of opportunities to prevent this incident taking place, starting with the onshore engineering team that sourced DMA3, the on-board supervisors who decided to use it and the divers who were working around it. The team were confronted by a change (different DMA design) which they failed to properly recognise and manage. There was a degree of complacency and poor perception of risk among all of the parties involved.
The company has a safe system of work that could have and should have compensated for inadequate equipment and stopped operations before the incident occurred. These systems failed in this instance.
While there are a number of actions specific to DMA operations, a great deal of focus has been put on behaviours and task supervision, captured in a vessel specific improvement plan.
- DMA rigging to be altered to allow divers to be outside of the DMA footprint;
- Appropriate review of company documentation and procedures (to include DMA design specification and diver positioning) and also of the MoC process;
Information sharing – video footage and details to be shared for training purposes.
*Deadman Anchor (DMA): A clump weight which sits on the seabed and is used as a temporary anchor point for seabed construction activity.
Members may wish to refer to the following incidents (search word: DMA):
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