Sudden and uncontrollable move of A&R head

What happened?

At the end of offshore pipeline installation operations, a vessel was preparing for pipeline abandonment. The pipe end clamp was in the Hand-off Module (HOM) and had been bevelled and prepared; and the team were in the process of installing and aligning the Abandonment & Recovery (A&R) head for welding. Prior to installing the A&R head, the required volume of water had been removed from the flooded pipe clamped in the HOM.

The A&R head was then lifted into position using the workstation crane. With the A&R head lifted into position, an external pipe clamp was used to help with line-up and to secure the head in the required welding position. As the final adjustments were being made, the A&R head assembly was moved upwards and then ejected in an uncontrolled manner from the pipe end. It swung uncontrollably for a short period but did not drop as it was still supported by the workstation crane. This was brought under control quickly by one of the deck team.

Crew members were nearby (see images) but no-one was injured.

What went wrong

• There were no vent holes in the A&R head, as was specified by the client;
• The ‘suck and blow’ effect from the residual water in the pipe had not been recognised as a risk, as this incident/event had never occurred at this magnitude before;
• There were more people present (and hence at risk) than strictly necessary.

Lessons learned

• A renewed focus on controls, barriers, and risk management where Line of Fire risks have been identified;
• Can the task be done safely with fewer people present?
• Challenge norms and specifications and assess if they introduce changes with additional risks;
• Consider and plan for “suck and blow” effects for similar operations.

Members may wish to refer to

• High potential stored energy incident: inner buoyancy module clamp failure during removal
• High potential near miss: working on pressurised pipeline
• Fatality: Stored pressure release