IMCA informs about a riser that moved unexpectedly away from the vessel. The incident occurred during the deployment of a production riser from a hang-off frame located starboard aft.
The incident
All rigging had been connected and the crane had taken the load and slewed inboard to remove the hang-off plates and beam. A 3-tonne lever hoist was also attached to assist in this activity. The rigging team was ready to remove the chain hoist when there an unexpected sudden movement of the riser to starboard took place. The chain hoist parted and the riser moved clear of the hang-off platform to about 8m off the vessels side.
[smlsubform prepend=”GET THE SAFETY4SEA IN YOUR INBOX!” showname=false emailtxt=”” emailholder=”Enter your email address” showsubmit=true submittxt=”Submit” jsthanks=false thankyou=”Thank you for subscribing to our mailing list”]
The proposed arrangement had been risk assessed and it was noted that the riser was leading away from the vessel. It was decided to install a soft sling around the riser which would be connected to a lever hoist.
The rigging was arranged and secured to the riser end fittings and the process of deployment continued. The soft sling was in addition to the existing procedural requirements, but there had been no management of change process followed for this addition.
The crane was then slewed inboard to allow the removal of the beam. Once the hang-off collars and beam had been removed, the crane operator requested a movement outboard as he was concerned with the 3° side lead on the crane wire. The confirmation was to move the crane outboard ‘just a touch’.
Two personnel remained in position to remove the additional rigging. The CCTV footage showed the crane slew to the left and then stop. Almost immediately, the soft sling failed. The riser suddenly moved left, bending a section of handrail on the hang off platform as it moved.
Probable cause
IMCA concluded that the causes of the incident were a lack of risk perception and the failure to follow procedures. Key points include the following:
- The introduction of the soft sling rigging was not identified as a change and therefore was not managed via the MoC process;
- The effects of moving the crane jib on the riser were not considered;
- As the risk was not identified, once the movement of the riser began, the 3-Tonne lever hoist was not able to prevent the incident from occurring;
- There was ineffective communication between the rigging supervisor and the crane operator;
- It was important to ensure supervisor involvement in shift briefings and toolbox talks (TBT) and communicatw relevant information which allowed personnel to understand the task and dangers.
Recommendations
After the incident, IMCA recommended the following:
- A clear task outline should be provided so that all personnel involved understand all the steps involved;
- Instructions should be precise, accurate and free of ambiguity;
- Any change should be subject to the MoC process.
