Safety Flash 

Dynamically Positioned Vessel Run-off / Severance of Bell Diver’s Umbilical

Incident Occurrence: 18 September 2012
Location: UK (North Sea)
Depth: 91m

Summary of Incident:
At the above date and location, two divers were located out of the bell working inside of a drilling template structure (with ROV monitoring).

Subsequently, the amber alert activated and the vessel started to drift from its stationary position. Attempts were made to re-select thrusters in DP. After some time, the DP red alert activated and the vessel continued to drift. All references and thrusters were not responsive to DP. A switch was made from DP to manual thruster control.

Diver 1 and 2 located themselves on the top of the template structure. Diver 1 was pulled off the template structure. Diver 2’s umbilical snagged on the transponder bucket, which was located on the side of the structure; Diver 2’s umbilical was severed. Diver 1 was able to make his way back to the bell stage. Diver 2’s locator beacon identified him to be at the template structure. An ROV was sent to the template structure and Diver 2 was located.

The vessel regained full auto DP and returned to the template structure. Diver 1 then left the bell stage to recover Diver 2. Diver 2 was recovered to the bell (unconscious and breathing). Within short order, Diver 2 displayed good vital signs and was talking.

The vessel’s operators and dive team displayed outstanding professionalism in the handling of this incident, which could have easily resulted in a fatality.

Recommendations:
Because of the possibly of DPV 2 vessels unexpectedly experiencing run-offs, umbilical management needs to a primary focus at the first sign of loss of station. Divers need to ensure that their umbilicals are free and clear to the bell.

Drills should be planned and conducted for DPV 2 run-offs while diver(s) are outside of the bell. All operations should be performed with ROV monitoring.

Clearly the presence of the ROV in this incident was instrumental in visually locating the diver. Additionally, the use of locator beacons on divers was also a major factor in keeping constant awareness of the location for both divers.

Careful consideration of marginal wind and sea conditions should be included in a hazard identification involving diver penetration and/or fouling points.