A hardware failure in a dynamic positioning system caused a dive support vessel to strike a natural gas platform off Nova Scotia.
The 410-foot Acergy Discovery drifted into the Deep Panuke platform at 0545 on Sept. 6, 2011, about 155 miles southeast of Halifax, said platform operator Encana Corp. There were divers in the water at the time.
"Essentially the vessel rubbed up against one of the four legs of the platform and the riser caisson," said Encana spokeswoman Lori MacLean.
The caisson is the tubular structure that gathers lines from the seafloor and connects them to the platform.
"It would look like a fifth leg, and it is the gathering point for the flow lines and umbilicals,â€ MacLean said. She said Acergy Discovery "rubbed up on one of the four legs and the riser caisson. Everyone was safe on the platform and vessel. The vessel works in pretty close proximity to the platform but shouldn't make contact."
After the incident, the vessel stopped work and returned to its base at the port of Mulgrave, Nova Scotia.
The 65-foot-wide Acergy Discovery is "one of the most versatile diving vessels in today's subsea and construction market." said owner Subsea 7 SA. Subsea 7 conducted an investigation upon Acergy Discovery's arrival at Mulgrave, MacLean said. The vessel returned to the field Sept. 14.
"What the investigation concluded was that the incident was caused by a hardware system fault that was within the Discovery's dynamic positioning system," MacLean said. "They took corrective action to address the problem and prevent any repeat. Encana is satisfied with the results and the work has resumed on their part of the program."