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STATS Group completes subsea isolation project

Published by , Assistant Editor
World Pipelines,

STATS Group has announced that it has completed its first subsea isolation project in China on the 780 km Yacheng pipeline, located in the South China Sea. This pipeline is crucial for supplying gas to Hong Kong.

STATS Group was contracted by COOEC Subsea Technology to provide a temporary isolation since the pipeline had been damaged by a ship’s anchor and had been left unpiggable at a location about 280 km from shore and in water depths of 90 m.

Detailed engineering studies and comprehensive risk assessments were conducted. It was then determined that most effective repair solution was to remove the severely dented section of pipeline and two pipeline end manifolds from the seabed on to a pipelay vessel, while the pipeline remained pressurised at 57 bar.

To ensure the safe recovery of both ends of the pipeline onto the pipelay vessel, without depressurising or allowing water ingress into the pipeline, STATS’ Tecno PlugTM and BISEPTM isolation tools were installed. This ensured that only the sections of pipeline that were being recovered from the seabed were isolated.

Deployed into the pressurised pipeline downstream of the damaged pipeline, the BISEP provided a fully proved double block and bleed isolation barrier against the pipeline gas pressure. This allowed the pipeline to be depressurised between the rear of the BISEP and the pipeline end manifold to allow the damaged section of pipeline to then be safely cut and removed.

Dale Millward, Director of EPRS and Subsea Services at STATS Group, said: “Since this pipeline is of crucial importance for the supply of gas to Hong Kong, the shutdown period for the repair work needed to be kept to a minimum. Therefore, the repair had to be done without depressurising and flooding the entire pipeline.

"Strategic use of the BISEP and Tecno Plug isolation tools ensured that the primary project objectives were successfully achieved. The pipeline was repaired as safely and quickly as possible, without depressurising or flooding the entire pipeline and while ensuring that any seawater that may have entered the system was removed before the pipeline resumed operation.”

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