Scope of work, which was performed on behalf of Interconnector UK, included facilitating valve remedial works at the terminal.
During the shutdown, a double block isolation was required for safe working conditions to change a 40in pig trap valve.
The pipeline landfall valve, located 1km away from the pig trap valve, was closed to provide the primary isolation against 80 Barg of gas pressure and minimize the impact on production.
STATS said it used a 40in Tethered Tecno Plug to provide a secondary isolation. Before deployment a client witnessed factory acceptance test (FAT) was conducted in a purpose-built test fixture.
Using a hydraulic system via the umbilical, the Tecno Plug was deployed to location past the pig trap valves and barred tee.
The 1km of pipeline between the Tecno Plug and the pig trap valve was opened to vent by utilizing the valve bypass arrangement with a 6in open vent.
To verify the integrity of the primary and secondary seals an annulus test was performed.
Isolation certificate was issued after both seals were tested and monitored for 12 hours and verified, while later, the valve was rigged away.
On completion of the valve maintenance, further umbilical management was carried out to allow the valve to be repositioned.
After replacing and confirming integrity of the valve, the Tecno Plug was unset and retrieved back into the pig trap for demobilization to allow the pipeline to re-pressurize and continue normal operations.
