STATS Group has provided double block and bleed isolation of a 12-inch gas pipeline while at an operating pressure of 72 barG.
The leak-tight and fully monitored isolation allowed the safe replacement of an ESD valve onshore at the Production Station in New Zealand.
To undertake this operation safely and efficiently, STATS Group proposed the use of a remotely operated Tecno Plug.
Conventional repairs like this would typically require the pipeline to be completely hydrocarbon free by flaring the gas and nitrogen purging the entire length of pipeline to enable a safe intervention.
However, STATS Group’s piggable isolation tools are non-invasive and have advantages over traditional hot tap and line stop technology as they require no welding or cutting into live lines and leave no residual fittings or holes in the pipeline.
A STATS Group isolation technician visited the Production Station prior to the activities. The technician carried out a site survey to gather critical information, complete a noise survey and to aid with the selection of the tool configuration.
The Tecno Plug was configured in a four-module arrangement with a full Factory Acceptance Test (FAT) performed in a purpose-built test-fixture.
Once onsite, a team of four isolation technicians successfully deployed the Tecno Plug and pigged it to the set location with MEG. The Tecno Plug was pigged through three ball valves and passed the production tee to the set location in the 5D bend where it was set in position using through-wall communication.
On location, the Tecno Plug was hydraulically set to activate the locks and dual seals. The dual seals of the Tecno Plug were then independently tested with full pipeline pressure in the correct direction to confirm leak-tight isolation. This allowed the pipeline to be bled down to ambient from the platform launcher to the rear of the Tecno Plug. The annulus between the Tecno Plug seals was vented to ambient to create a zero-energy zone before being subject to a 24-hour isolation stability hold period before the ‘Isolation Certificate’ was issued.
With the isolation in place and double block and bleed isolation verified, the valve replacement workscope was safely conducted.
The Tecno Plug was monitored closely and remained stable throughout the seven-day isolation period.
A reinstatement leak-test was conducted against the new valve before equalising the pipeline pressure and unsetting the Tecno Plug. The Tecno Plug was then pigged back to the launcher for demobilisation. This workscope is now one of many safety critical isolation projects recently completed in the region.
STATS Group were contacted to complete the works by OSD Limited on behalf of a national energy company.
For more information, visit STATS Group.
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