Double block and bleed isolation barrier provides safe tie-in of replacement pipeline section
STATS Group were contracted by a major operator to supply high pressure isolation plugs to provide a double block and bleed isolation barrier for the safe tie-in of a replacement section of the main 24” oil export line from the Platform. Located in the Central North Sea the isolation needed to be completed without having to de-oil the entire 80km pipeline.
To facilitate the double block isolation and enable a reinstatement leak test in accordance with the pipeline design code, STATS provided two remotely controlled Tecno Plugs. The first Tecno Plug provided a proven double block isolation from pipeline pressure. The second Tecno Plug provided a local leak test boundary. Using two plugs in this manner maintains a safe isolation until the leak test is completed and prevents pressurising the entire pipeline up to leak test pressure.
An expert isolation committee of a subsea engineering and construction company, which included their global technical risk experts, assessed the suitability of the high pressure remote isolation plug as a double block barrier for diver breaking containment activities. The critical operational areas of concern were scrutinised and the Tecno Plug was deemed to provide an acceptable isolation barrier for the required work scope.
Prior to award of the isolation work scope STATS conducted a detailed engineering and piggability study to confirm the fitness for purpose of the Tecno Plug. Further reassurance of piggability and reduction of risk was achieved by deploying a geometry proving pig and a high resolution Inline calliper survey tool.
The primary project objectives of safety and efficiency were delivered to ensure a minimal shut down period was achieved. Excellent project management, intercompany team working and appropriate use of isolation technology resulted in a successful pipeline replacement that was completed in a timely manner.
Dale Millward, STATS Group director of EPRS and subsea services, commented on the successful project: “Although not our first subsea isolation, this project is a milestone subsea isolation project that shows how far we and our technology have progressed since the introduction of STATS remote isolation plug technology 10 years ago.”