Hot tapping and plugging on a 6” natural gas pipeline to safely re-route a pipeline to allow construction of a new highway, while production was maintained.
STATS Group were contracted by Western Australia's largest gas distribution network operator to provide hot tapping and plugging services on a 6” natural gas pipeline. The purpose of the project was to safely re-route a 357 meter section of pipeline to allow construction of a new highway, while production was maintained at 19 bar.
The operator selected STATS hot tap installed BISEP® technology to provide double block and bleed isolation to ensure safety of personnel, residents, and the environment during the pipeline relocation. The BISEP features an integrated bypass which allows production to be maintained even after the isolation is installed and avoiding disruption to the gas supply.
To support the project STATS provided four BISEPs, slab valves, split tees and completion plugs, as well as hot tapping machines for 6” and 2” tapping. A team of four, including local technicians, supported the operation, carrying out hot tapping, isolation deployment and monitoring, and completion plug installation. Prior to deployment of equipment to site, function testing was conducted and witnessed by the client at STATS facility in Perth, Western Australia.
The workscope began by first excavating the pipeline at two locations, 357 metres apart, this provided access points for the newly re-routed pipeline to be tied into the existing pipeline. At this stage, two split-tee fittings were welded onto the pipeline 20 metres apart at each of the tie-in locations, this provided access points to hot tap and deploy the BISEP isolation plugs.
With four fittings successfully welded onto the pipeline, slab valves were attached, and pressure tests were conducted to confirm their integrity. The hot tap machine was then attached to each fitting in turn to conduct the cutting and recovery of the pipe coupon. With access points created for two BISEPs at each tie-in location the BISEPs were deployed into the pipeline and set, isolating a short section (20m) of pipeline at each tie-in location and allowing production to continue flowing through the bypass between the BISEPs. The pipe section between the BISEPs was then drained through a 2” hot tap point and nitrogen purged. Once it was confirmed all the gas had been removed, the pipe was cut and a short section of pipeline was safely removed. With the pipe cut the newly re-routed pipeline was welded into place and end caps were welded onto the existing pipeline prior to being vented, purged and decommissioned.
The outboard BISEPs were then unset and recovered into the launcher and the slab valves closed allowing the gas to flow through the newly re-routed pipeline.
The remaining BISEPs and bypass pipework were then removed from the pipeline and the slab valves were closed. The hot tap machine was then installed onto the slab valves and used to install 6” completion plugs into the flanges of the welded fittings.
Sam McKinnon, Business Development Manager for STATS Group in Australia, said: “The BISEP with integrated bypass allows production to be maintained while providing market leading double block and bleed isolation through a single hot tap fitting. Not only does this save clients time and reduce maintenance schedules, but it also provides significant efficiencies and cost savings by reducing the quantity of fittings and hot taps required for the project when compared to alternative line stop equipment.
“In addition, safety is increased as the BISEP provides fail-safe isolation with the differential pressure acting across the plugging head maintaining isolation, independent of the hydraulic set pressure. The dual elastomer seals are constantly monitored to confirm leak-tight isolation throughout the workscope”.
The pipeline relocation project was safely completed without incident and its success is testament to the teamwork and good communication between all parties.