Construction of the Main Onshore Pipeline (the Pipeline) has reached a significant milestone, with mainline welding of the 36-inch pipeline between Stanlow and Flint now successfully completed.
Since welding operations began in June 2026, our construction contractor, United Infrastructure (UI), and its specialist welding subcontractor, CRC Evans, have been working across the 31.3km route to join sections of pipe to form a secure and continuous connection.
Mainline welding is the process of joining sections of the Pipeline where no bending is required. It is a largely automated process that supports efficient pipeline construction, enabling up to 500 metres of pipeline to be welded each day.
Specialist back-end welding activities will continue at locations where the Pipeline requires bends, tie-ins, or other complex fabrications. This work is being carried out by eight specialist fabrication crews, using a semi-automatic welding process tailored to more intricate sections of the route.
Following completion of back-end welding operations, sections of the Pipeline will be lowered into the open-cut trench using pipelayers fitted with side booms for stability, a process known as "lower and lay".
Once installed, the trench will be backfilled using the excavated material and the surrounding land will be reinstated as close as practicable to its original condition.
As construction progresses into its later stages, residents may notice increased preparatory activity and a greater on-site workforce along sections of the route. Further updates will be provided through the Latest News section of the HyNet Hub.
Since welding operations began in June 2026, our construction contractor, United Infrastructure (UI), and its specialist welding subcontractor, CRC Evans, have been working across the 31.3km route to join sections of pipe to form a secure and continuous connection.
What is mainline welding?
Mainline welding is the process of joining sections of the Pipeline where no bending is required. It is a largely automated process that supports efficient pipeline construction, enabling up to 500 metres of pipeline to be welded each day.
What happens next?
Specialist back-end welding activities will continue at locations where the Pipeline requires bends, tie-ins, or other complex fabrications. This work is being carried out by eight specialist fabrication crews, using a semi-automatic welding process tailored to more intricate sections of the route.
Following completion of back-end welding operations, sections of the Pipeline will be lowered into the open-cut trench using pipelayers fitted with side booms for stability, a process known as "lower and lay".
Once installed, the trench will be backfilled using the excavated material and the surrounding land will be reinstated as close as practicable to its original condition.
As construction progresses into its later stages, residents may notice increased preparatory activity and a greater on-site workforce along sections of the route. Further updates will be provided through the Latest News section of the HyNet Hub.