Gas Transmission Networks
As explained above, National Grid Gas (NGG) design, construct and operate large diameter pipelines transporting natural gas. High pressure gas transmission pipelines are typically buried to a nominal depth of 1.2m. as required by pipeline design codes (IGE/TD/1, PD 8010). For such a depth, pipelines are installed using the well-established and proven ‘open-cut’ installation technique. This technique typically involves performing a surface excavation (surface stripping) and removing the soil to the depth and width as required, preparing the trench, installing the pipe and then backfilling the trench with soil in accordance with TD/1 and then reinstatement of the top soil. Each stage of the pipeline installation process requires careful and detailed design and safety considerations and National Grid have procedures and specifications to ensure a high quality installation is performed.
In locations where there is a requirement for a deeper burial depth to negotiate a constraint (such as a road/rail/river crossing, unstable ground, building proximity), trenchless techniques such as auger
boring, thrusting, pipe jacking and Horizontal Directional Drilling (HDD) are typically employed. These have successfully been performed by specialist drilling companies. In certain industries, the success of these installations has prompted the use of these techniques to replace the traditional open-cut installation technique as the impact on personnel and environment is greatly reduced.
The project seeks to investigate how existing and new pipeline installation technology is expected to evolve over the next 3, 5 and 10 year timescales and hence how the benefits seen in other industries can translate for NTS pipelines. The feasibility of using alternative technologies to those being deployed currently for pipelines in the National Grid Transmission Network will be extremely important in choosing the most appropriate technology for each installation.