2. Transmission and Distribution Systems and Design

Once natural gas is first extracted from corresponding well, this is followed by gas treatment plant (downstream process), then via transmission pipeline to distribution network systems, and to the consumers. Through this transmission gas delivery, the concept of pipeline design is established through its location, the type of fluid being carried and its operating pressure and temperature are also of prime importance within this process. Unusual examples of severe location are the trans-Alaska pipeline where long sections are laid above ground to protect the permafrost and the Middle East, where long pipelines are laid both above and below ground and can be subjected to large temperature changes that bring complex design concepts. The operating pressure will determine the grade and wall thickness of the material, and temperature will also affect the requirements for pipe coatings, insulation, expansion joints, anchor blocks, etc. Gas pipelines require special attention over and above the normal design requirements for liquids because of the vast quantity of stored energy in the pipeline steel due to the compressibility of gas. The design should therefore take account of the probable consequences of failure and the parameters that can be adjusted to minimise the possibility of failure in pipeline systems. This chapter therefore attempts to provide the wide guidelines related to issues with the design and integrity of the transmission and distribution pipelines together with safety aspects of the systems.