Gas transmission line pipe is typically 12 to 48 inches in diameter and constructed of 1/4- to 3/4-inch thick steel. Laterals off the main pipe may be constructed of smaller 6-inch to 16-inch diameter pipe to provide service to distribution systems or directly to large end-use customers such as industrial plants or power plants.
The pipe is buried underground for safety to reduce exposure to the elements and to accommodate other land use on the surface that is compatible with the presence of the buried pipeline. Sections of pipe are joined by welding in the field. Key design factors in line pipe include strength, toughness, weldability, and the process used to manufacture the pipe.