Through the decades, a variety of materials have been used to make natural gas pipelines. The selection of materials varies with the date the pipeline was placed in service, the diameter and pressurization requirements of the pipeline, and the characteristics of the local terrain. Listed below are the most common pipeline materials.
Steel is the material used in natural gas transmission systems pipes – these pipes are large in diameter and cover more than a quarter-million miles of our nation. Transmission system pipe is made of 1/4-inch to 1/2-inch thick steel, and has special coatings and "cathodic" protection -- an electric current that controls corrosion on the metal surface through electro-chemistry. Some distribution main pipe is also steel, although plastic has become the material of choice for pipe installed in the last 30 years.
Cast Iron Pipe
For much of the 20th century, cast iron was the choice for many urban utility systems because of its excellent resistance to corrosion. In the 1950s, steel replaced cast iron as the material of choice, mainly because of steel’s flexibility and strength.
During the past 30 years, plastic pipe has predominated in gas utility distribution systems operating at less than 100 pounds of pressure. In 2003, plastic pipe accounted for one-half million miles of distribution main. Plastic pipe is flexible, corrosion-resistant, easy to transport and costs less to install. Plastic pipe also can often be inserted into existing lines or through soil without traditional trenching along its entire route.