Pipe is used to move natural gas from one location to another and can also be used as a form of storage. Pipe size and type vary depending on various design considerations such as flow rate, pressure, and environmental factors. Pipe is used in all sectors of the gas delivery system from the well to inside each consumer’s facilities.
In today’s installations, gas pipe is made from either plastic or steel. Plastic pipe is used for lower pressures where external pressures are limited, while steel is used for higher pressures and where heavy loading or third-party damage are more likely to occur. Because of its characteristics, plastic pipe is easier to install than steel pipe and is less costly, but it is more susceptible to external damage and is limited in the amount of pressure it can safely carry.
Plastic pipe is typically used only in distribution systems with pressures of 60 pounds per square inch (psi) or less and diameters ranging from ½ to 8 inches. Steel may used for distribution as a substitute for plastic where external damage is likely but more commonly is used for higher-pressure transmission systems with pressures higher than 60 psi and with diameters ranging from ½ to as large as 55 inches.
In the early days of gas pipeline construction, pipes were made from cast and wrought iron and even from wood. While these materials are no longer used, older cast iron pipes still exist in some low-pressure gas distribution systems. Gas utilities typically try to replace cast iron systems as quickly as practicable because these older systems are prone to leaking and cause more accidents than do steel or plastic pipes.
The following chart compares steel pipe versus plastic pipe applications: