Natural gas travels from the wellhead to end consumers through a series of pipelines.
Purpose: Flowlines connect to a single wellhead in a producing field. Flowlines move natural gas from the wellhead to nearby storage tanks, transmission compressor stations, or processing plant booster stations.
Description: Flowlines are relatively narrow pipes that carry unodorized raw gas at a pressure of approximately 250 psi (pounds per square inch). Typically, flowlines are buried four feet underground.
Special considerations: Flowlines can corrode, especially if they are carrying wet gas. Flowlines are also prone to methane leakage. According to the EPA, "Methane leakage from flowlines is one of the largest sources of emissions in the gas industry."
2) Gathering Lines
Purpose: Gathering lines collect gas from multiple flowlines and move it to centralized points, such as processing facilities, tanks, or marine docks.
Description: Gathering lines are medium size steel pipes (usually under 18" diameter) that carry unodorized, raw gas at a pressure of approximately 715 psi. Typically, gathering lines are buried four feet underground.
3) Fluid Transportation Steel Pipe
Purpose: Transmission pipelines carry natural gas across long distances and occasionally across interstate boundaries, usually to and from compressors or to a distribution center or storage facility.
Description: Transmission lines are large steel pipes (usually 2" to 42" in diameter; most often more than 10" diameter) that are federally regulated. They carry unodorized gas at a pressure of approximately 200 to 1,200 psi.Special considerations: Transmission pipelines can fail due to: seam failures, corrosion, materials failure, or defective welding.
4) Distribution Pipelines
Purpose: Distribution pipelines, also known as "mains," are the middle step between high pressure transmission lines and low pressure service lines. Distribution pipelines operate at an intermediate pressure.
Description: Distribution pipelines are small to medium sized pipes (2" to 24" in diameter) that are federally regulated and carry odorized gas at varying pressure levels, from as little as 0.3 up to 200 psi. Distribution pipelines typically operate below their carrying capacity. Distribution pipelines are made from a variety of materials, including steel, cast iron, plastic, and occasionally copper.
5) Service Pipelines
Purpose: Service pipelines connect to a meter that delivers natural gas to individual customers.
Description: Service pipelines are narrow pipes (usually less than 2" diameter) that carry odorized gas at low pressures, such as 6 psi. Service pipelines are typically made from plastic, steel, or copper.
