A natural gas pipeline primer: The difference between gathering, transmission and distribution lines
Natural gas: Fueling our lives
Natural gas fuels almost a quarter of the energy consumed today in the United States—with an estimated 68 million residential customers and five million commercial customers.
Underground natural gas pipelines crisscross the landscape to capture, process and deliver this energy source to homes and businesses. But what’s the difference between a gathering line and a distribution line? And how do transmission lines fit into the equation?
Keep scrolling and find out!
Gathering lines
Gathering pipeline systems collect raw natural gas from wellheads in production fields, and move it either to a processing plant or to an interconnection with the mainline transmission grid (see transmission pipelines below), depending on the initial quality of the product.
These small-diameter underground pipelines are connected to a producing well, and converge with pipes from other wells. Here, the stream of natural gas may go through an extraction process to remove water and other impurities.
Transmission lines
Natural gas transmission pipelines are all about movement—large volumes, long distances.
Often designed as a grid or a trunkline system, transmission pipelines are wide-diameter lines that move natural gas from a gathering, processing or storage facility to a large-volume customer, distribution system or another processing/storage facility. It’s estimated that there are more than 300,000 miles of American interstate and intrastate transmission pipelines in the ground.
Grid-style transmission systems usually include a large number of laterals, or branches off the mainline, that serve major market areas.
During this stage of transportation, natural gas processing plants produce “pipeline-quality” dry natural gas by separating impurities and non-methane hydrocarbons and fluids. These processing plants also recover natural gas liquids (condensate, natural gasoline and liquefied petroleum gas), and usually remove sulfur and carbon dioxide as well.
Some natural gas processing plants also include fractionation facilities, where saturated hydrocarbons are removed from natural gas to create distinct “fractions,” such as propane, butane and ethane.
Call or click before you dig
Whether it’s gathering, transmission or distribution pipelines, you need to know what’s below.
Damage from third-party activities is a leading cause of pipeline incidents. To protect people and the environment, and to reduce the risk of pipeline damage, the law requires that you call your local toll-free one-call number in the U.S. or Canada before excavating near a pipeline right-of-way (ROW).
In the U.S., 811 is the free national one-call number that will connect you from anywhere in the country to the appropriate one-call center.
In Canada, the recently launched Click Before You Dig website represents Canada’s first national “one-window” approach for requesting location of buried utilities prior to ground disturbance.
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