Oil is moved through the pipelines by pumping stations along the pipeline. Natural gas (and similar gaseous fuels) is pressurized into liquids known as natural gas liquids (NGL). Natural gas pipelines are built with carbon steel. Hydrogen pipeline transport is the transport of hydrogen through a pipeline.
As gas flows through the system, regulators control the flow from higher to lower pressures. If a regulator detects that the pressure has dropped below a set point, it will open accordingly to allow more gas to flow. Conversely, when the pressure rises above a set point, the regulator closes to adjust. As an additional safety measure, relief valves are installed in the pipelines to vent gas to atmosphere when necessary.
Natural gas pipelines carry natural gas. Liquid petroleum (petroleum) pipelines carry liquid oil and some liquefied gases, including carbon dioxide. Liquid oil includes crude oil and refined products made from crude oil, such as gasoline, household heating oil, diesel fuel, aviation gasoline, jet fuels, and kerosene. Liquefied ethylene, propane, butane and some petrochemical feedstocks are also transported via pipelines.
Since then, the United States has developed an extensive network of natural gas pipelines, consisting of more than 300,000 miles of transmission pipelines and more than 210 separate natural gas pipeline systems. Sophisticated software is used to assess the supply capacity of the network and ensure that all customers receive adequate supplies of gas at or above the minimum pressure level required by their gas appliances. Most compressors in the natural gas supply system use a small amount of natural gas from their own lines as fuel. Supplying natural gas from natural gas and oil wells to consumers requires many infrastructure assets and processing steps, and includes several physical custody transfers.
Liquid propane gas and compressed natural gas, which are produced from natural gas, provide the convenience of natural gas to locations where pipeline distribution is not available. About half of the existing main natural gas transmission grid and a large part of the local distribution network were installed in the 1950s and 1960s because consumer demand for natural gas more than doubled after World War II. Storing natural gas during periods of low demand helps ensure that sufficient natural gas supplies are available during periods of high demand. Natural gas moves through the transmission system at a speed of up to 30 miles per hour, so it takes several days for Texas gas to reach a utility reception point in the northeast.
When natural gas from a transmission pipeline reaches a local gas company, it usually passes through an inlet station. The composition of wellhead natural gas determines the number of stages and processes required to produce pipeline quality dry natural gas. Gas flowing from higher to lower pressure is the fundamental principle of the natural gas supply system. Some natural gas collection systems include a processing facility, which performs functions such as removing impurities such as water, carbon dioxide or sulfur that could corrode a pipeline, or inert gases, such as helium, that would reduce the energy value of the gas.