Editor’s Note: This blog post is the second in a three-part series. Last week we discussed gas gathering pipelines and their regulation.
Over the course of the next few weeks, we’ll take a look at each category of natural gas pipeline.
The three main types of natural gas pipelines are gas gathering, gas distribution, and gas transmission.
This week, we’ll look at gas transmission lines.
What is a Gas Transmission Pipeline?
Gas transmission pipelines are used to transport natural gas from gathering systems to processing, refining and storage facilities.
In total, as of recent 2021 data, there are about 300,000 miles of transmission pipelines, this includes both offshore and onshore pipelines.
Transmission lines are large lines (generally 6-48 inches in diameter) and they move gas long distances around the country. This gas is often transported at high pressures, typically 200 – 1500 pounds per square inch (psi). Most recent transmission pipelines are now made out of high carbon steel.
On transmission lines, compressor stations are generally built every 50 to 100 miles along the length of the pipeline, this allows pressure to be increased as needed to keep the gas moving. Some gas transmission pipelines are bi-directional, which means gas can be coming from both ends of the pipeline, and depending on where gas is removed and where the compressors create the pressure differential, gas may flow either direction.
Many gas transmission pipelines are “looped,” which means there are two or more pipelines running parallel to each other normally in the same right-of-way. Looping provides increased storage of gas in the system in order to meet demands during peak use periods.
The “city gate” is where a transmission system feeds into a lower pressure distribution system that brings natural gas directly to homes and businesses.
Next week we’ll delve into gas distribution lines in greater detail.