Material Insights · Understanding the Material World

Gas pipelines and city gas: How it works

How compressors push gas across continents while pipes store it

What this tab covers How the energy actually moves, step by step: the science that makes it work and the engineering that makes it practical.

Gas flows through buried steel pipes from high to low pressure. Compressor stations keep the pressure up over long distances; city networks step it down for homes and factories.

Step by step

  1. Gather and treatGas from wells is cleaned of water, sulphur compounds and heavier liquids, then compressed.
  2. Push it along the trunk lineSteel pipes 60 to 90 cm or more across carry gas at about 55 to 83 bar across countries and under seas.
  3. Re-boostFriction drains pressure, so every 65 to 160 km a compressor station squeezes the gas back up, usually burning a little of it.
  4. Store and balanceGas packed into the pipe (line pack) and underground stores cover demand that swings with weather and time of day.
  5. Step down and deliverAt the city gate pressure is cut, an odorant is added so leaks can be smelled, and street mains carry gas to users.

The science

Gas is compressible, so a pipeline is both a pipe and a store. The pressure difference between the ends drives the flow; friction turns some pressure energy into heat, so pressure falls with distance. Higher pressure packs more gas into the same pipe, which is why trunk lines run at tens of bar. Compression also heats gas (about 7 to 8 F per 100 psi), so stations cool it to protect pipe coatings.

The engineering

Lines are welded, coated steel pipe in a cleared right of way, protected from rust by a small electric current (cathodic protection). Stations use gas turbines, engines or electric motors to drive centrifugal or reciprocating compressors. Valves isolate sections, and devices called pigs ride the flow to clean and inspect the pipe. A control centre monitors pressure and flow.

Key numbers

Transmission pressure (US interstate) 800 to 1,200 psi (about 55 to 83 bar)1 Compressor station spacing 40 to 100 miles (about 65 to 160 km)2 Gas speed in the pipe about 10 to 20 mph (16 to 32 km/h)2 Typical interstate pipe diameter 24 to 36 inches or larger3 US gas transmission network, 2025 300,217 miles (about 483,000 km, calculated)5 US distribution mains, 2025 1,394,662 miles6

Sources

  1. Understanding Natural Gas Compressor Stations Penn State Extension, 2015
  2. What is a Natural Gas Compressor Station? INGAA, 2023
  3. Pipelines 101 Energy Transfer, 2021
  4. Annual Report Mileage for Natural Gas Transmission and Gathering Systems PHMSA, 2026
  5. Annual Report Mileage for Gas Distribution Systems PHMSA, 2026