Material Insights · Understanding the Material World

Oil and product pipelines: How it works

How pumps, pigs and batches keep a long column of oil moving

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.

Oil pipelines are buried steel tubes. Pumps push crude oil or refined fuels through them from high pressure to low pressure. One large line moves about a million barrels a day, continuously and cheaply.

Step by step

  1. Gather at the inletCrude from fields, ports or refineries is stored, measured and scheduled into the line.
  2. Raise the pressureCentrifugal pumps driven by electric motors or gas turbines push the oil out at high pressure.
  3. Boost along the routeFriction slowly uses up the pressure, so pump stations along the line raise it again.
  4. Batch productsPetrol, diesel and jet fuel travel one after another; the short mixed zone (transmix) is reprocessed.
  5. Pig, monitor, deliverPigs clean the pipe and smart pigs check wall thickness. A control centre (SCADA) watches flows and can shut valves. Oil ends in terminal tanks, refineries or tanker berths.

The science

Liquids barely compress, so a full line behaves like a long column pushed by the pumps. Pressure lost to friction per kilometre rises roughly with the square of flow speed and falls as diameter grows, so wide, smooth pipes at moderate speed use least energy. Heavy crude or bitumen is thinned with diluent or heated. Batches can share a pipe because turbulent flow keeps the mixing zone short.

The engineering

Line pipe is high-strength carbon steel with an epoxy coating, backed by cathodic protection (a small current that stops rust). US rules allow operation at up to 72% of the steel's specified minimum yield strength (80% for Keystone under a 2007 permit). A 2011 US law requires automatic shut-off valves on new lines, and operators with 500 miles or more must run integrity management plans.

Key numbers

US hazardous-liquid pipeline network (2025) 228,242 miles (82,203 crude; 65,058 products)1 Share of US crude and refined products moved by pipeline over 83%2 Diameter of a large crude trunk line (model case) about 1 m, carrying about 1 million barrels a day3 Flow speed, 1 million b/d in a 1 m pipe about 2.3 m/s, roughly 200 km a day (calculated)3 Largest bypass line: Saudi East-West pipeline 7 million barrels a day capacity11 Trans Mountain system after its 2024 expansion 890,000 barrels a day21

Sources

  1. Annual Report Mileage for Hazardous Liquid or Carbon Dioxide Systems US DOT PHMSA, 2026
  2. DOT's Federal Pipeline Safety Program: Background and Issues for Congress (R44201) Congressional Research Service, 2025
  3. Pipelines: the energy economics (analyst model, updated 23 July 2026) Thunder Said Energy, 2026
  4. Saudi Arabia restores key pipeline to half its capacity (Bloomberg) Rigzone, 2026
  5. CER approves Trans Mountain settlement, establishing a new framework for tolls Canada Energy Regulator, 2026