Compressor station

A compressor station is a facility which helps the movement of gas from one location to another in a pipeline system. Gases typically transported over long distances in this way include natural gas, methane, ethylene, hydrogen, ammonia and carbon dioxide. While being transported through a pipeline the gas pressure gradually decreases due to frictional effects and needs to be periodically repressurized at intervals of about 40 to 100 miles (64 to 161 km).^[1] Siting of compressor stations is dependent on terrain, accessibility and whether there are other tie-ins such as gas wells in the vicinity. Frequent elevation changes and a greater number of gas wells will require more compressor stations.^[2]

The compressor station, also called a pumping station, is the "engine" that powers a long-distance gas pipelines. As the name suggests, the station compresses the gas (increasing its pressure) thereby providing additional energy to move it through the pipeline.^[3] The compressor is driven by an electric motor or an engine fueled by some of the natural gas bled from the pipeline or liquid fuel such as diesel.

Companies install compressor stations along a pipeline route. The size of the station and the number of compressors (pumps) varies, based on the diameter of the pipe and the volume of gas to be moved. Nevertheless, the basic components of a station are similar.

Natural gas may move through a pipeline system typically at speeds of up to 25 mph (11.2 m/s), depending on pressures and pipeline diameters. For a pipeline system operating at a nominal pressure of 1000 psi (such as the UK National Transmission System) compressor stations compress the gas from about 48 bar (700 psi) to 65 bar (950 psi). Compressor stations generally operate at a pressure ratio of 1:1.4. During compression the gas may increase in temperature from 5 °C (41°F) to 45 °C (113°F). Limiting the pressure ratio ensures that the temperature rise across the compressors is not high enough to require after-coolers to prevent damage to the pipeline protective coatings.^[4]