Prime movers are part of the equipment that make up a compressor station. The prime mover is a device that provides the power to drive the compressor. Three key types of prime movers are used depending on the specific design of a compressor station — gas turbines, reciprocating engines, and electric motors.
Gas turbines are the most common type. They turn the compressor shaft through impingement of exhaust gas on a turbine blade set. This causes the blades to spin, which turns the shaft of the compressor wheel. Gas turbines are fueled with natural gas that is drawn from the gas stream flowing through the pipeline. They are lower cost than other options, considered to have high reliability, are powerful, have relatively low emissions, and are fairly quiet.
Reciprocating engines are an alternative to a gas turbine for a prime mover fueled with pipeline gas. While reciprocating engines are cheaper to install, they require more maintenance than other prime movers. They also have higher emissions than other prime movers and are noisier. When they are used, it is often in conjunction with a reciprocating compressor.
Electric motors are an alternative to prime movers fueled with natural gas. Because electric motors are quiet and have no emissions, they are often used in more densely populated areas where there are concerns about noise or air quality. They are also used when quick start/stop is required, or where large variations in compressor speed are needed. Use of electric engines is sometimes restricted in rural areas if there is a lack of electric service availability. Due to the cost of electricity, they are typically more expensive to operate than gas-fueled compressors.