There are three commonly used types of engines that drive the compressors and are known as "prime movers":
Turbine / Centrifugal Compressor
This type of compression unit uses a natural gas-fired turbine to turn a centrifugal compressor. The centrifugal compressor is similar to a large fan inside a case, which pumps the gas as the fan turns. A small portion of natural gas from the pipeline is burned to power the turbine.
Electric Motor/Centrifugal Compressor
In this type of compressor unit, the centrifugal compressor is driven by a high voltage electric motor. An electrified compressor may still require an air permit, as regulations vary by state an applicability analysis should be conducted whenever a compressor station will be constructed. However, a highly reliable source of electric power must be available and near the station.
Reciprocating Engine/Reciprocating Compressor
These large piston engines resemble automobile engines, only much larger. Commonly known as "recips," these engines are fueled by natural gas from the pipeline. Reciprocating pistons, located in cylinder cases on the side of the unit, compress the natural gas. The compressor pistons and the power pistons are connected to a common crankshaft. The advantage of reciprocating compressors is that the volume of gas pushed through the pipeline can be adjusted incrementally to meet small changes in customer demand.