Compressor stations are facilities located along a natural gas pipeline which compress the gas to a specified pressure, thereby allowing it to continue traveling along the pipeline to the intended recipient.
Frequency of Compressor Stations – The total number of compressor station facilities required to move product varies depending on the region and conditions. Generally compressor stations are located about every 40-70 miles along the pipeline.
Operating Pressure of the Pipeline – There is a wide variation in the pressure within a given section of pipeline compared to other pipelines in other areas. The typical pressure may range anywhere from 200 psi (pounds per square inch) to 1,500 psi. This wide variation is also due to the type of area in which the pipeline is operating, its elevation, and the diameter of the pipeline. Because of the change in the environment, compressor stations may compress natural gas at different levels. Supply and demand can also be a factor at times in the level of compression required for the flow of the natural gas.
Liquid Separation and Filtering at Compressor Stations – Compressor stations typically include scrubbers, strainers or filter separators which remove liquids, dirt, particles, and other impurities from the natural gas. Though natural gas is considered “dry” as it passes through the pipeline, water and other hydrocarbons may condense out of the gas as it travels. Thus compressor stations will also remove these impurities from the gas so that they can be disposed of or sold as desired.
Compressor stations include several key component parts, the primary being the actual compressor unit. The main parts include:
Compressor Unit – The compressor unit is the piece of equipment which actually compresses the gas. Some compressor stations may have multiple compressor units depending on the needs of the pipeline. The compressor unit is a large engine which typically works in one of three ways:
Turbines with Centrifugal Compressors – This type of compressor is powered by a turbine to turn a centrifugal compressor and is powered by natural gas from the pipeline itself.
Electric Motors with Centrifugal Compressors – This type of compressor also utilizes centrifugal compressors to compress the gas; however, instead of being powered by a natural gas fueled turbine, they instead rely on high voltage electric motors.
Reciprocating Engine with Reciprocating Compressor – This type of compressor uses large piston engines to crank reciprocating pistons located within cylindrical cases on the side of the unit. These reciprocating pistons compress the gas. These engines are also fueled by natural gas.
Filters and Scrubbers – As mentioned above another component of compressor stations are filters and scrubbers which remove water, hydrocarbons, and other impurities from the natural gas.
Gas Cooling Systems – When the natural gas is compressed its temperature rises. This is usually offset by having the gas travel through cooling systems which return it to temperatures that will not damage the pipeline.
Mufflers – Mufflers are typically present to help reduce the noise level at compressor stations. These are especially important if the compressor station is located near residential or other inhabited areas.
Compressor stations enable the natural gas itself to travel through the pipelines which is crucial to the natural gas transport system. They also allow the gas to be rerouted into storage areas during periods of low demand. In addition, compressor stations are often accompanied by PIG launchers and PIG receivers which are vital for the maintenance and efficiency of the pipeline. They even include many safety features allowing the pipeline and station to function safely.