Compressor Starts
Summary
Compressors are used throughout the natural gas industry to move natural gas from production and processing sites to customer distribution systems. Most compressors are fueled by natural gas and driven by combustion gas engines often equipped with small gas expansion turbine motors to start the engine. These motors initiate startup of the engine with expansion of pressurized gas across the starter turbine; that gas is then vented to the atmosphere. Natural gas is also commonly vented from the compressor during start-up so that the starter does not have to turn the compressor under load.
Description
Compressors throughout the natural gas industry are started and stopped as required to move gas from producing wells through the entire natural gas system to the gas distribution sector. Reciprocating compressors in non-electrified production and gathering facilities often use small gas expansion turbine motors to turn the engine until it starts. High-pressure natural gas stored in a volume tank is used to activate the starter motor or turbine and is then vented to the atmosphere. The amount vented is dictated by the pressure of the natural gas in the volume tank or pipeline and size of the engine or turbine. The starter spins the engine up to speed until combustion can sustain the rotation on its own and then the starter motor is disengaged. The process is analogous to starting an automobile engine which uses a battery powered electric motor (instead of a pneumatic turbine) to turn the engine until internal combustion is initiated. However, unlike an automobile, which has a clutch or automatic transmission neutral gear, gas compressor engines cannot be disengaged from the drive train (compressor), so the compressor is commonly vented to the atmosphere during start-up to eliminate the load on the engine. Centrifugal compressors are normally driven by direct coupled turbines which are commonly started with an expansion turbine motor similar to reciprocating engines. High pressure gas is directed through the compressor to turn (i.e., “roll”) the turbine up to a speed until it generates sustaining power. The gas used to turn the turbine is commonly emitted to the atmosphere.
References
Almasi, A., (2018, December 17). Considerations for reciprocating compressors for processing units. Processingmagazine.com. https://www.processingmagazine.com/pumps-motors-drives/article/15587660/considerations-for-reciprocating-compressors-for-processing-units
Brun, K., & Kurz, R. (Eds.). (2018). Compression machinery for oil and gas. Gulf Professional Publishing.
Sloley, A., & Schroeder, S. (2019, August 28). Treat your reciprocating compressor right. Chemicalprocessing.com. https://www.chemicalprocessing.com/articles/2019/treat-your-reciprocating-compressor-right/
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