Roman Bershader, Independent Compressor Consultant, USA, details the best practices for compressor surge and choke protection in the LNG industry. ver the past four decades, LNG has established itself as the preferred fuel and energy source around the world. As demand for cleaner natural gas, replacing solid and liquid fossil fuels, continues to grow, emission standards will tighten in the long-term, requiring development and innovation in the LNG industry. Compressors play a central role in the transportation, processing, and liquefaction of natural gas, having a significant impact on the overall performance of LNG plants and production efficiency. Improvements in compressor control and protection, which have remained largely unchanged, can reduce energy consumption, resulting in lower emissions. Dynamic compressors used in the LNG industry have very different characteristics depending on licensed technology and plant capacity. Regardless of size and design, the operation of any dynamic compressor is limited by severe unstable conditions, known as surge, at relatively low flowrates; and at relatively high flowrates known as choke or stonewall. Both conditions must be considered when designing the control system so that they can be prevented. Due to the severity of surge and the much higher likelihood that compressors will operate at relatively low flowrates, this issue has received more attention. If the choke phenomenon is not as severe as surge, prolonged operation in the choke zone is not only very ineffective but can also damage the compressor. Compressors are usually tested for
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