COMPRESSION ENERGY MANAGEMENT LLC
Compressor controls and safety are almost always intertwined. While the main purpose of a control function is to maintain compressor operation within the safe limits, the role of a safety function is taking compressor and the surrounding process to a safe state should such control function fail to prevent an unsafe operational condition.
Usually controls failure manifests itself via a safety system action. For example, if surge control cannot keep compressor away from surge, a surge protection safety function will have to activate by quickly putting compressor on full bypass and likely shutting it down completely. A well-designed and diagnosed control function warrants high availability of the compressor for uninterrupted operation and thus reduces the demand for a safety function.
Surge control system one of the key components of the compressor control system. It includes several field instruments, signal conditioning, a usually sophisticated anti-surge control function, and one or more anti-surge valves. Some process equipment, such as heat exchangers, knockout drums, check valves affect reliability and performance of anti-surge control system.
Surge protection system must be capable of detecting and counting the surge cycles when compressor surge cannot be avoided. Improper counting of such cycles may result either in premature safety action or in not meeting the maximum safe number of cycles specified by the compressor OEM.
Compressor control system usually includes several controllers, each having its own manipulated variable. Each such manipulated variable affects the efficiency of the compressor and the adjacent process, The control system design should account for optimizing the efficiency by coordinating control actions between those controllers. Good operational example requiring such coordination are energy management of multiple networked compressors, and multi-valve controls in a multi-stage refrigerant compressor.
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