A Method for Safely Reducing Surge Margins in Centrifugal Compressors
Surge is an unstable condition that can occur in centrifugal compressors during low flow operations. Surge causes large transient forces on rotating components and can seriously damage a compressor as well as disrupt flow deliveries. Since centrifugal compressors are becoming increasingly common in the natural gas industry and because flexible operations are increasingly required, it is essential to be able to safely, reliably, and economically avoid surge in centrifugal compressors. This paper presents the background in terms of technology and previous GMRC research results and summarizes the new approach. Data from tests in small and moderate size laboratory compressors will be presented. This method is also supported by data from literature and CFD modeling, which will be presented. Plans for field testing, development of a prototype controller, and demonstrations of direct surge control with reduced surge margins will be presented. Benefits of direct surge detection and control in terms of reductions in fuel gas, wasted energy, and calibration and testing time, and savings in operating dollars will be summarized.