The compressor surge limit is not fixed with respect to any one measured variable such as compression ratio or pressure drop across the flow meter. Instead, it is a complex function that is dependent on the gas composition, RPM, suction temperature, and pressure. A closed loop PI controller would be unable to prevent surge during large or fast disturbances. Therefore, such a controller would be
. unable to stop surge. Rather, the controller would simply cycle the recycle valve open and closed in response to successive surge cycles.
