Compressor surge is an unstable operating condition where flow through a centrifugal or axial compressor reverses direction momentarily due to insufficient forward flow at a given discharge pressure. This cyclic flow reversal creates violent pressure pulsations, vibration, and rapid temperature fluctuations that can cause severe mechanical damage within seconds. Anti-surge control systems monitor operating conditions and modulate recycle valves to keep compressors operating safely to the right of their surge limit line.