As gas passes through a compressor, there are limitations on process, speed, power, and surge.
Flow instability occurs when the compressor cannot produce enough pressure head to overcome the downstream resistance. When the downstream demand decreases, flow rates can fall below the point of stable operation. Reversal of flow will occur if the downstream pressure becomes greater than the discharge compressor pressure. This fast, high energy action will be accompanied by a large breakdown of flow patterns within the compressor, as well as noise, vibration, and significant and costly damage.