"Axial Fan" 'tack' phenomenon not only affects the normal operation of a parallel arrangement, but may also cause vibration device, motor load or overload and other adverse consequences. Therefore, we should try to avoid instability in parallel fan operation. Such as low-load operation should be used for single wind turbine operation; can also take appropriate measures to prevent the adjustment method "wind rush" phenomenon. Pumps operating in parallel there are similar "water grab" phenomenon, in addition to the hazards, may also cause the pump cavitation, a greater harm.