Fan Surge Stall Limit
Surge Limit– The surge limit of a centrifugal fan is that point near the peak of the pressure curve corresponding to minimum flow rate at which the fan can be operated without instability.
Stall Limit– The stall limit of an axial fan is that point near the peak of the pressure curve at a particular blade angle corresponding to minimum flow rate at which the fan can be operated without separation airflow over the blades.
Stall occurs when angle of attack of fan blade (or aero plane wing) exceeds a certain value in relationship to air velocity.
Fan must not be operated in the surge or stall region, serious damage can occur
