I'm assuming you're talking about fractionation. In tray design, % flooding normally refers to jet flooding. In a tray, vapor and liquid are actually mixed in a "frost." When the vapor velocity is too high, this frost takes all the space beetween trays producing flooding. Now, % flooding could refer to downcomer flooding, which happens when the downcomer doesn’t have the capacity to handle the liquid.
The relationship between foaming and flooding is that foaming services promote flooding because foam affects the dynamics of the liquid-vapor frost. In foaming services, the tray designed plays with the pressure drop to balance capacity and flooding.
I don’t know what system factor is; maybe it’s a vendor parameter.
System factor is simply a technical term for safety factor or allowance for foaming. Basically it's a way of reducing velocity and allowing for more "foamy" fluids to settle down and not rise up to the next tray. Check out Kister - it's well documented.
