An axial flow pump, or AFP, is a common type of pump that essentially consists of a propeller in a pipe. The propeller can be driven directly by a sealed motor in the pipe or mounted to the pipe from the outside or by a right-angle drive shaft that pierces the pipe.
The main advantage of an AFP is that it can easily be adjusted to run at peak efficiency at low-flow/high-pressure and high-flow/low-pressure by changing the pitch on the propeller (some models only).
These pumps have the smallest of the dimensions among many of the conventional pumps and are more suited for low heads and higher discharges.
An application example of an AFP would be transfer pumps used for sailing ballast. In Power Plants they are used for pumping water from a reservoir, river, lake or sea for the refrigeration line. In chemical industry, they are used for the circulation of large masses of liquid, such as in evaporators and crystallizers. In sewage treatment an AFP is often used for internal mixed liquor recirculation (i.e. transferring nitrified mixed liquor from aeration zone to denitrification zone).