Functions of foot valves:
A foot valve is basically a check valve fitted to the end of a suction pipe leading to a pump. Its purpose is to keep fluid trapped in the suction pipe when the pump stops. thus maintaining a suitable prime for the pump. When the pump restarts. the suction created opens the valve, giving full flow to the pump inlet.
Foot valve is used to maintain hydraulic pressure within the pipeline to keep the water flow in accordance with given setting.
The foot valves usually come with surge blocks. It is used to remove residues which may block the smooth flow fluid inside the valve
Types of Foot valves
The poppet assembly consists of a plastic tripod which can be displaced along a bore above the seat valve. The travel of the poppet is controlled by a stop on the end of the poppet legs acting as supports for the return spring shouldered onto a washer. This spring ensures that the valve will work in any position. The main characteristics of this design are low head losses with good sealing provided by a nitrile rubber 0-ring.
This is a simple ball valve guided by an inclined cylindrical chamber and seating on an O-ring. The ball is displaced laterally along its chamber with the inward flow, but it runs down the chamber onto its seat when the flow rate decreases. [t is particularly suitable for use with contaminated waters or more viscous fluids.
Membrane foot valves consist of a cylindrical rubber membrane fitted inside a steel strainer. When there is a suction developed at the strainer, the membrane is displaced to allow fluid to flow through the valve. When back-flow conditions exist, the cylindrical membrane closes the apertures in the valve strainer, thus closing the valve,