Engineering/Design/Development >> Operating Principles, Slung Vaned Pumps

Operating Principle of Weldon Slung Vane Pumps (for cammed vane pumps, click here)
The Weldon “Slung Vane” Pump was developed in the early 1980’s to meet the need for a rugged, high out-put, high pressure pump to supply fuel to racing engines with electronic fuel injection. Due to its high flow rate, ability to go to pressure and extreme durability, the Weldon Slung Vane pump has found its way into a wide variety of applications in racing, aerospace and industry.

The pump element consists of a rotor, 4 or more vanes, a ring and (in Weldon billet line and traditional line slung vane pumps) a center pin. The ring is offset to one side and the rotor slotted to accept the vanes which, as the rotor turns, are forced out by centrifugal force against the ring which exerts centripetal force to keep them moving in a circular path. Due to the offset of the ring, the vanes also move in and out of the rotor as it spins. The area created by the ring offset between the inlet and outlet of the pump is referred to as the swept volume of the pump.

Fluid flows into the inlet of the pump due to the lower pressure created inside the pump as the rotor and vanes rotate within the ring creating suction. Atmospheric pressure then pushes liquid into the pump as the pressure inside the pump is reduced by the pumping element.* The liquid is then picked up by the vanes and carried around to the discharge (outlet) side of the pump. Just after the outlet, the rotor is in very close proximity to the ring (See seal area) leaving no room for the liquid to go anywhere other than through the outlet of the pump.

The pressure capability of a vane pump is determined by several factors including: the materials it is constructed of, the internal
clearances between the parts, the seal of the vanes to the ring, and on electrical pumps, the quality of the motor. Weldon vane pumps are constructed of heat treated high speed steel with close internal clearances. Our electric pumps employ high quality ball bearing motors. Remember the center pin mentioned earlier? Weldon slung vane pumps have a hardened steel pin attached to the pump cover which extends down into a counterbore in the rotor. The pin contacts the back edge of the vanes, mechanically forcing them to extend as the rotor turns. This positive method of vane extension insures that the vanes will move outward and
cannot be “stuck” in the rotor by varnish deposits from the fuel.

*That is why unvented fuel tanks can cave in from the external atmospheric pressure or, if the tank is strong enough, fuel ceases to flow into the pump.