Abstract: In a submerged pump system for pumping liquid from a well or vessel the vertical pipe through which the liquid is pumped by a submerged impeller pump is typically fitted at its upper end with an air valve. The air valve vents air from the pipe to atmosphere upon pump start up, then closes so that only water passes through a check valve to a pipe system and subsequently allows air to re-enter the pipe when the pump stops. A special throttling valve associated with the air valve restricts the outward rate of flow of air to atmosphere to thereby reduce the rate of the rising liquid and thus the shock of this liquid on the air valve and on the check valve but allows essentially unrestricted re-entry of atmospheric air to thereby allow the vertical pipe to fill with air rapidly. One form of throttling valve includes a valve plug mounted for axial movement into and out of a vent opening and spring-biased into the opening.

Abstract: A float-operated air release valve for a liquid transport system includes an internal float which has a downwardly concave impact surface arranged to be struck by any liquid entering the valve chamber thereby reducing the response time of the valve and rapidly closing the valve outlet before liquid can be discharged from the outlet. The impact force on the float can be enhanced by providing a depending flange around a substantial portion of the periphery of the concave surface.