A valve comprising a casing having a passageway therethrough for flow of fluid and a tapered bore intersecting the passageway, a tapered plug rotatably mounted in the tapered bore adapted to block the passageway in valve closed position of the plug and the plug having a port adapted to connect and be in communication with the passageway in valve open position,GATE VALVES the plug and casing providing chambers at opposite ends of the tapered plug, means for connecting the chambers to the port to dynamically balance the plug within the casing when the plug is partially or fully open, a biasing means is provided in the casing to axially bias the tapered plug in the direction of the larger end of the plug.
A balanced plug valve immune to interference lockup comprising: a casing; a conical tapered first bore formed in said casing along an axis; Water Power Control Valvesa flow passage formed in said casing transverse to said axis and having inner ends communicating with the tapered bore and outer ends adapted to be connected to a fluid flow line; Plug Valves a cylindrical second bore formed in said casing coaxial with the tapered first bore adjacent the smaller end thereof; a valve stem rotatably disposed in said second bore; a conical tapered plug adapted to be coaxially received in said first bore, said plug in a valve closed position having surfaces blocking said flow passage, said plug having a port formed therethrough transverse to said axis adapted to be fluidly connected to the inner ends of said passage when moved to a valve open position; means coupling said stem to said tapered plug whereby the latter may be rotated between said valve open position and said valve closed position by rotation of said stem; an end cap secured to said casing closing the large end of said tapered bore whereby the tapered plug in operative position defines with the casing and end cap a base chamber adjacent the larger end of the plug and an apex chamber adjacent the smaller end of the plug; an adjusting member threadedly extending through said end cap along said axis adjustably axially engaging the larger end of the plug to thereby establish an adjustable axial stop to limit movement of the plug toward said base chamber and establish a predetermined clearance relationship between said plug and tapered bore; a first passage formed in said tapered plug extending between said port and said base chamber in spaced relation to said axis; a second passage formed in said tapered plug extending between the apex chamber and said port along said axis whereby both chambers are communicated to said port such that the pressures therein are substantially identical as the valve moves toward the open position, the force differential acting toward the apex chamber during opening providing a slightly unequal force due to secondary forces including pressure transients caused by pressure rise in the port so that the pressure seen by the interface between the plug and the casing lags the pressure seen by the port and the first bore thereby resulting in a force vector tending to force the plug towards the apex chamber, such forces being at their maximum value when the valve is at its fully opened position; a helically wound compression spring disposed along said axis in said apex chamber biasing said plug along said axis away from said apex toward said adjusting member so as to maintain the axial position of the plug within the casing to counteract the gravitational force due to physical orientation of the plug and said force vector of said pressure transients thereby avoiding lockup after stabilization of any pressure or temperature transients.

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