A high pressure butterfly valve having a pressure actuatable valve element that is flexed by fluid pressure to enhance the sealing ability of the valve in direct proportion to the pressure of the fluid controlled by the valve.Cast Steel Valves The butterfly valve of this invention incorporates an annular seat element retained within the valve body by an upper valve actuating stem and a lower trunnion. A concavo-convex butterfly valve element is rotatably carried by the trunnion and valve actuating stem with the convex surface thereof facing upstream in the closed position. The valve element is capable of flexing responsive to application of fluid pressure in this manner as to expand the peripheral sealing surfaces thereof and enhance the mechanical sealing pressure as fluid pressure increases.Reducing Valves The butterfly element also floats relative to the trunnion and valve stem thereby allowing the valve element to float or self-align itself to obtain optimum sealing engagement as pressure is applied by the fluid controlled by the valve.BALANCING VALVES A preferred embodiment of the present invention may comprise a valve body having a relatively thin silhouette and may include either an integral one-piece body or a split body that may be disassembled by removing body bolts. The body may be provided with aligned opposed bores, one of which receives a trunnion for rotatably supporting a butterfly valve element and the other bore to receive a valve actuating stem capable of being mechanically interconnected with the valve element and being operative to impart driving rotation to the valve element for purposes of opening and closing the valve. The inner extremity of the trunnion may be of generally spherical configuration to adapt the same for bearing engagement with a socket formed in the valve element and being of generally spherical complimentary configuration. The ball and socket configuration of the mechanical connection between the trunnion and the valve element provides a universal journal to allow self-alignment of a valve element. Such self-alignment is also enhanced by an arcuate valve drive projection that is received within an arcuate socket defined in the valve element to provide nonrotatable driving connection between the actuating stem and the valve element. The arcuate drive connection is also designed to allow limited movement of the valve element downstream in the closed position thereof, thereby allowing the valve element to be self-aligning with respect to a valve seat assembly, removably secured by the trunnion and actuating stem within the valve body. The valve seat assembly presents a partially spherical surface of complimentary configuration with respect to the configuration of an annular sealing surface defined by the periphery of the butterfly valve element. The seat assembly carries a resilient sealing element, such as an O-ring, contained within an annular groove to establish optimum sealing engagement with the peripheral sealing surface of the butterfly valve element. The butterfly valve element may be concavo-convex configuration and may be relatively flexible with the convex surface thereof facing upstream in the closed position of the valve. As fluid pressure is applied against the covex surface of the valve element, the valve element will flex causing the annular sealing surface thereof to be urged radially outwardly thereby enhancing the forces of mechanical engagement between the sealing surface of the valve element and the working surface defined by the valve seat assembly. Mechanical forces applied by the pressurized fluid is transmitted directly to the valve seat assembly and is absorbed only to a limited degree by the trunnion and actuating stem mechanisms of the valve.

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