In a high pressure ball valve including a valve body having coaxially aligned inlet and outlet ports, a control chamber between said ports and a bonnet aligned with the control chamber, a ball in the closure chamber having a cylindrical passageway therethrough and rotatable between an open position where the passageway is coaxially aligned with said inlet and outlet ports and a closed position where the passageway is at right angles to the axis of the inlet and outlet ports,BALL VALVES annular seats within said body and aligned with said inlet and outlet ports guidably supporting said ball, and a stem in the bonnet interconnected to said ball such that the ball floats between said seats, Ball Valvesthe improvement being in said seats each of which comprise a molded plastic core having a heat deflection point of at least 400 degrees F. and elastomeric sealing means bonded to said core to seal between the ball and body, said core having a spherical ball engaging face of the same radius as the ball with a recess intermediate the opposite edges of the face, Ball Valvessaid ball engaging face defining a spherical volume, said elastomeric sealing means including a seal in said recess to seal between the seat and ball, and said seal including a convex portion disposed within the spherical volume defined by said ball engaging face and a concave portion disposed outside the spherical volume defined by said face, said concave portion being disposed on the side of said convex portion toward the center of said seat.

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