Patent ID: 8162288

Claim:
A composite butterfly valve comprising: first and second body halves each being of composite material, said body halves being secured together along a coupling plane to form a two-part valve body, said body having inlet and outlet flow passageways; a valve disk assembly disposed between said first and second body halves, said disk assembly having a valve disk and a valve stem having a longitudinal axis which lies in the coupling plane of the first and second body halves, said valve stem being within said valve disk along a central axis of said disk such that when said disk is rotated about said valve stem, the disk moves between an open position in which it faces across the flow path between the inlet and outlet flow passages so as to allow the passage of fluid therebetween and a closed position in which it faces along the flow path so as to block the passage of fluid therebetween; and a seal having a primary seal portion and a secondary seal portion disposed between the first and second body halves, the primary seal portion further having an internal surface for sealing against an outer surface of said disk, the secondary seal portion having a substantially triangular cross-section in a plane oriented perpendicular to the coupling plane.