Abstract: A sealing mechanism for a pair of conduits held together by means of one or more frangible connectors. Each conduit has a pivoted disc-shaped butterfly valve which is spring biased to a closed position. The butterfly valves are normally held open by a flat pivoted spacer, and are released when the frangible connectors are broken and the valves move away from the spacer. A mechanism for positively closing and latching the butterfly valves in a closed position is included in the valve assembly. The valves and the spacer together form a thin flat co-planar assembly when the valves are in their open position so as to minimize turbulence in the fluid passing through the conduits thereby reducing resistance to fluid flow to an absolute minimum.