Butterfly valves

Butterfly valve comprising a valve housing including a valve seat and a throttle arranged to be turned around a stem going through the valve housing between an open position and a shut-off position in which a seal face on the throttle is pressed against the seat in the valve housing, the seal face having two opposite, essentially spherical shaped sections intersected by a symmetry plane through the throttle coinciding with the torsional axis of the throttle, and two essentially conically shaped sections on each side of said symmetry plane between the two essentially spherical shaped sections, the essentially spherical and the essentially conical sections successively merging into each other, a curve around the circumference of the throttle having essentially the shape of a circle, and being the sealing line of the throttle said sealing line defining approximately a plane which is offset from said torsional axis, and a seat which is displaceable in the plane thereof so that the seat when the throttle is pressed against same essentially without sliding can adopt itself to the shape of said essentially circular curve extending around the circumference of the sealing face, and said seat can also adopt a proper orientation in the plane of said curve.