Abstract: A ball segment valve comprise a valve housing (23) with a circular annular valve seat (28), a valve body (26) which has the shape of a spherical segment which is rotatable about an axis of rotation (49) which intersects the center of the sphere of which the valve body constitutes a segment, a rotating spindle (41) which extends through and is mounted in one side of the valve housing, and a journal bar (43).The rotating spindle and the journal bar are interconnected by a bow (42) in order to form together with the bow a continuous rotating unit (25).The journal bar is mounted in a cover (24) which covers a hole (64) in the other side of the valve housing, which hole is sufficiently large that the rotating unit can be introduced through the hole into its intended operating position in the valve housing and be fixed in this position by subsequent mounting of the cover.