Abstract: A valve assembly has a valve body (10) which houses a pivotally mounted valve closure member (14) in the form of a valve closure flap secured to upper and lower spindles (16, 17). The valve housing is formed from two sections (20, 22) which are releasably secured together by means of an annular clamp (24) which engages with a peripheral upstanding rib (36) formed by the alignment of a flange (34) on one face of each of the valve housing sections.The valve closure member is located in the vicinity of the junction of the two valve housing portions. The provision of a clamp permits the valve assembly to be dismantled extremely quickly in the event of service or repair of the valve assembly.