Abstract: A tubular slow speed drag or aero mechanical conveyor assembly (1) for transporting particulate material, includes a tubular valve (11) positioned in line with conveyor tubes (1) of the assembly and rotatable relative thereto. The valve (11) has at least one elongate aperture (21) through which particulate material can leave the assembly (1) and means (24,25) are provided for sequentially rotating the tubular valve (11) between positions in which the at least one aperture (21) is in the open or closed position of the valve (11). In one arrangement the rotation imparting means comprises an air cylinder (23) operable to impart linear movement to a gear rack (24) which meshes with and imparts rotational movement to an annular gear wheel (25) carried by the tubular valve (11).