A rotary valve comprising a rotor shaft support assembly for maintaining a rotor shaft 5 in a level orientation when the rotor shaft is supported at a single end only. The rotor shaft support assembly (101) comprises a removable casing end plate (102) and a bearing assembly (106) for supporting an end portion of the rotor shaft (104) inserted into the rotor shaft support assembly (101) and through a rotor shaft aperture (105) of the removable casing end plate (102), and is adjustable to correct any deviation of 10 the pitch of the rotor shaft (104) from a level orientation relative to the removable casing end plate (102) when the rotor shaft (104) is supported at a single end only by the rotor shaft support assembly (101) with the inserted end portion of the rotor shaft (104) supported within the removable casing end plate (102) and the bearing assembly (106).