thereof which will mate with a corresponding generally planar face of valve body 29 note that in the preferred embodiment the middle region of face 37 is ground slightly concave leaving a slight gap between the planar sections of the valve bodies to enhance the tight fitting perimeter seal between valve body 27 and valve body 29 to prevent dust or other contaminants from getting on face 37 so that it is essentially free from powder from container ports 23 and 25 planar section 35 is secured to pivot shaft 39 which as illustrated is hemicylindrical to mate with a corresponding hemicylindrical pivot shaft of adjacent butterfly valve body 29 to form a cylindrical pivot shaft which is rotatable between the container ports a pair of handles such as handle 41 are secured to pivot shaft 39 handle 41 serves a dual function in the preferred embodiment the first function is to provide a convenient handle to grasp and pivot the butterfly valve bodies the second function is to provide locking engagement with a radially projecting locking tab discussed below of the corresponding locking member 31 specifically in this embodiment locking is provided by having the locking member engage locking surface 43 see fig9 and 10 on the bottom surfaces of the horizontal flange of handle 41 similar locking surfaces are provided on both handles of each butterfly valve body an elastomeric ring such as elastomeric ring 28 see fig5 lines the inner wall of port 23 to provide a snug seal with butterfly valve body 27 a similar seal is provided between valve body 29 and port 25 referring to fig6 and 7 locking member 31 is illustrated including annular ring member.