<p>Disclosed is a plug valve (10a) adapted to be placed in a chamber or vessel containing fluidized particles to control flow of the fluidized particles between the chamber or vessel and the open end of a conduit which has a contained purging system in a sealed space between the valve stem (14a) and guide tube (12a) effective to keep the fluidized particles out of the space. A purging medium is provided under pressure to the sealed space as a backup and only purges the space of fluidized particles which enter it due to leakage of one or both of the stuffing boxes (36). Other features of the plug valve are described. <IMAGE></p>
