Abstract: A knife gate valve for regulating particular material flow in a pneumatic or vacuum covering system. An actuated, reciprocative gate is mounted within the valve housing on guide bars which define the path of gate movement between open and closed positions. The guide bars seal the side edges of the gate and the adjacent portion of the lower gate surface. A seal plate is loaded by a pair of o-rings to seal against the top gate surface. Transverse seals are accessible for cleaning or replacement through releasable side seal assemblies. Fluid ports allow the transverse seals to be lubricated in place or air purged. The guide bars are cleaned by the gate during closure with the opposed gate surfaces being cleaned by the seal plate and an underlying wiper bar during gate movement. The cleaning actions cooperate with dynamic loading of the various seals to assure a proper seal about the gate upon closure.