"r-square” flush bottom valves are designed to provide drainage and dead space free shutoff for reactors, vessels and storage tanks. The dead space free shutoff is accomplished by placing the valve seat flush with the bottom of the vessel. This eliminates any buildup of product within the vessel nozzle itself. Advantage of disc type is short stroke for openclose operation. Design options are open on discharge side for nozzle fitting or flange end. Air cylinder operation is usual for saving labor.