SEI" Double Disc valves were designed to for on/off service in venting and conveying lines on high pressure pneumatic conveying applications. The design is rugged and clean operating. The Double disc valve ha metal to metal sealing to reduce wear in venting and discharge applications. The internal linkage drives the two spring loaded disks against the lapped body endplates. The disks move along a unique path and rotates with each stoke of the air cylinder which distributes the wear evenly and extends the life of the disks and endplates. "SEI" Double.