The Q648/649F(PPL, M)-16 pneumatic three-way flange ball valve produced and sold by Huadian Pump Valve Company can be divided into L type and T type. The L-type three-way ball valve is used to switch the medium flow direction and can connect two channels perpendicular to each other. Three-way ball valves generally adopt a two-seat structure, or a four-seat structure. Four-seat sealed three-way ball valve has beautiful shape, compact and reasonable structure, which can not only realize the switching of medium flow direction, but also make the three channels communicate with each other, but also close any channel, so that the other two channels are connected, and flexibly control the merging or diversion of the medium in the pipeline.