Pneumatic three-way flange ball valve can be divided into L type and T type. The L-type three-way ball valve is used to switch the flow direction of the medium, which can make the two mutually perpendicular channels communicate. Three-way ball valves generally adopt a two-seat structure, but can also adopt a four-seat structure. The four-seat sealed three-way ball valve has beautiful appearance, compact and reasonable structure. It can not only switch the flow direction of the medium, but also make the three channels communicate with each other. At the same time, it can also close any channel to connect the other two channels for flexible control. Confluence or divergence of media in pipelines.