The main advantages of the butterfly valve are simple structure, small size, light weight and low cost. The pneumatic butterfly valve is particularly prominent. It is installed in a dark tunnel at high altitude and is controlled by a two-position five-way solenoid valve. It is easy to operate and can also adjust the flow medium. The fluid resistance is small, the effective flow area of the medium and large diameter pneumatic butterfly valve is large when fully opened, and the opening and closing is quick and labor-saving. The opening and closing of the disk can be completed by rotating 90 degrees. Because the media force of the disk wrench on both sides of the shaft is nearly equal, The direction of the generated torque is opposite, so the opening and closing torque is small, and good sealing can be achieved under low pressure. The butterfly valve sealing materials include nitrile rubber, fluorine rubber, edible rubber, and PTFE lined so that the sealing performance is good. Among them, the hard sealing disc The valve is a soft and hard laminated metal sheet with the major advantages of metal hard seal and elastic seal, and it has excellent sealing performance regardless of low temperature.