The ventilation butterfly valve, made by steel - plate welding, features short dimensions, light weight and easy installation. With a small driving torque, it opens and closes flexibly and is easy to operate. An oil - sealed retaining ring on the valve body ensures minimal leakage with no visible gap between sealing pairs. A large expansion gap between the butterfly plate and valve body prevents jamming from thermal expansion and contraction. It can be fitted with various actuators like manual, worm - gear, pneumatic and electric ones. Widely used in industrial pipelines of metallurgy, chemical, power, building materials and mining sectors, it controls or regulates gas media.