A butterfly valve is a type of pipeline valve in which the shut-off or regulating element has the shape of a disk. The flow is blocked by turning it. The disk is positioned perpendicularly or at an angle to the direction of the working medium flow. Butterfly valves are one of the most modern and progressive types of valves. They have important advantages: small construction length and weight; simple design, small number of parts; ease of repair, possibility of quick replacement of sealing elements; possibility of use for large pipeline diameters. They are used as shut-off valves in process systems: cold and hot water supply, chemical water treatment shops of thermal power plants, state district power plants and boiler houses, on lines transporting aggressive environments and petroleum products.