The body and disc of the butterfly valve can be made of grey cast iron or ductile cast iron, all parts that come into contact with water are protected from corrosion. When the valve is in the open position, there may be small localised pressure drops, while there may be strong turbulence and vibration in the case of partial closure. Therefore, it is not suitable for regulation. It is recommended for vacuum sealing as it has a perfect bi-directional seal and is leak-free. For small diameters the manoeuvres can be done directly by hand with the handwheel or lever, for larger diameters or for very strong pressures, it is necessary to have manual handwheel reducers or electric or pneumatic actuators.
In case of high pressures, butterfly valves are often equipped with a small bypass with tap, with which, in the closed position, the pressures on the two faces (upstream and downstream) of the disc can be balanced beforehand, making it easier to open the valve. Butterfly valves are usually used for: seawater, industrial water, drinking water, wastewater, fuel, air and other inert fluids depending on the type of elastomer. They can be mounted, from DN40 to DN250, on both sides. From DN300 to DN1200 operate on one side (horizontal shaft). Maximum operating temperature 150°C.