Butterfly valves
Butterfly valves can be either Wafer (connection with four ears, two upper and two lower, centred in the valve body casting), Lug (connection with threaded annular ears in the valve body casting) or Bi-flanged (connection with PN-dependent drilled flanges in the valve body casting). The Lug model is used for mounting on flanged connections, through the threaded hole pattern body. The Wafer model is used for mounting between two counterflanges.
Since the seal is composed of an elastomer, the Wafer and Lug models cannot withstand high temperatures and pressures. For very large diameters, flanged butterfly valves are recommended.
The butterfly valve body and disc can be made of grey cast iron or spheroidal cast iron, all parts that come into contact with water are protected against 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 unsuitable for adjustment. It is recommended for vacuum sealing as it has a perfect bidirectional seal with no leakage. For small diameters, manoeuvring can be done directly by hand with the handwheel or lever, for larger diameters or very high pressures, manual handwheel gearboxes or electric or pneumatic actuators are required.
In the case of high pressures, butterfly valves are often equipped with a small bypass with a tap, with which, in the closed position, the pressures on the two faces (upstream and downstream) of the disc can be balanced in advance, making it easier to open the valve. Butterfly valves are usually used for: sea water, industrial water, drinking water, waste water, 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 from one side (horizontal shaft). Maximum operating temperature 150°C.
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