Pneumatic Butterfly Valve
Pneumatic butterfly valves use the rotating ability of one disc to make the seal. Like other internal pneumatic seals, the housing bore contains the disc that meets the gasket or seal at the seat, the actual point of contact. Most
butterfly valves are constructed from a metal such as
stainless steel or
cast iron while others are made of plastic. The diameter of these valves can be as small as a few inches to as large as a few feet because they are used in a variety of situations. Pneumatic butterfly valves are typically used with pressurized air but other kinds of butterfly valves are designed to control water flow, like
AWWA valves, or fluids under very high pressure such as triple offset butterfly valves. Pneumatic butterfly valves are used with equipment that uses compressed air, ventilation applications and other scenarios where fast and complete shutoff is beneficial.
Pneumatic butterfly valves work the same way as other standard butterfly valves. The round disc is centrally mounted on a shaft, or stem, that runs through the center of it as the axis around which the disc rotates. When the valve is open, the disc lays parallel to the direction of the air flow; the disc is not thick enough to greatly inhibit the current yet is strong enough to shut tightly when the control lever or wheel is moved to the closed position. These seals do not perform well in high pressure applications and are therefore used mostly with lower pressures. Pneumatic butterfly valves are able to complete the seal when working at high operating speeds as long as the pressure is not also high. Another advantage is that unlike other valves, butterfly valves do not trap volumes of liquids or gases between valve components because there is only one part that creates the seal and the flat disc has no space to hold any fluid. There are two main kinds of pneumatic seals: rotary and reciprocating. Pneumatic butterfly valves are rotary seals because they contain a single acting seating disc that seals in one direction whereas reciprocating seals have at least two agents, one for each direction of the seal.
