A wafer-style butterfly valve is the most economical version and it is sandwiched between two pipe flanges. Easy installation, many connection options. Butterfly valves are used for on-off or modulating services and are popular due to their light weight, small installation footprint, lower costs, quick operation and availability in very large sizes. These valves can be operated by handles, gears or automatic actuators.
Butterfly valves possess many advantages over gate, globe, plug, and ball valves, especially for large valve applications. Savings in weight, space, and cost are the most obvious advantages. The maintenance costs are usually low Butterfly valves are especially well-suited for the handling of large flows of liquids or gases at relatively low pressures and for the handling of slurries or liquids with large amounts of suspended solids.
There are several types of end connections that allow for easy installation of these valves, but the most common are lug and wafer style, both fitting between flanges. Lug style butterfly valves are similar to 3-piece ball valves -they allow adjacent piping to be removed independently. This is achieved by using two different set of bolts, with each attaching the pipe flanges at either end of the valve body. With this connection to the valve, the ends of the pipe sections can be removed and replaced independently. Installation is also fool-proof as the number of lugs make centering the valves easy.