Quarter Turn, On/Off Valve
While butterfly valves can be used to limit flow, they are typically used as on/off valves. Most companies will publish “Cv” rates for butterfly valves showing the rate of flow at various disc angles.
Face to Face
Butterfly valves are unique in that, while the outer diameter (OD) of the valve increases with the pipe diameter, the face to face (depth or thickness of the valves) remains somewhat constant. The face to face increases from 1.5-6” (38-152mm) as the pipe diameter increases from 2-24” (40-600mm). Ball, Plug, Globe, and Gate valves can range from 7-50” (178-1270mm) as the pipe diameter increases from 2-24” (40-600mm).
Advantages and Disadvantages of using a Butterfly Valve
Advantages
- In the bigger sizes, >2” (DN50), butterfly valves are lighter, smaller, and cheaper than competing Globe, Gate, Ball, and Plug valves.
- Butterfly valves most often compete against Ball valves in the smaller sizes, <4” (DN100).
Disadvantages
- Butterfly valves are not “piggable”, because the disc intrudes into the pipeline.
- Pigging a pipeline occurs when you send a device (often foam) through the pipe to clean it.
- The disc will reduce the amount of flow going through the pipeline. Other types of valves (Ball, Gate, etc.) do not have this issue.
