|Fig. A: Typical flanged-end butterfly valve|
The butterfly valves have a low-pressure drop and high-pressure recovery factor. They are suitable for low-pressure drop applications. These valves are extensively used in large water transmission, distribution, and cooling water lines.
Construction of a Butterfly Valve
|Fig. B: Wafer butterfly valve|
|Fig. C: Butterfly valve - welding end on one end|
Types of Butterfly Valves
Low Pressure or Concentric Butterfly Valves
High-Performance or Eccentric Butterfly Valves
Advantages of Butterfly Valves
1. The compact design requires considerably less space, compared to gate, globe, or other valves.
2. Light in weight.
3. Quick acting; as a quarter-turn valve, it requires less time to open or close.
4. It is available in large sizes, ranging from NPS 1¹⁄₂ (DN 40) to over NPS 200 (DN 5000).
5. They have low-pressure drop and high-pressure recovery.
6. Provide bubble-tight service.
Disadvantages of a Butterfly Valve
2. Throttling is restricted to a 30- to 80-degree disc opening. Location of valve, pipe routing, free, and closed discharge are to be considered while using a butterfly valve in a throttling application.
3. Cavitation and choked flow are two potential concerns.
4. The disc movement is unguided and affected by flow turbulence.
Typical Applications of Butterfly Valves
1. Cooling water, air, gases, and other similar applications, such as fire protection, circulating water, etc.
3. Food processing, chemical, and pharmaceutical services
4. Slurry and similar services
5. High-pressure and high-temperature water and steam services
6. Throttling service involving low differential pressures, as in cooling water or air supply systems
7. Vacuum service
Application Considerations for Butterfly Valves
● Orient the valve shaft in the same plane as the elbow or the pump outlet configuration. When there is more than one component on the upstream side of the valve, then the component adjacent to the valve is to be considered in determining the valve-shaft orientation.
3. Butterfly valves are essentially bidirectional. In the case of high-performance butterfly valves, and sometimes in the case of low-pressure and low-temperature butterfly valves, the valve design may require more actuating torque to open or close the valve when the flow is reversed. In such cases, the valve manufacturer must be contacted to ensure that the valve is designed and the actuator is sized for flow in both directions.