Types of Butterfly Valves
Low Pressure or Concentric Butterfly Valves
In low pressure and low temperature designs of a butterfly valves, the disc and shaft axes are concentric. In open position, the disc divides the flow in two equal halves, with the disc in the middle and parallel to the flow. These valves are provided with resilient seats. These valves are available as lined or unlined. Most commonly used lining and seating materials include: Buna N, Neoprene, Fluorcel, Hypalon, EPDM, TFE, Viton, among others. The application temperature is limited by the temperature capability of the resilient material. These valves are generally produced in Classes 150 and 300.
High-Performance or Eccentric Butterfly Valves
The disc in high performance butterfly valves is offset from the center of the valve, and the shaft is also offset from the center of the disc. The offsets provided allow the disc to move eccentrically uninterrupted away from or toward the valve seat. Thus, the uninterrupted motion of the disc until it seats against the valve seat prevents unwanted wear and tear of the valve seat and disc due to friction and rubbing of the seating surfaces. The high-performance butterfly valves are used for on-off and throttling services. Some butterfly valve manufacturers produce high performance butterfly valves with triple offset, which enhances their actuation and leak tightness.
Applications of Butterfly Valves
- Cooling water, air, gases, and other similar applications, such as fire protection, circulating water, etc.
- Corrosive services requiring lined valves
- Food processing, chemical, and pharmaceutical services
- Slurry and similar services
- High-pressure and high-temperature water and steam services
- Throttling service involving low differential pressures, as in cooling water or air supply systems
- Vacuum service