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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.

Advantages of Butterfly Valves

The following summarizes the 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

1. Throttling service is limited to low differential pressure.

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

Concentric or low-pressure and low-temperature butterfly valves, the high-performance

butterfly valves, cover a wide range of applications. These applications include:

1. Cooling water, air, gases, and other similar applications, such as fire protection,

circulating water, etc.

2. Corrosive services requiring lined valves

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

1. It is noted that the disc of butterfly valve is unguided; therefore, operability of the valve

is affected by the flow characteristics. A butterfly valve should not be located just

downstream of a source of flow turbulence, such as pump-discharge nozzle, elbow,

control valve, or a tee-branch. To minimize the effects of flow turbulence on the valve,

attempts should be made to

● Locate the valve 4 to 6 diameters downstream of the source of flow turbulence.

● 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.

2. When used in throttling applications, an attempt must be made to provide an adequate

straight length of pipe downstream of the valve to allow the flow turbulence to subsidize

prior to diverting the flow.

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.