What is a butterfly valve?

A butterfly valve is a compact, cost-effective, quarter-turn, flow control device to regulate or isolate the flow of liquids, gases or solids in a pipeline. Its disc functions by rotating to either allow or block fluid flow. It gets its name from its disc, which resembles a butterfly.

Known for its lightweight design and minimal space requirements, a butterfly valve is a popular choice in various industrial applications. It offers lower installation costs compared to gate, globe or ball valves, making it ideal for large-diameter pipes. With fewer moving parts, it requires less maintenance and delivers reliable performance over time.

Butterfly valves are versatile and ideal for low- to medium-pressure systems where corrosion resistance and tight sealing are needed. They can be actuated manually or with pneumatic and electric actuators, depending on the application's needs. Their bi-directional flow capability and quick quarter-turn operation make them perfect for fast flow control, especially in emergency shut-off scenarios.

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How does a butterfly valve work?

A butterfly valve controls the flow with a quarter-turn operation. The valve's disc rotates 90 degrees to either block or allow flow. In the closed position, the disc is perpendicular to the flow, creating a tight seal. In the open position, the disc aligns parallel to the flow, allowing fluid, gas or solids to pass with minimal resistance. The flow rate can be controlled by choosing a disc angle between around 20 to 70 degrees.

Components of a butterfly valve

A butterfly valve is made up of few components that ensure efficient flow control across various industries. Here’s a brief overview of its main parts:

1. Body
The valve's body is the central structure that houses all its essential components. It is made from robust materials providing a secure and leak-free enclosure for the valve's internals. Most common body types are Wafer, Lug and double-flanged design.

2. Disc
The valve disc is the rotating part, controlling the flow of fluids. The disc’s material and design (centric or eccentric) are critical for performance, especially in corrosive or mid-pressure applications.

3. Shaft
The shaft connects the disc to the actuator and transmits rotational force.

4. Liner (seat bei eccentric valves)
The liner creates a tight seal between the disc and body, preventing leakage. Materials vary depending on fluid, pressure and temperature conditions.

5. Actuator
The actuator is used to operate the valve. Actuators can be manual, pneumatic, electric, or hydraulic.

Body types of butterfly valves

Butterfly valve bodies are designed to fit various piping flange connections and pressure requirements. The body type depends on the system's installation needs and the level of pressure the valve must handle.

1. Wafer
The wafer body fits between two flanges in the pipeline, held by bolts passing through the flanges along the body. It is a lightweight and most cost-effective option.

2. Lug
The lug body includes threaded holes (lugs) allowing it to be bolted to the flanges. It is commonly used where the valve may need to be removed without affecting the piping on either side.

3. U-section (double flanged)
The double flanged body offers maximum stability, with flanges on both sides for secure installation. It is held by bolts passing through the flanges and the body. This design is commonly used for larger valve dimensions.

Butterfly valve types

InterApp's range of centric butterfly valves features the PTFE-lined Bianca, along with the elastomer-lined Aquaria plus, Desponia, and Desponia plus. The range is completed by the double eccentric butterfly valve Elara, as well as the triple eccentric butterfly valve Titania

1. Centric (concentric) butterfly valves
Centric butterfly valves have the shaft positioned in the centre of the body, disc and liner. This design is cost-effective and ideal for low to medium-pressure applications but are not suited for high-pressure applications or operating under high differential pressure.

2. Double eccentric butterfly valves
The double eccentric valve presents two offsets, reducing friction between the disc and seat. This design enables high-pressure and high-temperature applications. Commonly used in industries such as power generation, water distribution, and steam applications, these valves provide durability on heavy-duty applications.

3. Triple eccentric butterfly valves
The triple eccentric valve adds a third angular offset, ensuring zero friction between the disc and seat, enabling to zero leakage. These valves are designed for the highest temperature and pressure environments that can be handled with a butterfly valve, making them the best choice for the most critical industrial applications.

Advantages of butterfly valves

Butterfly valves offer several advantages, making them a preferred choice across various industries.

Key benefits:

Compact design: Butterfly valves are lightweight and require less space, making them ideal for large-diameter pipelines and installations with limited space.
Quick operation: Their quarter-turn mechanism allows fast opening and closing, perfect for emergency shut off and high-cycle applications.
Cost-effective: With fewer components and simple construction, butterfly valves are cheaper to manufacture, install, and maintain compared to other valve types.
Low maintenance: Fewer moving parts result in less wear and reduced maintenance, ensuring minimal downtime in industrial operations.
Versatility: Suitable for a wide range of media types, butterfly valves can handle various pressure and temperature conditions, with versions for corrosive or abrasive media.
Corrosion resistance: The lining protects the valve's metal body from corrosion, making it suitable for handling corrosive media.
Wide range of sizes and configurations: Available in a variety of sizes, body types (wafer, lug, double-flanged), and materials, butterfly valves can be used for a very wide range of applications.

Thanks to these properties, butterfly valves are extremely versatile and can be used for a wide range of industrial applications.

Despite all these advantages, butterfly valves have some limitations:

Throttling: While butterfly valves can be used for throttling, they may not be as precise as other valve types, such as globe valves, especially in small flow ranges.
High differential pressures: Centric butterfly valves are not typically suitable for high-pressure drop applications because of the hydrodynamic torque acting on the disc.

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Butterfly valve actuation

The actuation method for a butterfly valve determines how it is operated, whether manually or automatically. Choosing the right actuator is crucial for ensuring efficient operation based on system requirements.

Below are the types of actuators and their applications:

1. Manual actuation
Manual actuation is done by hand, typically with a hand lever or gearbox, and is ideal for easily accessible valves that are not often operated.

Hand lever: Best for smaller valves in low-pressure systems.
Gearbox: Provides mechanical advantage for larger valves in industrial applications where higher pressures are involved, or to avoid water hammer on small sizes.

2. Pneumatic actuation
Pneumatic actuators use compressed air for quick operation, making them ideal for automated systems requiring high cycling rates, typically in process automation systems.

Double-acting actuators: Uses air for both opening and closing.
Single-acting actuators: Uses air pressure for one operation, with a spring return for the other position.

3. Electric actuation
Electric actuators use electric motors for precise control, commonly found in HVAC, water treatment plants and power generation.

4. Hydraulic actuation
Hydraulic actuators use high pressure fluid to provide high torque, making them ideal for large-diameter valves and high-pressure systems like oil & gas and marine applications.

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Choosing the right actuator

Consider:

Control applications: Pneumatic or electric actuators are best for these applications, electric actuators reacting more accurately than pneumatic.
Frequency of operation: For frequent cycling, pneumatic actuators offer faster response.