Butterfly Valve

1. Definition of a Butterfly Valve

Butterfly valves manipulate the flow of water by completely or partially rotating a disk (butterfly plate) located within the valve. The disc only needs to rotate a quarter turn (90 degrees) for the valve to be in an open or closed position. Fluid can flow through the disc easily as it is thin which offers very little resistance to fluid flowing round them. Catalog, in general, Butterfly Valves these are easier structure type & low operation prices , Pressure-Rattings and Seal-Run .

2. Components of a butterfly valve

Valve Body

• The valve body is the main load-bearing part of a valve.
• It is mounted inside the piping system and serves as a junction point where pipelines are connected while housing the internal components.
• Common body designs include wafer type, lug type, and flanged face.

Disc / Butterfly Plate

• Flow Controlling Element
• The disc is the primary component responsible for flow control in a butterfly valve.
• It is mounted inside the valve body and regulates the flow rate of the medium by rotating around its axis.

Stem / Shaft

• The stem connects the actuator (usually a handle or electric/electronic device) to the disc.
• It transmits operating torque to the disc, allowing the valve to open or close.

Seat and Sealing Elements

• The seat and seals are housed within the valve body.
• They contact the periphery of the disc to create a reliable, pressure-tight seal when the valve is closed.
• Depending on operating conditions, seat materials may include elastomers (rubber, PTFE, etc.) or metal.

Actuator

• An actuator is the power source that opens and closes the butterfly valve.
• It can be selected based on the required level of automation and includes:
  • Manual (lever or gearbox)
  • Electric
  • Pneumatic
  • Hydraulic

3. How does a Butterfly Valve Function?

• The butterfly valve is a 1/4-turn rotary movement.
• A simple structure stable performance.

Operating Mechanism

• A circular disc allot to the stem is inside a butterfly valve.
• A disc closes and opens by rotating the stem an angle about 90 degrees, where it will move from a closed position (the perpendicular to flow path) to open up parallel with the direction of fluid flow.
• Intermediate angles will partially block the disc, providing a variable resistance and controlling flow.
• Because the disc is always in this path, there is a small and stable pressure drop even when the valve opens fully.

Operating Positions

• Fully Open Position (approximately 90°)

  • The disc should be as parallel with fluid flow direction to cause the least amount of obstruction.

• Semi-Closed Position (45° — 145°)

  • The above Food-grade Ball Valve has a disc positioned at an intermediate angle to modulate flow by adjusting degree of opening.

• Fully Closed Position (approximately 0°)

  • The disc is pressed against the seat by virtue of its being placed at right angles to the pipeline and thereby comes into line with a joint packer or elastomer lamination throughout full closure, ensuring non-flowable medium.

4. Types of butterfly valves

In Terms of Valve Body Connection Type

Wafer Butterfly Valve

• Wafer-body style sandwiched between two pipeline flanges
• Compact structure, lightweight, and cost-effective
• Suitable for space-limited and low to medium pressure applications
• Commonly applied in water treatment, HVAC systems, and chemical pipelines

Lug Type Butterfly Valve

• Valve body lugs are threaded for direct bolting to pipe flanges
• Permits dead-end disconnection
• Provides more stable installation and simpler maintenance
• Typically used in industrial piping and process control systems

Flanged Butterfly Valve

• Valve body features integrally cast flanges on both ends
• Ensures high-strength connection and reliable sealing performance
• Ideal for high-pressure and large-bore applications
• Widely applied in petrochemical, electric power, and metallurgical industries

Valve Structural Design (Eccentric Type) Classification

Double Eccentric Butterfly Valve

• Off-center stem design: the stem is offset from both the valve body centerline and disc center
• Reduces seat contact during opening and closing
• Requires lower operating torque and extends sealing life
• Well suited for medium to high pressure, large-diameter pipelines

Triple Offset Butterfly Valve

• Combines double eccentric design with a conical sealing offset
• Features friction-free operation with metal-to-metal sealing
• Resistant to high temperature, high pressure, and corrosive media
• Commonly used in oil, gas, and steam systems
• Considered a high-end butterfly valve solution

Classification by Actuation Method

Electric Butterfly Valve

• Driven by an electric actuator
• Allows remote control and integration with valve management systems (VMS)
• Available for ON/OFF and modulating duty (MD) control
• Widely used in smart factories and automated pipeline networks

Pneumatic Butterfly Valve

• Operated by a pneumatic actuator with fast response
• Secure and dependable for repeated operation
• Available with single-acting or double-acting actuators
• Mainly used in chemical, food, and pharmaceutical industries

5. Applications of Butterfly Valves

• Resilient seated butterfly valves are a kind of valve, and their closure part is a disc that rotates around the stem to open or close by rotary operation.
• Common applications include start/shutdown operations and proportional control of fluid flow.
• Butterfly valves are very popular because they can be used in large-diameter piping systems while still having a small face-to-face dimension compared to other gate valve types.

6. FAQ

How does a butterfly valve work?
A butterfly valve turns a disc located in the center of the pipe by 90 degrees to open or close the valve, thereby controlling the flow.

Where are butterfly valves used?
Butterfly valves are used in pipeline systems to open, shut off, or regulate the flow of liquids and gases.

Butterfly valve applications
Butterfly valves are employed for quick on/off control and flow modulation, particularly in medium- to large-diameter pipelines.