Working Principle of Pneumatic Butterfly Valves Explained

A pneumatic butterfly valve consists of a pneumatic actuator and a butterfly valve. It controls fluid flow by rotating a circular disc, allowing for quick opening, closing, and flow regulation. Primarily used for shutoff, it can also be designed for flow adjustment.

These valves are known for their simple structure, lightweight build, fast operation, easy maintenance, and cost-effectiveness. They work well in applications requiring high flow and low-pressure drop. With the ability to integrate into automated systems and remote control setups, pneumatic butterfly valves are widely used in industrial settings for their reliability and durability.

Working Principle of Pneumatic Butterfly Valve

The operation of a pneumatic butterfly valve relies on the coordination between the pneumatic actuator, valve stem, and butterfly disc. It primarily involves the following key components:  

1. Pneumatic Actuator: The core power source of the pneumatic butterfly valve comes from the pneumatic actuator, which typically consists of a cylinder and a piston. When compressed air enters the cylinder, it drives the piston movement, which in turn rotates the valve stem.  

2. Valve Stem and Butterfly Disc: The valve stem is connected to the butterfly disc (valve plate). As the actuator rotates the valve stem, the butterfly disc moves accordingly. The rotation angle of the disc determines the valve opening, thereby controlling the fluid flow.  

3. Opening and Closing Mechanism：

• Open Position: When compressed air enters one side of the cylinder, it pushes the piston, which drives the valve stem and butterfly disc to rotate parallel to the fluid flow direction, fully opening the valve and allowing fluid to pass freely.

• Closed Position: When compressed air enters the opposite side of the cylinder, it pushes the piston in the reverse direction, causing the valve stem and butterfly disc to rotate perpendicular to the fluid flow, closing the valve and blocking fluid passage.

4. Flow Regulation: By adjusting the air intake of the pneumatic actuator, the rotation angle of the butterfly disc can be precisely controlled, allowing for fine-tuned flow regulation.

Types of Modern Pneumatic Butterfly Valves

Modern pneumatic butterfly valves are categorized into single-acting and double-acting types based on their actuator mechanism. They differ significantly in terms of operation principle, structural characteristics, and application scenarios.

Single-Acting Pneumatic Butterfly Valve

A single-acting actuator has only one air chamber and relies on a one-way air supply to open the valve, while a built-in spring ensures automatic closure when the air supply is cut off.

Working Principle:

When compressed air is supplied, the air pressure pushes the piston or actuator, driving the valve to open. Once the air supply is cut off, the built-in spring automatically resets the valve to the closed position.

Key Features:

• Simple Structure: Typically consists of a single valve seat and a spring return mechanism.

• Failsafe Function: In case of air supply failure, the spring ensures automatic closure for safety.

• Lower Air Consumption: Uses compressed air only in one direction, making it more energy-efficient.

Double-Acting Pneumatic Butterfly Valve

A double-acting actuator controls flow in both directions and requires air supply in both directions to operate the valve.

Working Principle:

The actuator has two air chambers. Compressed air alternates between the chambers, driving the piston left or right to rotate the valve body in the desired direction, thus controlling the opening and closing of the valve.

Key Features:

• More Complex Structure: Typically has an integrated design with two valve seats at the inlet and outlet.

• No Automatic Reset: The valve’s position is entirely dependent on the air supply, without a spring return function.

• Higher Air Consumption: Requires compressed air in both directions, making it suitable for frequent operation scenarios.

Applications of Single-Acting Pneumatic Butterfly Valves

Single-acting pneumatic butterfly valves feature an automatic reset function, making them ideal for high-safety applications, emergency shutdowns, fire safety, and basic flow control. Common applications include:

1. In industries such as oil, gas, and chemicals, single-acting pneumatic butterfly valves are used for emergency shutdown.

   When the air supply is interrupted or a system failure occurs, the valve automatically closes to prevent hazardous substance leakage.

2. In fire emergency situations, the valve can automatically close to prevent fire spread.

3. Since single-acting valves consume less air, they are ideal for intermittent operation, such as in HVAC systems (heating, ventilation, and air conditioning).

4. Suitable for systems that do not require frequent operation or complex control, providing a simple and effective solution for regulating flow.

Applications of Double-Acting Pneumatic Butterfly Valves

Double-acting pneumatic butterfly valves allow for bidirectional flow control, making them ideal for applications requiring frequent operation, precise control, and complex flow adjustments. Common applications include:

1. Water Treatment Plants:Used in large-scale water treatment facilities to control the flow of water and chemicals efficiently.

2. Chemical, Pharmaceutical, and Food Processing Industries:Ideal for precise flow and pressure control, ensuring stability and efficiency in manufacturing processes.

3. Automated Production Lines:Frequently used in automated industrial processes where rapid response and precision control are critical.

When selecting a pneumatic butterfly valve, it is essential to determine the appropriate type based on actual needs and system requirements.

For applications requiring high safety standards and one-way flow control, a single-acting pneumatic butterfly valve is the ideal choice, as it ensures automatic closure in case of air supply failure.

For applications that require bidirectional flow control or frequent opening and closing, a double-acting pneumatic butterfly valve is more suitable due to its precise control and responsiveness.

TFW Valve is a professional manufacturer of pneumatic butterfly valves, offering high-quality, reliable solutions for various industries. If you're looking for a trusted partner, we might be your best choice.

For inquiries or further information, feel free to contact us!