Flanged Butterfly Valve: Working Principle and Selection Guide

A flanged butterfly valve is a heavy-duty flow-control device widely used in water supply, wastewater treatment, chemical processing, HVAC, oil and gas, and industrial pipeline systems. With its robust flanged-end connection and reliable sealing design, it provides safe and stable performance for both on/off and throttling applications. This guide explains everything you need to know about flanged butterfly valves, including how they work, key advantages, common materials, and how to choose the right model for your system.

What Is a Flanged Butterfly Valve?

A flanged butterfly valve is a type of butterfly valve whose body is equipped with integral flanges on both sides, allowing the valve to be bolted directly between pipeline flanges. Unlike wafer or lug-type valves, the flanged design provides higher structural strength, better resistance to pipeline stress, and improved sealing performance under high-pressure conditions.

Flanged butterfly valves are commonly used when pipeline stability, safety, and long service life are required.

How a Flanged Butterfly Valve Works

A flanged butterfly valve uses a quarter-turn disc to regulate flow.
The main components include:

• Valve Body – Flanged ends match ANSI, DIN, JIS, or BS flange standards.

• Disc – Rotates 90° to open or close the flow passage.

• Seat – Provides tight sealing; available in EPDM, NBR, PTFE, Viton, etc.

• Stem/Shaft – Connects the disc to the handle or actuator.

• Operator – Can be a manual lever, gear operator, electric actuator, or pneumatic actuator.

Working Process

• Open Position (0–90° Disc Rotation): The disc aligns with the flow direction, minimizing pressure drop.

• Closed Position: The disc is perpendicular to the flow and presses against the seat, creating a bubble-tight seal.

• Throttling: Intermediate positions allow precise flow regulation.

Key Features and Advantages of Flanged Butterfly Valves

1. High Structural Strength

Flanged ends provide strong mechanical support and better pipeline stability, especially in large-diameter and high-pressure systems.

2. Excellent Sealing Performance

The combination of flanged body design and resilient or PTFE seat ensures leak-free shutoff even at higher pressures.

3. Ideal for Large-Diameter Pipelines

Flanged butterfly valves are commonly used in sizes DN200–DN3000 because they maintain rigidity and alignment better than wafer or lug styles.

4. Easy Installation and Maintenance

Flanged connections allow predictable torque values and straightforward installation, reducing the risk of misalignment.

5. Versatile Operation Options

• Manual lever

• Gearbox

• Pneumatic actuator

• Electric actuator

• Hydraulic actuator

6. Wide Compatibility

Suitable for water, air, slurry, gas, steam, oils, and corrosive chemicals, depending on material selection.

Common Materials for Flanged Butterfly Valves

Body Materials

• Cast iron

• Ductile iron

• Carbon steel

• Stainless steel (304/316)

• Duplex stainless steel

• Aluminum bronze (marine and corrosive applications)

Disc Materials

• Stainless steel

• Nickel-plated ductile iron

• Aluminum bronze

• Duplex or super duplex stainless steel

Seat Materials

• EPDM: Water, air, mild chemicals

• NBR: Oil, fuel, hydrocarbons

• PTFE: Strong chemicals, high temperature

• Viton: Corrosive and high-temperature applications

Applications of Flanged Butterfly Valves

Flanged butterfly valves are used in a wide variety of industrial and commercial systems, including:

• Municipal water supply and distribution

• Wastewater treatment plants

• HVAC cooling and heating systems

• Oil & gas pipelines

• Chemical and petrochemical plants

• Marine and desalination systems

• Power generation and energy plants

• Food and beverage processing

Their durability and strong sealing characteristics make them ideal for harsh and continuous-operation environments.

Flanged Butterfly Valve vs. Wafer and Lug Types

When to Choose a Flanged Butterfly Valve:

• You need high reliability and structural rigidity

• Your pipeline operates under high pressure

• You handle large-diameter pipes

• You require long-term leak-free service

How to Select the Right Flanged Butterfly Valve

When choosing a flanged butterfly valve, consider the following:

1. Pressure and Temperature Rating

Confirm that the valve meets your system’s pressure class (PN10/16/25, Class 150/300).

2. Media Compatibility

Choose the correct body, disc, and seat materials for the fluid to prevent corrosion or wear.

3. Size and Flow Requirements

Ensure the valve provides adequate Cv value and minimal pressure loss.

4. Actuation Method

Select manual, pneumatic, electric, or hydraulic operation based on automation needs.

5. Standard Compliance

Look for certifications such as API 609, ISO, EN, ASME, or CE, depending on project requirements.

Conclusion

A flanged butterfly valve is a strong, reliable, and durable flow-control solution suitable for a wide range of industrial applications. Its robust flanged design offers superior sealing, easier installation, and stable performance in high-pressure and large-diameter systems. By selecting the right materials, connection standards, and actuation type, engineers can ensure optimal performance and long service life.