How Does Double Eccentric Butterfly Valve Balance Sealing And Long Life?

Table of Contents

1. Definition of Double Eccentric Butterfly Valve

2. Working Principle

3. Main Components

4. Connection Types and Materials

5. Main Features

6. FQA

1. Definition of Double Eccentric Butterfly Valve

The double eccentric butterfly valve is an improvement over the ordinary centerline butterfly valve. Its valve stem has two offsets relative to the center of the disc sealing surface and the centerline of the pipe, thereby changing the contact mode between the disc and the valve seat and reducing friction during opening and closing.

2. Working Principle

2.1 Meaning of the Two Offsets

• First offset (axial): The valve stem center is located behind the plane of the disc sealing surface.

• Second offset (radial): The valve stem center deviates from the pipe centerline.

  
  

  
  

2.2 Operation Process

• When closing: The two offsets generate a wedging force, pressing the disc tightly against the valve seat — the tighter it closes, the tighter it seals.

• When opening: The disc quickly disengages from the valve seat with almost no friction.

• When fully open: The disc is parallel to the flow passage, resulting in minimal pressure loss.

Conclusion: The disc presses tightly to achieve sealing when closing, and disengages to reduce wear when opening, thus achieving low friction, long life, and high sealing performance.

3. Main Components

The double eccentric butterfly valve mainly consists of the valve body, disc, stem, sealing ring, valve seat, and actuator. The core lies in the double eccentric structure, which allows the disc to disengage from the valve seat the moment it opens, significantly reducing wear and extending service life.

4. Connection Types and Materials

4.1 Connection Types

• Wafer type: Compact structure, suitable for space-limited applications.

• Lug type: Supports single-side disassembly, easy to maintain.

• Flanged type: High connection strength, suitable for high pressure or large-diameter pipelines.

4.2 Valve Body Materials

• Carbon steel: High cost-performance ratio, suitable for general working conditions.

• Stainless steel (304/316): Corrosion resistant, suitable for chemical and water treatment applications.

• Heat-resistant steel / Nickel-based alloy / Titanium alloy: Suitable for high temperature, strong corrosion, or marine engineering and other special conditions.

4.3 Sealing Materials

• PTFE: Corrosion resistant, suitable for low pressure conditions.

• RPTFE (Reinforced PTFE): Better wear resistance, suitable for oil, natural gas, steam and other systems.

  
  

5. Main Features

1. Low friction: The disc quickly disengages from the sealing surface during opening, resulting in low wear.

2. Reliable sealing: The double eccentric structure ensures reasonable stress on the sealing pair.

3. Low torque: Easy operation, suitable for automated control.

4. Wide application range: Can be used in medium pressure and some high temperature conditions.

6. FQA

1. What is the difference between a double eccentric butterfly valve and a centerline butterfly valve?

The double eccentric butterfly valve quickly disengages from the sealing surface during opening, resulting in low friction and long life; the centerline butterfly valve remains in constant contact with the sealing surface, causing greater wear.

2. What working conditions are suitable for the double eccentric butterfly valve?

It is suitable for medium pressure and some high temperature conditions in industries such as water treatment, petrochemical, and power, especially for systems with high sealing performance requirements.

3. Can it be used for automated control?

Yes. It can be equipped with pneumatic, electric, or hydraulic actuators and is widely used in automated control systems.