What Is A Double Eccentric Butterfly Valve?

In industrial piping systems, valves play a critical role in controlling fluid shut-off and regulation, directly affecting system safety and efficiency. Butterfly valves are widely used in industries such as water treatment, petrochemical, and power generation due to their simple structure, compact size, and low cost. Among them, the double eccentric butterfly valve, as an improved design, has gradually become a mainstream choice in mid-to-high-end applications thanks to its superior sealing performance and longer service life.

Table of Contents

1. Definition of Double Eccentric Butterfly Valve

2. Working Principle

3. Main Components

4. Connection Types & Materials

5. Key Features

6. Advantages

7. FAQ

Keywords: Double eccentric butterfly valve, Butterfly valve, Industrial valve, Sealing performance, Flow control

You can watch the following video for a quick understanding:

https://youtube.com/shorts/9QvpUUPL4PM

I. Definition of Double Eccentric Butterfly Valve

A double eccentric butterfly valve, also known as a high-performance butterfly valve, is developed based on the traditional concentric butterfly valve. Its stem is offset from both the disc center and the valve body center, which changes the contact mode between the disc and the sealing surface.

II. Working Principle

The two eccentricities refer to:

First Eccentricity (Axial Offset): The stem centerline is located behind the valve body centerline, meaning it is offset from the disc sealing surface along the flow direction.

Second Eccentricity (Radial Offset): The stem centerline deviates from the pipeline centerline, meaning it is offset perpendicular to the flow direction by a certain distance (a).

Closed Position: When the disc rotates to align with the valve body centerline, the sealing surface of the disc generates a wedging force due to the two eccentricities, pressing tightly against the seat to achieve sealing. The structure ensures tighter sealing as the valve closes.

Opening Process: As the stem rotates the disc, the sealing surface quickly disengages from the seat with minimal friction due to the eccentric design.

Fully Open Position: After rotating 90°, the disc aligns with the flow direction, resulting in minimal pressure loss.

Conclusion: The combination of eccentric distances (a and b) allows tight sealing during closure and quick separation during opening, achieving low friction, long service life, and high sealing performance.

III. Main Components

A high-performance double eccentric butterfly valve mainly consists of the valve body, disc, stem, sealing ring, seat, and actuator. Its compact structure ensures both strength and sealing performance. The core lies in the double eccentric design, which allows the disc to quickly disengage from the seat, reducing friction and wear, thus extending service life and improving sealing reliability.

IV. Connection Types & Materials

Connection Types

KST provides multiple connection types to meet different installation requirements:

Wafer Type: Compact and lightweight, suitable for space-limited piping systems with easy installation and lower cost.

Lug Type: Equipped with threaded lugs, allowing single-side disassembly, ideal for maintenance and isolation.

Flanged Type: High strength and stable sealing, suitable for high-pressure or large-diameter pipelines.

Body Materials

Carbon Steel (WCB): Good mechanical strength and cost-effective for general applications.

Heat-Resistant Steel: Maintains strength under high temperatures, suitable for thermal systems.

Stainless Steel (304/316): Excellent corrosion resistance for chemical, water treatment, and food industries.

Nickel-Based Alloy: Resistant to strong corrosion and high-temperature oxidation.

Titanium Alloy: Lightweight, high strength, and resistant to seawater corrosion.

Sealing Materials

PTFE: Excellent chemical stability and corrosion resistance, suitable for low-pressure applications.

RPTFE: Reinforced PTFE with improved wear resistance and strength, suitable for oil, gas, pharmaceutical, and steam systems.

Ⅴ. Key Features

(1) Low Friction Design: The disc quickly disengages from the seat during opening, reducing wear and extending service life.

(2) Excellent Sealing Performance: The eccentric structure ensures more reliable sealing.

(3) Low Operating Torque: Easier operation compared to concentric butterfly valves.

(4) Wide Application Range: Suitable for medium pressure and certain high-temperature conditions.

Ⅵ. Advantages

Compared with traditional butterfly valves:

1. Low operating torque, reducing actuator load and improving system efficiency;

2. Superior sealing performance with bidirectional sealing capability;

3. Low maintenance cost due to simple structure;

4. Compatible with pneumatic, electric, or hydraulic actuators;

5. Suitable for various industrial applications, including corrosive media.

With its advanced structural design and material combinations, KST high-performance double eccentric butterfly valves deliver high reliability and long-term stability, making them an ideal solution for industrial fluid control systems.

Ⅶ. FAQ

1. What is the difference between double eccentric and concentric butterfly valves?
A double eccentric butterfly valve uses an offset design that allows the disc to quickly disengage from the seat, reducing friction and wear. In contrast, a concentric butterfly valve maintains continuous contact, leading to higher wear.

2. What applications are suitable for double eccentric butterfly valves?
They are suitable for medium pressure and certain high-temperature conditions, commonly used in water treatment, petrochemical, and power industries.

3. Can double eccentric butterfly valves be used in automation systems?
Yes, they can be equipped with pneumatic, electric, or hydraulic actuators and are widely used in automated control systems.