1. Working Principle
The design of a triple eccentric butterfly valve involves three key eccentricities:
1.Offset of the stem axis from the center of the disc: Reduces scraping between the disc and seat during rotation.
2.Offset of the stem axis from the center of the valve body: Optimizes the opening and closing characteristics.
3.Angle offset of the seat rotation axis from the channel axis: Creates an elliptical sealing surface after the third offset.
This unique design is centered around “torque sealing,” which differs fundamentally from traditional “position sealing.” Instead of relying on the elastic deformation of the valve seat, triple eccentric valves achieve a tight seal through surface contact pressure.
When opening: The disc sealing surface completely disengages from the seat, minimizing friction and prolonging service life.
When closing: The disc rotates and aligns with the seat sealing surface, achieving a zero-leakage seal.
The sealing pressure increases proportionally with the medium pressure, making these valves ideal for high-temperature and high-pressure environments.
2. Key Features of Triple Eccentric Butterfly Valves
1.High Efficiency Sealing for Extreme Conditions
Suitable for temperatures ranging from -196°C to 700°C and pressures up to 2500 psi.
The sealing surface pressure adjusts with the medium pressure, ensuring zero leakage even under high pressure.
2.Enhanced Safety Design
Equipped with double thrust rings to prevent deformation of the disc or misalignment of the stem caused by high pressure or temperature.
Anti-blowout mechanisms on the valve stem ensure operational safety even in extreme conditions.
3.Friction-Free Operation for Longer Service Life
During operation, there is no scraping between the disc and the seat, significantly reducing wear.
Torque is directly transmitted to the sealing surface, eliminating issues like control dead zones at low opening levels.
4.Fire-Safe and Environmentally Friendly
Certified for API607, API6FA, and BS6755 Part2 fire safety standards, ensuring reliable sealing during fire emergencies.
Complies with EPA21 emission standards, with external leakage kept below 100 ppm, meeting modern environmental regulations.
5.Versatility and Cost-Effectiveness
Available in materials like cast iron, cast steel, and stainless steel to handle corrosive or extreme temperature environments.
Its lightweight and compact structure makes it an excellent replacement for traditional gate valves and globe valves, especially in large-diameter pipelines.
3. Innovative Structural Features
Multi-Layered Laminate Seat
The seat consists of stacked stainless steel and graphite layers, effectively resisting thermal expansion and preventing minor sealing surface damage from causing leakage.
Replaceable Seal Components
The disc sealing surface and seat are independently replaceable, reducing maintenance costs.
Uniformly distributed bolts ensure even stress, preventing loosening or leakage of the sealing components.
Body-Mounted Seat Design
The seat is installed on the valve body rather than the disc, reducing exposure to the medium, minimizing corrosion, and extending service life.
4. Evolution of Triple Eccentric Butterfly Valves
Butterfly valves have undergone several developmental stages:
1.Concentric Butterfly Valves
The stem axis, disc center, and body center are aligned. These valves are simple and easy to manufacture but suffer from excessive friction and wear due to continuous contact between the disc and seat. They rely on soft materials for sealing, limiting their temperature range.
2.Single Eccentric Butterfly Valves
The stem axis is offset from the disc center, reducing excessive contact at the upper and lower ends of the disc. However, scraping issues persist, limiting their application.
3.Double Eccentric Butterfly Valves
The stem axis is offset from both the disc center and the body center, significantly reducing scraping and friction. This allows for the use of metal seats, expanding the valve’s high-temperature applications. However, double eccentric valves use “position sealing,” which relies on the elastic deformation of the seat, limiting their pressure tolerance and sealing performance.
4.Triple Eccentric Butterfly Valves
By introducing a third eccentricity, the cone axis of the sealing surface is slanted relative to the cylindrical axis of the body, creating an elliptical, asymmetrical sealing surface. This fundamental change shifts the sealing method from “position sealing” to “torque sealing,” solving the leakage issues of metal seats. The contact pressure is proportional to the medium pressure, ensuring both zero leakage and high resistance to extreme pressure and temperature.
5. Applications
Triple eccentric butterfly valves are widely used in industries such as:
Oil and gas extraction and refining;
Petrochemical and chemical industries;
Power generation and metallurgy;
Municipal water supply and drainage.
They are highly versatile, accommodating diameters up to 48 inches, and available in wafer, lug, flange, and welded configurations. These valves are becoming the preferred choice for large-diameter pipelines due to their lightweight, compact structure, and exceptional sealing performance.
