Why Use A Triple Eccentric Butterfly Valve?

Because of its unique structural design, the three-eccentric butterfly valves is superior to the traditional butterfly valves in sealing performance, abrasion resistance, operating torque and applicable working conditions. Especially suitable for high pressure, high temperature, serious corrosion or frequent opening and closing of industrial piping systems. Below is a detailed analysis of its core advantages and application scenarios:
1.Analysis on the Structure of ``Three Eccentricity"of the Triple-Eccentric Butterfly Valve
The triple eccentric butterfly valve achieves high performance sealing through three key eccentric design features:
First Eccentricity: Axial Eccentricity
Design: Axial deviation of valve stem The centerline from the valve disc sealing surface the centerline (usually 10-20% of surface width).
Function: Removes the interference between valve stem and cover, causes the disc to separate from cover during opening, reduces friction and abrasion.
Second Eccentricity: Radial Eccentricity
Design: radial deviation of The centerline from body the centerline (usually 5-10% of valve disc diameter).
Function: wedge contact is formed between disc and sealing surface when rotating to improve sealing effectiveness. Third Eccentricity: Angular Eccentricity
Design: Sealed cover at an angle (usually 5°-15°) to the the centerline of the valve body.
Function: When sealing, the seal is a "self-tightening" seal by eccentricity of angle. The more pressure, the tighter the seal.
ii. Core Advantages of the Trieccentric Butterfly Valve
1. Zero-Leakage Sealing Performance
Self-Tightening Sealing Mechanism:
The third eccentricity is designed to form a radial force component on the sealing surface under the action of dielectric pressure, bringing the disc into close contact with the sealing ring to form a ``pressure-assisted seal ''.
For example, in a high pressure steam pipe, the leakage rate of a trieccentric butterfly valve can be as low as ≤0.1ml/min, far higher than that of a butterfly valves valve ≤ 10ml / min.
Bidirectional Sealing Capability:
Traditional butterfly valve only provides one-way sealing, while the three-eccentric butterfly valves is designed to seal in both directions by wedge extrusion. Suitable for situations where the flow direction of medium changes frequently (such as pump outlets, heat exchanger inlets, outlet). High temperature and high pressure resistance
Metal Hard Seal Structure:
The sealing surface is made of metal (e.g. stainless steel or carbide) and can withstand high temperatures (≤800°C) and pressures (≤25 MPa).
For example, the three-eccentric butterfly valves is widely used in the main steam pipelines of thermal power plants (temperature 540°C, pressure 17.5 MPa).
Rubber free ageing:
The rubber seals of traditional soft butterfly valves is easy to age and deform in high temperature, but the metal seal structure of triple eccentric butterfly valves completely eliminates this problem.
3. Low Operating Torque and long service life;
Reduced Friction Coefficient:
The first eccentric design allows the disc to detach from the seal when opened, reducing friction by 50%-70% and operating torque by one-third of that of a conventional butterfly valves.
For example, the working torque of a DN500 triple-eccentric butterfly valve can be as low as 200Nm, compared to more than 600Nm for a conventional butterfly valve of the same size. Increasing abrasion resistance:
Metal seal surfaces and valve discs are hard-to-hard (e.g. STL6 + WCB) or hard-to-soft (e.g. tungsten carbide + graphite), making them more abrasive than rubber seals.
Laboratory tests show that the sealing surface life of the three-eccentric butterfly valve can reach more than 100,000 weeks, which is 5-10 times longer than the traditional butterfly valve.
4. Corrosion and Scaling Resistance
Smooth Sealing Surface Design:
The sealing surface of the trieccentric butterfly valve is usually finelyground (surface roughness Ra ≤ 0.4μm), so it is not easy to absorb impurities in the medium and reduce the risk of scaling.
In seawater desalination pipelines, for example, the sealing scale of a three-eccentric butterfly valve is 80% lower than that of a conventional butterfly valve.
Corrosion-Resistant Material Selection:
Corrosion-resistant alloys (such as hartensils and dual-phase stainless steel) are available for use in corrosive media such as acid and alkalis.
III. Typical Application of Trieccentric Butterfly Valve
Petrochemical Industry
Uses: High temperature and high pressure steam pipe, catalytic cracking unit, hydrogenation reactor inlets and outlet. Advantages: The metal hard seal structure is resistant to hydrogen permeation and hydrogen sulfide corrosion, ensuring zero leakage in the long run.
Power industry
Main applications: steam systems of thermal power plant and cooling water system of nuclear power plant.
Advantages: Bidirectional sealing meets the bidirectional flow requirements of steam pipelines, low torque design, convenient for emergency shutoff operations.
Metallurgical Industry
Purpose: Blast furnace gas pipelines and converter gas recovery system.
Advantages: The wear-resistant sealing surface against gas dust erosion, extending valve life.
Water Treatment Industry
Uses: high-temperature, high-pressure seawater desalination and wastewater treatment.
Advantages: Corrosion-resistant materials and smooth seal design reduce scaling and maintenance costs. IV. INTRODUCTION Comparison of the Performance of Triple-Eccentric Butterfly Valves and Traditional Butterfly Valves
Performance Indicators: Triple-Eccentric Butterfly Valve
Traditional Butterfly Valve (Centerline/Double-Eccentric)
Sealing Performance: Zero Leakage (Bidirectional Seal)
Minor Leakage (Unidirectional Seal)
Temperature range: -196°C to 800°C
-20°C to 150°C (Soft Seal)
Pressure range: ≤25MPa
≤4.0MPa
Operating Torque: Low (1/3 of Traditional Butterfly Valves)
High (requires Higher Actuating Force)
Sealing Surface Life ≥ 100,000 openings and Closings
≤20,000 Openings and Closings
Applicable Media: vapour, gas, liquid, Corrosive Media
Clean Liquids, gases (Low-Pressure Conditions)
V. Triple-Eccentric Butterfly Valve Selection Recommendations
seal type selected according to conditions of use:
High temperature, high pressure conditions: the use of metal hard seal triple eccentric butterfly valve is preferable.
For corrosive media: select corrosion resistant alloys (e.g. Hastelloy C-276). Focus on frequency of operations:
Frequent opening and closing conditions (e.g. ≥10 times per hour): Valves are verified to have a satisfactory service life (typically ≥100,000 openings and closures).
Consider installing space:
The triple-eccentric butterfly valve's compact structure and suitable for space-limited piping systems (e.g. ship piping, underground pipe galleries, etc.).