Concentric vs Double vs Triple Eccentric Butterfly Valves: Key Differences

July 12, 2024
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A butterfly valve is a type of valve in which the closing mechanism (valve disc or butterfly plate) is a disc that rotates around the valve shaft to open and close the valve. It is mainly used for cutting off and throttling in pipelines. According to structural differences, butterfly valves can be classified into three types: concentric butterfly valves, double eccentric butterfly valves, and triple eccentric butterfly valves.

Overview

Concentric, double eccentric, and triple eccentric butterfly valves mainly differ in stem position, disc movement, seat contact, and sealing design.

As the offset increases, the disc separates from the seat more quickly, helping reduce friction and seat wear. Operating torque, however, also depends on valve size, differential pressure, seat material, and operating conditions.

What Are the Structural Differences Between Concentric, Double and Triple Eccentric Butterfly Valves?

Concentric Butterfly Valve

In a concentric butterfly valve, the stem axis, disc center, and valve body centerline are aligned.

The disc remains in contact with the seat during much of its movement, so soft seats such as EPDM, NBR, or PTFE are commonly used.

This design is widely used in water supply, HVAC, irrigation, and other general industrial applications.

Double eccentric butterfly valve

In a double eccentric butterfly valve, the stem is offset from both the disc center and the valve body centerline.

This design allows the disc to move away from the seat quickly, reducing friction, seat wear, and operating torque.

Double eccentric butterfly valves can use soft, high-performance, or metal seats depending on the application.

They are commonly used in water treatment, pump stations, large pipelines, and industrial systems

Double eccentric butterfly valve

Triple Eccentric Butterfly Valve

A triple eccentric butterfly valve adds a third offset to the double eccentric design.

This creates a cam-like sealing movement, allowing the sealing surfaces to separate quickly with very little rubbing.

Triple eccentric butterfly valves are commonly used with metal seats in higher-temperature and more demanding services.

Typical applications include steam, power generation, petrochemical systems, and other severe industrial conditions.

Triple eccentric butterfly valve first eccentric

The first eccentricity - the eccentricity between the valve stem axis and the sealing surface

Triple eccentric butterfly valve second eccentric

The second eccentricity - eccentricity between the valve stem axis and the valve body center

Triple eccentric butterfly valve third eccentric

The third eccentricity - the rotation axis of the sealing surface is eccentric to the axis of the valve body channel

Double eccentric butterfly valve working principle diagram

Drawing of triple eccentric butterfly valve

Feature	Concentric	Double Eccentric	Triple Eccentric
Offset Design	No offset	Two offsets	Three offsets
Disc-Seat Contact	More contact	Reduced contact	Minimal rubbing
Seat Wear	Higher	Lower	Very low
Typical Seat	Soft seat	Soft, high-performance, or metal seat	Mainly metal or laminated metal seat
Typical Applications	Water, HVAC, irrigation	Water treatment, pump stations, industrial systems	Steam, power, petrochemical, severe service

How to Choose Between Double Eccentric and Triple Eccentric Butterfly Valves?

Applications of Double Eccentric Butterfly Valves

Double eccentric butterfly valves have detachable seats and can be made from materials that resist corrosion, light, and aging, depending on the physical and chemical properties of different media. They are widely used in water supply and drainage, sewage, construction, air conditioning, petroleum, chemical, food, pharmaceuticals, textiles, paper making, hydropower, ships, metallurgy, and energy systems, serving as regulating and shut-off devices in fluid pipelines.

Double eccentric butterfly valves typically use PTFE (polytetrafluoroethylene) as the sealing seat material. They can also use metal sealing seats to extend their application in high-temperature areas. However, metal-seated double eccentric butterfly valves still have a positional sealing structure, where the sealing surface of the disc and seat is in line contact. Therefore, they cannot withstand high pressure. Using them in high-pressure systems can result in significant leakage. Thus, metal-seated double eccentric butterfly valves should be avoided in high-pressure or systems requiring tight shut-off.

Applications of Triple Eccentric Butterfly Valves

Triple eccentric butterfly valves, with their optimized sealing performance and high-temperature resistance, are widely used in various critical pipelines across major industrial sectors. These sectors include oil and gas extraction, offshore platforms, oil refining, petrochemicals, inorganic chemicals, energy generation, and process control in industries in China and worldwide.

Concluding Remarks

Double eccentric and triple eccentric butterfly valves differ significantly in structural design, working principles, and application scenarios. Double eccentric butterfly valves are suitable for medium to low pressure and general fluid control, while triple eccentric butterfly valves are designed for higher pressure and more demanding conditions. Choosing and applying the appropriate valve is crucial for ensuring the proper operation and safety of the system.

Due to the more complex structure and manufacturing technology of triple eccentric butterfly valves, they are more expensive than double eccentric ones. Therefore, in practical applications, selecting the most suitable valve type based on specific needs and operating conditions is an important decision.

Union Valves is a professional manufacturer of triple eccentric butterfly valves in China, offering various models and specifications. For more information, please contact us.