Difference Between Double Offset and Triple Offset Butterfly Valve

Butterfly valves are essential components in various industries, providing control over the flow of fluids within pipelines. They are known for their versatility, ease of operation, and cost-effectiveness. Among the different types of butterfly valves available, double offset and triple offset butterfly valves stand out due to their unique designs and applications. Butterfly valve’s body is a cylindrical or disc-shaped structure that houses the valve’s components. It is typically made of materials such as cast iron, carbon steel, stainless steel, or special alloys. The disc, also known as the “butterfly,” is a circular plate that rotates within the valve body to control the flow of fluid. It can be made from a variety of materials, including metal and resilient materials like elastomers or rubber. The stem connects to the disc and allows for the rotation of the disc when the valve is operated. It extends through the valve body and is connected to the actuator. The actuator is the mechanism responsible for opening and closing the valve. It can be manual, electric, pneumatic, or hydraulic, depending on the application. Lastly the seat provides a sealing surface for the disc when the valve is closed. It ensures a tight shut-off to prevent leakage.

Double Offset Butterfly Valve

Double offset butterfly valves are designed with two distinct offsets: one at the centerline of the valve body and the other at the centerline of the disc. These offsets result in a slightly conical shape for the disc and a tilted axis of rotation. These butterfly valves achieve sealing through interference fit between the disc and the seat. When the valve is closed, the disc’s conical shape presses against the seat, creating a tight seal. The double offset design includes both a shaft offset and a disc offset. This reduces the wear and friction between the disc and the seat, extending the valve’s lifespan. Due to the reduced contact area between the disc and the seat, double offset butterfly valves require less torque to operate, making them suitable for applications with electric or manual actuators. Double offset butterfly valves are commonly used in various industries, including water treatment, Chemical Processing, Power Generation, Oil and Gas Industry and Petrochemical Plants where moderate control is required.

Triple Offset Butterfly Valve

Triple offset butterfly valves are designed with three distinct offsets, one at the centerline of the valve body, the second at the centerline of the disc, and the third in the form of an eccentrically tapered cone on the sealing surface of the disc. These offsets contribute to a cone-shaped seating, which enables tight sealing with minimal friction. Triple offset butterfly valves have sealing through a combination of the eccentrically tapered cone on the disc and the metal seat ring. This design provides a metal-to-metal, bubble-tight seal, making them suitable for high-pressure and high-temperature applications. These valves have the most advanced offset configuration among butterfly valves, resulting in a virtually frictionless operation and minimal wear on the sealing components. Due to their excellent sealing capabilities and ability to withstand high pressures and temperatures, triple offset butterfly valves are commonly used in industries such as oil and gas, petrochemicals, and power generation. Triple offset butterfly valves generally require higher torque for operation compared to double offset valves due to the increased sealing force.

The main difference is that triple offset butterfly valves have an additional offset in the seat geometry, providing enhanced sealing performance compared to double offset butterfly valves. Triple offset valves are typically used in more demanding applications where a high level of tight shut-off is required.

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