What is Expansion Flanged Butterfly Valve

An expansion flanged butterfly valve is an innovative valve that combines the functions of a flanged butterfly valve and a pipeline expansion joint. It can regulate flow, throttle fluid, and compensate for pipeline thermal expansion and contraction caused by temperature fluctuations. This butterfly valve effectively addresses internal stress issues that arise from temperature changes. It is widely used in industries like oil, chemical, metallurgy, and hydropower to control flow and regulate fluid in pipeline systems.

Working Principle and Structure of the Expansion Flanged Butterfly Valve

The expansion flanged butterfly valve combines the functions of a flanged butterfly valve and a pipeline expansion joint. It regulates flow and compensates for the thermal expansion and contraction of pipelines caused by temperature differences. Its working principle and design ensure excellent performance in flow regulation and temperature compensation.

1. Working Principle

The valve's core component is the butterfly disc. The disc is installed along the diameter of the pipeline. It rotates around its axis within a cylindrical passage in the valve body. As the disc rotates, it gradually adjusts the valve's opening and controls fluid flow. The rotation typically ranges from 0° to 90°. When the disc reaches 90°, the valve is fully open, allowing maximum flow. The valve automatically adjusts to the thermal expansion and contraction of the pipeline, minimizing stress caused by temperature changes. This ensures system stability and durability.

2. Structural Features

Valve Body and Butterfly Disc: The valve body is generally cylindrical, and the butterfly disc is circular, installed inside the valve body. The disc is connected to a drive mechanism, which can be manual, pneumatic, or electric, and controls the rotation of the disc.

Expansion Function: The unique expansion feature of this valve allows it to expand and contract within a certain range. It compensates for pipeline thermal expansion and contraction, which reduces stress buildup from temperature fluctuations.

Applications: The valve is suitable for environments where the maximum working temperature is 80°C. It is used in industries such as oil, chemical, food, pharmaceuticals, textiles, paper, power generation, water supply and drainage, and gas pipelines.

Advantages and Disadvantages of Expansion Flanged Butterfly Valves

The expansion flanged butterfly valve has clear advantages in flow regulation and temperature compensation. However, it also has some limitations and considerations for use. Understanding these pros and cons is important when selecting and applying the valve.

1. Expansion Flanged Butterfly Valve Advantages

Flow Regulation: The valve provides precise control of fluid flow. Its opening can be adjusted to meet different operating conditions.

Temperature Compensation: The valve automatically compensates for thermal expansion and contraction, reducing stress on pipelines and equipment. This extends the system's lifespan.

Compact Structure and Easy Installation: The valve combines the functions of a flanged butterfly valve and an expansion joint. It saves space and is easy to install. No additional maintenance space is required, and it is suitable for confined spaces.

Low Maintenance: The valve design allows for easy disassembly and maintenance. It typically requires minimal maintenance, which reduces long-term operating costs.

2. Expansion Flanged Butterfly Valve Disadvantages

No Online Maintenance: If the sealing part of the butterfly valve is damaged, the entire valve, including the expansion section, must be replaced. This can lead to significant losses.

Higher Long-Term Costs: Although the initial installation cost is lower compared to combining a flanged butterfly valve and an expansion joint, the inability to perform online maintenance results in higher long-term maintenance costs.

High Requirements for Expansion Components: The expansion parts must be designed and made from materials with high temperature and pressure resistance to avoid performance degradation in extreme temperature conditions.

Installation and Usage Guidelines for Expansion Flanged Butterfly Valves

When installing the expansion flanged butterfly valve, strict procedures must be followed to ensure proper operation and extend the valve's service life. Here are key installation and usage considerations.

1. Disassembly and Installation

Never disassemble or remove the valve randomly at the construction site. The pipeline on both ends of the valve must be concentric, and the flange surfaces must be parallel. The flange bolts should be tightened symmetrically to avoid applying force to one side.

2. Expansion Section Use

The expansion section of the valve should not be installed at pipe corners or at the end of the pipeline. The valve should be laid flat before installation to avoid damage. The valve's length is set to the minimum when it leaves the factory. During installation, adjust the length to the design specification.

3. Temperature Compensation

If the valve is used for temperature compensation, supports must be added along the pipeline axis to prevent the expansion valve from being pulled out. The support strength should be calculated based on the mechanical properties of the pipeline. The support must not be removed during operation.

4. Limiting and Fixing

If the valve is not used for temperature compensation but only for easier installation and maintenance, limit bolts should be used to symmetrically clamp the valve to prevent the expansion pipe from being pulled out. The design and strength of the limit bolts must be calculated based on the flange bolt diameter and pressure the valve will endure.

Conclusion

The expansion flanged butterfly valve is an efficient device that integrates flow regulation, temperature compensation, and pipeline stress relief functions. It is widely used in modern pipeline systems. By following proper installation procedures and regular maintenance, the valve can improve pipeline stability, reduce damage caused by temperature fluctuations, and extend the system's service life. Although the initial investment is low, the higher long-term maintenance costs should be considered when choosing the right installation and design plan.