In water supply networks, water treatment plants, HVAC systems, and other projects that require flow control, people often ask: "How is a butterfly valves used for flow control?" This question requires us to have a certain understanding of the characteristics of the valves and their operating conditions before we can know the answer. Therefore, this article will discuss the advantages of butterfly valves in throttling applications and their limitations. This will help us weigh various factors and select the most economical and reliable solution in actual scenarios and projects.
The working principle of butterfly valves in flow control
The structure of a butterfly valve consists of a valve body, a disc-shaped plate and a valve stem. Its working principle is similar to the movement of a butterfly's wings. Firstly, by rotating the valve stem, the disc-shaped plate can be adjusted within the range of 0° to 90°. This changes the flow passage area and controls the flow rate. When the disc-shaped plate is fully opened at 90°, the valve plate is parallel to the flow direction of the fluid, resulting in low resistance and low pressure loss. When it is half-opened at 45°, the valve plate will produce a throttling effect, reducing the flow rate. When it is less than 10°, the channel becomes narrow, significantly reducing the flow rate, but this also exposes the valve plate to severe erosion. Through this method, the butterfly valve has the ability to regulate the flow rate.
The advantages of butterfly valves in flow control
1. Simple structure, lightweight design: Especially in large-diameter pipelines, the butterfly valve is much lighter and more compact than the cumbersome gate valve or ball valve, reducing installation and support costs.
2. Economical and efficient: Under certain circumstances, the butterfly valve is more cost-effective than specialized control valves. Its purchase price and maintenance requirements are very low, which can significantly reduce costs in the project.
3. Convenient operation, automation: Through a 90° rotation covering the entire stroke, the butterfly valve is easy to operate and can be easily equipped with manual, pneumatic or electric actuators, making it highly suitable for integration into automated control systems.
4. Widely applied: For example, in real application scenarios such as flow distribution in water treatment plants, outlet pressure control in pumping stations, and rough flow regulation in cooling water circuits.
The limitations of butterfly valves in flow control
1. Poor accuracy and poor linearity: The butterfly valve does not have a dedicated control valve that is more precise. The relationship between the valve disc opening and the flow rate is not completely linear, especially at the mid-position, which limits precise control.
2. Erosion and cavitation at small opening: Operating the valve for a long time at a small opening (for example, below 20°) will cause the valve disc and the downstream valve seat to be impacted by high-speed fluid. This may lead to vibration, noise and cavitation, all of which will accelerate wear and seriously damage the sealing performance and service life.
3. Sealing wear under throttling conditions: In applications, it is more susceptible to erosion than simple on-off applications. At the same time, over time, this will cause damage to the valve seat seal or failure of the seal to cause leakage.
4. Unable to work under high pressure difference: Using it under a large pressure difference will increase the risk of erosion. Therefore, butterfly valves are usually not suitable for such harsh conditions.
