Swing Check Valve: Performance and Connection Methods Analysis
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The swing check valve is a crucial component in pipeline systems, primarily designed to prevent backflow and ensure the safety and stability of the system. As a type of check valve, the swing check valve operates through the rotational movement of a disc, closely related to the fluid direction. This article delves into the working principles, structural features, performance advantages, and applications of swing check valves across various industrial sectors.

Structure and Working Principle

 
The key components of a swing check valve include the body, cover, disc, lever, and seat. Its operation is based on a combination of fluid pressure and gravity. When the fluid flows in the forward direction, the pressure causes the disc to rotate around the lever axis, lifting it off the seat and allowing fluid to pass through the valve. When the fluid pressure decreases or a reverse flow occurs, the disc automatically closes under the influence of gravity and reverse pressure, preventing backflow. The disc in a swing check valve rotates around an axis rather than moving vertically. The fluid inlet direction must be designed to impact the side of the disc that allows it to open smoothly and stay in the open position.

Performance Characteristics and Applications

 
After understanding the structure and working principle of the swing check valve, we can explore its performance characteristics and specific applications. This will provide better insight into the advantages of this valve in real-world conditions and its widespread use across various industrial fields.

1. Low Flow Resistance

 
The streamlined design of the internal passage in swing check valves results in minimal resistance as fluid passes through, making it particularly suitable for large-diameter pipeline systems. This design reduces energy loss and improves system efficiency.

2. Suitable for Large-Diameter Pipelines

 
The structural design of swing check valves makes them especially suitable for use in large-diameter pipelines, as they can effectively control the unidirectional flow of large volumes of fluid with low flow resistance.

3. Sealing Performance

 
Although the sealing performance of swing check valves under low-pressure conditions is not as strong as that of lift check valves, adding auxiliary springs or counterweights can effectively improve sealing, thus expanding their range of applications.

4. Pressure Drop

 
Due to the disc's suspended state in the fluid, turbulence may occur, leading to a significant pressure drop as fluid passes through the swing check valve. This characteristic must be considered when designing and selecting valves, especially for high-pressure and high-velocity fluid applications.

5. Prevention of Water Hammer

 
When the fluid flow direction changes suddenly, the disc may close rapidly, generating a significant impact force on the seat, leading to seat wear and potential water hammer. To mitigate this risk, damping devices can be installed on the disc, and metal seats can be used to enhance durability and reliability.

Connection Methods Analysis

 
The connection between the lever and the valve body in swing check valves can vary, with different methods tailored to specific application needs.

1. Direct Machining of Lever Holes on the Valve Body

 
This method involves designing lever shaft holes on the valve body, with the lever installed from outside the body, then sealed with a cover after assembly. While this design is simple and easy to process, external connection points may pose a risk of leakage, particularly in applications requiring strict sealing.

2. Internal Chamber Attachments

 
By casting crossbars in the internal chamber of the valve body and installing a bracket above them, the lever shaft connects to the bracket, reducing external connection points and minimizing leakage risks. However, this design increases the height and manufacturing cost of the valve body.

3. Threaded Connections Inside the Valve Chamber

 
In this method, two bosses are cast on the upper side of the inlet channel of the valve body and threaded. Tightening the flattened ends of the lever reduces external connections and prevents leaks, while also reducing the number of components and manufacturing costs.

4. Combination Connections

 
The valve body consists of left and right sections, with a seat clamped in between, and the disc connected to the seat via the lever shaft. This design minimizes leaks while facilitating machining and maintenance.

5. Connecting Components on the Seat

 
In this design, support columns are installed on the seat, connecting the lever and the disc, thus driving the valve's operation. This structure is stable and easy to operate.

Advantages and Limitations

 
Swing check valves perform excellently in specific applications, particularly in systems requiring large diameters and low resistance. However, they also have some limitations, such as less effective sealing under low-pressure conditions compared to lift check valves, higher fluid pressure drops, and the potential for water hammer. Therefore, in practical applications, the appropriate valve type should be selected based on specific conditions, and necessary improvements, such as installing damping devices or using metal seats, should be considered to ensure system reliability and longevity.
 
Swing check valves, with their unique structural design and working principle, are widely applicable in industrial settings. They offer low flow resistance, suitability for large-diameter pipelines, simple structure, and easy maintenance. However, they also present challenges in low-pressure sealing performance and water hammer prevention. Through thoughtful design and enhancements, swing check valves can meet the demands of various working conditions, ensuring the safe operation of fluid systems.
 
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