A Concise Guide to Soft-Seated Butterfly Valve

 
A soft-seated butterfly valve is a common pipeline control device widely used across various industries, such as oil and gas, chemical processing, metallurgy, municipal construction, water treatment, food processing, and pharmaceuticals. As a critical component in pipeline systems, it is primarily utilized for opening and closing fluid flow and regulating flow rates. Compared to other types of valves, the soft-seated butterfly valve has become the preferred choice in many applications due to its simple structure, flexible operation, and excellent sealing performance.

Sealing Structure of Soft-Seated Butterfly Valves

 
The sealing structure is one of the core features of a soft-seated butterfly valve, directly impacting its performance and range of applications. Based on the sealing material, the soft-seated butterfly valve can be categorized into two types.

1. Non-Metal to Non-Metal

 
This type of sealing pair consists of two sides made of non-metallic soft materials, such as rubber to rubber or PTFE to PTFE. These seals offer excellent sealing performance and are especially suitable for low-temperature, low-pressure, and non-abrasive environments.

2. Metal to Non-Metal

 
In this configuration, one side of the sealing pair is made of a hard metal material, while the other side is made of a soft non-metallic material, such as steel to rubber or steel to PTFE. This structure combines the mechanical strength of metal with the flexibility of non-metallic materials, providing reliable sealing at lower temperatures and pressures, but it is not suitable for high-temperature or high-abrasion conditions.

Design Features of Soft-Seated Butterfly Valves

 
Soft-seated butterfly valves are designed with both ease of operation and sealing reliability in mind. The key design features include the following aspects.
 
Double Eccentric Structure: The valve adopts a double eccentric design, where the valve stem axis is offset from the center of the disc and the center of the valve body, reducing sliding friction between the disc and the sealing ring. This design significantly improves the wear resistance of the sealing surface, extending the valve's service life.
 
Pinless Connection: The connection between the disc and the valve stem usually employs a pinless structure, eliminating potential internal leakage points and enhancing overall sealing performance and structural stability.
 
Replaceable Seals: The seals can be replaced as needed, making maintenance and repair convenient and reducing long-term operating costs.
 
Diverse Material Options: Depending on user requirements, the disc can be coated with different materials, such as nylon or PTFE, to enhance corrosion resistance and adapt to specific media.

Advantages of Soft-Seated Butterfly Valves

 
Soft-seated butterfly valves offer several advantages in various industrial applications.
 
Excellent Sealing Performance: By using soft sealing materials like rubber and PTFE, which have good elasticity and recovery properties, these valves achieve zero leakage sealing at low pressures.
 
Lightweight and Compact Structure: The valve has a simple and compact design, making it small in size and light in weight, which facilitates installation and maintenance, especially in space-constrained applications.
 
Ease of Operation: Soft-seated butterfly valves require low operating torque and can be quickly opened or closed with a 90-degree turn, improving system efficiency.
 
Good Flow Regulation Performance: The flow characteristics of soft-seated butterfly valves are close to linear, making them suitable for processes that require precise flow control.

Limitations of Soft-Seated Butterfly Valves

 
Despite their many advantages, soft-seated butterfly valves have some limitations in their application range.
 
Poor Temperature and Pressure Resistance: Due to the use of non-metallic soft materials for sealing, soft-seated butterfly valves are not suitable for high-temperature (above 120°C) or high-pressure (typically below 10 MPa) environments, where they are prone to failure.
 
Susceptible to Aging and Wear: Soft sealing materials like rubber and PTFE may degrade over time, leading to a decline in sealing performance. Additionally, soft seals are prone to wear from fluid medium erosion, affecting the valve's lifespan.
 
Lower Mechanical Strength: Compared to metal-seated butterfly valves, soft-seated butterfly valves have relatively lower mechanical strength, making them unsuitable for high-wear conditions and applications requiring high strength.

Applications of Soft-Seated Butterfly Valves

 
Due to their excellent sealing performance and ease of operation, soft-seated butterfly valves are suitable for various pipeline systems requiring tight closure.
 
Water Treatment Systems: Used for controlling water flow and pressure to ensure the normal operation of water treatment equipment.
 
Food Processing and Pharmaceutical Industries: Ideal for applications requiring stringent hygiene standards and leak-free operation, as the soft sealing materials used meet food-grade and pharmaceutical-grade standards.
 
Chemical Industry: Suitable for controlling the flow of various chemical media, particularly in low-temperature, low-pressure chemical processes.
 
HVAC Systems: Commonly used to regulate air circulation and water circulation systems, ensuring efficient system operation.
 
Soft-seated butterfly valves, with their unique design and material selection, offer excellent sealing performance and ease of operation, making them ideal for low-temperature and low-pressure environments. However, their temperature and pressure limitations restrict their use in high-temperature and high-pressure environments. Therefore, when selecting a valve, it is important to choose between soft-seated and hard-seated butterfly valves based on specific working conditions and usage requirements to achieve optimal performance and cost-effectiveness. Through proper selection and application, the efficiency and reliability of pipeline systems can be effectively enhanced.