High-Temperature Ball Valve Material Selection

In industrial production, high-temperature ball valves play a crucial role. They are widely used in various high-temperature environments, such as chemical, petroleum, and food processing industries, ensuring the safe and efficient control of fluid flow. However, in the face of different high-temperature conditions, selecting the appropriate materials and design structures is key to ensuring the performance of high-temperature ball valves. This article will delve into the material selection, structural design, and performance characteristics of high-temperature ball valves, helping you better understand and choose the right high-temperature ball valve.

A high-temperature ball valve is a type of ball valve that can operate normally in high-temperature environments, typically classified based on its working temperature. Generally, ball valves with a working temperature of 250°C or above are referred to as high-temperature ball valves. Depending on different temperature ranges, high-temperature ball valves can be divided into the following categories:

These ball valves are commonly used in scenarios such as ordinary hot water, heating water, steam systems, oil products, and food. They perform well in environments where the working temperature does not exceed 250°C. The sealing surface material generally uses PPL (polyphenylene sulfide), which has good temperature resistance and sealing performance, meeting the requirements of working environments below 250°C.

When the working temperature exceeds 250°C, hard-sealing materials are required to ensure the performance of the ball valve. The valve body of hard-sealing high-temperature ball valves usually adopts WCB (cast steel) material, with a maximum working temperature of up to 425°C and a hardness coefficient of HRC45-58. This type of ball valve features a double-seat single-face sealing structure, with the valve body made of cast steel (WCB), the ball treated with 2CR13+nitriding (2CR13+STL), and the sealing material being STL hard alloy. This design not only enhances the wear resistance and high-temperature performance of the ball valve but also makes it easier to operate and extends its service life.

For ultra-high-temperature environments where the working temperature exceeds 425°C, higher-performance materials are necessary. These ball valves typically use WC6 material, with a maximum working temperature of up to 590°C. The valve seats at both ends of this type of ball valve feature a spring-loaded design, which tightly holds the ball core to ensure good sealing. The sealing material is tungsten carbide, and the spherical surface is treated with spray welding, achieving a hardness coefficient of HRC68-72. This design not only improves the sealing performance of the ball valve but also provides better wear resistance and opening/closing performance in high-temperature environments.

Choosing the right materials is key to ensuring the performance of high-temperature ball valves. Different working temperatures and environmental conditions impose different requirements on the performance of materials. Here are some common materials for high-temperature ball valves and their characteristics:

Cast steel is a commonly used material for the valve body of high-temperature ball valves, with good mechanical and high-temperature performance. Its maximum working temperature can reach 425°C, with a hardness coefficient of HRC45-58. The strength and toughness of cast steel enable it to withstand high pressure and temperature, while also offering good machinability and weldability, making it suitable for manufacturing large ball valves.

2CR13 is a type of stainless steel that, after nitriding treatment, has significantly improved surface hardness and wear resistance. This material is often used to manufacture the ball of high-temperature ball valves, capable of withstanding high temperatures and pressures while also having good corrosion resistance. Its hardness coefficient can reach HRC45-58, making it suitable for use in the temperature range of 250°C-425°C.

STL hard alloy is a high-performance sealing material with extremely high hardness and wear resistance. Its hardness coefficient can reach HRC68-72, allowing it to withstand extremely high temperatures and pressures while also having good corrosion resistance. This material is commonly used to manufacture the sealing surface of high-temperature ball valves, ensuring their sealing performance in high-temperature environments.

ASTM A217 WC6 is a high-performance chromium-molybdenum steel material with extremely high heat resistance and mechanical properties. Its maximum working temperature can reach 590°C, with a hardness coefficient of HRC68-72. This material is commonly used to manufacture the valve body and internal components of ultra-high-temperature ball valves, capable of withstanding extremely high temperatures and pressures while also having good corrosion resistance and wear resistance.

SUS310S stainless steel is a high-temperature resistant stainless steel material with a maximum working temperature of up to 1035°C. This material has good high-temperature stability and mechanical properties, but the carbon content needs to be strictly controlled to ensure it remains between 0.04％-0.08% to maintain its performance. This material is commonly used to manufacture ball valves in extremely high-temperature environments, capable of withstanding extremely high temperatures and pressures while also having good corrosion resistance.

For even higher temperature conditions, it is recommended to use non-metallic heat-resistant materials as linings, such as ceramics and silicon carbide. These materials can withstand extreme high-temperature environments up to 1200°C, with good high-temperature stability and corrosion resistance. They are commonly used to manufacture ball valves in ultra-high-temperature environments, ensuring their performance under extreme high-temperature conditions.

Special high-temperature high-strength alloys, such as those used in engine combustion chambers, can withstand high-temperature environments up to 1000°C. These alloys have excellent high-temperature stability and strength, capable of withstanding extremely high temperatures and pressures while also having good corrosion resistance. They are commonly used to manufacture ball valves in ultra-high-temperature environments, ensuring their performance under extreme high-temperature conditions.

In addition to material selection, structural design is also an important factor in ensuring the performance of high-temperature ball valves. Different structural designs can meet different working requirements, improving the performance and reliability of ball valves. Here are some common structural designs of high-temperature ball valves and their characteristics.

This type of high-temperature ball valve features a double-seat single-face sealing structure, with one side using graphite sealing and the other side using a spring to push the valve seat and ball towards the opposite side to achieve sealing. This design not only enhances the sealing performance of the ball valve but also makes it easier to operate and extends its service life. This structure is suitable for the temperature range of 250°C-425°C, meeting the requirements of most high-temperature environments.

For ultra-high-temperature ball valves above 425°C, a spring-loaded sealing structure is commonly used. The valve seats at both ends of this type of ball valve feature a spring-loaded design, which tightly holds the ball core to ensure good sealing. This design not only enhances the sealing performance of the ball valve but also provides better wear resistance and opening/closing performance in high-temperature environments. This structure is suitable for the temperature range of 425°C-590°C, meeting the requirements of ultra-high-temperature environments.

The elastic sealing pair structure is a commonly used design in high-temperature ball valves. This structure uses a metal sealing pair, with the advantage of a wide applicable temperature range. The thermal expansion coefficients of various metals are not significantly different, and as long as they are properly selected, they can be made basically consistent, which is conducive to coordinating thermal deformation. However, the disadvantage of this structure is that the material has high hardness, and the specific pressure required for sealing is high. Even if pre-tightening force is used to achieve sealing, the wear between the valve seat and the ball is significant due to the high specific pressure. Moreover, the high friction coefficient of the metal sealing surface leads to a larger opening/closing torque for the ball valve. Therefore, most high-temperature ball valves adopt an elastic sealing pair, which is reliable in performance, has strong elastic compensation capability, and is applicable to a wide temperature range, suitable for both floating ball and fixed ball ball valves.

In high-temperature and ultra-high-temperature conditions, the sealing issue of ball valves is a significant challenge. The temperature resistance of packing directly affects the sealing effectiveness and service life of ball valves. Here are some common types of packing and their temperature resistance characteristics:

PTFE packing is a commonly used packing for ball valves, with good corrosion resistance and sealing performance. However, this packing has poor temperature resistance and is typically only suitable for applications below 150°C. If ball valves need to be used in medium to high-temperature environments, an extended valve bonnet must be used to reduce the risk of packing being affected by high temperatures, commonly known as the "extended stem structure." However, this design may lead to insufficient stem strength, causing bending, which further increases the difficulty of maintenance and operation.

Flexible graphite packing is a packing with excellent temperature resistance, with a temperature resistance up to 600°C, exceeding the limit of traditional packing. This packing not only reduces the issues of packing being affected by high temperatures but also lowers the height of the extended valve bonnet, making the valve more compact and suitable for high-temperature environments. Ball valves using flexible graphite packing have better sealing performance and reliability in high-temperature environments, effectively solving sealing problems in high-temperature conditions.

High-temperature ball valves have significant application value in industrial production, and their performance and reliability directly affect production efficiency and safety. Choosing the right materials and structural design is key to ensuring the performance of high-temperature ball valves. In environments below 250°C, PPL material for the sealing surface can meet the requirements; while in environments above 250°C, hard-sealing materials such as STL hard alloy and WC6 are more suitable. For even higher temperature conditions, such as around 1035°C, SUS310S stainless steel and special high-temperature high-strength alloys are ideal choices. Additionally, flexible graphite packing and the "rotary valve with a thick stem" design can effectively improve the sealing performance and stability of ball valves in high-temperature environments.