In the nuclear power industry, stop valves are important equipment for controlling the flow of media and cutting off pipelines, and have high safety and reliability requirements. Especially in nuclear-level applications, the design of stop valves needs to meet stringent working conditions, including high temperature, high pressure, corrosive environments, etc. CHNLGVF丨中國大乾閥門 is committed to promoting the high-quality R&D and manufacturing of nuclear-grade pneumatic stop valves. This article will start with the flow capacity and two-way sealing characteristics, discuss the design optimization of stop valves, and propose new design concepts to improve nuclear power Globe valve performance in application.

The pneumatic stop valve controls the flow of media by driving the opening and closing movement of the valve disc through a pneumatic actuator. Due to its fast response speed and high control accuracy, pneumatic stop valves are widely used in nuclear power systems. Nuclear grade pneumatic stop valves usually need to have the following characteristics:

Under high flow rate conditions, the valve must maintain a low flow resistance to ensure smooth flow of the medium. The flow capacity is usually measured by the flow coefficient (Cv value) of the valve. The higher the Cv value, the better the flow performance of the valve.

Bidirectional sealing means that the valve can still ensure effective sealing when the pressure of the medium on both sides is balanced or reversed. Traditional stop valves generally only have one-way sealing capabilities, but in nuclear power operating conditions, the flow direction often changes, so a two-way seal design is particularly important.

Globe valves in nuclear power systems are often required to withstand extreme temperatures and pressures, so the valve materials and sealing structures must be able to maintain stable performance under these conditions for a long time.

The flow capacity of a globe valve is mainly affected by the design of the valve channel and the shape of the valve disc. In the traditional globe valve design, the valve disc usually adopts a flat or conical structure. However, these two structures will still produce resistance to the flow of the medium when fully open, reducing the flow coefficient of the valve. In order to improve the flow capacity, optimizing the valve channel design and reducing local flow resistance have become key.

In order to reduce the flow resistance, CHNLGVF optimized the geometry of the internal channel of the stop valve through fluid mechanics simulation analysis. The streamlined channel design can effectively reduce the turbulence and vortex of the medium when flowing through the valve, thereby increasing the Cv value. This optimization not only improves flow performance, but also reduces pressure loss while ensuring sealing performance.

Cone seals are widely used in the sealing design of globe valves. Its tapered structure provides a larger contact area when the valve is closed, thereby improving the sealing effect. However, when the valve is open, the cone seal structure may have a certain impact on the flow capacity. To this end, CHNLGVF adopts an optimized design of the cone angle to ensure the sealing effect while minimizing the obstruction of the valve disc to the fluid.

In nuclear power systems, the direction of medium flow may reverse as the system operating conditions change, and the traditional one-way seal design cannot meet this demand. In order to improve the bidirectional sealing capability of the stop valve, a sealing structure with bidirectional pressure bearing capability must be adopted to ensure that the valve can provide reliable sealing performance no matter how the flow direction changes.

To enhance the bidirectional sealing performance, CHNLGVF introduced a metal C-ring sealing structure into the design of the stop valve. The C-ring possesses outstanding elastic recovery capability and can sustain excellent adaptive sealing performance across various pressure conditions. Metal C-rings exhibit a more stable sealing effect under high temperature and pressure compared to traditional soft seals, maintaining consistent sealing ability even when the flow direction changes.

CHNLGVF丨China Daqian Valve adopts a design scheme that combines cone seals and metal C-ring seals to ensure that the stop valve can provide stable bidirectional sealing performance under different flow directions and different pressure conditions. The cone seal provides a preliminary mechanical seal when the valve is closed, while the metal C-ring further enhances the sealing effect through its elastic deformation. This design significantly improves the sealing reliability of the stop valve under complex working conditions.

Under extreme working conditions, traditional pneumatic stop valves often suffer from valve seal failure or difficulty in operation due to thermal expansion and high pressure difference. In order to meet this challenge, CHNLGVF proposed a new valve body structure design, using an adaptive compensation valve body and valve stem structure. Under high temperature conditions, the different expansion rates of the valve body and valve stem are balanced through the designed compensation mechanism to ensure that the valve opens and closes flexibly without affecting the sealing performance.

While improving the flow capacity of the stop valve, the sealing performance cannot be ignored. CHNLGVF proposes a balanced design concept and found the best balance point between flow and sealing through fluid simulation and experimental testing. Specifically, by optimizing parameters such as the cone angle and surface roughness of the valve disc and valve seat, the flow resistance of the valve is greatly reduced when it is fully open, while it can still provide reliable two-way sealing when it is closed.

With the continuous advancement of intelligent technology, CHNLGVF | China Daqian Valve has also introduced intelligent control and monitoring technology into pneumatic stop valves. Through sensors and data acquisition systems, the working status of the valve is monitored in real time, including key parameters such as opening and closing positions, sealing pressure, etc. Through the intelligent control system, not only can the valve be remotely controlled, but the operating parameters of the valve can also be automatically adjusted according to changes in the working environment to ensure that the valve is always in the best working condition. This design greatly improves the safety and reliability of nuclear-grade stop valves.

The manufacturing of nuclear-grade stop valves requires extremely high precision to ensure their stable operation under extreme working conditions. CHNLGVF丨中國大乾閥門 has introduced advanced CNC machining technology and precision testing equipment to ensure the processing accuracy of key components of the valve (such as valve seats, valve discs and sealing components). Through the high-precision control of the CNC machining center, the various dimensional errors of the valve can be controlled within a very small range, ensuring its stable performance under different working conditions.

Before the valve leaves the factory, all nuclear-grade pneumatic stop valves must undergo strict reliability testing, including flow capacity testing under high temperature and high pressure conditions, two-way sealing performance testing and fatigue life testing. CHNLGVF丨中國大乾閥門 simulates the real nuclear power system environment to verify the performance of the valve to ensure its long-term stable operation in practical applications. In addition, the company has established more stringent internal testing standards to further ensure the high quality of its products.

With the development of material science, nuclear-grade pneumatic stop valves will have more room for innovation in material selection in the future. CHNLGVF plans to further research new high-temperature-resistant and corrosion-resistant materials, such as ceramic matrix composite materials, high melting point alloys, etc., to improve the performance of stop valves under extreme working conditions.

Although metal C-ring seals have performed well in current applications, in future designs, the adaptability and durability of the seal structure need to be further improved. Through the improvement of materials and processes, it is ensured that the sealing performance of the stop valve can operate stably under higher temperatures and more complex working conditions.

In the future, with the popularization of intelligent manufacturing, the production and management of nuclear-grade pneumatic stop valves will further develop in the direction of intelligence and digitalization. CHNLGVF丨中國大乾閥門 will continue to introduce intelligent production lines and digital management systems, and continuously optimize the production and management of stop valves through big data analysis and machine learning.