Abstract: To meet the growing demand for high-performance cryogenic control valves in the liquefied natural gas (LNG) industry, this study introduces the design of an advanced cryogenic ball valve. With a nominal diameter of NPS 4 and a pressure rating of ANSI Class 900, this cryogenic ball valve ensures stable performance in extreme low-temperature environments as cold as -196°C. This paper provides a comprehensive analysis of key technologies for the valve, including flow control principles, cryogenic material selection and treatment, structural design, and performance simulation. The design further optimizes the valve core, pilot mechanism, and pressure balancing system. Detailed inspection procedures and performance testing protocols are implemented to ensure the valve's safety and reliability in real-world applications. Finally, the study summarizes the key challenges faced during the design process— including sealing effectiveness under high differential pressure, valve opening resistance, and unbalanced stem forces caused by fluid dynamics— and presents effective solutions for each issue.
As the global energy landscape rapidly evolves, environmental sustainability has emerged as a critical concern, driving increased demand for clean energy sources. Liquefied natural gas (LNG), known for its high efficiency, low emissions, and environmental benefits, is increasingly becoming the preferred alternative to traditional fossil fuels like oil and coal. In recent years, China’s domestic LNG industry has seen rapid expansion, alongside significant advancements in cryogenic valve technology. Although high-performance cryogenic valves have traditionally been imported, an increasing number of domestic manufacturers are actively collaborating with international oil and gas companies to advance the independent research, development, and localization of cryogenic valve technology. These initiatives aim to satisfy the growing demand for reliable LNG equipment in the domestic market. On the innovation front, China Oil & Gas Pipeline Network Corporation (PipeChina) has successfully achieved the localization of a full range of cryogenic butterfly valves for LNG receiving terminals. These valves have been successfully deployed in real-world applications, marking a significant milestone in the localization of key LNG equipment. This breakthrough has not only lowered procurement costs but also greatly shortened delivery lead times. Meanwhile, domestic research institutions and enterprises are rapidly advancing natural gas liquefaction technologies and related equipment, providing a strong foundation for the localization and self-reliance of China’s cryogenic valve industry. This study presents a newly developed cryogenic ball control valve featuring a nominal diameter of NPS 4, a temperature range from -196°C to 150°C, butt-weld (BW) connections, and a top-mounted design. The external sealing performance meets ISO 15848-2 Class B standards. The valve combines a pneumatic diaphragm actuator with an intelligent electric positioner, supporting 4–20 mA plus HART signal control, positive action operation, and linear cam characteristics. With a control accuracy of ±0.5%, this valve is ideal for precise regulation of cryogenic fluids. The sealing structure, pilot design, and pressure balancing mechanism have been optimized to meet the stringent performance demands of the LNG industry’s cryogenic control valves.
The ball control valve is a rotary valve commonly used for precise fluid regulation. Its core component—a ball-shaped element—rotates along the axis to adjust the flow passage opening, enabling accurate flow rate control. Depending on process requirements, the flow channel inside the ball valve can be designed in various configurations—such as straight or curved—to accommodate different flow characteristics and optimize fluid control. Its streamlined flow path design minimizes the buildup of solid particles within the fluid, providing a self-cleaning effect. Additionally, the valve’s bidirectional sealing structure guarantees reliable sealing performance even when the flow direction reverses. The sealing surfaces of the ball valve are designed for superior corrosion and wear resistance, allowing the valve to perform reliably in harsh chemical environments. This durability extends the valve’s service life and ensures consistent performance under demanding operating conditions. During operation, the actuator rotates the ball, with the valve opening degree directly proportional to the ball’s rotation angle. The valve’s flow regulation accuracy relies heavily on the precise design of the ball, the effectiveness of the sealing mechanism, and the structural optimization of the valve body. Ball control valves can regulate flow as well as maintain critical parameters like fluid pressure and temperature. As shown in Figure 1, their fundamental operating principle makes them ideal for controlling the flow of liquids, gases, steam, and other media. In cryogenic applications, such as liquefied natural gas (LNG) systems, valve designs must consider the impact of extremely low temperatures on materials, sealing components, and actuation mechanisms to ensure reliable and long-lasting performance. These design considerations ensure long-term stability, superior sealing performance, and increased durability in ultra-low temperature environments.
Figure 1 Basic principle of control valves
Liquefied natural gas (LNG) is stored at an ultra-low temperature of -162°C. Under these extreme conditions, metal materials are susceptible to embrittlement, leading to reduced impact toughness and ductility, which increases the risk of brittle fracture. Therefore, when operating under cryogenic conditions—particularly in LNG applications—valve materials must exhibit excellent toughness, impact resistance, and a stable microstructure. Austenitic stainless steels, such as grades 304 and 316, are the preferred materials for cryogenic control valves because of their excellent corrosion resistance and their ability to maintain ductility even at temperatures as low as -196°C. These materials provide high durability and retain stable mechanical properties in extreme low-temperature environments, making them ideal choices for manufacturing LNG valves. In addition to stainless steel, nickel-based alloys are widely used in cryogenic valve applications due to their excellent resistance to low-temperature embrittlement and corrosion, making them highly effective in preventing brittle failure. Although aluminum alloys have lower corrosion resistance, their strength increases at low temperatures, making them suitable for specific lightweight cryogenic applications. To further enhance the performance of metals in cryogenic environments, deep cryogenic processing—such as low-temperature tempering—is often employed to improve the toughness and impact resistance of stainless steel. Additionally, surface coating treatments are applied to critical components to significantly enhance corrosion and wear resistance, ensuring long-term stability and reliability under harsh operating conditions.
In ultra-low-temperature environments, the selection of non-metallic materials is crucial to ensuring the sealing performance and overall reliability of cryogenic valves, especially in seal and gasket components. These materials must maintain excellent elasticity and sealing integrity under extreme cryogenic conditions. PTFE (polytetrafluoroethylene) is one of the most widely used non-metallic materials in cryogenic applications. Owing to its exceptional chemical stability and compression resistance, it delivers reliable sealing performance and long-term durability at low temperatures. It also offers excellent resistance to temperature fluctuations, and its high hardness makes it well-suited for high-pressure sealing systems. Another key material is PCTFE (polychlorotrifluoroethylene), known for its superior resistance to embrittlement and its ability to maintain reliable sealing performance in extremely low temperatures. It is widely regarded as an ideal sealing material for LNG valves and other cryogenic service applications. In addition, fluororubber and silicone rubber are elastomeric materials that retain flexibility and elasticity at low temperatures, making them suitable for seals used in cryogenic valves. To improve low-temperature performance, special plasticizers are often incorporated to prevent hardening. However, the operating temperature range of rubber seals remains more limited than that of fluoropolymers, so material selection must be carefully aligned with the specific service conditions.
