Abstract: Based on the author's research on ball valves for long-distance pipelines in China over the past few years, this paper introduces a newly designed pipeline valve—the emergency shut-off ball valve—and provides a detailed description of its main structure. Keywords: Long-distance pipeline ball valve design research I. Overview To promote the rapid economic development of western China, the state has made the major decision to develop the western region. Developing oil and natural gas resources in Xinjiang is one of the major initiatives in this development. The only way to fully utilize the oil and gas resources in the west is to transport them to eastern China via pipelines. To this end, the state will construct the "West-East Gas Pipeline" project, laying a main pipeline from the Lunnan Gas Field in Tarim to the Shanghai area, with a total length of approximately 4200 km. From international experience in construction and transportation, it is more economical to build one large-diameter pipeline than several small-diameter pipelines for the same transport capacity; moreover, increasing the transport pressure of the medium within a certain range can also increase efficiency. Therefore, the West-East Gas Pipeline adopts a pipe diameter of DN = 1000 mm and PN = 10.0 MPa. Such parameters are unprecedented in China's previous gas pipeline networks. The West-East Gas Pipeline in China is long, traversing deserts, rainforests, swamps, mountains, rivers (Yangtze and Yellow Rivers), and plains. The climate along the route is harsh, with ambient temperatures ranging from -30°C to 80°C, resulting in poor environmental conditions. Therefore, the requirements for valves in long-distance pipelines are much higher than those for general-purpose valves, demanding higher reliability, better sealing, and greater strength to ensure the safe and reliable operation of the pipeline. II. Development of Pipeline Ball Valves The development of long-distance pipelines in China has reached a considerable scale over several decades, especially in the development of pipeline ball valves. Currently, domestically produced pipeline ball valves used in domestic pipelines have achieved parameters of PN = 6.4 MPa and DN = 1000 mm, but this is still some distance from the parameters required for the West-East Gas Pipeline project. Furthermore, emergency shut-off devices for pipeline ball valves cannot yet be produced domestically. Furthermore, there is no history of domestic application of fully welded ball valves. III. Relevant Standards for Pipeline Ball Valves: AP16D Pipeline Valves; AP16FA Valve Fire Resistance Test; AP1607 Resistant Sealing and 90°C; Fire Resistance Test for Diverting Valves; AP1598 Valve Inspection and Testing; ANSI B16.34 Flange, Threaded and Welded End Valves; JB/T7745 Pipeline Ball Valves . IV. Characteristics and Requirements of Pipeline Ball Valves : In long-distance pipelines, pipeline ball valves are required to control the medium in the pipeline, functioning as on/off valves, changing the direction of medium flow and preventing backflow, sending or passing a cleaning ball through the pipeline, preventing accidents, automatically and urgently shutting off, closing or opening the pipeline, etc. 1. Reliable Sealing Performance : Long-distance pipelines can only be inspected periodically, and sometimes need to pass through remote areas (high mountains, deserts, grasslands, and earthquake-prone regions). Even small leaks can cause large amounts of medium loss, wasting energy, especially in the West-East Gas Pipeline project, where the sealing performance of natural gas pipelines is even more stringent. In addition, it must have sealing performance for emergency grease injection. 2. Long service life requirement Once a pipeline is put into operation, it cannot be shut down for several years or even decades; the longer the operation time, the better. Natural gas serves large users, acting as raw materials or energy for factories and enterprises, and cannot tolerate even a moment's interruption. Therefore, key components such as valve seats must have a long service life. 3. High strength and resistance to external forces for pipeline valves In the West-East Gas Pipeline project, the pressure of pipeline ball valves reaches 10.0 MPa, and the diameter reaches 1000 mm. Furthermore, the pipeline has long station spacing, reaching approximately 20 km in length. During use, valves are subjected to complex external forces such as thermal expansion and contraction, equipment vibration, earthquakes, and foundation changes. Valves in the pipeline are frequently affected by combined stresses such as tension, bending, and compression. To ensure normal operation, valves must possess sufficient strength. 4. Corrosion resistance of pipeline ball valves Because natural gas contains hydrogen sulfide, which can react with iron to form iron sulfide, corroding valves and penetrating machinery, pipeline ball valves should be made of corrosion-resistant materials. 5. High Degree of Automation The control of pipeline ball valves is located in a central control room, which is relatively far away. Therefore, remote control is required, and emergency shut-off is necessary in case of an accident, with a shut-off time of approximately 15 seconds. During normal pipeline operation, valves may not operate for several years; once activated, they must be accurate and reliable. 6. Pipeline Valves Require Lightweight, Compact Structure, and Full Bore To ensure valves can be installed in complex environments, meet underground requirements, and are easy to maintain, they must be lightweight, compact, and full bore, facilitating cleaning during normal pipeline operation. V. Design Research Main technical parameters of the pipeline ball valve: Nominal pressure PN = 10.0 MPa; Nominal diameter DN = 1000 mm; Actual diameter DN = 1016 mm; Ambient extreme temperature: -36-80℃; Medium: Natural gas (containing hydrogen sulfide and carbon dioxide); Opening and closing time: Closing <15s, Opening = 60s. Based on the requirements of usage and standards, as well as the requirements for long-distance pipeline ball valves, and combined with the technical parameters of the pipeline ball valve, we conducted the following design research: 1. Fully welded emergency shut-off pipeline ball valve The fully forged and welded structure uses a forged valve body, which is welded after assembly. This changes the previous casting and bolted connection structure, eliminating external leakage from the valve body. Compared to castings, forgings allow for thinner walls and higher strength, eliminating the need for a middle flange and dozens of bolts, significantly reducing weight. Tests show a weight reduction of 1/4. 2. Sealing Structure The sealing structure is the key design for the sealing performance of ball valves. Providing a good sealing structure directly affects the service life of ball valves. Based on research, we provide the following structures that meet practical requirements: (1) Double Piston Effect Seat The basic principle of the double piston effect valve seat is that the valve has two valve seat seals. If the upstream valve seat is damaged, the medium enters the middle cavity, but the pressure in the middle cavity can still make the downstream valve seat achieve a seal. P2>P1 P2+P0>P1 Where P0 is the spring force, and the unit is N. Therefore, when there is pressure in the middle cavity, the medium force can make the valve seat press against the ball to achieve the purpose of sealing. (2) Double Seal To make the valve seal more effectively, this structure adopts a double sealing structure, namely, a polytetrafluoroethylene (PTFE) soft seal. In addition, a metal hard seal is added. If the soft seal has a problem, the metal seal can also play a role, as shown in Figure 2. At the same time, the metal hard seal is also a fireproof structure design, that is, when the soft seal is burned by fire, the metal hard seal can seal. (3) Emergency Grease Sealing: If the sealing surface is damaged by foreign objects or other reasons, the grease filling system in the valve seat can provide a quick and simple way to restore tight closure by filling grease to achieve a seal. In addition, the filling system can also be used for the sealing area of ​​the valve seat in periodic situations. Simultaneously, an emergency grease filling system is added to the valve stem seal for supplementary sealing. 3. Anti-static and Fireproof Structure: The standard requires that the ball valve must have an anti-static and fireproof structure. An anti-static structure is installed between the ball, valve stem, and valve body, and a fireproof structure is installed on the sealing ring. In the event of a fire, the metal sealing ring can still achieve a seal. 4. Emergency Shut-off Device: When a pipeline accident occurs, the ball valves at both ends of the pipeline are required to perform emergency shut-off. Generally, it is required to close both valves within 15 seconds, or even less. Currently, most valve manufacturers use foreign pneumatic-hydraulic linkage emergency shut-off devices. This device directly utilizes the medium transported in the pipeline, using the pressure of the medium, and is controlled by a sensing device or instructions from the main control room to sense the accident signal and directly control the valve to achieve the purpose of emergency shut-off. 5. Fixed Ball Structure To reduce the bending stress caused by the medium pressure on the ball and valve stem, the connection between the valve stem and the ball is designed as a segmented structure to avoid the medium pressure acting directly on the valve stem, which would make it difficult to open and close the valve. In addition, the supporting cross-sectional area of ​​the ball is increased to improve the rigidity of the ball. In summary, the above-mentioned schemes can meet the requirements of the standard for valves and also meet the needs of the project. VI. Development Trend of Pipeline Ball Valves In recent years, with the rapid development of long-distance pipelines, pipeline ball valves, as one of the emergency shut-off valves, have also developed very rapidly, mainly showing the following development trends: (1) Larger size and higher parameters Currently, pipeline ball valves have developed to a nominal pressure of PN=14.0 MPa and a nominal diameter of DN=1400mm. Larger size and higher parameters will bring greater economic benefits to transportation. (2) High-strength corrosion-resistant materials The increase in valve size and pressure urgently requires the research of new high-strength corrosion-resistant forging materials to meet the needs of continuously increasing valve size. (3) Multiple sealing structure: To ensure the valve's sealing performance, a multi-composite sealing structure is being researched to ensure a service life of 50 years or even longer. (4) High reliability and rapid closure: Emergency shut-off ball valves are often left open for extended periods in gas pipelines, sometimes not operating for up to ten years. However, once activated, they must be accurate and reliable, ensuring higher reliability and rapid closure in a shorter time. (5) Higher degree of automation: Emergency shut-off ball valves can detect accidents and automatically close, with a longer detection distance. VII. Conclusion Emergency shut-off ball valves are increasingly widely used in the construction of long-distance pipelines. The above design structure ensures the valve's sealing performance, long service life, safety, and corrosion resistance, making it perfectly suitable for use in the construction of long-distance pipelines.