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The closing element of a globe valve is a plug-shaped disc, whose sealing surface is either flat or conical; the disc moves in a straight line along the centerline of the fluid. Depending on the operating conditions, the disc of a US standard check valve can be of all-metal construction, or it can consist of a rubber gasket or ring embedded in a disc frame. A pneumatic check valve is a valve in which the valve disc slides along the center line of the valve body. The pipe-type check valve is a newly developed type of valve; it is small in size, light in weight, and easy to manufacture, making it one of the future development directions for check valves. However, the fluid resistance coefficient is slightly higher than that of the swing check valve. Swing check valves can also be used in pipelines that supply auxiliary systems whose pressure may rise above the system pressure. The movement patterns of the valve stem include a rising and falling stem type (where the stem moves up and down while the handwheel does not move), as well as a rotating stem type via a lifting system (where the handwheel and the stem rotate together to achieve elevation, with a nut mechanism mounted on the control valve body). Stop valves are only suitable for being in the fully open or fully closed position; they cannot be used for regulation or throttling. Globe valves belong to the category of valves with forced sealing; therefore, when the valve is closed, pressure must be applied to the valve disc in order to prevent leakage at the sealing surface. When the medium enters the valve from below the valve disc, the forces that oppose the operating force include the friction between the valve stem and the packing, as well as the thrust generated by the pressure of the medium. The force required to close the valve is greater than that needed to open it, which is why the diameter of the valve stem is relatively large – otherwise, bending and failure of the valve stem may occur. In recent years, with the advent of self-sealing valves, the flow direction in globe valves has changed from above the valve disc to within the valve chamber. Additionally, due to the action of the medium, these types of valves achieve a tighter seal. There are regulations regarding valves in our country; for globe valves, the flow rate is always measured from top to bottom. When a globe valve is open, the flow rate reaches its maximum when the valve’s opening degree is between 25% and 30% of the diameter, at which point the valve is fully open. Therefore, the fully closed position of the valve and the valve disc stroke must be determined. Globe valves have the following advantages: 1. They have a simple structure, making them easy to manufacture and maintain. 2. Short operating stroke and brief opening/closing time. 3. Good sealing performance, with low friction at the sealing surfaces, resulting in a longer service life. The disadvantages of globe valves are as follows: 1. High fluid flow resistance, and significant force is required to open and close them. 2. Not suitable for media with particles, high viscosity, or a tendency to coking. 3. Poor adjustment performance. The valve stem threads of globe valves are of a type where the external threads and internal threads are separated by position. Flow distribution by medium, straight-through type, DC type, and corner type. Some shut-off valves are classified by sealing type: valves with packing seals and those with bellows seals. The main development features of ball valves are a compact economic structure designed by the manufacturers, a reliable sealing system, a simple design, and ease of maintenance and management. The sealing surface and the ball surface remain in a closed state, making them resistant to erosion by the medium flowing through them. They are easy to operate and maintain, and are suitable for use with media found in various industrial environments such as water, solvents, acids, and natural gas. They are also appropriate for use with media that exist under harsh conditions, such as oxygen, hydrogen peroxide, methane, and ethylene, allowing for their broader application across different industries. The ball valve body can be integral or modular. Ball valves have the following advantages: 1. Low fluid resistance; ball valves with a full bore have no flow resistance. 2. Simple structure, small size, and light weight. 3. Tight and reliable. It has two sealing surfaces, and in China, various plastics are widely studied and used as materials for the sealing surfaces of ball valves; these materials provide good sealing performance, enabling complete sealing in industrial applications. It is also widely used in vacuum management systems. 4. It is easy to operate, with quick opening and closing; only a 90-degree rotation is required to go from fully open to fully closed, which facilitates remote control. It is also easy to maintain – being a simple ball valve, its seals are usually movable, making disassembly and replacement simpler.