The five most common types of valves in chemical process pipelines

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①Globe valves are widely used in medium and low-pressure pipelines due to their simple structure and ease of manufacturing and maintenance. It achieves the purpose of stopping fluid flow by utilizing a circular valve disc (valve head) mounted below the valve stem, which fits together with the flanged portion inside the valve body (valve seat). The valve stem can be raised or lowered via threads to adjust the degree of opening of the valve, thereby serving a regulatory function. Since the shut-off action of the valve relies on sealing through the contact between the valve stem and the valve seat surface, it is not suitable for use in pipelines carrying fluids containing solid particles. For stop valves, the appropriate materials for the valve disc, seat, and housing can be selected based on the properties of the medium used. For valves that are damaged during use due to poor sealing or issues with components such as the valve stem and seat, methods such as grinding, honing, or welding inlays can be employed to repair them and extend their service life. ②A ball valve, also known as a sphere valve, is a type of valve that has seen rapid development in recent years. It uses a sphere with an opening in the middle as the valve core, and relies on the rotation of the sphere to control whether the valve is open or closed. It is similar to a plug, but has a smaller sealing surface than one; it is compact in design, requires less effort to operate, and is far more widely used than plugs. With the improvement in the manufacturing precision of ball valves, they are now used not only in medium and low-pressure pipelines but also in high-pressure pipelines. However, due to limitations of the sealing material, it is not yet suitable for use in high-temperature pipelines. ③A gate valve achieves sealing by using one or two plates perpendicular to the direction of fluid flow, which work in conjunction with the valve body’s sealing surface. The raising of the valve plate opens the valve. The plate rises and falls as the valve stem rotates, and the flow rate of the fluid is adjusted by the degree of opening. This type of valve features low resistance, good sealing performance, and easy operation; it is particularly suitable for large-diameter pipelines. However, gate valves have a more complex structure and come in many different types. Depending on the structure of the valve stem, there are open-type stems and concealed-type stems ； Based on the structural design of the valve plate, it is further divided into wedge type, parallel type, etc. Generally, wedge-shaped valve plates are single-plate, while parallel types use two valve plates. Parallel types are easier to manufacture and repair than wedge types, and they do not deform easily during use; however, they are not suitable for use in pipelines transporting fluids containing impurities. They are commonly used in pipelines for transporting water, clean gases, oils, etc. ④A butterfly valve operates by using a rotatable disc (or elliptical disc) inside the pipe to control the opening and closing of the pipeline. It has a simple structure and small external dimensions. Due to issues with the sealing structure and materials, this valve has poor sealing performance and is only suitable for regulation in low-pressure, large-diameter pipelines; it is commonly used in pipelines that transport media such as water, air, and gas. ⑤A check valve is also known as a non-return valve or a one-way valve. A check valve in the pipeline ensures that fluid can flow only in one direction, preventing reverse flow. It is a valve that closes automatically, with a valve disc or flap inside the valve body. When the medium flows in the forward direction, the fluid automatically pushes the valve disc open ； When the fluid flows back, the fluid (or spring force) automatically closes the valve disc. Based on the structure of the check valve, they are divided into lift-type and swing-type categories. The lift-type check valve disc moves up and down perpendicular to the valve body channel, and is generally used in horizontal or vertical pipelines ； The disc of a swing check valve is often referred to as a flap; one side of this flap is connected to the shaft, allowing it to rotate around that shaft. Swing check valves are generally installed in horizontal pipes, and those with smaller diameters can also be used in vertical pipes, but care must be taken to ensure that the flow rate is not too high. Check valves are generally suitable for use in pipelines carrying clean fluids; they are not appropriate for use in pipelines with solid particles or fluids of high viscosity. Lift-type check valves have better sealing performance than swing-type ones, but swing-type check valves present less fluid resistance compared to lift-type ones. Under normal circumstances, swing check valves are suitable for large-diameter pipelines. Check valves are generally suitable for use in pipelines carrying clean fluids; they are not appropriate for use in pipelines with solid particles or fluids of high viscosity. Lift-type check valves have better sealing performance than swing-type ones, but swing-type check valves present less fluid resistance compared to lift-type ones. Under normal circumstances, swing check valves are suitable for large-diameter pipelines.