Some knowledge about valves (I)

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Throttle valve Definition: A valve that regulates flow and pressure by changing the cross-sectional area of the passage through the movement of a closing element (valve disc). Throttle valves are primarily used to regulate flow rate and pressure. When selecting such valves, factors such as the flow control range, pressure drop, and the load must be taken into account to prevent premature failure and ensure safe use. Throttle valves are very similar to globe valves in terms of appearance and structure; the only differences lie in the shape of the valve disc and its stroke. The components of throttle valves and globe valves are highly interchangeable. Various cut-off valves can change the cross-sectional area of the medium flow path, and thus can also serve a regulating function to a certain extent. Since the opening and closing element of the shut-off valve and the valve stem are connected in a movable manner, there is a gap at the connection point, which makes adjustment difficult ； The elevation of the opening/closing element is not proportional to the change in the channel area, making accurate and continuous adjustment difficult to achieve ； When the channel area is small and the medium flow velocity is high, it can cause severe erosion of the sealing surface. and causes vibration of the valve disc. Therefore, throttle valves with specialized structures and valve element shapes are typically used for regulation. The throttle valve seat has poor sealing performance, and it is often unreliable when used as a stop valve. Gate Valve Definition: A gate valve is one of the most common types of isolation valves; its primary purpose is to stop the flow of fluids, and it is also known as a shut-off valve or blocking valve. Gate valves are generally used in applications that require full open or full closed operation. Advantages: Thanks to the fit between the gate valve and the seat ring, almost no leakage occurs when the gate valve is closed. Normally, gate valves open and close slowly, and this characteristic helps prevent fluid water hammer effects from damaging the pipeline system. Limitation: It cannot be applied to throttling conditions. Generally, gate valves are more prone to wear on the valve seat and gate plate sealing surfaces than globe valves, and the repair of such wear. It is difficult to achieve this through grinding and polishing. Definition of ball valve: A ball valve operates by rotating a sphere 90 degrees around the axis of the valve stem to achieve opening and closing. Its function in pipelines is primarily to shut off, distribute, and change the direction of fluid flow. Ball valves not only have a simple structure and good sealing performance, but also feature a small size, light weight, reduced material consumption, and compact installation dimensions within a certain nominal diameter range. Additionally, they require low driving torque, are easy to operate, and allow for quick opening and closing. Definition of a globe valve: It allows fluid to flow in one direction only; it can be used with the fluid entering from a lower level to a higher level or from a higher level to a lower level. Function: A globe valve is a type of shut-off valve used to stop or allow the flow of fluid through a pipeline. It is not suitable for regulating the pressure or flow rate of the fluid. If it is used for throttling over an extended period, the sealing surfaces will be eroded by the fluid, resulting in a loss of sealing integrity.