From turning off the main water valve at home, controlling oil transport in industrial pipelines, to regulating flow in municipal water supply networks, all these scenarios involve an unobtrusive yet crucial industrial component—a gate valve.
As one of the most widely used shut-off valves, many people only perceive it as a “valve that can open and close.” In fact, every detail, from structural design to selection and installation, directly affects the operational safety of the piping system. Today, we will break down the complete knowledge system of gate valves, which can serve as a reference for both daily household use and industrial procurement.
Working Principle
The core function of a gate valve is to control the flow of the pipeline. Its internal structure is not complicated: the key component is a gate plate oriented perpendicular to the direction of the fluid flow. When we turn the valve stem, the gate plate moves up or down. When fully lowered, it can completely shut off the pipeline; when fully raised, the fluid can pass smoothly.
Compared with other valves such as ball valves and butterfly valves, the biggest advantage of a gate valve is “minimal flow resistance”: when the gate plate is fully open, the entire pipeline is unobstructed, and the fluid experiences almost no pressure loss, making it especially suitable for large-diameter, high-flow scenarios. However, it also has notable drawbacks: the opening and closing stroke is long. A DN100 gate valve often requires more than ten turns of the stem to fully open or close, which is unsuitable for situations requiring frequent flow adjustments. Moreover, when left partially open for extended periods, the high-speed flowing medium can erode the sealing surface of the gate plate, leading to leakage.
Classification and Applications of Gate Valves
Applications of gate valves under different classifications. According to structure and function, gate valves on the market can be divided into three types, each suitable for entirely different scenarios:
Rising Stem Gate Valve
The valve stem thread is exposed outside the valve body. When turning the handwheel, the height of the stem’s rise is visible, making it easier for operators to judge the open or closed status. Additionally, the external thread facilitates lubrication and is less prone to corrosion by the medium. This type is generally selected for industrial water transport, oil and gas pipelines, and other applications requiring high reliability.
Non-Rising Stem Gate Valve
The valve stem thread is hidden inside the valve body. When opening or closing, the stem does not protrude, resulting in a more compact footprint. This is particularly suitable for space-limited underground networks or fire protection pipes. The downside is that the opening position cannot be easily observed, leading to issues such as incomplete closure or over-opening.
Elastic Seated Gate Valve
The surface of its gate plate is covered with a layer of rubber, which achieves sealing through the elastic deformation of the rubber. Compared with traditional metal-sealed gate valves, it offers better sealing performance. Even if the medium contains small amounts of sand or impurities, it is less likely to leak. Currently, household water pipes and municipal water supply systems have basically switched to this type.
Three Key Points for Selection
The first is the nominal pressure, which directly corresponds to the maximum pressure the valve can withstand. For example, household pipeline pressure is typically below 1 MPa, so a product with a nominal pressure of 1.6 MPa is sufficient, whereas industrial high-pressure pipelines should select a product 1–2 levels higher than the system design pressure to avoid pressure overload and potential bursting.
The second point is the nominal diameter, which refers to the pipe size that the valve fits. Be careful not to only look at the external diameter of the valve; it should match the nominal diameter of the piping to avoid issues such as insufficient flow or leakage after installation.
The third point is medium compatibility. If the valve is used to transport special media such as acids, alkalis, oils, or high-temperature steam, special attention must be paid to the materials of the gate plate and sealing components. For example, if transporting strong acids, a gate valve with a fluorine-lined material should be selected. For high-temperature steam, a high-temperature resistant alloy steel gate valve is needed. Using an ordinary cast iron gate valve for special media will result in corrosion and leakage within a few months.
Maintenance Tips
Firstly, do not use a gate valve to regulate flow. When kept in a partially open state for a long time, the medium will erode the sealing surface of the gate dozens of times more than in the fully open state, which can easily cause wear and internal leakage.
Secondly, for gate valves that are rarely operated, it is best to turn the handwheel once every 2-3 months to prevent the valve stem from rusting. Before turning, apply a small amount of lubricant to the stem threads. Do not use excessive force when opening or closing. If it cannot turn, do not pry it with a wrench. First, check if the stem is rusted or obstructed. Forcing it may easily break the stem.
If a gate valve is found not to seal properly, there is no need to rush to replace it. Often, the sealing surface is simply stuck with debris. Repeatedly operating the valve a few times to flush out the debris can restore sealing performance. If it still leaks, then disassemble and replace the sealing gasket.
