Directional gate valve
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I would like to ask the experts here; I’ve encountered two types of gate valves. They are all marked with arrows. What is the difference between those with arrows and those without? Can a gate valve with arrows be installed in reverse, and what are the consequences of doing so?
In some gate valves, especially those with a single gate, the sealing between the gate and the seat is achieved through the pressure of the medium; this pressure presses the sealing surface of the gate against the sealing surface of the seat, thereby providing sealing. This requires a fixed direction of installation, which is indicated by arrows. Some double-plate gate valves provide two-way forced sealing, and they do not rely on the pressure of the medium for sealing; therefore, it doesn’t matter whether such valves have arrows indicating the flow direction or not.
Valves with one-way sealing are likely to experience internal leakage if installed in the wrong direction.
This type of gate valve has a specific orientation for installation. The key feature is that the gate plate is equipped with relief holes, which serve to prevent low-temperature media from causing the valve to fail to open due to thermal expansion when the system is shut down or other valves are closed. In more severe cases, this could even lead to the valve bursting and resulting in accidents. Some gate valves have direction indicators, which indicate the direction of sealing; the direction pointed to by the arrow is the direction from the high-pressure side to the low-pressure side for sealing. In the case of gate valves with a single sealing surface, the end of the arrow indicates the sealing side.
It cannot be installed in reverse. Gate valves have fixed seats and floating seats. One end of the floating valve seat is usually equipped with a spring, which serves to ensure sealing between the gate and the fixed valve seat; in addition, a pressure relief hole is provided on the floating valve seat ； If it is installed backwards, the gate valve will leak.
With flow direction indicators, it’s likely that the valve seat structures on both sides will differ; it won’t work if installed in the reverse order
It cannot be installed in reverse; the sealing types of the gate plates are different, and installing it in reverse may prevent the valve from achieving an effective seal. Installing a wedge-type gate valve in reverse may prevent it from opening properly.
May I ask what the purpose of the relief holes is? On my liquid ammonia gate valves, there are cut marks indicating the direction opposite to that of the fluid flow. Thank you.
May I ask what the structure of a pressure relief hole is and what its function is?
This device measures pressure; for pipelines with a slight positive pressure, it doesn’t matter whether they are installed in the correct or reversed orientation. But since valves have a direction, why not operate in accordance with that direction? . .