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Xinxu Sharing: Application Conditions and Operational Guidelines for Gate Valves

2018-11-28

Gate valve refers to the valve whose closing part (gate) moves vertically along the central line of the passage. Gate valves can only be fully opened and disconnected in the pipeline, and can not be used for regulation and throttling. Gate valve is a kind of valve with a wide range of applications. It is usually used for cutting devices with diameter DN (> 50mm), and sometimes for cutting devices with very small diameter.

The gate has two sealing surfaces. The two sealing surfaces of the most commonly used mode gate valves form wedges. The wedge angle varies with the valve parameters, usually 50. When the medium temperature is not high, it is 2 degrees 52 minutes. Wedge gate valve can be made into a whole, called rigid gate; it can also be made into a gate that can produce slight deformation to improve its workability, make up for the deviation of sealing surface angle in the process of processing. This kind of gate is called elastic gate.

When the gate valve closes, the sealing surface can be sealed only by medium pressure, that is to say, the sealing surface of the gate can be pressed to the seat on the other side to ensure the sealing surface sealing, which is self-sealing. Most gate valves are forced to seal, that is, when the valve closes, the gate must be forced to the seat by external force to ensure the sealing surface.

The gate plate of the gate valve moves in a straight line with the stem, which is called the lift bar gate valve (also known as the open bar gate valve). Usually there are trapezoidal threads on the lifting rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is to say, the operating torque is changed into the operating thrust.

When opening the valve, when the gate lifting height is equal to 1:1 times the valve diameter, the flow passage is completely open, but when running, this position can not be monitored. In practical use, the vertex of the valve stem is used as the sign, that is, the position of the valve stem that is not moving is used as its full open position. In order to consider the locking phenomenon of temperature change, the valve is usually opened to the vertex position and reversed to 1/2-1 turn as the position of the fully open valve. Therefore, the full open position of the valve is determined by the position of the gate (i.e. stroke).

1. Gate valves are usually used in open-close situations and cannot be used in throttling applications.

2. Gate valves are usually installed in horizontal pipes with the stem upright. It can also be installed in vertical pipes or horizontal pipes where the stem is not vertical upward, but special structures may be required depending on the size of the valve, application environment and material conditions. If the purchased valve is to be installed in a special way, the direction of the valve should be indicated when ordering.

3. For applications where the temperature exceeds 260 C, flexible or assembled wedge-shaped gate is recommended to avoid the wedge-shaped gate being stuck due to thermal expansion. This may occur when the valve is cold closed and then hot opened.

4. Threaded seat rings should be locked and welded on the body to avoid loosening when used for high-speed fluid (turbulence) or thermal cycling applications. Please specify when ordering.

5. After closing the gate valve, the stem should be slightly rotated (1/8 to 1/4 turns) to release the stem load. This allows the stem to expand slightly without jamming or damaging the valve or affecting the closing effect.

6. If the seat ring is removed to install the handle, the highly integrated shut-off gate valve can be used in hot water outlets or in piping systems using soft iron. Please specify when ordering.

7. Pumping stations can use valves that are not restricted by site, with more debris in water and easy to block important positions, and can use hand-electric gate valves; on the contrary, butterfly valves can be used, especially in pump room renovation projects, in order to effectively utilize the space of the original pump room and achieve the purpose of increasing water supply (discharge) without changing the area of the original pump room.

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