HONGDA Valves

How Does A Gate Valve Work

How Does A Gate Valve Work?

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A gate valve refers to a valve in which the closing member (gate) moves in the vertical direction of the centerline of the passage. The gate valve can only be used to cut off fully open and fully closed in the pipeline, and cannot be used for adjustment and throttling. Gate valve is a kind of valve with a wide range of use. Generally, it is selected for the cut-off device with a diameter of DN50, and sometimes a gate valve is also used for the cut-off device with a small diameter. The gate valve is used as a cut-off medium. When fully open, the entire flow is straight, and the pressure loss of the medium is minimal at this time. Gate valves are usually suitable for conditions that do not require frequent opening and closing, and keep the gate fully open or fully closed. Not intended for use as regulation or throttling. For high-speed flowing media, the gate can cause vibration of the gate when it is partially opened, and the vibration may damage the sealing surface of the gate and the valve seat, and the throttling will cause the gate to be eroded by the medium.

From the structural form, the main difference is the form of the sealing element used. According to the form of the sealing element, the gate valve is often divided into several different types, such as: wedge gate valve, parallel gate valve, parallel double gate valve, wedge double gate gate valve, etc. The most common forms are the wedge gate valve and the parallel gate valve.

From the structural form, the main difference is the form of the sealing element used. According to the form of the sealing element, the gate valve is often divided into several different types, such as: wedge gate valve, parallel gate valve, parallel double gate valve, wedge double gate gate valve, etc. The most common forms are the wedge gate valve and the parallel gate valve.

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

The gate of the gate valve moves linearly with the valve stem, which is called a lift-rod gate valve (also called a rising-rod gate valve). Usually, there are trapezoidal threads on the lift rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into a linear motion, that is, the operating torque is changed into an operating thrust.

When the valve is opened, when the lift height of the gate is equal to 1:1 times the diameter of the valve, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a sign, that is, the position where it cannot be opened, as its fully open position. In order to take into account the lock-up phenomenon caused by temperature changes, it is usually opened to the apex position and then reversed by 1/2 to 1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve is determined according to the position (ie stroke) of the gate.

Advantages of gate valves

(1) Small fluid resistance Because the medium channel inside the gate valve body is straight, the medium does not change its flow direction when it flows through the gate valve, so the fluid resistance is small.

(2) The opening and closing torque is small, and the opening and closing is more labor-saving because the gate movement direction is perpendicular to the medium flow direction when the gate valve is opened and closed. Compared with the globe valve, the opening and closing of the gate valve is more labor-saving.

(3) The flow direction of the medium is not restricted, and the medium can flow in any direction from both sides of the gate valve without disturbing the flow or reducing the pressure, and the purpose of use can be achieved. It is more suitable for pipelines where the flow direction of the medium may change.

(4) The structural length is shorter because the gate of the gate valve is placed vertically in the valve body, while the disc of the globe valve is placed in the valve body horizontally, so the structural length is shorter than that of the globe valve.

(5) The sealing performance is good and the sealing surface is less eroded when fully open.

(6) When fully opened, the erosion of the sealing surface by the working medium is smaller than that of the globe valve.

(7) The shape is relatively simple, the casting process is good, and the scope of application is wide.

Disadvantages of gate valves

(1) The sealing surface is easily damaged. There is relative friction between the two seals that are in contact with the valve seat during opening and closing, which is easy to damage, affects the performance and service life of the seal, and is difficult to maintain.


(2) The opening and closing time is long and the height is large. Because the gate valve must be fully opened or fully closed when opening and closing, the gate travel is large, and a certain space is required for opening, the external dimensions are high, and the installation space is large.


(3) Gate valves with complex structures generally have two sealing surfaces, which increase processing, grinding and maintenance. There are many difficult parts, manufacturing and maintenance are more difficult, and the cost is higher than that of globe valves.

Installation and maintenance tips

1. The handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited.

2. The double gate gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).

2. The double gate gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).


4. The gate valve with transmission mechanism shall be installed according to the provisions of the product instruction manual.


5. If the valve is frequently switched on and off, lubricate it at least once a month.

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