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Why do gate valves require an upper sealing device?

2023-10-13 17:18:41

When the valve is fully open, a sealing device that prevents medium from leaking to the stuffing box is called an upper sealing device.

When the gate valve, globe valve, and throttle valve are in a closed state, because the medium flow direction of the globe valve and throttle valve is upward from the bottom of the valve disc, there is no pressure in the body cavity. When the gate valve is in a closed state, the pressure in the body cavity is lower than Working pressure, so the pressure of the medium on the filler is very small.

When it is opened, the packing will bear the working pressure. If there is an upper sealing structure, it can prevent the working medium pressure from acting on the sealing packing, extend the life of the sealing packing, and prevent the valve from leaking.

Another function of it is that when there is leakage at the sealing packing, the valve can be fully opened to seal the upper seal. In this way, the packing gland or packing sleeve can be loosened, the packing can be added, and then the packing gland can be tightened to ensure The valve packing is tight and there is no leakage. Therefore, upper sealing devices must be provided for gate valves, stop valves, and throttle valves.

Advantages of gate valves:

1. Small flow resistance. The internal medium channel of the valve body is straight, the medium flows in a straight line, and the flow resistance is small.

2. It saves effort when opening and closing. It is compared with the stop valve, because whether it is open or closed, the movement direction of the gate is perpendicular to the direction of medium flow.

3. Large height, long opening and closing time. The opening and closing stroke of the gate is relatively large, and the lifting and lowering is performed by a screw.

4. Water hammer is not easy to occur. The reason is the long shutdown time.

5. The medium can flow in any direction on both sides, making it easy to install. The gate valve passage is symmetrical on both sides.

6. The structural length (the distance between the two connecting end faces of the shell) is small.

7. Simple shape, short structural length, good manufacturing process, and wide application range.

8. The structure is compact, the valve has good rigidity, the channel is smooth, and the flow resistance is small. The sealing surface is made of stainless steel and carbide, which has a long service life. It uses PTFE packing to ensure reliable sealing and light and flexible operation.

Thrust bearing/reduce friction/lower resistance/effort-saving operation

Precision-machined valve stem can reduce operating torque

There is no groove at the bottom of the valve, making it less likely to cause debris to accumulate.

The “O” ring can greatly reduce water leakage, and the “O” ring can be replaced when there is pressure and water is not flowing.

The inside and outside are designed with rubber lamination molding to avoid falling off due to long-term use.

The inside and outside of the valve are coated with non-toxic powder epoxy resin to enhance corrosion resistance and improve water supply quality.

gate valve of wesdom

Gate valve’s features:

Light weight

The body is made of high-grade ductile iron, which is about 20% to 30% lighter than traditional gate valves and is easy to install and maintain.

Flat bottom gate seat

Traditional gate valves often have foreign objects such as stones, wood blocks, cement, iron filings, debris, etc. accumulated in the groove at the bottom of the valve after the pipe is washed with water, which can easily cause leakage due to inability to close tightly. The elastic seat seals the bottom of the gate valve. It adopts the same flat bottom design as the water pipe machine, which is not easy to cause debris accumulation and allows the fluid to flow smoothly.

Overall rubber coating

The gate is made of high-quality rubber for the entire inner and outer cover. European rubber vulcanization technology enables the vulcanized gate to ensure precise geometric dimensions, and the rubber and ductile cast gate are firmly connected, not easy to fall off, and have good elastic memory.

Precision cast valve body

The valve body is precision cast, and its precise geometric dimensions ensure the sealing of the valve without any finishing work inside.

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