Characteristics and Applications of Gate Valves

A gate valve is a very common and important shut-off valve, whose core feature is to use the lifting motion of the gate (wedge-shaped or parallel) to control the flow of fluid. It is mainly used in fully open or fully closed operating conditions and is not suitable for regulating flow. The following are the main characteristics and applications of gate valves.

I. Main features

1. Low flow resistance

When the gate valve is fully opened, the medium channel is almost straight, and the flow resistance coefficient is almost the smallest among all valves. The pressure loss is minimal when the fluid passes through.

Advantages: It is especially suitable for situations that require low flow resistance and high flow rate (such as pump outlets and main pipelines).

2. Small opening and closing torque

Whether opened or closed, the direction of movement of the gate is perpendicular to the direction of medium flow. When fully open, the force of the medium is perpendicular to the direction of the gate's movement and does not form any obstruction. When fully closed, the force formed by the pressure difference between the media on both sides helps to press the cover tightly.

Advantages: The operation is relatively effortless (especially for large-diameter gate valves, which are often equipped with gearboxes or electric actuators).

3. Relatively short structural length

Compared to globe valves, gate valves typically have shorter structural lengths under the same nominal diameter and pressure rating.

Advantages: It has certain advantages on pipelines with limited installation space.

4. Unrestricted flow direction of the medium

The structure of gate valves is usually symmetrical (bidirectional sealing design), and the medium can flow in any direction from both sides of the gate.

Advantages: There is no need to specifically consider the flow direction of the medium during installation, which facilitates pipeline layout.

5. Good sealing performance (when fully closed)

When the gate is completely lowered, the gate is tightly attached to the sealing surface of the valve seat, which can achieve good sealing (especially for metal hard seals or elastic gate structures).

Advantages: Suitable for situations that require reliable cutting.

6. High structural height

Due to the need to lift the gate valve completely out of the channel in order to fully open it, the valve stem stroke of the gate valve is longer, resulting in a higher overall height of the valve.

Disadvantage: It is inconvenient to install in places with limited height and space, such as underground pipeline wells.

7. Long opening and closing time

The gate needs to complete a long lifting stroke to reach the fully open or fully closed state.

Disadvantages: Slow opening and closing speed, and it's not suitable for situations that require quick cutting.

8. The sealing surface is prone to wear and tear

During the opening and closing process, there is relative friction between the gate and the valve seat sealing surface (especially when the medium contains solid particles), which can easily cause wear.

Disadvantages: After long-term use, the sealing performance may decrease, making it difficult to repair or replace the sealing surface (usually requiring the valve to be removed from the pipeline).

9. Not suitable for regulating flow

When the gate is partially open, the medium flows through the narrow channel at high speed, causing eddy currents and vibrations behind the gate, which can easily lead to erosion and wear of the sealing surfaces of the gate and valve seat, and even cause valve stem vibration.

Disadvantage: It's strictly prohibited for throttling and can only be used for fully open or fully closed.

10. Relatively complex structure (especially large caliber)

Large diameter gate valves have a bulky structure and are difficult to cast, process, and assemble.

Disadvantage: Relatively high cost.

II.Main applications

Based on the above characteristics, gate valves are widely used in the following situations.

1. Cutting occasions that require fully open or fully closed: This is the main purpose of gate valves.

2. Require pipelines with low flow resistance and high flow rate

Main pipelines for water supply and drainage (municipal, building).

Raw water and clean water transmission pipeline (water treatment plant).

Pump outlet valve (to reduce starting resistance).

Circulating water and condensate systems in thermal power plants.

3. Pipeline with bidirectional flow of medium: utilizing its bidirectional sealing characteristics.

4. In situations of medium low pressure, room temperature or medium temperature

Petroleum and natural gas industry: long-distance pipeline stations, refineries, and terminals (at normal and medium temperatures) for crude oil, refined oil, and natural gas.

Chemical industry: Various chemical medium pipelines with low corrosive requirements (depending on the material selection).

Ship: ballast water, bilge water, fire water and other systems.

5. Large diameter pipelines: For large-diameter pipelines that need to be cut off, gate valves are usually an economical and reliable choice (compared to large-diameter globe valves or ball valves).

Summary

The core advantages of gate valves are minimal flow resistance when fully open, reliable sealing when fully closed, bidirectional flow, and relatively effortless opening and closing. Its main limitation is that it cannot be used to regulate flow, and its opening and closing speed is slow, height is high, and maintenance is inconvenient.

When choosing a gate valve, it is important to consider the following points.

Whether the pipeline needs to be reliably cut off (rather than adjusted)?

Is a very low flow resistance required?

Is the pipeline space (especially the height) allowed?

Whether the working conditions of the medium (pressure, temperature, corrosive? Whether it contains particles?) are within the allowable range of valve material selection and structure?

Simply put, when you need to fully open or close a pipeline (especially a large pipeline) like turning on and off a faucet, and want the water flow to be unobstructed when opening, a gate valve is usually the first choice.