The Definition, Structure, and Applications of Gate Valves

The Definition, Structure, and Application Analysis of Gate Valves

Gate valves have become key components for pipeline control due to their low flow resistance, strong sealing, and wide applicability. From the wedge type to the parallel type, different structures meet special working conditions such as high temperature and easy coking. During installation, attention should be paid to cleaning and fastening to ensure performance.

Definition and Function of Gate Valves

Gate valves, as a widely used valve in pipelines, are mainly used to connect or cut off media. Gate valves are mainly used to connect or cut off medium flow, and are suitable for a wide range of pressures, temperatures, and diameters. Compared to other valves, gate valves have a wider range of applications in terms of pressure, temperature, and diameter.

Structural Types of Gate Valves

The interior of gate valves is divided into various structures such as wedge type single gate plate, elastic gate plate, double gate plate, and parallel gate plate. At the same time, according to the different valve stem supports, they can be divided into rising stem gate valves and hidden stem gate valves. The internal structure of gate valves is diverse, including wedge type single gate plate, elastic gate plate, etc., and can be divided into rising stem and hidden stem gate valves according to the valve stem.

The Body and Flow Channel of Gate Valves

Valve body manufacturing and flow channel design

The manufacturing methods of gate valve bodies include casting, forging, etc., while flow channels are divided into two types: full bore gate valves and reduced bore gate valves. The valve body of a gate valve is made by casting or forging, and the flow passage can be divided into full diameter gate valves and reduced diameter gate valves, which affects flow resistance and energy consumption. The diameter of the full diameter flow channel is basically the same as the nominal diameter of the valve, while the diameter of the reduced diameter flow channel is smaller than the nominal diameter.

The impact of reduced diameter channels

Shrinkage flow channels can reduce gate size, opening and closing force, and torque, but at the same time, they can increase flow resistance, pressure drop, and energy consumption, so the size of the shrinkage hole needs to be moderate. For tapered pipe reduction, the ratio of the inner diameter of the valve seat to the nominal diameter is usually between 0.8 and 0.95. The reduced diameter flow channel reduces the size of the gate and the opening and closing force, but increases the flow resistance, requiring the selection of an appropriate reduced diameter size.

The Movement and Sealing Methods of Gate Valves

Sealing method of gate valves

When the gate valve is closed, the sealing surface can rely on the medium pressure to perform self-sealing, that is, the sealing surface of the gate is pressed against the valve seat on the other side by the medium pressure, thereby ensuring the tightness of the sealing surface. However, the forced sealing is preferred to use, which requires external force to forcefully press the gate plate against the valve seat when closing to ensure sealing effectiveness.

The movement mode of gate valves

Gate valves achieve opening and closing operations through the linear movement of the valve stem, and this type of gate valve is called a rising stem gate valve. The gate and valve stem move in a straight line together, which is converted into a straight line action through rotational motion. In addition, there is a special type of gate valve whose valve stem nut is set on the gate plate, and the rotation of the handwheel drives the valve stem to rotate, thereby lifting the gate plate. This type of gate valve is called a concealed stem gate valve. Gate valves achieve opening and closing operations through the linear movement of the valve stem, with different structures and operating methods for the open stem and hidden stem.

Performance of gate valves with different structures

Wedge type single gate valves: simple design, suitable for high-temperature and coking prone media, but slightly weaker sealing performance.

Elastic gate valves: excellent sealing performance, suitable for high temperature and frequent switching occasions, but not suitable for media that are prone to coking.

Double gate valves: with good sealing effect, suitable for steam and oil products. After wearing, it can continue to be used by replacing the gasket.

Parallel gate valves: suitable for low-pressure environments, simple to process, but not as sealed as other types

Performance Advantages and Disadvantages of Gate Valves

Advantages of gate valves

Gate valves have many advantages, such as relatively low fluid resistance and a straight through valve body design that maintains the direction of medium flow, thereby reducing fluid resistance. In terms of sealing performance, gate valves perform better than globe valves, and opening and closing operations are also more effortless. In addition, gate valves have a wide range of applications, not only suitable for media such as steam and oil, but also particularly for media containing granular solids and high viscosity.

Disadvantages of gate valves

However, gate valves also have some performance shortcomings, such as high size and long opening and closing time, and the sealing surface is easily damaged, which may cause scratches on the sealing surface, affecting its sealing performance and service life. In addition, the design of gate valves increases the difficulty of maintenance.

Analysis of Different Types of Gate Valves

Wedge type single gate valves

Compared to elastic gate valves, its structure is simpler, especially in high-temperature environments. Its sealing performance may be slightly inferior to elastic gate valves or double gate valves, but it is particularly suitable for high-temperature media that are prone to coking.

Elastic gate valves

As a variant of the wedge type single gate valve, its sealing performance is better in high-temperature environments, and the gate is less likely to get stuck when heated. It's especially suitable for steam, high-temperature oil products, and oil and gas media, and suitable for occasions that require frequent switching.

Double gate valves

Compared to wedge gate valves, its sealing performance is superior. Even if the inclination angle of the sealing surface is not precise enough to match the valve seat, it can still maintain excellent sealing effect. When the sealing surface of the gate is worn, simply replace the metal pad at the top and bottom of the spherical surface to use it.

Parallel gate valves
In terms of sealing performance, it is slightly inferior to other types of gate valves. This type of gate valve is more suitable for medium environments with relatively low temperature and pressure, but the processing and maintenance process of its gate and valve seat sealing surface is relatively simple.

Notes for Installing Gate Valves

Inspections before installation
Before installation, it is necessary to inspect key parts such as the valve chamber and sealing surface to ensure that there are no dirt or sand particles attached.

Notes during installation process
During the installation process, attention should be paid to the tightening of bolts and the compression of fillers to ensure the stability of the connection and the flexibility of the gate opening. During the installation process, attention should be paid to bolt tightening and packing compression, as well as matching the valve model with the flow direction of the medium.

Production and Process of Gate Valves

CNC machine tool production process
In the automated production process of CNC machine tools, the process flow of gate valves is crucial. Through precise CNC technology combined with automated production equipment, the production process of gate valves can be efficiently completed, including raw material preparation, processing and forming, quality inspection, etc. This process not only improves production efficiency, but also ensures the quality and performance of gate valve products.