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What Are the Differences Between Wedge Gate Valves and Parallel Gate Valves?
2024-09-27

Gate valves are a common type of valve in industrial pipelines, primarily used for shutting off the flow of fluids. Based on the design of the gate and the sealing method, gate valves can be divided into wedge gate valves and parallel gate valves. Although these two types of gate valves serve similar purposes, there are significant differences in their structure, working principles, and application scenarios.

1. Valve plate design

Wedge Gate Valves

The gate of the wedge gate valve is wedge-shaped, and the contact surface between the gate and the seat is inclined. When the valve is closed, the wedge-shaped gate wedges into the seat, creating a tight seal. The wedge design enhances the sealing effect through the wedging action.

Depending on the working conditions, the wedge gate valve can be designed as a rigid wedge, elastic wedge, or double parallel wedge. The rigid wedge gate has a simple structure but may jam due to thermal expansion in high-temperature conditions; the elastic wedge gate can adapt to temperature changes through deformation, reducing the risk of jamming.

Parallel Gate Valves

The valve plate of the parallel gate valve features a parallel double-plate structure, with the plates making parallel contact with the seat rather than wedging in. When the valve is closed, the valve plates are pressed against the seat by the pressure of the medium or external force, achieving a seal.

The parallel design reduces the impact of thermal expansion on sealing, making it less likely to experience sticking due to temperature changes.


2. Sealing Method

Wedge Gate Valves

Wedge gate valves achieve sealing through the wedging action of the gate. When closed, the wedge-shaped gate makes tight contact with the seat, ensuring stable sealing performance even under high temperature and high pressure conditions.

One advantage of the wedge design is that it can provide good sealing even without media pressure, thanks to the mechanical wedging action. Therefore, wedge gate valves are particularly suitable for applications requiring high sealing performance, such as steam and high-temperature fluids.

Parallel Gate Valves

The sealing of the parallel gate valve relies on the pressure of the medium or external force. If the medium pressure is low, the sealing performance may not be as effective as that of the wedge gate valve. The parallel design is typically used for low-pressure conditions, but some parallel gate valves utilize spring or lever mechanisms to assist with sealing.

The parallel double-plate design of the parallel gate valve can adapt to temperature changes, preventing it from seizing due to thermal expansion like the wedge gate valve.


3. Operating Torque

Wedge Gate Valves

Due to the wedge design, the gate wedges into the seat when closed, requiring a larger torque for opening and closing. This is especially true in high-pressure conditions, where the friction between the gate and the seat increases, making the operation relatively laborious.

For applications requiring frequent opening and closing, the operation of wedge gate valves is relatively cumbersome and not as convenient as that of parallel gate valves.

Parallel Gate Valves

The valve plates of the parallel gate valve move up and down along parallel guides, resulting in lower friction and a reduced operating torque. This makes the parallel gate valve particularly suitable for applications that require frequent opening and closing.


4. Application Scenarios

Wedge Gate Valves

Due to the high sealing capability and resistance to high temperature and pressure of wedge gate valves, they are widely used in demanding conditions such as steam pipelines, petrochemical applications, and thermal oil transmission systems. The wedge design ensures reliable sealing performance in these environments.

Wedge gate valves are suitable for situations where frequent operation is not required, as the opening and closing actions can be labor-intensive and sensitive to thermal expansion.

Parallel Gate Valves

Parallel gate valves are typically used in low-temperature, low-pressure, and frequently operated conditions, such as in water, natural gas, and low-pressure steam transmission systems. Due to their lightweight operation and simple structure, parallel gate valves perform exceptionally well in applications that require frequent operation.

The parallel gate valve is suitable for applications without extreme temperature variations, and its sealing performance relies more on the pressure of the medium. Therefore, it is less commonly used in high-pressure or high-temperature environments.


5. Maintenance and Service Life

Wedge Gate Valves

Due to the wedging design, the valve may experience slight sticking between the gate and the seat when left closed for an extended period, especially in high-temperature conditions, necessitating regular inspection and maintenance. Elastic wedge gate valves somewhat mitigate this issue; however, wedge gate valves may require a higher frequency of maintenance overall.

Parallel Gate Valves

Parallel gate valves experience less jamming since there is no wedging action, making maintenance relatively simple. Due to the minimal friction between the valve gate and the seat, they have a relatively long service life, making them especially suitable for pipeline systems that do not require complex maintenance.


6. Effects of Thermal Expansion

Wedge Gate Valves

In high-temperature environments, wedge gate valves may experience the gate becoming stuck to the seat due to thermal expansion, especially in rigid wedge gate valves. In such cases, it is recommended to use an elastic wedge design, which can better accommodate thermal expansion under high-temperature conditions.

Parallel Gate Valves

Parallel gate valves do not have the wedging issue, making them perform better in environments with significant temperature fluctuations. They are less prone to jamming due to thermal expansion, making them suitable for conditions with large temperature variations.

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