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A Complete Guide To Gate Valve

A gate valve is a common type of valve used to start or stop the flow of a medium.

It is named after the shape of its closure element, which is typically a flat plate resembling a gate, hence called a “Gate Valve.”

The movement direction of the gate valve’s closure element is perpendicular to the fluid direction. Gate valves can only be fully open or fully closed and cannot be used for throttling. Here is a complete guide to gate valve.

 

Cast Steel WCB 6” 1500LB RF Flange Gate Valve With Gear Box
Cast Steel WCB 6” 1500LB RF Flange Gate Valve With Gear Box
Source: Tainyu Valve

 

Gate Valve Parts

 

The picture shows the main components of the gate valve. The disc of the gate valve is also called the wedge plate.

Gate Valve Parts
Source: Trouvay & Cauvin

 

Types of Gate Valves

 

1. Classified by Value Disc Type

 

(1) Slab Gate Valve:

Slab Gate Valve
Cast Steel WCB 16” 600LB RTJ Flange Slab Gate Valve With Electric Actuator
Source: Tianyu

— Features:

The gate is parallel to the fluid flow, and opening or closing control is achieved by lifting or lowering the gate.Simple and compact structure, easy for maintenance.

Suitable for cutting off fluid flow, typically used for fully open or fully closed operations.

— Applications:

  • Fluid cutoff: Parallel gate valves are suitable for situations that require quickly cutting off fluid flow, such as emergency shutdown of liquid or gas in pipelines.
  • Low to medium-pressure applications: Suitable for applications in the low to medium-pressure range, commonly used in regular industrial scenarios.

(2) Wedge Gate Valve:

Wedge Gate Valve
Source: ACI

— Features:

The bottom of the gate and the valve seat form a wedge-shaped gap, changing the flow passage by lifting or lowering the gate.

Due to the wedge-shaped gap, there is resistance during opening and closing, requiring greater operating force than parallel gate valves.

— Applications:

  • High-temperature and high-pressure applications: Wedge gate valves are typically used in high-temperature and high-pressure fluid control, such as steam systems.
  • Fluid flow control: Suitable for situations that require regulating fluid flow, providing good fluid control performance.
  • High-sealing requirements: Due to the design of the wedge-shaped gap, wedge gate valves can offer good sealing when closed.

 

2. Classified by Valve Seat Sealing Surface Type

 

(1) Elastic Gate Valve:

— Features:

The gate is covered with elastic materials like rubber or polystyrene to improve sealing performance.

Suitable for general temperature and pressure conditions, with good sealing.

— Applications:

  • General fluid control: Elastic gate valves are suitable for general fluid control, especially in cases requiring higher sealing.

(2) Rigid Gate Valve:

— Features:

The gate is usually made of metal, and the sealing surface is also metal, suitable for harsh conditions like high temperature and pressure.

Suitable for high-temperature, high-pressure environments, with strong pressure and wear resistance.

— Applications:

  • High-temperature and high-pressure applications: Rigid gate valves are suitable for high-temperature and high-pressure fluid control environments, such as steam systems and chemical processes.
  • Corrosive media: Due to the metal construction, rigid gate valves exhibit good corrosion resistance.
  • Frequent opening and closing operations: Suitable for situations requiring frequent opening and closing operations, with good wear resistance due to the metal construction.

 

3. Classified by Valve Stem Type

 

(1) OS & Y Type Rising Stem Gate Valve:

OS & Y Type Rising Stem Gate Valve
Source: AVK

— Features:

The stem is exposed during use, visible to the outside. OS & Y stands for Outside Screw and Yoke.

— Applications:

 Applicable Scenes:

  • High-Temperature and High-Pressure Environment:

OS & Y type rising stem gate valves are suitable for high-temperature and high-pressure conditions, such as steam systems and petrochemical industries. The exposed design of the valve stem facilitates operation in high-temperature environments, and the position of the stem can be observed to understand the valve’s status.

  • Ease of Maintenance:

Due to the exposed state of the valve stem, maintenance and inspection operations are facilitated. Operators can directly observe the position of the valve stem to determine the open or closed status, making daily maintenance more convenient.

  • Corrosion Resistance Requirements:

In environments requiring corrosion resistance, the OS & Y design can reduce direct contact between the stem and the medium, lowering the risk of corrosion. This design makes this type of valve suitable for corrosive environments such as chemical and marine applications.

(2) Non-Rising Stem Gate Valve:

Non-Rising Stem Gate Valve
Source: AVK

— Features: 

The stem is hidden during use, not visible.

— Applicable :

  • Limited Space:

The design of the Non-Rising Stem Gate Valve is suitable for situations with limited space since the stem does not ascend or descend, eliminating the need to consider the height during operation. This makes this type of valve more convenient for vertical pipes or compact spaces.

  • Underground Installation:

As the stem does not ascend during operation, the Non-Rising Stem Gate Valve is suitable for underground installations without the need to consider space limitations underground.

  • Ease of Maintenance:

Compared to the rising stem design, the Non-Rising Stem Gate Valve is easier to maintain. Repairs and operations in compact spaces are more convenient.

  • Economic Considerations:

Due to its relatively simple design, the Non-Rising Stem Gate Valve is usually more economical and suitable for projects with limited budgets.

  • Horizontal Installation:

Applicable for scenes that require horizontal installation, the Non-Rising Stem design helps simplify operations and maintenance in horizontal installations.

 

Gate Valve Performance Characteristics

 

1. High Sealing Performance: Gate valves adopt a bidirectional sealing structure, ensuring complete fluid cutoff in the closed state and exhibiting excellent sealing performance.

2. Low Flow Resistance: In the open state, the gate is perpendicular to the fluid channel, minimizing fluid resistance and ensuring smooth fluid flow.

3. Corrosion Resistance: Material selection and surface treatment give gate valves strong corrosion resistance, making them suitable for various harsh environments.

4. High-Temperature and High-Pressure Resistance: Suitable for high-temperature and high-pressure conditions, maintaining stable performance and widely used in fields like petrochemicals and thermal power generation.

 

Gate Valve Advantages and Disadvantages

 

1. Advantages

 

  • Low Fluid Resistance

Because the gate valve has its valve disc fully open during medium flow, and the direction of the medium remains unchanged, the fluid resistance is minimized.

  • Small Pressure Drop

When fully open, the entire passage allows direct flow, resulting in minimal pressure loss as the medium moves through.

  • Low Operating Torque, Easy to Open and Close

The movement direction of the gate valve’s disc is perpendicular to the flow direction of the medium during opening and closing. Compared to globe valves, gate valves require less force for operation.

  • Unrestricted Flow Direction of the Medium

The medium can flow through the gate valve from either side without restrictions, achieving the intended purpose. This feature is more suitable for pipelines where the flow direction of the medium may change.

  • Shorter Structural Length

The gate valve’s disc is vertically positioned inside the valve body, making the structural length shorter compared to globe valves where the disc is horizontally placed.

  • Good Sealing Performance

The sealing surfaces experience minimal erosion when fully open.

  • Less Erosion on Sealing Surfaces in Fully Open Position Compared to Globe Valves.

Simple Structure, Good Casting Process, Wide Applicability.

 

2. Disadvantages

 

  • Relatively slow opening and closing processes, not suitable for frequent adjustments.
  • Not suitable for use as a regulating or throttling device.
  • Not suitable for high-speed flowing media, partial opening of the gate can cause vibration in the gate, which may damage the sealing surfaces of the gate and valve seat.
  • Not suitable for throttling, can lead to erosion of the gate by the flowing media.

 

Gate Valve Operational Principles

 

Gate valves control fluid flow through the vertical movement of the gate. In the closed state, the gate is positioned within the fluid channel, completely cutting off the fluid. In the open state, the gate is perpendicular to the fluid channel, minimizing fluid resistance and facilitating smooth fluid flow.

 

Gate Valve Operating Process

 

1. Closing Process

 

The operating device initiates, causing the gate to start lowering.

The gate completely descends into the fluid channel, achieving complete fluid cutoff.

2. Opening Process

 

The operating device initiates, causing the gate to start rising.

The gate is perpendicular to the fluid channel, minimizing fluid resistance and facilitating smooth fluid flow.

 

 

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