Gate valves, also known as quarter valves, are primarily used for isolation. In engineering, especially in large industrial systems, choosing an unsuitable valve can cause damage to the entire system. Therefore, careful selection is crucial.

Like other valves, gate valves are used in pipeline industrial systems. However, their primary function is isolation, opened and closed by turning a handle. The placement of the gate valve in an industrial pipeline system must be clearly defined by engineers.

Understanding its importance makes selection extremely important. Below, I will provide a detailed introduction to the working principle and main applications of gate valves.

What is the Main Function of a Gate Valve?

The main function of a gate valve is to isolate a pipeline. When the valve is open, the pipelines at both ends are interconnected. When closed, maintenance of the pipelines at both ends can be performed.

The following are the two states of a gate valve:

The design characteristics of gate valves allow them to remain in an open or closed state for extended periods, but they are not suitable for use in a partially open state. This is because gate valves are not designed for flow regulation; flow regulation is handled by specialized valves.

How Does a Gate Valve Start and Stop Flow?

Gate valves are opened and closed using handles, handwheels, or actuators. The principle is that turning the handwheel drives the valve stem, converting its rotational motion into linear motion, thus raising or lowering the gate to open or close.

Opening:

• Turn the handle
• The valve stem raises the gate
• The opening area gradually increases
• The gate completely exits the flow port.

Closed:

• Turn the handle
• The valve stem lowers the gate
• It slowly descends until it fully engages with the valve seat ring.

The difference between rising stem and non-rising stem gate valves lies only in the opening and closing mechanism; the principle is the same.

Why Does a Fully Open Gate Valve Have Low Flow Resistance?

Because when a gate valve is fully open, the gate is completely away from the flow port, ensuring complete communication between the valve passage and the pipe fittings.

In this state, the fluid is unobstructed and does not need to change direction. Therefore, no pressure or resistance is generated. This is an advantage of gate valves.

The low flow resistance characteristic of gate valves offers the following advantages:

• Reduced pump energy consumption
• Maintaining pipeline flowability
• Reducing unnecessary pressure drop
• Reducing resistance and vibration
• Improving flow efficiency

However, pressure is also related to the bore diameter, valve body shape, and seat arrangement.

Therefore, it is best to provide drawings or clear data specifications when purchasing.

How Does a Gate Valve Provide Shutoff Sealing?

The sealing performance of a gate valve mainly depends on the valve seat and sealing surface. Therefore, in some carbon steel and stainless steel valves, the sealing surface is also made of metal.

The following factors affect sealing performance:

Therefore, the surface of the valve seat must be strictly controlled. It must be smooth and aligned.

The choice of sealing surface material is related to its application. For environments with high grinding, high temperature, or high circulation, hard alloys should be selected.

However, it should be noted that prolonged use may also cause sealing problems. Testing is required.

Can a Gate Valve Control Flow?

While gate valves are not designed for flow regulation, they can indeed regulate flow, but prolonged flow regulation can damage them.

This is because flow regulation generates:

• turbulent flow
• vibration
• cavitation
• partial corrosion
• seat wear
• gate wear

If the gate wears down, it will become less tight, leading to leakage.

Therefore, gate valves are mostly used for shut-off and isolation, not for precision flow regulation.

Can a Gate Valve Allow Flow in Both Directions?

Gate valves don’t have a directional rule; it depends on how they are installed. Their primary function is isolation, and there is no directional restriction.

Although this is their design, not all gate valves allow bidirectional flow; it depends on their design and installation.

The internal flow of a gate valve is affected by:

• pressure sealing device
• connection to other devices
• seat and body design
• cavity venting requirements
• actor configuration
• any special requirements during production

When installing a gate valve, always carefully read the markings and drawings.

What Role Do the Main Components Play in Gate Valve Function?

All components of a gate valve are important, but their interrelationships and individual functions are illustrated in the table below.

The valve body and cover constitute the main pressure boundary. Internal sealing and isolation are primarily provided by the gate and seat. The stem and handle perform the on/off action.

How Do Manual and Actuated Gate Valves Perform the Same Function?

Manual and actuated gate valves differ only in their on/off method; the internal function of the gate valve is the same.

Manual operation is often used for smaller gate valves, operated with a handwheel. Gearboxes are used in larger diameters. Electric actuators signify automation and allow for remote control. They offer rapid response.

When selecting an actuator, the following factors need to be considered:

• The stem thrust required for on/off operation
• The load on the seat and disseat
• Operating frequency and stroke
• On/off time
• Availability of power supply in the environment
• Safety and fail-safe requirements

Incorrect on/off limits and torque can affect the stem, gate, and seat. Therefore, the choice of actuator is crucial.

How Do Carbon Steel and Stainless Steel Affect Gate Valve Function?

Different materials do not affect the function itself, but rather its applicability and service life.

Carbon steel gate valves are mostly used in applications where mechanical strength and pressure requirements are not high. They are also non-corrosive.

Stainless steel is mostly used in environments containing corrosive substances or where rust resistance is required.

If unsure which material to choose, consider the following:

• Fluid composition (e.g., whether it contains corrosive substances)
• Chloride concentration
• Operating temperature
• Design pressure
• External atmospheric conditions

However, the entire valve may not be made of a single material; the choice must be based on the operating environment and design requirements.

Where Is the Isolation Function Most Useful?

Isolation is most useful when performing partial maintenance on some system pipelines. It is also commonly used in systems with high flow rates.

Gate valves are used in any industrial system, only in different locations.

Therefore, the location of the gate valve needs to be determined at the initial stage of industrial system design.

What Functional Limitations Should Buyers Understand?

The primary function of a gate valve is isolation. It is a quarter-turn slow-rotation valve. It is not suitable for applications requiring rapid opening or operation.

Rising stem gate valves require a certain amount of vertical operating space. In locations with insufficient height, non-rising stem gate valves are preferable.

Gate valve limitations include:

• Not suitable for flow regulation.
• Debris or small particles in the fluid can damage it.
• Torque increases after prolonged periods of inactivity.
• Excessive force during closure can damage the valve stem.

What Should Buyers Confirm Before Ordering?

Points to consider when purchasing valves include:

In addition to the above, check the seller’s qualifications and relevant standards. Assess their reputation and production compliance.

How Can Buyers Verify Functional Performance?

Functional performance includes documentation and physical testing.

• Gate valve drawings
• Complete bill of materials
• Material certificates
• Inspection certificates (pressure test, leakage test)
• Actuator installation instructions

Summary

The above is an introduction to gate valves. It’s important to understand that the primary function of a gate valve is isolation. Its sealing performance mainly depends on the gate and valve seat. The selection of materials must be related to the actual application. Various tests must also be carried out after production.