What are knife gate valves best used to regulate the flow of?

Knife gate valves are an essential component of many industrial and municipal water systems.

They are designed to be durable and easy to operate, making them a popular choice for many applications.

In this article, we will take a closer look at the features, applications, and advantages of knife gate valves to help you understand how they work and why they are a popular choice for industrial and commercial operations.

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How does a knife gate valve work?

A knife gate valve is a type of valve that is used to control the flow of liquids, slurries, and other similar materials in industrial and commercial applications. These valves are known for their durability and reliability and are commonly used as an industrial control valve in a wide range of operations, including mining, power generation, water treatment, and more.

The unique design of a knife gate valve features a stainless steel knife that moves up and down to open or close the flow of the media. Its gate is connected to a hand wheel or an actuator, which is used to open and close the valve. When the valve is open, the gate is raised, allowing the media to flow through, and when the valve is closed, the gate is lowered, blocking the flow.

Additionally, knife gate valves can be actuated by hand wheel, pneumatic, hydraulic, electric, and electro-hydraulic actuators. They can be made for bidirectional flow or unidirectional flow, and a wide range of pressure and temperature ranges.

What are knife gate valves used for?

Knife gate valves are used in a wide range of industrial and commercial applications. Some of the most common applications of knife gate valves include:

HVAC Systems: Used in heating, ventilation and air conditioning systems to control the flow of water and other liquids.
Industrial Processes: Used to control the flow of liquids, gasses, and powders. They are commonly used in the chemical, food and beverage, and pharmaceutical industries, as well as in paper and pulp mills, and cement plants.
Pneumatic Conveying: Controls the flow of materials in pneumatic conveying systems, such as in the mining, fertilizer, and cement industries.
Water and Sewage: Used in water treatment plants and sewage treatment plants to control the flow of water, sewage, and other liquids. Often used in applications where a tight shut-off is required, such as in high-pressure and high-temperature applications.

What are the different types of knife gate valves?

There are several different types of knife gate valves, each with its own unique characteristics and features. Some of the most common types include:Conventional Knife Gate Valve: Designed with a simple gate or wedge-shaped disk that moves up and down to open or close the flow of material. Also known as a traditional knife gate valve.
Bonneted Knife Gate Valve: Features a bonnet (a removable cover), which is typically secured to the valve body by a number of bolts. Used to protect the internal components of the valve from damage and wear.
Through Conduit Knife Gate Valve: Its gate passes through the body of the valve, rather than being located on one side of the valve. Allows for a larger flow area and less pressure drop.
Push-Through Knife Gate Valve: Its gate is pushed through the valve body to open or close the flow of material. Its design helps prevent blockages.
Severe Service Knife Gate Valve: Specifically designed to withstand high pressure, extreme temperatures, high flow rates, and heavy debris. Typically made from high-grade, corrosion-resistant materials.
Rising Stem Knife Gate Valve: Features a stem that rises and lowers as the valve is opened and closed.
Non-Rising Stem Knife Gate Valve: Its stem does not move in relation to the valve body and is instead connected to a hand wheel or an actuator.
Wafer Knife Gate Valve: Has a typically smaller and thinner body meant to be installed between two pipe flanges.

It is important to note that some knife gate valves are also classified based on the material they are made of, such as cast or ductile iron, stainless steel, and others, each of them having different suitability for certain applications.

What are the parts of a knife gate valve?

A knife gate valve typically has the following parts:

Gate: A disk-shaped component that moves up and down within the valve body to open or close the flow of material.
Body: The main component that holds the valve’s internal parts together, and also serves as the conduit through which the material flows.
Seats: The surfaces that the gate comes into contact with when the valve is closed, which helps to form a tight seal.
Bolts: Typically found on the outside of the valve body and are used to clamp the two halves of the valve body together.
Packing: A set of seals that are used to prevent leakage around the stem and gate.
Gland: The component that holds the packing in place around the stem, providing a seal to prevent leakage.
Stem: The part that connects the gate to the hand wheel or actuator and is used to raise and lower the gate within the valve body.
Yoke: A large, U-shaped piece mounted to the top of the valve body and connects the stem to the gate.
Stem Nut: A nut-shaped component that is typically located at the top of the stem and is used to secure the stem to the hand wheel or actuator.
Hand Wheel or Actuator: A component used to open and close the valve. It can be operated by manual hand wheel, pneumatic, hydraulic, electric, and electro-hydraulic actuators.

Some knife gate valves may have additional features or parts such as a flange or bearing to guide the gate, or a hopper shape to fit snugly with the hopper or silo.

Conclusion

The proper selection of a knife gate valve depends on the specific application and the characteristics of the material being transported. With proper maintenance and proper selection, knife gate valves can provide a long service life and minimal downtime, making them a cost-effective solution in the long run.