Everything You Need To Know To Find The Best gate valve vs knife gate valve

Where are knife gate valves used? 

Knife gate valves are designed to work in some of the harshest environments, typically having a sharpened blade to cut through heavy liquids.

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They are especially useful in wastewater applications where corrosion is an important issue. So, in addition to the valve design optimised for slurry media, it is beneficial to have a knife made of acid-proof stainless steel as this makes it less susceptible to damages caused by corrosion and as a consequence it needs less frequent maintenance or even replacement.

Knife gate valves should only be used for applications requiring a completely open or completely closed position and should not be used to regulate flow unless they are designed for it. Whenever fluid is forced against a partially closed gate, there will be a vibration, gradually eroding the disc and seat. In addition, the knife gate valves are designed to slowly open and close to safeguard against the impacts of water hammer.

What is the difference between knife gate valves and gate valves?

Both the wedge type gate valves and the knife gate valves are primarily designed for on-off services where the valve is completely opened or completely closed. It is not recommended to use neither of these to regulate flow because when fluid pushes against a partially closed gate, vibration occurs, and cavitation will eventually damage the seat and the body. Also, both valve types are designed to open and close slowly in order to reduce the risk of water hammer. 

Both types can be used in applications involving: 

Knife and gate valves are primarily used for on and off service in industries. They are suitable to open and close slowly to protect the device from the effects of a water hammer. Since these shut-off valves are used in applications involving heavy oil, slurries, wastewater, non-flammable viscous fluids, and clean water, people tend to confuse one for the other.

None is suitable for regulating the flow because vibrations occur when fluid pushes against a partially closed gate. It may wear and erode the seat and disk eventually. Due to such a reason, valves bought from a valve manufacturer in China should be either completely open or closed.

Although the applications of a knife and a gate valve are mostly the same, many design features set them apart. It is essential to learn about these variances to be able to pick the right one for a process application. So, let’s put the two head-to-head to know everything about knife valve vs. gate valve!

Everything to Know About a Knife Valve:

A knife gate valve was initially designed for the pulp and paper industry. When stringy pulp impinges between the wedge and the sand seat to prevent flow shut-off, a knife valve is used to deal with it. It features a sharp edge to cut through the pulp and seal to deal with viscous fluids with a similar impingement risk.

This valve type is typically employed in heavy oil, wastewater, paper and pulp, and sludge and slurry industries. These devices are generally specified in larger sizes to handle viscous flows in several demanding applications.

Primary Advantages of Using a Knife Valve:

• It is easy to actuate and light and is available in several affordable options.
• It is best for applications with viscous fluids as its blades can easily cut through thick liquids.

Despite these advantages, a knife valve may sometimes cause significant inconvenience to the users.

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Some Disadvantages of Using a Knife Valve:

• It is widely known for its low-pressure limitations.
• It is a less-desirable shut-off valve for applications requiring cleanliness and optimal hygiene conditions.

The function of a knife valve diminishes when used in dry bulk applications. Its blade fits into an elastomer seal after it cuts through the media. Over time, the seal becomes abraded and may influence the sealing performance, leading to downtime, decreased production, and negatively impacting revenue streams.

Everything to Know About a Gate Valve:

As opposed to flowing regulation operations, a gate valve is often used for shut-off operations as it offers only on and off settings to a user.

A butterfly gate valve operates by lifting a round or a rectangle-shaped gate from the path of the media, typically fluids. The sealing surface lying between the gate and the seats is called planar. It is often suitable for applications requiring a straight flow of fluids with minimal restrictions. It has a flat closure that slides in or out, up or down between the two parallel plates to open or close.

It is widely used in oil and gas, pharmaceuticals, automotive, power plants, mining, offshore, general process manufacturing, and water treatment.

Primary Advantages of Using a Gate Valve:

• The pressure drop is shallow when the valve is fully open.
• It is used as a shut-off device and to perform bi-directional action.

Although a valve bought from gate valve manufacturers is a valuable device in industries, it has some downsides too.

Some Disadvantages of Using a Gate Valve:

• It requires a large amount of force to operate and may even need automatic actuators to function.
• It is not the quickest valve to perform the open and close function.
• It is not ideal for space-sensitive applications as it takes up a lot of space.
• It is prone to thermal expansion and shrinking when exposed to high-temperature variations.

Learning Everything About Knife Valve vs. Gate Valve:

Here is a table to learn about knife valve vs. gate valve available at a reliable industrial valves company:

In brief, a knife valve employs a blade to cut through thick fluids, while a gate valve uses a slide plate to shut off the flow of dry bulk material. The sharp and beveled edge of a knife valve makes it ideal for large-sized applications involving varnish, paper pulp, light grease, and wastewater. Its easy actuation and low cost make it perfect for several industries.

A China actuated gate valve is perfect for handling dry bulk powders, pellets, and granules. It has a flat, rectangular slide plate to shut off or permit dry material flow. It actuates between two compressed-loaded, rigid polymer plates reinforced by a compressed, hard rubber.

When the gate experiences frictional wear to the rugged polymer seals from several actuators over time, its rubber backing ensures the seal constantly forces against the slide plate. But sometimes, the hard polymer seals may wear and lose their effectiveness. When it happens, the bolts may loosen, and remove shim along each lateral aspect of the gate to re-tighten the bolts. It will help restore the compression load of the gate.

Parting Thoughts

Hopefully, this article helps everyone learn about knife valve vs. gate valve to pick a suitable option according to the application.

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