A knife gate valve is a common component of piping systems that uses a knife-edge to penetrate through existing clogs in the system. They are commonly found in industries with high volumes of fluids containing suspended solids.
They specialize in dealing with pulp, slurry, and highly viscous (little flow) liquids. Knife gate valves are often confused with gate valves due to a number of characteristics they share.
How Gate Valves and Knife Gate Valves Work
Gate valves operate by fitting a wedge in the path of the fluid, creating a watertight seal in the process. The wedge is a flat surface that slides in and out, along parallel railings inside the fitting to dictate the open or closed position. Gate valves, therefore, have only two settings; either on or off.
Knife gate valves operate in exactly the same manner as their gate valve components. Initially designed for dealing with blockages due to pulp in the paper industry, the knife-edge has the sole purpose of separating clogged, viscous fluids.
The knife-edge cuts through the slurry thus preventing it from building up and eventual blockage of the pipe. Another difference between the two lies in their basic structure. A knife gate valve has a packing gland part that completely seals it, while the gate valve has a V-ring that closes the shaft.
Advantages of Knife Gate Valves
An advantage of these valves is that they are cheap and easy to operate compared to other components of the piping system. They are also designed to operate in very harsh circumstances such as high temperature and pressure.
The knife gate valve is shorter in length (face to face) as compared to the normal gate valve which is also bigger in size. This means that it is generally lighter in weight due to less material used in its construction.
Disadvantages of the Knife Gate Valve
They operate only in the completely open or closed positions. This means that there is no middle ground thus making it almost impossible to use them for controlling the amount flowing through them.
The knife-edge also gets eroded over time due to the impact of the fluid constantly hitting against it. They are also meant to open and shut slowly, to prevent damage from the impact of fast-moving fluids in the piping structure.
Another disadvantage is that they are limited by low-pressure applications. This means that they are not favorable for processes that demand a sanitary environment.
Conclusion
Knife gate valves are generally used in industrial applications that demand the use of a shut-off valve. Such industries include the paper industry, the oil and gas industry, manufacturing, water treatment, and wastewater facilities among many others.
Acid proof, stainless steel blades ensure that the maintenance costs are low and provide better quality services. They also come in handy in handling wastewater where we consider corrosion and toxicity of the material flowing through them. Their ability to unclog sludge and viscous liquids has made them a real industry favorite.
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