Biogas plant in southern Europe with AVK valve

What is a Knife gate valve?

Knife gate valves are primarily intended for isolation and on/off functions in systems that have a high suspended solids concentration. Knife gate valves are particularly useful for managing viscous, corrosive, and abrasive media especially for slurry handling. The valve are lighweight, easy to operate, have a minimal pressure loss when fully open, and are cost-effective.

Where do we use a knife gate valve?

Knife gate valves usually have a sharpened blade to cut through thick liquids, and they are made to operate in the harshest environment.

They are useful in wastewater applications where corrosion is an important issue. Therefore, having a knife made of acid-proof stainless steel is advantageous in addition to the valve design that is optimized for slurry medium. This is because the knife is less prone to corrosion-related problems, requiring less regular maintenance or even replacement.

Knife gate valves should only be used for situations needing a completely open or completely closed position and should not be used to regulate flow unless they are built for it. There will be a vibration whenever fluid is pushed up against a partially closed gate, which will eventually erode 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.

The difference between knife gate valve and gate valves:

  • Knife gate valves have a sharpened disc to cut through the slurry/viscous media.
  • Knife gate valves have a short face-to-face length compared to a gate valve that is dimensionally wider
  • Knife gate valves is lighter than a gate valve
  • Knife gate valves are often used in wastewater treatment plants, chemical plants, mining, cement plants and many other industrial applications while gate valve are usually for drinking water, distribution networks and drinking water pumping stations.

 

Cutaway AVK knife gate valve, series 702
AVK gate valve cutaway

The wedge type gate valve and the knife gate valve are mostly intended for on-off applications in which the valve is either fully closed or fully opened. It is not advised to use either of these to control flow because cavitation will eventually harm the seat and the body when fluid presses against a partially closed gate. In addition, the slow opening and closing of both types of valves lowers the possibility of water hammer.

Both types can be used in applications such as:

  • Heavy oils
  • Slurries
  • Clean water
  • Wastewater
  • Non-flammable viscous fluids
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Knife gate valves

Animation about the features of our knife gate valves series 702