For applications involving slurries, and other thick viscous fluids, a knife gate valve is more often than not an essential component. These specialist shut-off valves cut through slurry media like, well, a knife! Here’s our ultimate guide to the functions and advantages of knife gate valves.
Not only do knife gate valves minimise pressure drop in the fully opened position, but they’re also easy to actuate and offer cost and weight benefits in comparison to standard gate valves. If you’re handling slurries or viscous media, the following overview should make essential reading.
What is a knife gate valve?
Knife gate valves are primarily designed for on-off services in systems that require infrequent use of the valve. They are designed for full-area flow to minimise pressure drop.
Since most of the flow change occurs near the shut-off, the relatively high fluid velocity causes disk and seat wear and eventual leakage if the valve is used to regulate flow.
Knife gate valves minimise pressure drop across the valve in the fully opened position and stop the flow of fluid completely. The direction of fluid flow doesn’t alter and the diameter through which the process fluid passes is equal to that of the pipe. This is why they display minimal pressure drop when opened fully.
Knife gate valves also have a very thin profile compared to standard gate valves. They are uni-directional – although bi-directional versions are available – and come in either wafer or lugged body, which means no flanges. The seats on knife gate valves come in a variety of different materials, from metal to resilient types.
Where are knife gate valves used?
Knife gate valves are commonly used in applications involving slurries. This is because their so-called “knife” cuts right through the slurry.
They are also used in applications that involve viscous liquids, such as heavy oils, light grease, honey and other non-flammable viscous liquids.
Larger sized models are available to better handle thick flow and, whatever the size of valve, knife gate valves are excellent for use anywhere that a shut-off valve is needed.
Advantages of knife gate valves
Knife gate valves benefit from being lightweight, easy to actuate and cheap to produce.
Disadvantages of knife gate valves
Knife gate valves do have low-pressure limitations. They are therefore not ideal for use in applications that require cleanliness or sanitary conditions.