Although gate valves and knife gate valves serve similar functions—both are designed for on-off applications and can handle slurries and other viscous media—there are key design differences that set them apart. These differences should be carefully considered when determining which valve type is best suited for your specific application.
How Do Gate Valves and Knife Gate Valves Work?
Gate valves operate by lifting a round or rectangular gate (or wedge) to allow fluid to flow through. The sealing surfaces between the gate and seats are flat, making gate valves ideal for applications requiring a straight, unobstructed flow path with minimal pressure drop. The gate slides vertically between two parallel seats to either fully open or fully close the valve. Gate valves are intended for on/off control only and are not suitable for throttling, as they only function in fully open or fully closed positions.
Knife gate valves, on the other hand, are designed to “cut” through challenging media—true to their name. Originally developed for the pulp and paper industry, they were engineered to handle stringy pulp that would otherwise clog traditional gate valves. The sharp-edged blade of a knife gate valve slices through thick, viscous materials and slurries, ensuring a tight seal and reliable shut-off. This design makes them particularly valuable in applications where clogging and media buildup are common.
Applications of Gate Valves and Knife Gate Valves
Gate valves are widely used across various industries that require reliable shut-off solutions, including oil and gas, pharmaceuticals, manufacturing, and automotive. Known for their durability, they perform well in demanding conditions such as high-pressure and high-temperature environments. Common applications include power plants, water treatment facilities, mining operations, and offshore installations.
Knife gate valves, on the other hand, are particularly well-suited for handling thick, viscous, or abrasive media. Their sharp-edged blades allow them to cut through sludge, slurry, and other dense materials with ease. Typically used in larger sizes, knife gate valves are ideal for applications involving heavy oils, light grease, paper pulp, varnish, and wastewater—making them a preferred choice for industries where flow media can be challenging to manage.
Advantages and Disadvantages of Gate and Knife Gate Valves
Gate valves offer a low pressure drop when fully open, making them efficient for fluid flow. They are suitable for bi-directional use and function well as on-off valves. However, they require significant force to operate, especially in larger sizes, which often necessitates the use of automatic actuators. Compared to other valve types, gate valves are slower to open and close and occupy more installation space. Additionally, exposure to significant temperature fluctuations can cause thermal expansion or contraction, potentially leading to leakage.
The advantages of knife gate valves are that they’re cheap, easy to actuate, and light. One of the most notable disadvantages of knife gate valves is that they’re known to have low-pressure limitations. This makes them less desirable for use in applications that require cleanliness or sanitary conditions.
Speak to LEFLOW today
If you’re in any doubt about which type of valve to opt for, or would simply like more information and guidance, LEFLOW would be only too happy to chat through your options with you. Our knowledgeable and experienced technical team can help you to pinpoint the right valve for your specific requirements in no time.