Difference Between Gate Valves And Knife Valves

Gate valves may not be used as often as they used to be since ball valves started becoming more popular, but for some applications, they are perfect for the job. Irrigation applications still use gate valves because some of the drawbacks that led to the replacement of ball valves are not an issue when it comes to irrigation.

In this article, we'll learn the differences between gate valves and knife valves and explore why gate valves are still popular in certain applications. Let's get started.

Gate Valves and Knife Valves

Angle gate and knife valves are linear motion valves that include a flat closing element called a gate. The gate inside the valve slides up and down by turning the 09SGS-15 handwheel counterclockwise to open and clockwise to close. For knife valves, the gate is slid by simply pushing or pulling the handle. Both valves move the gate into the flow stream to completely stop fluid flow.

Gate and knife valves are designed to minimize the pressure drop across the valve. In the fully open position, the diameter of the opening through which the fluid passes is equal to the diameter of the pipe and the direction of flow remains the same.

 Gate Valve

Applications and Benefits

Gate valves can be found anywhere economic shutoff is required. Gate valves are suitable for any application involving slurry because the gate can pass right through. Gate valves are also common in applications where liquids such as heavy oils, light greases, varnishes, and other non-flammable liquids are used.

Irrigation Applications

Gate valves are ideal for irrigation systems that require high flow rates. Gate valves close slowly, as it takes several turns to open or close the gate, so the flow starts and stops more slowly than with ball valves. Gate valves are extremely common in irrigation applications because the speed of closing is not as important as the strength to support high flow rates.

Gate Valve Limitations

Most gate valves have metal-to-metal seats that do not create a reliable seal, sometimes resulting in leaks, while ball valves close tightly. Gate valves also have a tendency to jam if not used for a period of time, causing stem packing to leak. My post (268)

As shown in the diagram above, gate valves tend to be larger in size compared to ball valves. They stick out more, which is not ideal for tight spaces. For some applications, ball valves would be a better choice because they can provide a leak-free seal.

Throttling (restricting flow)

Gate valves can be used anywhere a throttling function is required, however, this is usually not recommended because of seat and valve corrosion due to valve vibration causing the valve to leak over time.

While gate valves may not be the most popular valves on the market, they are still a suitable choice for certain functions. Please note the location and situation in which you need the valve to determine which type of valve is best for you.