Knife Gate Valves

A knife gate valve is used to isolate media in a line by closing off the line by lowering the knife down onto its seat. This is most commonly achieved through turning a hand wheel or by using a linear pneumatic actuator but can also have other types of actuation. 

A knife gate valve works very similarly to a gate valve in that it lowers a wedge down onto a seat to seal off the flow. The difference is the gate is very thin and has a knife type blade at its end hence the word knife gate. The gate can be raised or lowered by a variety of ways including hand wheel (rising and non rising stem), linear pneumatic or linear electric. The seat itself can be a resilient seat, such as nbr or viton etc or a metal to metal seat. You will not achieve a bubble type seal in a metal to metal seat arrangement so these are commonly used in applications where this is not critical and a soft seat may wear out.

This really depends upon the media, environment, cycle rate and type of knife gate valve selected. If the media is clean and the valve is not cycled that often the lifetime could well be decades. If it is a corrosive environment or something that will wear the seat out the life will be much shorter. Other features such as deflector cones can also be added to enhance the life of the valve whereby they defelect media away from the seat of the valve when it is opened.

 Knife Gate Valves can be either unidirectional or bi directional in function so it is first important to establish this prior to installation. If it is bi directional it doesn't matter what way (in relation to direction of flow) it is installed; however if it is unidirectional it must be installed in accordance to the arrow which is cast on the side of the valve. This indicates the direction of flow. Most knife gates are designed to sit between two flanges with either a wafer or lugged connection, so this must be taken into account prior to installation to ensure it fits the flanges provided.

Knife Gate valves are generally used in areas where there may be sediment or other semi solids in the line that would block another type of valve. The knife on the end of the gate will usually part these as it closes to seat itself. These are even used on dry powder applications. The lugged version is usually used for valve end of line applications such as tailing dams or ship side liquid transfers.

This depends upon where you are based and the freight method chosen. If the express freight option is selected it is usually next day delivery to metropolitan areas in Australia for under 5kg. If free freight has been selected it will go by road freight which can be anywhere from 1 to 10 days depending upon your location. It usually averages 3 days.

All of our products come standard with a 12 month warranty. The good news is we have very strict quality controls and all valves leave our warehouse tested (full material and testing certificates to API598 are available) and inspected so there are rarely any issues.