Gate Valve is an isolation valve used for fully open and fully close applications. The main part in the gate valve is the disk, which is called wedge, and it is moved by linear motion of the stem. Gate valves can be made of ductile iron, WCB steel or stainless steel.
A gate valve type is defined through its construction peculiarities, such as, wedge shape, sealing type, manufacturing standard, body material, disk material, and so on.
Gate valves are typically used in gaseous and fluid applications. Gate valve can be mainly categorised depending on the wedge type, there are resilient-seated gate valves, metal-seated gate valves, or the spindle (shaft) type as gate valves with a rising or a non-rising stem (NRS).
On the other hand, knife gate valve is a lighter valve used for media with high solid contents, it comes witj low operating pressure. The main part in a knife gate valve is the shut-off plate which ensures a tight closure for the media, because it cuts into the media with solid matter in a fashion similar to a knife. Furthermore, knife gate valve has an advantage of small stagnant areas which allows to avoid clogging.
The most widely used mode of operation for the gate valves is manual, with a handwheel or just a bare shaft. If gate valves are used for a frequent switching or for critical aplications, then they are operated via electric, pneumatic or hydraulic actuators.