Gate valves, also called sluice valve, is a valve where the valve stem drives the disc that provides a linear movement along the sealing surfaces. It is mainly used for fully closed or fully opened applications with low to high temperature or pressure conditions. It can be made of different materials to suit the different media the pipeline has to carry.
A gate valve uses the gate to control the material flow. It is achieved by lifting and lowering the gates. A handle wheel placed on the valve will help move the gates. When you rotate the handle wheel, it will move the gate up or down. When you move the gate in the clockwise direction, the gate will lower across the flow line will be securely placed between the two seats. So, once you close the valve completely, there will not be any fluid leakages. When you move the handle in the anti-clockwise direction, the gate will move up, allowing the flow of material through the valve. It provides unobstructed flow with no or minimal resistance. Gate valve manufacturers in India recommend that gate valves should not be used in the semi-open or semi-closed state as the flow speed of the material will strike the valve gate causing erosion.
The valve comprises a body, bonnet, gate disc, stem, seat and package material. Each component varies in design to meet different application requirements. Let us take a closer look at the different designs of the stem, gate and bonnet.
Also Read : Gate Valves: Gate Valve Manufacturer's Point Of View
Stem
The threaded stem will raise and lower the gate by the spinning motion initiated by an actuator or a manual wheel. The stem can either be raising or non-raising.
In a rising stem valve, the stem will move up and down as you lower and raise the gate. Since they have moving parts, a manual wheel will be more suitable than actuation. You can easily view the state of the valves and also lubricate the stem.
A non-rising stem is threaded to the gate and fixed to an actuator. An indicator threaded to the stem will show the open and closed state.
Gates
The gates are made of varying designs that suit the requirements of differing applications. It includes –
Knife Gates
Knife gate valves have just a piece of pointed metal as the gate. The valves self-clean as they move the seat rings each time it closes and opens.
Slab Gates
Also called as Through-Conduit gate valves, slab gates have a single unit gate with a bore. The bore provides a smooth flow of material without any turbulence.
Wedge Gates
It is a wedge-shaped gate that sits on two seats. Since the gate does not sit on the seat, there is tiny friction, can handle fluid pressure and offers tight sealing.
Parallel Slide Gates
The Flat gates have parallel seats and a spring in the middle. This valve uses positioning and line pressure for tight sealing.
Parallel Expanding Gates
These gates have two matched slab gates that provide a smooth and unrestricted material flow when open and tight sealing when closed.
Bonnets
A bonnet is a special cover that protects the internal parts of the valve. It acts as a proper seal attached to the valve body. You can choose between bolted, screw-in, pressure seal or union bonnets for gate valves.
When you choose the gate valve for the right application, it offers many benefits. Some of them are –
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