The wedge-shaped gate in a wedge gate valve is held in place between two slanted seats. Instead than controlling the flow of liquids, gate valves are utilised to completely stop the flow. When a standard gate valve is fully open, there is nothing in the flow route to hinder the water’s movement.
In most cases, the open flow path’s size varies nonlinearly with gate position. This indicates that there is an inhomogeneity in the rate of flow as a result of stem movement. Depending on how it’s built, fluid passage via a partially open gate can cause vibrations.
Gate valves are commonly utilised with bigger pipe diameters (ranging from 2″ to the largest pipelines) because they are less complex to build than other types of large-size valves.
Friction can be an issue at high pressures. The valve becomes more difficult to operate as the medium’s pressure pushes the gate against its guiding rail. To reduce pressure before operating the gate valve, large gate valves are sometimes equipped with a bypass controlled by a smaller valve.
When a small amount of leakage from the valve is acceptable, such as in heating systems or sewer pipes, a gate valve can function without an additional sealing ring on the gate or the seat.
Typically, a gate valve’s actuator (such as a handwheel or motor) is attached to the gate via a threaded stem. According to which end of the stem is threaded, they can be classified as rising or nonrising.
Attached to the gate, the rising stems move up and down in unison whenever the valve is opened or closed. To manipulate the actuator, a nut must be screwed onto the stem and turned in a counterclockwise direction.
Threaded into the gate, nonrising stem valves are attached to the actuator and rotate in tandem with it. Because the gate’s motion is hidden inside the valve, a pointer may be threaded onto the stem to indicate valve position. Wherever there is a lack of vertical space, nonrising stems are used.
Flanged ends on gate valves can be drilled to meet pipeline-compatible flange dimensional criteria.
Gate valves are typically made of cast iron, cast carbon steel, ductile iron, gunmetal, stainless steel, alloy steels, and forged steels.
In ultra-high vacuum chambers, all-metal gate valves are utilized to isolate chamber regions.
Bonnets prevent the valve body from leaking. The bonnet of a gate valve can be screwed in, unioned, or bolted. The quickest and easiest way to ensure a secure seal against the buildup of pressure is with a bonnet that screws in place.
There are many uses for a union bonnet, especially in situations where it must be regularly checked and cleaned. Additionally, the body gains strength from this. For larger valves or increased pressure, a bolted bonnet is used.
The pressure seal bonnet is an alternative construction for gate valves’ bonnets. Valves that will be subjected to pressures in excess of 2250 psi typically utilise this design (15 MPa). One distinguishing characteristic of a pressure seal bonnet is that its end forms a cup that fits inside the valve’s body and faces downward.
The cup’s sides are pushed outward as the pressure inside the valve rises. sealing the body to the bonnet better. Leaks are common in the body-bonnet joint of other structures where the seal is supplied by external clamping pressure.