Gate Valve Types
A gate valve is the most widely used in industrial valves for pipelines. its wide range application. The gate valves operated with a handwheel or with the help of electric actuators are popular. A pneumatic or a hydraulic actuator can be applied as well.
Types of gate valves are there
Conduct gate valve
Knife gate valve
High pressure gate valve
Wedge gate valve
Parallel gate valve
Conduct gate valve
A conduct gate valve is a special type of variation in the gate valve that has a circular hole in the closure member that passes a sphere of the nominal size of the specified application. They may require an extra smaller bore at the weld end. The conduct gate valves we offer vary in dimensions, material and features. They are presented in various specifications to suit the need of the client.
The valve design includes a rising stem that accommodates the upward and downward movements of the gate allowing it to open and close under the line pressure.
In normal operation, line fluid fills the cavity and the gate is lifted by the pressure generated from the flow path assisting the actuator spring to open the valve, resulting in a fail-open configuration.
Slab through conduit gate valves are piggable in the fully open position and generate pressure drop across the valve equal to the inside diameter of the connecting pipe.
Through-conduit gate valves are isolating valves designed for full closing of the working media flow. They can be used for temperatures up to 200°C. If the gate valves are used for regulating or throttling purposes, the manufacturer does not guarantee the tightness. The gate valves are full-bore piggable valves with a flow resistance coefficient equal to that of the piping. Therefore they are suitable especially for long-distance pipeline systems.
Knife gate valve (Slurry gate valve)Knife gate valve is the valve that has a narrow and parallel gate with an edge that is inclined to cut through the substance in the slurries. The valves are made from top quality material to ensure their effective working and long durability. The knife gate valve we provide are made according to industrial specifications and are even customized on customers request. The structure characteristic of knife gate valve is, in its at the bottom of the valve plate has a oblique incision, like the blade, the knife type of oblique incision can easily cut the pipe flow medium, make the closing of the valve is not blocked by the medium, specific can see under the knife gate valve structure. Compared with the traditional gate valve, the knife gate valve has a simpler structure, a smaller length, and is easier to install, disassemble and maintain. Knife gate valves are suitable for use in medium pipes with high consistency and solid particles.The gate like a knife, has a better effect of the gate breaking, can effectively break all kinds of impurities contained in the medium in the pipeline,
Application of knife gate valve :
Knife gate valve generally used in pulp, slag, coal ash and sewage, chemical raw materials such as medium in the pipeline, and can only be fully open and close, for block valve is used, cannot be used to adjust flow use.
Advantage of knife gate valve
Advantages of the Knife Gate Valve include the ability to cut through slurries, scale and surface build ups, unobstructed ow paths, small face-to-face dimensions and large line size availability. The unobstructed ow path not only provides high ow capacity (Cv), but even allows large objects, rocks and items routinely found in mining processes to safely pass through the valve. Similar to a buttery valve, the knife gate valve has a small face-to-face dimension, greatly reducing the weight of this valve and facilitating piping design.
Disadvantages of knife gate valve
Disadvantages of a knife gate valve are the relatively low pressure limitation, lack of cleanliness and general inability to provide bubble-tight shut-off. As mentioned above, general pressure limitations are 150 psi maximum. Relative to cleanliness, the knife gate valve contains cavities which promote contamination. Hence this valve is not recommended for high purity applications. For abrasive and slurry applications, the knife gate valve is an excellent choice. For proper selection the Technical Sales Representative should be consulted since the application is key to developing the proper valve conguration particularly in larger line sizes. Many users are not aware of the recent design developments and capabilities
Wedge gate valve :
Solid wedge gate valveThe solid wedge gate valve shown in Figure is the most commonly used disk because of its simplicity and strength. A valve with this type of wedge may be installed in any position and it is suitable for almost all fluids. It is practical for turbulent flow.
Flexible Wedge gate valve
The flexible wedge gate valve illustrated in Figure 6 is aone-piece disk with a cut around the perimeter to improve the ability to match error or change in the angle between the seats. The cut varies in size, shape, and depth. A shallow, narrow cut gives little flexibility but retains strength. A deeper and wider cut, or cast-in recess, leaves little material at the center, which allows more flexibility but compromises strength. A correct profile of the disk half in the Figure Flexible Wedge Gate Valve flexible wedge design can give uniform deflection properties at the disk edge, so that the wedging force applied in seating will force the disk seating surface uniformly and tightly against the seat.
Gate valves used in steam systems have flexible wedges. Thereason for using a flexible gate is to prevent binding of the gatewithin the valve when the valve is in the closed position. When steam lines are heated, they expand and cause some distortion of valve bodies. If a solid gate fits snugly between the seat of a valve in a cold steam system, when the system is heated and pipeselon gate, the seats will compress against the gate and clamp the valve shut. This problem is overcome by using a flexible gate, whose design allows the gate to flex as the valve seat compresses it. The major problem associated with flexible gates is that water tends to collect in the body neck. Under certain conditions, the admission of steam may cause the valve body neck to rupture, the bonnet to liftoff, or the seat ring to collapse. Following correct warming procedures prevent these problems.
Split Wedge Gate valve :
Split wedge gate valves, as shown in Figure , are of the ball and socket design. These are self-adjusting and self-aligning to both seating surfaces. The disk is free to adjust itself to the seating surface if one-half of the disk is slightly out of alignment because of foreign matter lodged between the disk half and the seat ring. This type of wedge is suitable for handling noncondensing gases and liquids at normal temperatures, particularly corrosive liquids. Freedom of movement of the disk in the carrier prevents binding even though the valve may have been closed when hot and later contracted due to cooling. This type of valve should be installed with the stem in the vertical position.
Parallel gate valve:
The parallel disk gate valve illustrated in Figure is designed to prevent valve binding due to thermal transients. This design is used in both low and high pressure applications.
The wedge surfaces between the parallel face disk halves are caused to press together under stem thrust and spread apart the disks to seal against the seats. The tape red wedges may be part of the disk halves or they may be separate elements. The lower wedge may bottom out on a rib at the valve bottom so that the stem can develop seating force. In one version, the wedge contact surfaces are curved to keep the point of contact close to the optimum.
In other parallel disk gates, the two halves do not move apart under wedge action. Instead, the upstream pressure holds the downstream disk against the seat. A carrier ring lifts the disks, and a spring or springs hold the disks apart and seated when there is no upstream pressure.
Another parallel gate disk design provides for sealing only one port. In these designs, the high pressure side pushes the disk open (relieving the disk) on the high pressure side, but forces the disk closed on the low pressure side. With such designs, the amount ofseat leakage tends to decrease as differential pressure across the seat increases. These valves will usually have a flow direction marking which will show which side is the high pressure (relieving) side. Care should be taken to ensure that these valves are not installed backwards in the system.
Some parallel disk gate valves used in high pressure systems are made with an integral bonnet vent and bypass line. A three-way valve is used to position the line to bypass in order to equalize pressure across the disks prior to opening. When the gate valve is closed, the three-way valve is positioned to vent the bonnet to one side or the other. This prevents moisture from accumulating in the bonnet. The three-way valve is positioned to the high pressure side of the gate valve when closed to ensure that flow does not bypass the isolation valve. The high pressure acts against spring compression and forces one gate off of its seat. The three-way valve vents this flow back to the pressure source.
- Oil and natural gas production wellhead device, conveying and storage pipelines operating temperature
- Pipes with suspended particle media.
- Urban gas pipeline.
- Water engineering.