Industrial machinery relies heavily on valves. They are widely employed in a variety of sectors. A valve’s basic function is to allow for the guided flow of various fluids. A valve has an inner layer that may be opened and closed. Industrial valves have evolved in parallel with the emergence of new mechanical technology. Industrial valves are now more efficient and reliable than they have ever been.
Many new types of industrial valves are being introduced, each with its own set of capabilities. Here we will discuss the Gate valve in detail. Steel was the most common material used to make these valves in the past, but other materials are currently being employed as well. The material used for the valve by Gate Valve Manufacturers is determined by its intended use. This article will provide you with an overview of Gate valves.
High Pressure Gate Valve
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What is a Gate Valve?
A gate valve is a type of valve that starts or stops fluid flow in pipes by moving a gate or wedge type disc perpendicular to the flow. A gate valve is one of the types of shut-off/on valve. It is a linear motion valve which allows you to start and shut the flow of fluid. The flow of media is controlled by a gate valve that lifts (opens) and lowers (closes). These valves are either completely open or completely closed while in service. As a result, there is almost little resistance to flow. When fluid runs through a gate valve, relatively little pressure is lost as a result of this. It is possible to utilise it as a throttling valve, although this is not recommended since media vibration may harm the disc. When gate valves are used half-closed in a throttling application, the surge of the media might destroy the disc.
Gate valves come in a variety of sizes, materials, temperature, and pressure ratings, as well as gate and bonnet configurations.
Construction and working of a Gate Valve
Working: The primary working mechanism is really simple. When the operator turns the handwheel, it rotates the stem with it, which is converted into vertical gate movement via threads. They are classified as multi-turn valves because they require more than one 360° rotation to fully open or close. The valve opens when the gate is lifted out of the flow channel, and when it is returned to its closed position, it seals the bore, resulting in a complete closing of the valve.
Construction: Gate valve consists of major parts like Valve Body, Bonnet, Valve Stem, Disc & Seat. And some common small parts like Stem nut, gasket, gland flange, handwheel, etc.
- Valve Body: A valve body is a housing for all the components and a pressure-retaining part of the valve. It channelises the fluid from inlet to outlet. It connects directly to the piping via flanges that are part of the valve body. So, it is very important to choose the size of the valve in accordance with piping.
- Bonnet: It is an assembly that includes a portion that allows a valve plug stem to move and a way to prevent leaking along the stem. It generally has a place for the actuator to be mounted. Packing or a bellows can be used to prevent leaking. A packing lubricator assembly with or without an isolating valve may be included in a bonnet assembly.
- Stem: The stem is responsible for the disk’s appropriate location since it joins the hand-wheel or actuator with the disc. Stems are normally forged and threaded or otherwise linked to the disc. In a Gate Valve, the stems are either rising or non-rising depending on which end of the stem is threaded.
- Disc: A disc that functions as a closing element in a Gate Valve is also known as a gate. It is available in a range of designs and technologies to provide excellent sealing for several applications. Gate valve closing members are often divided into two categories, each with its own set of variations.
- Parallel Gate Valve.
- Wedge Gate Valve.
- Seat: A valve seat is a very important part of a valve where the valve disc rests to prevent the flow of fluid through the valve. It can be metallic or non-metallic. This is the main part of the valve which directly affects the rate of the leakage of a valve.
- Handwheel or actuators: The actuator is a valve-operating device. It is attached to the disc and stem assembly. It can be operated manually using a handwheel, manual lever, gear, or chain, or it can be powered by a motor and solenoid.
Classification of a Gate Valve.
- Type of Disc
- Solid Wedge Gate Valve: This is the most common wedge design for the Gate valve. They have a very simple design and the strength is very good compared to other types. These wedges can be installed in any position and are suitable for turbulent flow.
- Flexible Wedge Gate Valve: The flexible wedge gate valve is a one-piece disc with a slit around the periphery to help match errors or changes in the angle between the seats. The size, shape, and depth of the slit vary. The flexibility of a shallow, narrow cut is limited, yet it keeps its strength. A cast-in recess, or a deeper and broader cut, leaves little material at the center, allowing for additional flexibility but with reduced strength.
Flexible wedges are utilized in steam system gate valves. The use of a flexible gate prevents the gate from binding within the valve while the valve is in the closed position.
- Split Wedge Gate Valve: Ball and socket split wedge gate valves are the most common kind. They adapt and orient themselves to both sitting surfaces.
If one-half of the disc is slightly out of alignment due to foreign matter stuck between the disc half and the seat ring, the disc is free to realign itself to the sitting surface.
Non-condensing gases and liquids, particularly corrosive liquids, can be handled with this type of wedge at normal temperatures.
- Parallel Wedge Gate Valve: The parallel disc gate valve is intended to keep valves from binding as a result of thermal transients. This design is suitable for both low and high-pressure situations.
- Type of Stem movement
- Raising Stem movement: Rising stems are attached to the gate and rise and fall simultaneously as the valve is opened and closed, providing a visible indication of the valve position and allowing the stem to be greased. The threaded stem is moved by a nut rotating around it. Because of the up and down movement and turning motion of the stem, this type of valve has an inside screwed stem, and the packing is prone to wear. This kind is only appropriate for installation above ground.
- Non-Raising Stem Movement: Threaded into the gate, non-rising stems spin with the wedge rising and falling inside the valve. The valve is operated by turning the wheel, but the stem does not come out of the housing. Because the stem is contained within the valve body, they take up less vertical area. Non-rising valves are always equipped with a local visual indicator that shows the valve’s location. Non-rising stem gate valves can be used in both above-ground and below-the-ground applications.
- Type of Body-Bonnet Joint
- Welded Bonnet
- Screwed Bonnet
- Bolted Bonnet
- Pressure Sealed Bonnet
Advantages & Disadvantages of Gate Valve.
- Gate valve provides a good shut-off feature with very few pressure drops during operation. They are bi-directional and can be used on either side for shut-off. They are suitable for high pressure & temperature applications. They are almost maintenance-free and thus are very cheap & economical.
- Gate valves are slow in operation and can’t be used for quick opening and closing applications. They can not be used for throttling & regulation of the fluid. They require larger space for operation, maintenance & installation as well.
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