A valve is, in the most basic sense, a device used to regulate the flow of a medium via a pipe system, whether it is liquid, gas, or solid. Most frequently, valves are employed to start and halt media flow. Some valves, known as control valves, have the ability to regulate the flow rate.
Control Valve
A control valve is used in industrial machine systems to control the flow, pressure, temperature or the level of fluids. Valve body, actuator and positioner are the different parts of a control valve .
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Valves come in a vast variety of mechanical modifications due to their many distinct applications. The smoothest, safest operation of your application and the most effective achievement of the intended aim are ensured by the use of the proper valve in a specific situation.
Despite the fact that there are several distinct valve classifications, the majority of valves fall into one of three groups: rotary, linear, or self-actuated.
Rotary
Rotating closure components are used by rotary valves to stop flow inside a pipe system. Rotary valves are also sometimes referred to as quarter-turn valves since this rotation is typically confined to 90 degrees. These valves have two positions: closed (0 degrees) and open (90 degrees).
Some rotary valves have more than two locations and can rotate to a greater degree. Butterfly, plug, and ball valves are common examples of rotary valve types.
Linear
To initiate, halt, or modify flow via a pipe system, linear valves employ a flow obstruction that travels in a straight line, such as a disc, slat, or diaphragm. These valves can be divided into two different categories: axial and rising stem (multi-turn).
Globe valves, gate valves, and needle valves are examples of multi-turn linear valves that excel in control applications. Fast-acting axial valves utilised largely in on/off process applications include coaxial and angle seat valves.
Rotary valves often have shorter cycle periods than other types of valves, such as linear motion valves.
Self-actuated
Self-actuated valves do not require direct operator input, in contrast to linear and rotary valves. Instead, they operate a pressure control valve by changing the pressure along the process line. This type of valve is frequently employed as a pressure relief valve and only opens when the system’s maximum permissible pressure is reached. Because of this mechanism, self-actuated valves are frequently required for safety in several applications.
Relief valves, safety valves, check valves, and steam traps are examples of typical self-actuated valves.
Quarter-turn valve types
Quarter-turn valves are frequently employed in applications that value speed and convenience over accuracy because they permit a large range of motion with the turn of a handle.
Ball valves
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The majority of situations when a fluid flow has to be stopped can be handled using ball valves. They are really the most used process control valve. To start or halt the flow, these rotary valves employ port spheres that revolve in the pipe stream.
Ball valves provide little head loss because the port may be precisely adjusted to match the pipe’s diameter. While ball valves may cost more than other rotary valve alternatives, they provide greater sealing than designs like butterfly valves.
Flush bottom valve
A flush bottom valve is used for draining of tanks and vessels. This is essential as it leaves no liquid residue behind. It is conical in shape and has a flat or concave seat that allows unrestricted flow of liquid when opened fully. This is used in the food processing, pharmaceuticals and chemical industry as they help in preventing product contamination, reduce the loss of product and help in cleaning and maintenance. These can be used manually or automatically.
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Butterfly valves
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Butterfly valves function by swinging a disc-shaped obstruction, which is located in the middle, in and out of the flow of the pipe system. When shut-off, control, and isolation are required, these quarter-turn valves are typically utilised with larger pipe diameters in wastewater treatment facilities, power plants, and other process plants.
Butterfly valves provide benefits such as cheaper cost and smaller size. These typical valve types, however, may not function as effectively against high-pressure flows and are more prone to leaks and head losses than ball valves.
Plug valves
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Ball valves and plug valves are quite similar in design and function. However, plug valves restrict or allow flow utilising a tapered cylinder that swings into or out of the flow stream as opposed to a ball-shaped obstruction. Plug valves come in two basic varieties: lubricated and unlubricated.
For wastewater treatment facilities, processing plants, and chemical processing industries, this type of rotary valve is widely employed as a control valve and for shut-off. Because they don’t have any spaces or cavities and may be modified to accommodate leaks that manifest over time, plug valves may be preferred. As a result, these valves are frequently employed in demanding operating conditions, such as corrosive settings like chemical and oil refineries.
Flow regulating valve
A flow regulating valve controls and regulates the flow rate of liquids or gases in a system. These are used in industrial systems. These valves can be operated by throttling the flow of the valve or by modulating to adjust the flow.
Back pressure regulating valve
A back pressure regulating valve is used to control a specific back pressure in a system. This is used to prevent unwanted pressure fluctuations.
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Different multi-turn valve types
Multi-turn valves, which are frequently used in flow control applications, function by turning a handle to insert an obstruction into the flow stream.
Globe valves
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When a globe-shaped disc of a globe valve is closed up against a restriction orifice, it blocks flow. These multi-turn valves are frequently employed in throttling and on/off applications. Globe valves can close both with and against fluid flow.
While 3-way globe valves are appropriate for blending material from two intake ports and delivering the resultant mixture via an output port, two-way globe valves are advised for accuracy. Globe valves are often used in food processing facilities and wastewater treatment plants. Although there are other varieties of this valve type, the Z-style valve is the most common.
Gate valves
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Gate valves are multi-turn valves that are frequently employed to obstruct flow streams as well as occasionally (and occasionally unsuccessfully) for throttling. This form of multi-turn valve stops a flowing stream using a barrier that resembles a plate.
Compared to other valve types, gate valves offer smaller head losses while open. Gate valves have less ability to limit and regulate flow, although operating similarly to globe valves.
Needle valves
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With a few important exceptions, needle valves and globe valves are quite similar. In smaller systems, they enable more accurate flow control due to their reduced size compared to globe valves. They also have a cone-shaped needle that slides into and out of an aperture to start and halt flow, as opposed to a disc-shaped stopper.
A precise method of adjusting fluid flow across a system is provided by needle valves. They can be utilised in on/on applications; however, they might not be the greatest choice because they take a lot of turns to shut.
On/off valve types
On/off valves are quick-acting, unrestricted flow-enabling or flow-blocking devices, as their name would imply.
Solenoid Valve
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A linear sliding obstructer is used by solenoid valves to open or stop the valve or switch the flow from one exit to another. These valve types come in a wide range of diameters, ranging from one millimetre to one hundred millimetres. They can also be made of many materials, including cast iron, stainless steel, aluminium, plastic, and brass.
High-pressure systems and emergency shut-off service applications frequently employ solenoid valves. Additionally, they can withstand a broad variety of temperatures; certain types can withstand high temperatures of -418° F to 1472° F.
Valve coaxial
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Coaxial valves have two positions and can be operated electrically or pneumatically. An electromagnetic coil is used in place of a spring in electric coaxial valves. In place of a spring, pneumatic coaxial valves may employ air pressure or double acting air pressure (air pressure that comes from both directions). To open or close and direct flow to the proper exit, these valves employ shuttle obstructors.
In a lot of on/off applications, coaxial valves work well in place of ball valves. In actuality, they are a more readily available, more compact, lighter, safer, and quicker substitute. Coaxial valve drawbacks include reduced flow capacity and restricted fluid compatibility.
Angle-seated valves
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The angle seat valve, another form of valve that may take the place of a ball valve in on/off applications, rounds out the list of various types of valves and their applications. The pneumatic actuator used by seat angle valves might be double acting or spring return.
This two-position valve has an obstruction plug which fits into the flow path’s inclined seat by entering the valve at an angle. This type of valve has the maximum flow rate and the lowest pressure drop when it is open because the plug retracts almost totally out of the flow passage.
FAQs
What distinguishes rotational valves from linear valves?
While linear valves work by raising or lowering a flow obstruction like a gate, globe, or diaphragm, rotary valves stop flow in a pipe system using a revolving closure component.
What purpose do on/off valves serve?
Applications, where the purpose of the valve is to stop or start the flow of medium should utilise on/off valves. It is not recommended to adjust the flow rate using on/off valves.
