A throttling valve is a type of valve that controls the flow of fluid from one point to another. In general, there will be a significant pressure difference between the throttle valve’s upstream and downstream sides. The pressure drop increases as the flow restriction inside the throttling valve increases. These types of valves are controlled using a variety of methods. Different valves can function as throttling valves under various operating conditions. In this article, we’ll go over the fundamentals of throttling valves.
What is Throttling Valves?
Throttling valves are used to open, close, or regulate the flow of a fluid. Throttling valves are essentially regulating valves because their discs can control the flow, temperature, or pressure of the medium passing through them.
Examples of a Throttling Valve
Different valves can work as throttling valves. Some common examples of valves working as a throttling valves are:
- Diaphragm valve
- Butterfly valve
- Ball valve
- Globe valve
- Pinch valve
- Needle valves
Throttling Valve Applications
Throttling valves are found in a wide variety of industries. Throttling valves are commonly used in the following applications:
- Refrigeration system
- Air conditioning systems
- Steam applications
- Chemical applications
- Pharmaceutical applications
- Fuel oil systems
- High-temperature applications
- Food processing applications
- Automobile systems
- Power generation systems
- Metering systems
Working of a Throttling Valve
A throttling valve obstructs the valve to obtain the required parameters such as flow velocity, temperature, and pressure. The designed restriction and friction generated while flowing affect the flow. The valve stem is generally raised or lowered to change the size of the flow path through the valve. They can even completely close the valve to stop the flow.
Common Valves used as Throttling Valves
Throttle valves are not found in all industrial valves. The valve’s design must be suitable for use as a throttle valve. Throttle valves are typically made up of the following valves:
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Globe Valves:
One of the most common throttle valves used in industrial applications is the globe valve. The globe valve’s disk/plug provides the necessary restriction to function as a throttle valve, allowing only the required amount of media to pass through. Globe valves, on the other hand, require power or an automatic actuator for high-pressure applications.
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Butterfly Valves:
The butterfly valve is best suited for throttling applications because it can easily create throttling by simply opening a small amount to allow the media to pass through.
Needle valves are designed with a needle-like disc that moves to regulate fluid flow. Needle valves are throttle valves used in high-precision applications. Thicker and more viscous media should not be used as a throttle valve.
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Pinch Valves:
Pinch valves are lightweight and simple to maintain, and they are widely used as throttle valves in sterility and sanitary applications. The pinch valves’ best efficiency is 50% due to their soft liner and smooth walls.
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Diaphragm Valves
Diaphragm valves are a good choice for throttle valves in moderate temperature and pressure applications.
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Expansion Valves
Manual expansion valves, thermal expansion valves, capillary expansion valves, and floating ball-type expansion valves are all commonly used as throttle valves in refrigeration systems.
Selecting the Throttle Valves for Specific Applications
The process of selecting throttle valves for a specific application is quite complicated. To zero in on a specific valve to be used as a throttle valve, various parameters must be thoroughly checked. The following are some of the parameters that influence throttle valve selection:
- Pressure drop required
- Range of flow control required
- Flow medium (gas or liquid)
- Design temperature and pressure.
- Purpose of the throttle valve
- Valve MOC
- Actuation required