A needle valve is a manual valve used where continuous flow throttling is required for regulation. Needle valves are similar to the globe valve in design, with the biggest difference being the sharp needle-like disk.
Needle valves are designed to give very accurate flow control in small diameter piping systems. They get their name from their sharp-pointed conical disc and matching seat.
Image – Swagelok
Fluid flowing through the valve turns 90 degrees and passes through an orifice. Due to needle shape disk, a certain portion of the disk will pass through the seat opening before the disk comes in contact with the seat, which has to match the tapered design as a disk. This arrangement permits a very gradual increase or decrease in the size of the opening.
The needle valve has a forged and machined body. This body can be of forged carbon steel or stainless steel, depending on the requirements of the services. A seat can be a soft, metal, or composite, same as a globe valve. Normally needle valves are used in smaller sizes and are provided with either screwed or socket weld end.
All the aspects of a needle valve are the same as a global valve except its size and pointed needle-like disk. You can refer to a globe valve for more detail.
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Needle Valve Application
- All field analog instruments are fitted with a needle valve to control flow entry, where sudden surges of fluid under pressure can damage the instruments.
- Needle valves can be used in situations where the flow must stop gradually and in the application where precise adjustments of flow are required or where a small flow rate is desired, such as sample points in the piping.
- Needle valves can be used as both on/off and throttle valves
- Used in all industries for controlling and metering fluid applications such as steam, air, gas, oil, water, or other non-viscous liquids.
Click here to learn about Other Types of Valve.
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