What are Needle Valves? Definition, Parts, Types, FAQ’s [PDF]

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Needle Valve Definition

Needle valves regulates the amount of stuff that flows through pipes. You can also use them to stop the flow entirely. They come in sizes ranging from 1/8 inch to 2 inches. When you turn them, the changes in flow happen slowly and steadily. But, one downside is that they can cause a decent amount of pressure to be lost.

needle valve definition

What is the function of Needle Valves

Needle valves have a special design with a long, screw-like stick. At the end there is a point that looks like a needle. This needle part can fit into a matching tapered hole in the valve. When you twist the stick, you can move the needle closer or farther from the hole. This controls how much stuff can flow through the valve, from wide open to completely closed. Usually, the valve has the entry and exit holes in a straight line, but there are other designs too. You can operate these valves by hand or use a machine to make them work automatically.

Selection Criteria of Needle valves

Following are the main criteria’s that you must consider while selecting a needle valve:

Pressure

When you’re picking a needle valve, the pressure it can handle is crucial. Strong ones can deal with pressures between 4000 to 5000 psi (that’s like 275 to 413 times the air pressure at sea level) at a temperature of 100°F (38°C). If you need higher pressures, there are better valves that can handle up to 10,000 psi at the same temperature.

Size

You can find needle valves in lots of different sizes and ways to attach them. They come with threaded connections, like screws, in both inch and metric sizes. The usual ones are between 2 to 12 millimeters or 1/8 inch to 2 inches in size. It is very important to choose the right one. This is because it helps things to flow smoothly. It avoids your system from wearing out or leaking.

Temperature

Needle valves can work in really hot or really cold conditions. But to make sure they don’t leak, the stuff they use to seal them is crucial. The two main sealing materials are PTFE (you might know it as Teflon) for temperatures from super cold -65°F to hot 450°F (-54°C to 232°C), and PEEK (Polyether Ether Ketone) for even hotter temperatures, going up to 600°F (315°C).

Materials

Valves are made from various materials, and some common ones are brass, stainless steel (either 304 or 316), carbon steel, and Alloy 400, which is a type of nickel-based alloy.

Parts of Needle Valve

needle valve diagram

Following are the main parts of a needle valve:

  • Valve handle
  • Nut
  • Bonnet
  • Valve body
  • Seat
  • O-ring
  • Packing
  • Stem
  • Handle screw

Main types of needle valve

Needle valves are classified into 3 main types:

Manually Operated Threaded Needle Valve: These valves are turned by hand to control flow.

Manually Operated Threaded Needle Valve

Motorized Needle Valve: These valves use an electric or pneumatic actuator (a machine that moves things) to control them. It’s like a robot for the valve.

Motorized Needle Valve

Angle Needle Valve: Instead of having the entry and exit holes in a straight line, these valves turn the flow by 90 degrees, making it come out to the side.

Angle Needle Valve

How does Needle Valves work?

Needle valves can be operated in two ways:

  • Manual
  • Automatic

Manual Needle Valves: These valves use a handwheel. Turning the handle clockwise lifts the plunger to open the valve, allowing fluid to pass. Turning it anti-clockwise moves the plunger closer to the seat, reducing the flow, and eventually, it stops the fluid flow.

Manual Needle Valves

Automated Needle Valves: These valves are connected to a hydraulic motor or air actuator, which automatically opens and closes the valve. The motor or actuator adjusts the plunger’s position based on timing or external data collected from monitoring the system.

Automated Needle Valves

Both manual and automated needle valves are excellent for controlling the flow rate precisely. The handwheel is precisely threaded, so it takes several turns to move the plunger, allowing for fine control over the flow rate in the system.

Design Standards of needle valves

Following are the most commonly used Needle Valve Standards:

  • ASME B16.34
  • BS 7174 P4
  • MIL-V-24586
  • PIP PNDMV09N

Pros and Cons of Needle Valves

Advantages of Needle ValvesDisadvantages of Needle Valves
This valve allows for highly precise flow control at very low rates.Needle valves can cause significant pressure loss due to their flow restriction.
Needle valves are compact, making them easy to install in tight spaces.Needle valves are suitable primarily for low-flow rate piping systems.
You can use this valve to control the flow even when there’s a small amount of fluid.Solid particles in the fluid can potentially damage the seat and needle of the valve.
You can finely adjust the flow rates with precision using this valve.You can’t tell if it’s open or closed just by looking at the handle position.
Operating it is straightforward and user-friendly.Quickly opening or closing these valves isn’t recommended because it can harm the valve seat.

Difference between Needle Valve and Ball Valve

Needle ValveBall Valve
A needle is employed to both open and close the valve.Ball valves operate using a spherical ball.
Needle valves are a type of linear motion valve.Ball valves are considered quarter-turn valves.
Needle valves are known for their precision in controlling flow.Ball valves are generally not ideal for precise flow control.

Applications of Needle Valves

  • Needle valves protect analog instruments from fluid pressure surges.
  • They are suitable for precise flow adjustments and small flow rates.
  • Needle valves can function as on/off or throttle valves.
  • They are used for controlling steam, air, gas, oil, water, or similar fluids.

FAQ’s

What is a needle valve used for?

A needle valve controls fluid flow in a system using a small, tapered plunger that resembles a needle.

Does a needle valve alters fluid pressure?

Needle valves are employed to control both fluid flow and pressure in a system.

Conclusion

Whether you’re an industry expert or simply curious about machinery, this article would have definitely made the concept clear. This was all about needle valves. If you have any questions feel free to write in comments.

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