What is a needle valve?
A needle valve is used to precisely control the flow of clean gases or fluids. For managing the flow rate, the modifications are progressive and smooth. They can also function as a dependable shut-off valve. They are, however, typically employed for modest flow rates with a relatively considerable pressure drop from the input to the output. The most common use is to regulate gas flow, such as propane flow in a propane tank.
Types of needle valves
- Motorized needle valve
- Angle needle valve
Motorized needle valve: An electric or pneumatic actuator connects to and turns the plunger in these needle valves. These can be operated remotely, utilised in a closed loop system, and/or set on a timer to accurately control the flow rate.
Angle needle valve: Rather than being in-line, these needle valves turn the flow from the inlet by 90 degrees. The operation concept is the same, but the 90-degree angle allows for better system integration.
What are the parts of the needle valve?
- Handle
- Set screw
- Stem
- Body
- Nut
- Gland
- Packing
- Bonnet
- Handle screw
Handle
A handle is used to control a valve manually from outside the valve body. Automatically controlled valves frequently lack handles, however, some, such as a stop-check valve, may have a handle (or something similar) to manually override automated control.
Set screw
A set screw is a screw that is used to secure an object within or against another object using pressure and/or friction, such as attaching a pulley or gear to a shaft. A set screw is generally used without a nut (to differentiate it from a bolt) and is screwed into a threaded hole drilled in only one of the two objects to be secured. A set screw is frequently headless and threaded along its entire length, allowing it to sit totally inside the hole; in this instance, it is known as a grub screw or blind screw.
Stem
The stem conveys rotational motion from the hand wheel to the plug, and the power screw on it translates the hand wheel’s rotational motion into a vertical motion, placing the disc in its seat and blocking the flow opening. The valve’s stem is joined to the hand wheel through four flat edges at the top, screwing into the power screw and then locking it into place with a nut. At the bottom, the plug is screwed into the stem and secured with the disc stem nut. As a result, the power screw will exert torsional pressures on the stem.
Body
The major part of a needle valve is the valve body and it is also known as the shell. The body is the framework that keeps all the elements together and serves as the major component of a valve assembly. A valve’s body, or initial pressure barrier, resists fluid pressure loads from connecting pipes.
Gland
In valves, the packing gland is a component of the valve that is inserted into the bonnet to maintain the stem packing in place. For smooth operation of the valve, the top of the packing gland is also employed with the bottom bearing set of the stem adapter.
Bonnet
The bonnet is the component of the valve that closes the opening. It is a pressure-bearing portion that holds the full pressure of the fluid as it flows through the valve with the body as its service loads. A threaded stud and nuts hold it in place. It also serves as a support for the gland, and in this case, constructed of bronze, the bonnet is normally made of the same material as the valve body.
Advantages and Disadvantages of Needle valve
Advantages of Needle valve
- Flow control at a very low rate with improved accuracy is feasible with the help of this valve.
- Needle valves are more compact.
- With this valve, you can throttle even with a small amount of fluid.
- Flow rates can be accurately adjusted.
- It is simpler to use.
Disadvantages of Needle valve
- Because of the significant restriction of fluid flow, there is a substantial pressure loss in the needle valve.
- Needle valve is only suitable for low flow rate piping systems.
- The seat and needle may lead to breaking if any solid particles in the fluid.
- It is impossible to tell whether it is open or closed simply by looking at the handle position.
- Can’t open and close quickly.