Needle valves in Dubai UAE
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Needle Valve and its Working Principals
A needle valve is used to precisely control the flow rate of clean gases or fluids. The settings for flow control are gradual and smooth, however, they can also be used as a reliable shut-off valve. However, they are usually used only for low flow and have a relatively large pressure drop from inlet to outlet. Common port sizes for needle valves range from 1/8 inch to 2 inches. The most common application is gas flow control, such as a propane needle valve.
How needle valves work
Needle valves open and close a hole with a tapered end that rotates up and down the handle. The handle is attached to a piston, also called a stem. When you turn the handle, the piston moves up or down based on the threads. The locking nut prevents it from fully opening. As the piston moves down, the narrow end of the tip contacts the valve seat to close the opening completely. Often, the valve seat is also tapered. There are several options and sizes for connecting it to a pipe or hose by connecting a port at the inlet and outlet. The hood is attached to the valve housing, which can be made of various materials such as brass or stainless steel.
Depending on the threads, you can carefully adjust the tip of the piston at a very distant distance from the valve seat to precisely control the flow rate. Therefore, by moving the piston, you will control the flow rate between maximum and zero.
Types of needle valves
The manual threaded needle valve is the most common type of needle valve. However, there are two additional types: Motorized and angle.
These needle valves do not have a handle for manual labor, but instead, use an electric or pneumatic actuator to connect and rotate the piston. These can be remotely controlled, used in a closed-loop system, and/or a timer can be set to accurately control the flow rate.
These needle valves rotate the outlet from the 90-degree inlet instead of into the line. The same operational concept applies, but a 90-degree angle can improve system integrity. Figure 3 shows an example of an angled needle valve.
Consider when selecting the needle valve
When choosing a needle valve, four main characteristics and/or functional requirements must be considered: material, pressure, size, and temperature.
Needle valve housing material is specified according to the application. The most common valve chamber materials are brass and stainless steel due to their range of chemical resistance, however, other materials are also available for specific applications.
Brass needle valves are suitable for hydraulic systems, drinking water, high-temperature applications, and gas piping. They are suitable for neutral and non-corrosive environments and are the most common for drinking water applications. However, they should not be used for saltwater (seawater), distilled water, acids, or chlorides.
Stainless steel needle valves have excellent general chemical resistance to almost any medium. This material is very durable and can withstand high temperatures and pressures. Suitable for aggressive and corrosive media such as seawater.
Understanding the pressure requirements in your system is important for choosing the right needle valve. Durable needle valves can withstand pressures up to 4,000 to 5,000 psi (275 to 413 bar) at 100 degrees Fahrenheit (38 degrees Celsius). When higher pressures are required, such as in high-pressure hydraulic applications, high-performance valves are available that can withstand pressures up to 10,000 psi (689 bar) at 100 degrees Fahrenheit (38 degrees Celsius). Special designs are also available when you need a vacuum needle valve to control low pressure.
Port and aperture size
Needle valves are available in a wide range of port and orifice sizes. Connection ports can also be male or female. Common thread standards used are NPT (National American Pipe Thread), BSP (British Standard Pipe), or Metric (ISO standards). The most common needle valves are from 2 to 12 mm or 1/8 inch to 2 inches. Ensuring the correct port size and orifice size ensures efficient flow and system performance with less risk of wear and/or leakage.
Needle valves are suitable for high or low-temperature applications. You need to properly specify the valve housing and packing/sealing material, especially for extreme temperatures, to make sure it can withstand the demands. Two common sealing materials are PTFE (Teflon) for the temperature range of -65 degrees Fahrenheit to 450 degrees Fahrenheit (-54 degrees Celsius to 232 degrees Celsius) and PEEK (Polyether Ether Ketone) for increasing temperature resistance up to 600 degrees Fahrenheit (315 degrees Celsius).
Applications of needle valve
Because of their ability to precisely control the flow rate, you will see needle valves in all fluid control programs. By choosing the right valve material and size for temperature and pressure, they can be used for almost any clean gas or fluid. One of the most common places used for needle valves is to monitor the flow of gas, such as propane, in a system. A propane needle valve can precisely close it and/or flow rate and effectively control the amount of burn for applications.