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The needle valve is a fine-tuning valve with a needle-shaped valve plug, which is mainly used to adjust the airflow. Needle valve plugs are generally made of quenched steel long needles, while the valve seat is made of soft materials such as tin and copper. The seal between the valve needle and the valve seat is achieved by the tight fit of its conical surfaces. The taper of the valve needle has two taper angles of 1:50 and 60, and the taper surface should be finely ground. The sealing between the valve stem and the valve seat is realized by the bellows.
Valves are used to precisely control the flow of clean fluids and gases. They can be used in electric power, chemical industry, nuclear power, petroleum, and other industries. The application range is very large. When considering the selection of needle valves, according to the words of relevant engineers, it is recommended to consider several factors:
1. Size
Needle valves are available in a variety of bore sizes and end connection types. For connection type, there are imperial/metric. Orifice size is critical to ensuring that the valve can meet flow requirements.
2. Stress
The working pressure of the system is an important factor to understand before selecting a needle valve. Common needle valves can withstand pressures up to 4,000-5,000 psi (275-413 bar) at 100°F (38°C). There are some specially designed needle valves that can withstand 2 times the pressure of ordinary valves and can work in low pressure environments, such as in vacuum.
3. Materials
The housing material of the needle valve is critical to ensure that the valve has sufficient durability and withstands the characteristics of the medium (such as high temperature, high pressure, corrosion, etc.). The most common types of needle valve housings are brass or stainless steel (304 or 316). Can also be made from carbon steel or nickel-based alloy 400. Stainless steel is widely used for its chemical stability, corrosion resistance, durability, and high-temperature resistance. Brass needle valves are used in potable water, high temperature applications, hydraulic systems and gas lines. Needle valves made of Alloy 400 have good corrosion resistance and high strength, making them suitable for chemical processing and marine applications.
4. Temperature
Needle valves operate at low and high temperatures. In extreme temperatures, consider the packing/seals used when selecting a valve. The two most commonly used sealing materials are PTFE (polytetrafluoroethylene), which is used in the temperature range of -65°F to 450°F (-54°C to 232°C); and PEEK (polyetheretherketone) material, For improved high temperature resistance up to 600°F (315°C).
