Needle Valve

Needle Valve

A Needle Valve is used to make relatively fine adjustments in the amount of fluid flow. The distinguishing characteristic of a needle valve is the long, tapered, needle-like point on the end of the valve stem. This “needle” acts as a disk.

The longer part of the needle is smaller than the orifice in the valve seat and passes through the orifice before the needle seats. This arrangement permits a very gradual increase or decrease in the size of the opening. Needle valves are often used as component parts of other, more complicated valves. For example, they are used in some types of reducing valves.

Needle Valve Application

Most constant pressure pump governors have needle valves to minimize the effects of fluctuations in pump discharge pressure. Needle valves are used in almost every industry in an incredibly wide range of applications – anywhere control or metering of steam, air, gas, oil, water or other non-viscous liquids is required.

Needle Valve application in industries

• Zoological sciences
• Gas and liquid dispensation
• Instrumentation control
• Cooling
• Power generation
• Automatic combustion control systems
• precise flow regulation

Needle valves can also be used as on/off valves or for throttling service.

ADVANTAGES OF NEEDLE VALVES

Needle valves give us great control over the flow rate of a liquid or gas which in reality, gives us the luxury to consume the fuel according to our desire. For example, in a motorcar engine, it is a needle valve which is responsible to regulate the fuel flow rate.

These valves can work both ways. Whether you want to increase the flow rate or decreasing it.

Besides the control on flow rate, it also stables the pressure too. The pressure loss is on the minimum side as compared to the other same as valves that are available in the market.

DISADVANTAGES OF NEEDLE VALVES

Unlike other types, you can’t visually observe the position of the screw or the handle used to control the positioning of the screw in the valve that determines if the valve is open or closed. To tackle it, other devices are often included in the equipment design that makes it possible to monitor the flow and use the valve to adjust that flow accordingly.

Needle valve selection

Items that you should consider when selecting a needle valve:

Pressure

The working pressure is an important factor in selecting the right needle valve. Robust needle valves can handle pressures of up to 4000-5000 psi (275-413 bar) at 100°F (38°C). When still higher pressures are required, high-performance valves are available that can handle up to 10000 psi (689 bar) pressure at 100°F (38°C).

Size

Needle valves are available in a wide range of sizes and end connections. Male/female connections with inch/metric threads can be used. The most commonly available valves have the size from 2 to 12 mm or 1/8” to 2”. Using the right valve size facilitates efficient flow and system operation with fewer chances of wear and leakage.

Temperature

Needle valves can be operated at high or low temperatures. For extreme temperatures, the packing/sealing used is particularly relevant. Two most commonly used packing materials are PTFE (Teflon) for a temperature range of -65°F to 450°F (-54° C to 232°C) and PEEK (Polyether Ether Ketone) for increased temperature resistance up to 600°F (315 °C).

Materials

Different materials are used in needle valve construction. The commonly used materials include brass, 304 or 316 stainless steel, carbon steel and Alloy 400 (Nickel based alloy).

Stainless steel is widely used for its corrosion resistance, chemical stability, and high-temperature resistance. Brass needle valves are used in hydraulic systems, high-temperature applications, and gas piping. Alloy 400 is used for its high strength, corrosion resistance and used mainly in marine and chemical processing applications.