What Are the Needle Valves? (Part One)

All the valves are operated for cutting off fluids. According to various valve cores, valves can be divided into globe valves, gate valves, plug valves, ball valves, butterfly valves, needle valves, etc. 

Valve cores of needle valves are tapered and cylindrical objects. The name of the needle valves comes from their needle-shaped parts able to be inserted into valve seats.

 

Needle valves belong to vacuum needle valves. At the same time, needle valve have plugs in the shape of needles and are mainly used to adjust airflows. Furthermore, needle valves can provide fine adjustments of air flows continually.

Meanwhile, needle valves also belong to throttle valves, with the great continual precise adjustment capability.

With the capability of fine control, needle valves have wide applications. For instance, needle valves can be installed on saws of flame cutting machines as rotary knobs.

Valve plugs of needle valves, generally, have slender needle shapes and are made of chilled steel. Valve seats of needle valves are made of soft materials such as tin and copper. The joints of valve needles and the valve seats are sealed by the close contact of valve seats and conical surfaces of valve needles.

The taper of the valve needle has two kinds of cone angles: 1:50 or 1:60. The conical surface is supposed to have the fine grinding treatment. The vale stem and the valve seat are sealed by bellows.

Needle valves can withstand higher pressures than other valves and are with great sealing performance. They are usually used to seal high-pressure gases and liquids at low flow rates. At the same time, needle valves are suitable to be operated in combination of pressure gauges. Generally, needle valves adopt threaded connections.

The general knowledge of needle valves
Needle valves are basically small globe valves. They are usually used as cut-off valves for instruments and pressure gauges, regulating small flows of air, natural gases and hydraulic fluids in pipelines connected to gauges. At the same time, needle valves are used to reduce the fluctuation if pressure in pipelines connected to gauges.

Needle valves are easily clogged because of their own narrow flow channels. This characteristic needs to be paid attention to during operation. 

Applications of needle valves
There exists two kinds of needle valves. One kind of needle valve is used for the pipeline to throttle the flow and reduce the pipe pressure, particularly suitable for regulating flow at the low flow rate. 

The other kind of needle valve is used for maintenance, such as adding oil and fluorine. This kind of needle valve is similar to the one-way valve in the aspect of operation.

Some centrifugal machines have structures with needle valves. During maintenance and debugging, the needle valve can be connected to the pressure gauge.