Needle valve is a micro metering valve, with valve plug in shape of needles, mainly used for adjusting the gas flow. Micro metering valve requires that the valve port is larger, enabling fine adjustments continuously from completely shut to completely open position. Needle valve is used for this. Generally, needle valve is made of long steel needles that are quenched, and the valve seat is made of soft materials, such as copper or tin, etc. The seal between needle valve and valve seat is achieved with the help of conical surface.
There are two kinds of needle valves, one used in pipelines to reduce pressure and throttle.
The other is for maintenance (with fluorine and oil), which operates like one-way valve, can be opened by the thimble located inside the joint of the fluorine hose.
Needle valve is slender, and looks like a needle with taper, which is suitable for throttle in low discharge circumstances.
Needle valve can be used by repairing mechanics, for instance, some centrifugal machines are equipped with needle valves, which can be connected with a pressure gauge during the maintenance to systems.
