Needle Valve

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Needle Valve

Post  landoo on Tue Jan 08, 2013 11:52 pm

Needle valve is a valve can be precisely adjusted, wider use, such as flame cutting, cut away from the flame temperature adjustment knob is the needle valve. Instrumentation needle valve is an important part of the instrument measuring piping systems, the main shut-off valve and ball valve, its purpose is for open or cut off the pipeline path with. Needle valve spool is a very sharp cone, the same as if the needle inserted into the valve seat, hence the name.
Any valve to cut off the fluid. Depending on the spool, can be divided into the shut-off valve, gate valve, plug valves, ball valves, butterfly valves, needle valves, etc.
Needle valve shape than other types of valves can withstand greater pressure, good sealing performance, it is generally used for smaller flows, the sealing of the higher pressure of the gas or liquid medium. Needle valve used in conjunction with a pressure gauge is most appropriate. generally shaped needle valve threaded connections are made. Nominal pressure: PN2.5 PN4 PN6.4 PN16 PN32Mpa nominal diameter: DN5 ~ DN25 Applicable medium: oil, water, gas and a variety of non-corrosive or corrosive media applicable temperature: -20 ° C to +440 ° C -70 ° C ~ -240 ℃ ≤ 540 ℃ ≤ 570 ℃ manufacturing materials: 20 #, 1Cr18Ni9Ti, 304, 316, 316L, 12Cr1Mov etc.
Needle valve, is typically used in a flow metering applications, particularly constant, after calibration, the low flow rate, must be maintained for some time, such as idle in the fuel flow of the carburetor.
Please note that the said float valve of the carburetor (carburetor fuel level within the control) is not a needle valve, although it is usually described as a. It uses a bluntly tapered needle, but it is fixed in a four seat, rather than matching tapered. The purpose here is to obtain a clear two narrow between the mating surfaces of the seating, so that only the float pressure, firmly closed flow.
As the velocity is low, the number of turns stem is required to fully open or closed, the needle valve is not used for simple off applications.
The advantage of the hole small and fine threaded rod force is usually easily, the needle valve is completely closed, just "finger-tight" pressure. The spindle and / or the seats of the needle valve, and in particular is made of brass and are easily damaged by an excessive rotational force, off the flow.
Small, are often used as a simple needle valve bleeder valve hot water heating applications.
Unlike a ball valve, or the valve with rising stem, it is not easy to tell from the check the handle position the valve is open or closed.

landoo

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