A needle valve is a type of valve having a small orifice and a threaded, needle-like plunger. It allows precise regulation of flow, although it is generally used for, and is capable of, only relatively small flow rates.

Construction and operation

A needle valve has a relatively small orifice with a long, tapered, conical seat. A needle-shaped plunger, on the end of a screw, exactly fits this seat. As the screw is turned and the plunger retracted, flow between the seat and the plunger is possible; however, until the plunger is completely retracted the fluid flow is significantly impeded. Therefore, and since it takes many turns of the fine-threaded screw to retract the plunger, precise regulation of the flow rate is possible.

Uses

Needle valves are usually used in flow metering applications, especially when a constant, calibrated, low flow rate must be maintained for some time, such as the idle fuel flow in a carburetor. A carburetor (North American spelling or carburettor ( Commonwealth spelling) is a device that blends air and Fuel for an Internal

Since flow rates are low and many turns of the valve stem are required to completely open or close, needle valves are not used for simple shutoff applications.

Since the orifice is small and the force advantage of the fine-threaded stem is high, needle valves are usually easy to shut off completely, with merely "finger tight" pressure. Small, simple needle valves are often used as bleed valves in hot water heating applications.

Unlike a ball valve, it is not easy to tell from examining the handle position whether the valve is open or closed. A ball valve (like the Butterfly valve and Plug valve are one of the family of valves called quarter turn valves) is a Valve that opens

See also

• Ball valve
• Butterfly valve
• Control valve
• Gate valve
• Globe valve
• Plastic pressure pipe systems
• Valve

A ball valve (like the Butterfly valve and Plug valve are one of the family of valves called quarter turn valves) is a Valve that opens A butterfly valve is a type of flow control device typically used to regulate a fluid flowing through a section of pipe Control valves are Valves used mainly within industrial plants to control operating conditions such as Temperature, Pressure, Flow, and A Gate Valve, or Sluice Valve as it is sometimes known is a Valve that opens by lifting a round or rectangular gate/wedge out of the path of the Fluid. A Globe valve is a type of Valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally Spherical Plastic pressure pipe systems are used for the conveyance of Drinking water, Waste water, Chemicals, heating and cooling fluids foodstuffs ultra-pure For other uses see Valve (disambiguation. For the electronic component see Thermionic valve.

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic