Needle valves are valve designs that are constructed with a small opening accompanied by a plunger that looks a great deal like a common sewing needle. The purpose of this type of valve is to create a means of controlling the flow of liquids or gases through the valve mechanism. It is possible to easily adjust the flow rate to any specific amount desired, making the needle valve useful in a number of applications, including engines.
Along with the elongated and somewhat tapered plunger, a needle valve also features a screw that fits into what is known as a seat. The seat is situated so that it is possible to turn the screw and either increase or decrease the flow through the valve. Since the device is constructed so that it takes a number of turns to move the plunger, it is possible to regulate that flow with a great deal of precision.
It is this ability to control flow with such exactness that makes the needle flow ideal for situations in which the desired flow must be maintained with little to no variance. One common use of both stainless steel and brass needle valves is with utility meters where there is a need to measure precisely the amount of power, water or natural gas that a customer has consumed during a given billing period. At the plant level, valves of this type are often used to regulate the flow into the system used to deliver the product to various points of destination. By controlling the needle valve rate, stress on the delivery system is kept to a minimum, which in turn helps to enhance the safety of personnel who work at various points along that system.
For engines in which carburetors are commonly included, a needle valve is often the device that helps to regulate the flow of fuel into the device. This is very important, since an excessive amount of fuel can choke the carburetor, and shut down the engine. At the same time, a lack of sufficient fuel flowing into the carburetor will result in additional wear and stress on the engine over time, a factor that may lead to costly repairs. An alternative to using a needle valve is the inclusion of what is known as a float valve. In some situations, this type of valve is also identified as a needle-type valve, although the design is different.
A needle valve is also sometimes used in equipment that controls the temperature of water within a specific system. For example, some residential water heaters utilize this type of valve as a type of bleed valve that makes it possible to relieve pressure on the water flowing through the device. As with other applications, the valve makes it possible to control the flow of water through the heater, a factor that can also aid in minimizing the amount of energy needed to maintain an equitable supply of hot water.
While there are many advantages to using a needle valve, the basic design does include one disadvantage. Unlike other types of valves, there is no way to visually observe the position of the screw or the handle used to control the positioning of the screw and determine if the valve is open or closed. For this reason, 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.