Needle valves are generally small valves that have a needle like device. This is used for relatively lesser level of flow. It is not suited for bigger flow rates.

Needle valves have a small orifice and a cone shaped seat. A needle shaped device is fitted at the end of this cone shaped seat on the valve. The flow is possible when the screw is turned and the needle shaped device is turned back. The fluid flow and the level of such relevant fluid flow depend on the retractability of the needle shaped device. It has to completely make way in order for the fluid flow to be at the maximum. Accurate rate of flow of the liquid or the fluid depends on various turns of the screw that is fitted to the cone shaped seat.

Needle valves are used in flow metered purposes and have their significance in regulating the flow of the liquid in such cases. These are extremely useful when the flow rate is needed to be less and the rate of flow of the fluid or the liquid is desired to be at a constant rate throughout for optimum usage of the respective application.

Needle valves are unsuitable for simple shut down applications as they require many turns of the screw that is prevalent in the valve for the flow to be kept at a desired level required for the particular application. Sometimes the small needle valves have their usage in the water heating applications. In this context they are used as bleed valves. It is very difficult to say whether a needle valve is open or shut. The particular position of the handle of the needle valve and its examination is not adequate to conclude that such a valve has been kept open or it has been closed. In case of other valves the position of the handle or the rising stem is enough to come to the conclusion that the relevant type of valve is open or shut. In this case however caution has to be exercised to ascertain the position of the valve.