It is not uncommon to hear the term flow control valve used to describe a needle valve. While there are similarities between the two, there are also significant differences. A flow control valve and a needle flow control valve are different, and ordering the incorrect type of valve will result in a downtime for the equipment until the correct valve arrives.
The flow control valve and the needle flow control valve, often just called a needle valve, are both used to reduce the flow of air through the system. By slowing the flow of air, the actuator speed is reduced and can be easily controlled by tightening or loosening the stem of the valve until the desired flow is obtained.
The Needle Valve
A needle flow control valve is able to control the flow of air through the system in both directions. It is a bi-directional valve, which uses a thin, needle-like plunger to insert into the tapered seat. By turning the spindle outward, the needle plunger is retracted, allowing for greater air flow. Turning the spindle down will lower the needle plunger into the tapered seat, gradually limiting the amount of air through the valve.
The spindle is designed to move the plunger very slowly, creating fine control through just fingertip turns of the valve spindle. It is ideal for vacuum systems in dental offices, allowing for precise control of the suction level for devices used to remove saliva and liquid from the mouth of the patient.
The precise fingertip adjustment of a needle flow control valve also makes it very easy to completely shut the valve with minimal pressure. The slow opening of the valve also prevents a sudden suction or the flow of air, which is also important in many precision types of applications.