Control valves operate a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point.


A control valve is used to control a flowing fluid flow by varying the size of the flow passage. This enables the valve to automatically regulate flow rate and the consequential control of pressure,  and liquid level.


The opening or closing of control valves is done by a controller (mechanical or electrical) to any position between fully open and fully closed.