Control valves are mechanical devices used to regulate the flow of fluid or gas in a system. They are commonly used in industries such as oil and gas, power generation, chemical processing, and wastewater treatment. Control valves have a valve body that contains a movable element, such as a disc or a plug, which can be adjusted to vary the amount of flow passing through the valve. This adjustment is achieved by changing the position of the valve actuator, which can be pneumatic, hydraulic, electric, or manual. Control valves are essential for maintaining precise control over process variables such as flow rate, pressure, temperature, and level in a wide range of industrial applications.