An automatic valve actuator is a device used to control the opening and closing of a valve. It is typically used in industrial applications, such as in water, oil, and gas pipelines, to regulate the flow of fluids. The actuator is connected to the valve and uses either electrical, hydraulic, or pneumatic power to move the valve stem and control the flow of the fluid. The actuator is usually programmed to open and close the valve at certain intervals or when certain conditions are met. This allows for the automatic regulation of the flow of the fluid, which can be used to maintain a certain pressure or temperature. Automatic valve actuators are used in a variety of applications, including controlling the flow of water in irrigation systems, controlling the flow of oil and gas in pipelines, and controlling the flow of air in HVAC systems. They are also used in medical applications, such as controlling the flow of medication in an IV drip.