An actuator can be defined as a mechanism that moves or controls a device, such as a valve. Actuators reduce the need for operators to go to every valve that needs repositioning and operate it by hand. When actuators are used, valves can be repositioned from a central location, such as a control room. This is very important in processes where many valves have to be repositioned accurately and quickly. This course focuses on the design and operation of electric and hydraulic actuators.