A manual actuator employs levers, gears, or wheels to facilitate movement while an automatic actuator has an external power source to provide the force and motion to operate a valve remotely or automatically. Power actuators are a necessity on valves in pipelines located in remote areas; they are also used on valves that are frequently operated or throttled. Valves that are particularly large may be impossible or impractical to operate manually simply because of the sheer horsepower requirements. Some valves may be located in extremely hostile or toxic environments that preclude manual operation. Additionally, as a safety feature, certain types of power actuators may be required to operate quickly, shutting down a valve in case of emergency.