Final Answer:
If a valve is controlled by an actuator, it is 3) automatic
Step-by-step explanation:
If a valve is controlled by an actuator, it is categorized as an 3) automatic valve. Actuators are devices that provide the mechanism for opening and closing valves automatically, eliminating the need for manual operation. The actuator can be powered by various means, such as electric, pneumatic, or hydraulic, enabling automated control of the valve.
Option 1, "manual," refers to valves that are operated by hand, without the use of an actuator. Option 2, "electric," specifies one type of actuator where the valve is controlled by an electrically powered device. Option 4, "vacuum," does not directly relate to the type of actuation but rather the conditions under which a valve may operate.
In summary, an actuator-controlled valve falls under the category of automatic valves. This automation allows for precise control and regulation of fluid flow in various industrial processes. The choice of actuator type, whether electric, pneumatic, or hydraulic, depends on the specific application requirements and the desired level of automation in the system.