In a process control loop, the final element is typically a valve or damper used to control what?

• A. Fluid flow.
• B. Temperature.
• C. Pressure.
• D. Sound.

Answer: (A)

The final control element in a process loop is the actuator that adjusts the manipulated variable. A valve or damper directly throttles the flow of a process fluid, opening or closing (or partially restricting) to change how much fluid moves through the system. That change in flow is the primary way the loop acts to move the process variable toward the setpoint. Temperature or pressure can shift as side effects of altering flow, but the actuator’s main job is to regulate fluid flow. Sound isn’t something a valve or damper is used to control in this context.