Describe the basic feedback control loop for a separator level.

• A. Level sensor measures level; controller computes error; output adjusts control valve to regulate inflow/outflow
• B. Operator manually adjusts valves without sensors
• C. Temperature sensor controls heating
• D. Pressure relief valve controls flow

Answer: (A)

This is a closed-loop feedback approach: the separator’s level is measured, a desired level is set, and the system automatically adjusts flow to keep that level steady. A level sensor provides the actual height, which is compared to the setpoint. The controller computes the error (how far off you are) and sends a signal to an actuator, typically a control valve (or pump), to modify the inflow or outflow. By increasing or decreasing flow, the level moves toward the setpoint, and the sensor keeps feeding the updated level to repeat the correction. This continuous sensing, comparison, and actuation is what maintains stable level despite disturbances like changes in feed or withdrawal.

Manual valve adjustment without sensors isn’t automatic feedback. A temperature sensor with a heater controls a different variable, temperature, not level. A pressure relief valve manages pressure, not the liquid level.