The reverse-acting actuator on a control valve is pneumatic. The valve is 50% open. As you decrease the input signal to the valve, it opens 60%. The valve is functioning normally. True/False?

The reverse-acting actuator on a control valve is pneumatic. The valve is 50% open. As you decrease the input signal to the valve, it opens 60%. The valve is functioning normally. True/False?

• A. False
• B. Not sure
• C. Depends on valve
• D. True

Answer: (D)

Reverse-acting pneumatic actuation causes the valve to move opposite to changes in the input signal. Decreasing the input signal should open the valve more, while increasing the signal tends to close it. Here the valve goes from 50% open to 60% open when the signal is decreased, which matches that inverse relationship. That’s why this behavior indicates normal operation for a reverse-acting actuator.

Reverse-acting pneumatic actuation causes the valve to move opposite to changes in the input signal. Decreasing the input signal should open the valve more, while increasing the signal tends to close it. Here the valve goes from 50% open to 60% open when the signal is decreased, which matches that inverse relationship. That’s why this behavior indicates normal operation for a reverse-acting actuator.