Statement (I): Process control valves are used to control the rate of fluid flow and are used where, perhaps, the rate of flow of a liquid into a tank has to be controlled. Statement (II): A common form of pneumatic actuator used with process control valves is the diaphragm actuator.

Statement (I): Process control valves are used to control the rate of fluid flow and are used where, perhaps, the rate of flow of a liquid into a tank has to be controlled. Statement (II): A common form of pneumatic actuator used with process control valves is the diaphragm actuator. Correct Answer Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)

Concept:

• Control valves are generally used to control various conditions such as flow, pressure, temperature, and liquid level by fully or partially opening or closing in response to signals received from controllers. 
• Process control values are used to regulate the flow in both directions of flow and magnitude of flow rate in the process industry. So statement (I) is correct.
• Diaphragm actuator is a basic control valve, which provides stem movement corresponding to input pressure and stem movement is used to regulate the flow rate. So statement (II) is correct.

Here both the statements are individually true but Statement (II) is not the correct explanation of Statement (I).