Control valves are imperative elements in any system where fluid flow must be monitored and manipulated. A complete control valve is made of the valve itself, an actuator, and, if necessary, a valve control device. The actuator is what provides the required force to cause the closing part of the valve to move and the valve control devices keep the valves in the proper operating conditions; they can ensure appropriate position, interpret signals, and manipulate responses. Selection of the proper valve involves a thorough knowledge of the process for which it will be used. When implementing a control valve into a process, one must consider not only the appropriate type of valve and its material of construction, but also the correct sizing to ensure it performs its designated task without any adverse occurrences in the system.

Learning Objectives

• Differentiate between various types of valves and the benefits of each;
• Understand the operation of control valve in a control loop;
• Understand how to evaluate and apply actuators and positioners for specific applications;
• Understand the basic hydraulics and the relationship between the Cv, flow rate and pressure drop;
• Understand how to size valves for any flow condition likely to be found in a process plant;
• Understand how to select the proper valve characteristic for a given process;
• Understand how the installed characteristics can match closely to the inherent characteristics;
• Understand the methods to address system performance issues such as cavitation, flashing and chocked conditions;
• Understand the factors influencing the selection of control valves.