Control Valve Sizing Parameters, Inherent and Installed Characteristics

In this video, we dive deep into the concept of control valve flow coefficient (Cv) and how it impacts valve behavior in process systems. We explain what Cv represents and how it varies with valve opening and pressure drop.

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We then explore the three main types of control valve inherent characteristics - linear, equal percentage, and quick opening. Using examples, we illustrate how each characteristic relates Cv to valve opening at constant pressure drop.

Next, we introduce the important concept of control valve authority, which represents the fraction of system pressure drop occurring over the valve. We show how the actual system pressure drop changes the valve's installed characteristics compared to its inherent characteristics.

Through calculations, we demonstrate how equal percentage valves tend towards linear behavior and linear valves tend towards quick opening behavior when system pressure drop is significant. We discuss the implications for controllability and the importance of considering valve authority in system design.

This video is a must-watch for chemical engineering students, process engineers, and anyone wanting to truly understand control valve behavior and selection. After watching, you'll have a solid grasp of Cv, valve characteristics, and how to optimize control loop performance.

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▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬

0:00 - Intro
1:00 - Introduction to valve CV (flow coefficient)
2:15 - Examples of how CV changes with valve opening percentage
3:30 - Control valve characteristic curves
5:10 - Actual valve pressure drop
6:30 - Control valve authority
8:00 - Equal percentage curve installed conditions
9:40 - General behavior of different valve types under installed conditions
11:30 - Importance of considering control valve authority
13:10 - Effect of not considering control valve authority on valve rangeability
14:30 - Control valve authority VS pump power optimization