Sizing Control Valves for Intended Applications

by | May 4, 2020 | Valves, Actuators & Regulators

Jim Cahill

Chief Blogger, Editor

I received a LinkedIn message earlier today. Here’s a portion of the message:

I want abstract or article for fisher control valves issues faced during sizing selection mainly because of process and their solutions. if you could provide something, it is very helpful. Thank you!!!

I connected with my friends who work with Emerson’s Fisher brand of control valves. It’s a very broad question and the best place to begin is with the Control Valve Handbook, currently in its fifth edition.

The early chapters 1-4 provide a good overview on control valves, related terminology, performance, valve and actuator types, and associated technologies including digital valve controllers, analog positioners, boosters and other accessories.

It’s really chapter 5 that gets into the question about sizing selection. Chapter 5 is a comprehensive guide to selecting the best control valve for your application.

Applications for control valve vary widely, so it’s important to understand the conditions in which they will be operating. The chapter opens with a long list of considerations:

  • Type of fluid to be controlled
  • Temperature of fluid
  • Viscosity of fluid
  • Concentrations of all constituents including trace impurities
  • Process conditions during startup, normal operations, and shutdowns
  • Chemical cleaning that may occur periodically
  • Specific gravity or density of fluid
  • Fluid flow rate
  • Inlet pressure at valve
  • Outlet pressure or pressure drop
  • Pressure drop at shutoff
  • Maximum permissible noise level, if pertinent, and the measurement reference point
  • Degrees of superheat or existence of flashing, if known
  • Inlet and outlet pipeline size and schedule
  • Special tagging information required
  • Cast body material (ASTM A216 grade WCC, ASTM A217 grade WC9, ASTM A351 CF8M, etc.)
  • End connections and valve rating (screwed, Class 600 RF flanged, Class 1500 RTJ flanges, etc.)
  • Action desired on air failure (valve to open, close, or retain last controlled position)
  • Instrument air supply available Instrument signal (3 to 15 psig, 4 to 20 mA, HART, etc.)

The earlier chapters help with some of the terms referenced in this list if you are unfamiliar with them. There are also helpful videos embedded with hotlinks embedded in video play icons through the handbook.

For example, the bullet “Pressure drop at shutoff” has a video link going to this video, Control Valve Sizing Basics: What is Pressure Drop?

Chapter 5 contains much more on control valve dimensions, seat leakage classifications, flow characteristics, sizing, equation constants, sizing for liquid applications, sizing for compressible fluids, and much more.

If understanding control valves is part of your responsibilities or you need to better know about their operation to optimize your process, spend some time with the Control Valve Handbook. These skills are highly coveted across the world.

Visit the Fisher flow control technologies section on Emerson.com for more tools and help to make sure you have the right control valve for your application. You can also connect and interact with other valve experts in the Valves, Actuators & Regulators group in the Emerson Exchange 365 community.

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The opinions expressed here are the personal opinions of the authors. Content published here is not read or approved by Emerson before it is posted and does not necessarily represent the views and opinions of Emerson.