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Ask The Experts"Ask The Experts" is moderated on ControlGlobal.com by noted process control authority and CONTROL Columnist Bela Liptak. Liptak either answers the questions himself, or brings in one or more experts from his cadre of co-authors that worked with him on the Instrument Engineers' Handbook, Fourth Edition. Save yourself the hefty consulting fees by getting the answers to your questions here.

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Assigning control valve pressure drop

Energy efficiency and control repercussions dominate the discussion of ideal DPs.

By Béla Lipták
Oct 29, 2019

*Q: I am an energy engineer currently looking at optimizing the pumping circuits in process plants by reducing unnecessary pressure drop across the system. Please advise me on my understanding. Your handbook, Volume 2, Chapter 6, ”Control Valve Selection and Sizing,” says, "The proper approach to the selection of valve pressure drop is to first determine the total friction energy loss (excluding static energy) of the system at normal flow, and assign 50% of that to valve pressure drop." In your view, during the new pumping hydraulic circuit design/new pump sizing, what is the recommended percentage of differential pressure (DP) across control valve to the total system pressure drop (i.e. including control valve DP)? In your opinion, at the design stage, what are the recommended rules of thumb (the percent of control valve DP of the total system DP) that one can apply in the real process operation?*

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