Why is the pressure drop of a Control Valve at the discharge of a pump in a liquid hydrocarbon service taken as 0.7 bar as a first guess?
Answers
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21/07/2013
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A:
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
You must be referring to a simulation, which has nothing to do with a real design. When specifying a control valve on the pump discharge, consider the system. For example, for a hydrotreater, start with pressure profiles for SOR and EOR. Specify the CV (preferably an equal percentage valve) to be 15% open at SOR and 85% open at EOR. If the piping is sized properly, the CV will be smaller than the pipe size. Do not be surprised if the CV is actually less than 15% open at SOR. It is typical for allowable delta P’s for piping between pieces of equipment to be greater than actually experienced. That is why it is common practice to pinch a valve in the CV manifold to make the CV 50% open for good control.
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