What is the typical design velocity of a liquid flowing in a pipe?
A. 1 meter per second
B. 3 meters per second
C. 5 meters per second
D. Any of the above
Commentary
If you already selected Answers A, B, or C, you likely “jumped the gun” because the question is incomplete if the service and fluid properties have not been defined.
Piping for liquids with low viscosity (such as water) are typically designed to operate at between 2 and 3 meters per second (Answer B). However, lower velocities may result when the piping is oversized to include provisions for future plant expansion and future increased flow.
In other applications, liquid viscosity may be so high that even flow at low velocity (Answer A) may result in an extremely high pressure drop in the piping.
I suggest that Answer D is pragmatic.
Additional Complicating Factors
There are many factors that can dominate the fluid velocity design in pipes. Can you think of any others?
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David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes, LLC offering engineering, seminars, strategic marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies. He has more than 35 years of experience and has written over 10 books and 250 articles about flow measurement, instrumentation and process control.
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