Quiz Corner: Installation of straight run requirements upstream and downstream of a flowmeter
What is the rule of thumb for the amount of straight run required upstream and downstream of a flowmeter?
A. 0 diameters upstream and 0 diameters downstream
B. 5 diameters upstream and 3 diameters downstream
C. 10 diameters upstream and 5 diameters downstream
D. 40 diameters upstream and 5 diameters downstream
Responses from students in my Industrial Flow Measurement seminar (and many others) would indicate that the rule of thumb for installation is 10 diameters of straight run upstream of the flowmeter and 5 diameters of straight run downstream of the flowmeter, so it would seem that Answer C would be correct. However, there is no valid rule of thumb for installation because every flowmeter has straight-run requirements that result from multiple considerations, including the flowmeter technology, flowmeter design and the geometry of the piping in which the flowmeter is installed. All of the answers can apply to one or more flow technologies and/or flowmeter designs.
Additional complicating factors
The ramifications associated with not having one rule of thumb are many. Consider that many flowmeters are installed in locations where limited space does not allow for the required amount of straight run. In such instances, flowmeter performance would be degraded so another technology and/or flowmeter with shorter straight-run requirements should be applied.
David W. Spitzer is a principal at Spitzer and Boyes, LLC, which offers engineering, focused market research, writing/editing white papers, strategic marketing consulting, distribution consulting, seminars and expert witness services for manufacturing and automation companies. Spitzer has written more than 400 technical articles and 10 books about flow measurement, instrumentation and process control. He can be reached at 845-623-1830 or via spitzerandboyes.com.
David W. Spitzer
David W Spitzer’s new book Global Warming (aka Climate Change): An Understandable Data-Driven Explanation and Pathway to Mitigation (Amazon.com) adds to his over 500 technical articles and 10 books on flow measurement, instrumentation, process control and variable speed drives. David offers consulting services and keynote speeches, writes/edits white papers, presents seminars, and provides expert witness services at Spitzer and Boyes LLC (spitzerandboyes.com or +1.845.623.1830).
