David W. Spitzer

Which of the following flowmeter technologies are applicable for measuring the flow of multiple liquid products with different densities and high viscosity?
A. Coriolis mass
B. Differential pressure
C. Magnetic
D. Positive displacement
E. Vortex shedding

Commentary
The most likely selections for this application are Coriolis mass flowmeters (Answer A) and positive-displacement flowmeters (Answer D). Coriolis mass flowmeters have good accuracy and have the advantage of measuring mass flow directly without having to compensate for density. Positive-displacement flowmeters also measure accurately but do not inherently compensate for density, so independent temperature compensation may be advisable in some applications. In general, there appears to be a trend away from positive-displacement flowmeters (traditionally used in this service) toward the application of Coriolis mass flowmeters.

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The other technologies could be applied in some applications. For example, some differential-pressure flowmeter geometries (Answer B) could be applicable if Reynolds number constraints are satisfied. When the liquid is conductive, magnetic flowmeters (Answer C) might be applicable. Vortex shedding flowmeters (Answer E) can sometimes be used in applications where the liquid is viscous at ambient temperature, but less viscous at (higher) operating temperatures.

Additional Complicating Factors
The actual fluid composition and temperature can affect the density of the liquid, viscosity of the liquid, and Reynolds number at flowing conditions. Coriolis mass flow measurement systems tend to inherently compensate for many of these variations whereas positive-displacement flow measurement systems may do so to a lesser extent.

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.

Mr. Spitzer can be reached at 845 623-1830 or www.spitzerandboyes.com. Click on the “Products” tab in the navigation menu to find his “Consumer Guides” to various flow and level measurement technologies.