Quiz Corner: Flowmeters for high-viscosity liquids

Which of the following flowmeters can be applied to high-viscosity liquids?

A. Coriolis mass
B. Differential pressure
C. Magnetic
D. Positive displacement
E. Vortex shedding

The question is vague in the sense that “high viscosity” can mean different things to different people in different industries. All of these technologies are potentially applicable when dealing with a liquid viscosity of 20 centipoise (cP), which could be termed “high” in some industries.

Additional complicating factors

Defining “high viscosity” as more than (say) 1000 cP reveals an entirely different set of considerations. Positive displacement flowmeters that continually entrap liquid are often used in these applications because they exhibit low slippage (unmeasured liquid) at high viscosity. However, they are mechanical and tend to exhibit higher pressure drop with increasing viscosity.

Coriolis mass flowmeters can measure high-viscosity liquids; however, performance can sometimes be compromised if the pressure drop across the flowmeter limits accurate flow measurement to the lower part of the flow range.

Magnetic flowmeters can also measure electrically conductive liquids that exhibit high viscosity. As a practical matter, magnetic flowmeters are not often applied to high-viscosity liquids because the majority of such applications involve hydrocarbons that are not sufficiently conductive.

Differential pressure and vortex shedding flowmeters are generally not applied to high-viscosity liquids because of their Reynolds number constraints.

David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes LLC, which offers engineering, seminars, strategic, marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies.

Spitzer and Boyes is also the publisher of the Industrial Automation INSIDER. He has more than 40 years of experience and has written more than 10 books and 350 articles about flow measurement, instrumentation and process control. Spitzer may be reached at 845-623-1830 or via spitzerandboyes.com. Click on the "Products" tab to find his Consumer Guides to various flow and level measurement technologies.