Knowing the Whens and Whys of Flow Measurement to Ensure Solution Success

David W. Spitzer

Raw materials for processes can be expensive. Using 1 liter per minute of a raw material that costs $1 per liter represents an annual expenditure of over $500,000. Many raw materials are used in higher quantities, and some are more expensive, so total annual expenditures can easily be many millions of dollars. On the other hand, water flowing at a low flow rate can be relatively inexpensive. However, dollar value is not the only worthy consideration, as it is often important for operating companies to precisely measure and control the use of raw materials to effectively and efficiently facilitate a critical process.

READ ALSO: QUIZ CORNER: Which Is More Important for Flow Measurement — Repeatability or Accuracy?

That said, there are many technologies that can be applied to measure the flow of raw materials, such as Coriolis mass, differential pressure, positive-displacement, and vortex shedding flowmeters. Which technology should you select assuming all will operate reliably in the service? How would you analyze this problem?

The overall objective is to feed the correct amount of raw material to the process. Feeding too much or too little will have adverse financial and/or operational consequences. Feeding the correct amount of raw material requires precise measurement of its flow. Therefore, the measurement objective might be to measure the flow of raw material as accurately as possible.

Each potential technology can be evaluated and compared based upon its accuracy in the application at hand. Coriolis mass and positive-displacement flowmeters generally offer better accuracy than either differential-pressure or vortex shedding flowmeters in liquid applications. Coriolis mass flowmeters have the advantage of measuring mass flow, while positive-displacement flowmeters can measure high-viscosity liquids with relatively low pressure drop and high accuracy.

In many applications, positive-displacement and Coriolis mass flowmeters will perform similarly. However, in other applications, one or the other may be clearly superior. A clear understanding of the application details and the strengths and weaknesses of the available flow measurement technologies will lead you to the proper solution in any given scenario.

David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes, LLC, offering engineering, training, 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. Mr. Spitzer can be reached at 845 623-1830 or via www.spitzerandboyes.com.