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DAVID W SPITZER'S E-ZINE (February 2022)


Vortex Shedding and Fluidic Flowmeters (Part 2 of 4) by David W Spitzer and Walt Boyes

Coanda effect fluidic flowmeters contain passages or other hydraulic mechanisms that allow a portion of the downstream fluid to be fed back near the inlet of its fluidic oscillator. By impacting the incoming fluid, the feedback flow causes the main flow to preferentially attach itself to the opposite surface of the flowmeter. This increases the opposite feedback flow and forces the main flow away from that surface. This process repeats and causes flow in the feedback passages to oscillate in proportion to flow, such that doubling the flow will create twice as many oscillations. A variety of electronic and mechanical techniques can be used to sense the feedback flow oscillations. The frequency of feedback flow changes is used to generate a flow measurement signal.

Damaged Flowmeter Causes Overbilling by David W Spitzer

Existing plant flowmeters that exhibit a (say) 5% error may not be that good, but it is not all that bad considering that most flowmeters in the plant are installed to operate the process and provide little or no economic benefit. In other words, they enable the plant to keep operating, even though they measure inaccurately. Accurate measurements would be better for other reasons such as when performing heat and material balances to better understand and optimize the process. Nonetheless, the plant will still operate with flowmeters that are not accurate.

Potential Actions to Reconcile Flow Measurements by David W Spitzer

What potential actions can be taken if a problem is suspected because the measured flow leaving a reactor is higher than the measured flow entering the vessel?


In addition to over 40 years of experience as an instrument user, consultant and expert witness, David W Spitzer has written over 10 books and 500 articles about flow measurement, level measurement, instrumentation and process control. David teaches his flow measurement seminars in both English and Portuguese.


Spitzer and Boyes, LLC provides engineering, technical writing, training seminars, strategic marketing consulting and expert witness services worldwide.


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