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Ultrasonic Flowmeter Applications
(Part 1 of 2)

By David W. Spitzer

E-Zine August 2010

Ultrasonic flowmeters can be applied to fluids that are ultrasonically conductive.

Doppler ultrasonic flowmeters may be applied to fluids that have a sufficient number and size of discontinuities that reflect ultrasonic energy, such as particles, bubbles, and eddies in the flow stream. Transit time and pulse repetition ultrasonic flowmeters can be applied to measure fluids that do not have these discontinuities. Ultrasonic flowmeters generally add little or no pressure drop to the piping system.

Ultrasonic flowmeter sensors are available with wetted and non-wetted designs. Clamp-on sensors have no wetted parts, and are desirable when the fluid is corrosive, toxic, or when contamination is an issue. Clamp-on sensor installation is often more convenient and less expensive because few piping modifications are typically needed to attach the sensors to the outside of the pipe.

Clamp-on technology cannot be used to directly measure the transit time across the flowing fluid because the ultrasonic energy also takes time to travel through the pipe walls and interfaces. In addition, the angle of refraction of the ultrasonic energy at the inside pipe wall can vary with the speed of sound of the fluid. Some ultrasonic flowmeters measure the speed of sound in the fluid and perform calculations to correct the flow measurement.

Wetted sensors directly interface the sensor to the fluid to provide superior ultrasonic connections and eliminate the effects of the pipe walls and their interfaces on the measurement. Hot-tapped wetted sensor designs allow sensor installation and removal without shutting down flow. Retractable wetted sensor designs allow sensor removal without shutting down flow.

Click here to read Part 2

Excerpted from The Consumer Guide to Ultrasonic and Correlation Flowmeters

ISSN 1538-5280

Spitzer and Boyes, LLC
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