E-Zine December 2010
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Clamp-on Ultrasonic Flowmeters
Many ultrasonic flowmeters designs use sensors that are clamped onto the pipe. The concept of clamping a device onto a pipe to determine the flow inside the pipe has a certain appeal. This not only reduces piping changes, but also allows flow measurement using an instrument that has no wetted parts.
Spool Ultrasonic Flowmeters
Some ultrasonic flowmeters designs utilize sensors mounted on a spool piece that is inserted in the pipe. This design requires that the pipe be taken out of service for installation. The spool piece design allows the spool piece, sensors, and transmitter to be calibrated under flowing conditions in a flow laboratory prior to installation.
Probe Ultrasonic Flowmeters
Probe designs use wetted sensors that are in contact with the fluid. Some designs allow the probes to be installed (hot-tapped) onto an existing pipe without taking the existing pipe out of service. Most designs require that the pipe be taken out of service for installation.
Gas, Stack Gas, and Flare Gas Ultrasonic Flowmeters
Ultrasonic flowmeters are typically designed for use in liquid service. Applying this technology to gas service introduces additional sources of uncertainty that include (but not limited to) the effects of pressure, temperature, and composition. To overcome these issues, many gas ultrasonic flowmeters are designed for multi-path operation for gases with well-known properties.
Excerpted from The Consumer Guide to Ultrasonic and Correlation Flowmeters