UltraTap Gas Flow Meter

The Daniel UltraTap Gas Flow Meter measures the transmit times of ultrasonic waves passing through the flowing gas in a pipeline to determine the mean velocity of the gas movement. The measurement path is angled with respect to the pipe axis. The path has two transducers which act alternately as a transmitter and receiver for the ultrasonic signal's energy, permitting the upstream and downstream transit times to be measured. Since the path length and angles are known, and since the electronic characteristics of the transducer pair can be measured, the transit time measurements contain all of the information necessary to determine the velocity of the moving gas along the measurement path.

Since the UltraTap Gas Flow Meter is a single-path meter, an additional piece of information is needed to determine the mean velocity of the moving gas (remember that not all of the gas is moving at the same velocity). A "flow profile correction factor," sometimes called the Reynold's Number correction factor, is needed to reduce the velocity measured along the path to the correct average for the cross sectional area. This can be accomplished either by using a fixed value or more accurately by measuring pressure and temperature, and then applying an active correction to the measured transmit times. Once the corrected mean velocity is determined, the flowrate is calculated by multiplying the mean velocity by the cross sectional area of the pipe.

Daniel Industries, P.O. Box 19097, Houston, TX 77224-9097. Tel: 713-467-6000; Fax: 713-827-3880.