Washington: U.S. Army Corps of Engineers (Waterways Experiment Station), 1997. - 165 p.Abstract: The conventional techniques for high-accuracy ultrasonic flow measurement using multiple chordal paths in a pipe require drilling holes in the pipe for inserting the sensors. Under the Construction Productivity Advancement Research (CPAR) program, a research project was jointly undertaken by ORE and the U.S. Army Corps of Engineers for development of a new flow meter. The product developed is an externally mounted acoustic flow meter. The advantages of the 'clamp-on' type flow meter are as follows: (a) no contact with the fluid, (b) no welding or cutting of pipe necessary, (c) no operational shutdown needed for installation, repairs, or maintenance, (d) quick and easy installation, and (c) low cost of installation. The technology consists of the following: (a) conformal phased array transducers applied to a prepared surface at four to six locations on the exterior of the pipeline, and (b) a signal processing unit that generates acoustic signals for transmission between pairs of transducers installed above; receives and time-compresses the signals; determines precise acoustic travel times between one or more transducer pairs; and employs these measured travel times to determine the flow rate using algorithms well known to the flow measurement industry. The transducers are constructed of a relatively new material, PVDF. This material is found to be ideal for a flexible production transducer easily installable in the field conforming to a variety of pipe exterior dimensions. The new meter is a differential travel-time acoustic meter. The system measures the difference in travel time between signals propagating upstream and downstream between multiple pairs of transducers. Under no-flow conditions the travel time in each direction will be the same.
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