Flow Measurement Using Low Cost Portable Clamp-On Ultrasonic Flowmeters

Flow measurement is a basic parameter for evaluating the performance of hydroelectric turbines. However, the cost for obtaining code-accepted flow measurements is so high that rigorous performance testing is omitted at many hydroelectric facilities. Pacific Gas and Electric Company (PG&E) compared the accuracy of low cost, portable, clamp-on ultrasonic meters against the laboratory {open_quotes}standard{close_quotes} (a weighing tank - calibrated Universal Venturi Tube) at the Alden Research Laboratory (ARL) in 1990 and against eight-path ultrasonic systems at three California State Department of Water Resources (DWR) pumping plants in 1993. The clamp-on meter flow measurements were within 0.6 percent of the venturi tube measurements on all tests at the ARL and within 1 percent of the eight-path systems` measurements at the DWR plants. The portable clamp-on, ultrasonic flowmeter is inexpensive, easy to use, and appears to be as accurate as code-accepted flow measurement methods. If the clamp-on, ultrasonic meters were code accepted, hydroelectric plant owners would have a low cost method to determine whether guaranteed turbine performance has been achieved. In order to fully utilize the turbine-generator unit performance test data, PG&E has also developed a Hydro Unit Database, designed to provide to its LAN users historical and current turbine-discharge.