In situ calibration of large water meters

Abstract

The establishment of a flow reference standard for the cost-effective in situ calibration of large in-line water meters consists of the combined accuracy of point velocity measurements within pipes, a velocity-area method and a velocity-profile function. Tests were carried out in compliance with the requirements of international standards relating to large water meters. Velocity profiles were measured within pipe sections of 250, 300, 400, 500, 600 and 800 mm dia. and compared to the flow measured by Eskom’s Flow Laboratory. This flow laboratory has a best measurement capability of 0,1% uncertainty for the 95% confidence level as accredited by the National Laboratory Accreditation Service (NLA). The physical dimensions of the pipes dictated at which position the turbine insertion meter should be placed within the pipe in accordance with the log-linear method adopted for this research. This resulted in the need to calculate the velocities near the pipe wall within pipes smaller than 700 mm dia.

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