INSTALLATION EFFECTS ON SINGLE- AND MULTI-PATH ULTRASONIC METERS
Klaus J. Zanker
Abstract:
This paper takes an analytical approach to examine the effects of swirl, asymmetry, pipe roughness, and Reynolds Number on the performance of a meter that utilizes a single bounce path through the center line (e.g., Daniel JuniorSonic) and a meter that employs four chordal paths (e.g., Daniel SeniorSonic). A simple “power law” velocity profile is used to study the effects of pipe roughness and Reynolds Number. Mathematically generated axial velocity profiles, similar to those from bends and Tees, are used to study the effects of asymmetry. A solid body rotation is used to study the effects of swirl on the performance of both meters. The single path meter requires typical corrections from 4 to 8% for changes in velocity profile due to variations in pipe roughness and Reynolds Number. The single path meter output varies about 6%, depending on the path orientation relative to the asymmetry and creates a bias error of about +/-3%. The 4-path meter does an excellent job of integrating the velocity profile to give the correct flow rate over a wide range of both Reynolds Number and roughness values. The 4-path meter integrates the asymmetric profiles to give an answer within 0.1 to 0.3% of the flow, irrespective of orientation. Furthermore, it has sufficient diagnostics to recognize changes in operating conditions. Simple bulk swirl, centered on the pipe axis, has no effect on the performance of either meter. This paper examines the effects of deviations from this simple ideal swirl.
