PR-015-07604-R01 Clamp-On Ultrasonic Flow Meters as Diagnostic Tools

Over the past several years, improvements in clamp-on ultrasonic meter technology have caused increased interest in applying this technology within the natural gas industry. Clamp-on ultrasonic meters (CUSMs), which are mounted on the outside of a pipe, send and receive ultrasonic waveforms through the pipe wall. This configuration offers several potential advantages over in-line meters, including portability and the ability to be installed without shutdown and disassembly of the pipeline. CUSMs, like their in-line counterparts, use sophisticated electronics to control the meter operation and to monitor parameters such as transducer signal strength, path velocities, and speed of sound. Because of these features, CUSMs are being considered for their potential as in-situ verification and as diagnostic tools. Having such portable tools to quickly verify meter performance would save considerable time in troubleshooting causes of lost and unaccounted-for (LAUF) gas, thus, minimizing overall LAUF totals. The ability to validate meter performance in-situ would also significantly reduce operating and maintenance costs of metering stations, particularly costs of unnecessary recalibrations. This project specifically addressed the ability of a CUSM to measure distorted profiles with sufficient resolution to determine if the flow is properly conditioned for flow measurement by other meter types. It also addressed the accuracy with which CUSM measurements, performed with sufficient spatial fidelity, can be used to provide a reference flow rate for in-situ meter proving. The test approach was to traverse a single ultrasonic transducer pair around the perimeter of the pipe in sufficiently small increments to measure the flow field at a given pipe cross section independent of the amount of flow distortion present. Velocity profile measurements performed at the same locations were used as an independent check of the CUSMs profile sensitivity.