Features & BenefitsThe Elastic Wave vehicle can also be used to report changes and disbonding in most types of external coating. This part of the service is in development as part of the standard report to give valuable early warning of coating problems. Analysis & ReportingThe Elastic Wave vehicle collects large volumes of data. Sophisticated software processes this data to provide analysis engineers with views of the ultrasonic echoes and transmission information that is unique to this tool. Custom display software allows crack-like features to be bookmarked for detailed assessment. This bookmarking allows a feature list to be generated. Crack-like features are then studied individually, and a scoring process is used to establish their nature. Those that pass this discrimination stage are subject to a comparative sizing procedure prior to reporting. Unlike other tools, the Elastic Wave vehicle is sensitive to changes in the nature and the bonding of the external pipeline coating. This can be used to indicate coating disbondment in problem areas, giving very useful advance warning before corrosion or cracking occurs. When changes are identified, they are noted and listed in the pipe tally generated with every report
The final report lists crack-like flaws with estimates of maximum probable depth and location information Images of the C-Scan type are provided for all documented features that satisfy the selection criteria. When appropriate, data and report information can be supplied on a CD. OperationThe unique adaptation of ultrasound technology embodied in the Elastic Wave vehicle makes cracks visible by looking at them in high profile from the side. Ultrasound waves are injected into the pipewall at a 65° angle so they travel circumferentially around the pipe. When they encounter an axial crack or other defect within the pipewall, the waves are reflected and the echo is detected by the transducers. To better pinpoint the position of anomalies, elastic waves are injected into the pipe in both clockwise and counterclockwise directions. Because ultrasound waves do not propagate in gas, each transducer is enclosed in a fluid-filled wheel mounted on the outer surface of the tool. The specially-tired rim of the wheel runs in contact with the inner surface of the pipe. The material used for the wheel is permeable to the ultrasound waves, and is sufficiently robust to survive impact with weld beads, bore changes and other surface features. The tool performs equally well in liquid or dry pipelines. To provide full-body coverage of the pipewall, the wheels are arranged in staggered arrays. Large volumes of data are generated, with the level of redundancy necessary for accurate positioning of defects. At speeds of up to 6.7 miles per hour, the scanning pulse rate is adjusted automatically to provide the constant scan pitch of 5 mm necessary for the characterization of defects. The tool is available with a bypass arrangement for speed control, allowing in-line inspections to be carried out at the optimum tool speed without loss of production. |
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Stress Corrosion Cracking DetectionWhen we launched the first PII Pipeline Solutions Elastic Wave inspection vehicle in 1993, it became possible for the first time to detect one of the most dangerous types of pipeline anomaly: stress corrosion cracking. Trials of the Elastic Wave vehicle proved it could detect such defects provided they were above a certain threshold level. This goal was achieved without requiring a liquid coupling between the transducers and the pipewall. |
