埋地管道防腐层状况地面评估技术评价和验证(英).pdf

Final Technical Report EVALUATION AND VALIDATION OF ABOVEGROUND TECHNIQUES FOR COATING CONDITION ASSESSMENT 埋地管道防腐层状况 地面评估技术的评价与验证 天津嘉信技术工程公司 TIANJIN GENIUS TECHNOLOGY AND ENGINEERING CO. SEP. 2008 EXECUTIVE SUMMARY The overall objective was to determine the accuracy, resolution, and limitations of equipment typically used for modern aboveground ECDA work with respect to locating holidays and disbondments with commonly used coatings with varying spatial relationships and geometrical configurations. The specific tasks of this program were the following: 1. Perform aboveground coating surveys on several underground pipelines using at least four (4) different survey techniques - DCVG, ACVG, PCM, C- scan, and Pearson surveys were performed. 2. Compare the results of the surveys with visual examinations of the coating defects after excavation of the surveyed pipelines. Both DCVG and ACVG were the most accurate survey techniques, better able to resolve individual indications than the other surveys. DCVG and ACVG provided very similar data, with DCVG better able to size defects. Both techniques showed an ability to “pinpoint” a defect, after which some effort was necessary to determine defect size. While the pinpointing provided more exact data, for long sections of pipe the voltage gradient surveys were more cumbersome than C-scan or PCM, which divided the pipe sections into discrete sections. PCM appeared to be appropriate for large areas of disbondment. The DCVG and ACVG signals for these large disbonded region