DEVELOPMENT OF A DEFECT DETECTION & EVALUATION SYSTEM FOR PROTECTIVE COATINGS OF BURIED STEEL PIPELINES

A defect detection and evaluation system of protective coatings for buried steel pipelines based on the combined technique of DCVG and CIPS has been developed by multi-language programming of VB with Matlab.Its main functional modules including data storage and inquiry,defect location,breaking level evaluation,protective coating quality evaluation and other modules as well as their implementation techniques are introduced in detail.The theory of signal singularity detection by wavelet transform was used to process the detection signals of ON potential,OFF potential and voltage gradient,by which the broken position of the protective coating can be located accurately.The lateral resistance computing method of protective coating was put forward based on field detecting data,which was applied to establish the quality evaluation system of protective coating for pipeline.And the engineering tests and verification were carried out.The engineering experience shows that the system is convenient to operate,the defect position is accurate to be located and the result of analysis and evaluation is reliable,which can meet the needs of engineering application.