Integrity inspection and evaluation on the pipe with steel casing in the crossing section

When oil or gas pipeline crosses the highway or railway with steel casing, the information in coating and pipe defects is hard to know by conventional potential method. Therefore, it is a blackspot in ECDA detection method. Taking the pipeline crossing Encheng-Pingyuan Highway in Zhongyuan-Cangzhou Gas Pipeline and Beijing-Shanghai Railway as examples, the method of CIPS, PCM, ACVG, On/Off potential and ultrasonic guided wave were employed to test and evaluate the insulativity between pipe and steel casing, corrosion of pipe and cathodic protection of pipeline at the both sides of the crossing section. In addition, the situation of sealing at the ends of steel casing was inspected with excavation method. The results showed that the electric connection or electric channel between the pipe and steel casing was not existed, and the condition of pipeline's cathodic protection was well, and no any corrosion of the pipes in crossing section could be seen. It is considered that the inspecting methods above are effective and can be used to test and evaluate the integrity of the pipeline with steel casing crossing.