Inspection Scheme Design And Experiment Research For Small-diameter Oil Pipeline Corrosion

Pipelines provide the most economical means of carrying oil and gas. Pipeline transportation has become one of the five biggest transportation businesses, which plays an important role in national economy and production. During the Tenth-Five Plan,nearly twenty thousand Km pipe-net of"gas transfer from western to eastern"were finished. But the failures are often occurred by internal corrosion in Pipelines. Most of pipelines which have small-diameter or middle-diameter are distributed in densely populated areas. Once the leaks happened,the damages are greatly serious. Therefore, inspection of oil and gas pipelines is particularly important.At present, oil pipeline detection means at home and abroad mainly depend on magnetic flux leakage-based and ultrasonic testing which are used more in practice. In this paper, we take the project of Daqing Petroleum Administration,"small-diameter oil pipeline wall thickness of surface defects and the detection device development"as the background of the subject. A small-diameter pipeline surface defects detection system is designed using a method which combines CCD imaging technology and ultrasonic detection, and taking means of tests to verify the two detection methods.This paper focus on the following aspects:Firstly, considering the characteristic of pipelines is mall-diameter in the detection scheme, crawl dynamic way, namely the passive walking test device, is used outside the pipe. On a small diameter pipeline inspection system design, and design the internal structure and composition of climbing machine.Secondly, a pipeline testing method is established by integrating CCD's visibility and ultrasonic thickness testing. This detection method can achieve real-time visualization of pipeline inspection, so that more of the visual inspection. The depth values of corrosion location can be obtained through a formula which is derived from the principles of optics and geometry of the triangular relationship of the CCD image, it can calculate corrosion depth and judge corrosion situation. Finally, CCD and ultrasonic inspection tests are designed according to the characteristics of the pipeline corrosion. Three specimens were tested by CCD and ultrasonic testing methods. The two experimental results are analyzed and compared. The accuracy of CCD and ultrasonic test method is increasing with the increase of the corrosion depth, but the ultrasound experimental results are more accurate than the CCD's.