Internal Inspection Device for Detection of Longitudinal Cracks in Oil and Gas Pipelines: Results From an Operational Experience

Abstract

Pipetronix has developed a new generation of internal inspection device for the detection of cracks in pipelines. Since its commercial introduction in October 1994 the tool, UltraScan CD (Crack Detection), has successfully inspected nearly 1,000 km of operating oil and gas pipelines. The runs were followed by verification excavations at specific locations selected from the collected data. Comparison of the findings with corresponding verifications from excavations illustrate the sensitivity and reliability of the inspection method and the ability of the tool to accurately discriminate between different types of defects. The performance has proved the UltraScan CD to be a reliable internal inspection device for the detection of cracks (SCC, fatigue and other crack like defects) on pipelines. As a result, the German TÜV (authorized by the German Government to verify the compliance with Regulations covering the operation and inspection of pipelines) has approved the use of UltraScan CD as a substitute for hydrostatic pressure testing of pipelines.

Pipeline in-line inspection challenges to NDT

“…MFL technology can successfully overcome the physical and practical inspection challenges presented by transmission pipelines. Ultrasonic systems are also useful in liquid pipelines for both corrosion and cracks [2][3]. However, many anomalies can affect the serviceability of a pipeline.…”

Innovative Sensors for Pipeline Crawlers: Rotating Permanent Magnet Inspection

“…High frequency sound waves have been employed to inspect pipelines from the inside since the mid 1980s [4,5]. The basic principle, illustrated in Figure 4, is similar to handheld ultrasonic equipment used to measure wall thickness and detect cracks.…”

“…For example, for a 1-inch x 1-inch magnet, the wall thickness must be at least 0.207 inches. A good design would include 10 to 25 percent more material; therefore a wall thickness of 0.25 inches will be appropriate 5 . A spring is useful in maintaining the magnet in full extension position; however the attraction force between the pipe and magnet keeps the spring force requirement low.…”

“…A spring is useful in maintaining the magnet in full extension position; however the attraction force between the pipe and magnet keeps the spring force requirement low. 5 The other dimension of the sleeve is 1.5 inches. The base area is 2.25 square inches.…”