Ultrasonic Testing - Reconstruction of Reflectors from Time-Delay and Amplitude-Locus Curves

For ultrasonic testing (pulse-echo or tandem) the surface of a test piece is scanned by a probe or a probe array. Time-delay and amplitude for each pulse, locus of incidence, reflector inside the beam and wave path, are measured. Shape and position of reflectors are reconstructed from time-delay locus curves. In addition, isolated amplitude-locus curves derived from measurements are compared to calculations for several reflector modes. The best fitting model is selected. Diameter or width and inclination are determined

Influence of Filtering Techniques on Holographic Images

Broadband Holography has become a powerful tool in computerized non-destructive testing. Interpretation of images, however, is difficult due to the fact that perfect imaging of flaw sizes is impossible until now. The situation is even more complex, since multiple scattering, wave mode conversions, and inhomogeneities in the material give rise to artifacts in the holographic image. Thus, signal and data processing techniques at different levels of the signal flow path may help improve the situation. Within this paper the following methods are discussed: (1) Inverse filtering. Inverse filters improve echo shape and duration. This in turn influences lateral and axial resolutions of the image. Since inverse filtering is known to be an ill posed problem we apply a standard Tychonoff regularization. It turns out to be equivalent to Wiener filtering in its simplest form.; (2) The ALOK i, k-filter. This is a non linear filter mainly used for data reduction purposes during the inspection of large scale components. An attempt is made to at least partly recover the original signal from ALOK data.; (3) Image processing. Using the holographic image of a natural crack we show different image processing techniques. This may be a tool to gain more insight into the flaw size and geometry under test

Challenges for the development of nondestructive testing (NDT) in pipeline inspection

Compared with all other technologies pipelines are the most technical save facilities to transport oil, gas and derivatives of them. Worlwide more than 3 millions of km are in use and every year an increase in the range of 25000 km pipelines are to observe. However, like each technical component, also a pipeline suffers under aging phenomena like corrosion and fatigue. In order to avoid catastrophic failure and damage of human beings and environment pipelines are regularly inspected by using NDT. Describing the state of the art in pipeline inspection applying in-line tools, so called 'intelligent pigs', recent developments are presented. The special emphasis of the contribution is on crack detection and sizing an inspection task with increasing importance

Ultrasonic Testing - Reconstruction of Reflectors from Time-Delay and Amplitude-Locus Curves

For ultrasonic testing (pulse-echo or tandem) the surface of a test piece is scanned by a probe or a probe array. Time-delay and amplitude for each pulse, locus of incidence, reflector inside the beam and wave path, are measured. Shape and position of reflectors are reconstructed from time-delay locus curves. In addition, isolated amplitude-locus curves derived from measurements are compared to calculations for several reflector modes. The best fitting model is selected. Diameter or width and inclination are determined.</p

Detecting Cracks in Pipelines Using Ultrascan CD

Stress Corrosion Cracks (SCC) are among the defects in pipelines that are least understood and most difficult to detect, but which have accounted for some of the severest ruptures in pipelines throughout the world. Pipetronix has developed a new generation of internal inspection device for detecting SCC and other cracks and crack-like defects in pipelines, the UltraScan CD. It is a completely autonomous device that travels through the pipeline, carried by the fluid, uniformly scanning the pipe wall for defects with full circumferential coverage and for lengths of several hundreds of km. The information is processed on-line to allow for storage of huge amounts of data to be processed when the tool is retrieved from the pipeline. The UltraScan CD has, up to now, successfully inspected more than 1,000 km of oil and gas pipelines. Comparison of the findings with corresponding verifications from excavations illustrate the sensitivity and reliability of the inspection method and its ability to discriminate between different types of defects found in the pipelines

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

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 TUV (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.Copyright © 1996 by ASM

Detecting Cracks in Pipelines Using Ultrascan CD

Stress Corrosion Cracks (SCC) are among the defects in pipelines that are least understood and most difficult to detect, but which have accounted for some of the severest ruptures in pipelines throughout the world. Pipetronix has developed a new generation of internal inspection device for detecting SCC and other cracks and crack-like defects in pipelines, the UltraScan CD. It is a completely autonomous device that travels through the pipeline, carried by the fluid, uniformly scanning the pipe wall for defects with full circumferential coverage and for lengths of several hundreds of km. The information is processed on-line to allow for storage of huge amounts of data to be processed when the tool is retrieved from the pipeline. The UltraScan CD has, up to now, successfully inspected more than 1,000 km of oil and gas pipelines. Comparison of the findings with corresponding verifications from excavations illustrate the sensitivity and reliability of the inspection method and its ability to discriminate between different types of defects found in the pipelines.</p

Ultrasonic Testing - Reconstruction of Reflectors from Time-Delay and Amplitude-Locus Curves

For ultrasonic testing (pulse-echo or tandem) the surface of a test piece is scanned by a probe or a probe array. Time-delay and amplitude for each pulse, locus of incidence, reflector inside the beam and wave path, are measured. Shape and position of reflectors are reconstructed from time-delay locus curves. In addition, isolated amplitude-locus curves derived from measurements are compared to calculations for several reflector modes. The best fitting model is selected. Diameter or width and inclination are determined.</p

Detection and Verification of SCC in a Gas Transmission Pipeline

Two sections of a 914mm OD (36 in.) TransCanada (TCPL) gas transmission pipeline (predominantly with 9.14 mm wall thickness) were inspected using an ultrasonic liquid coupled crack detection In-Line Inspection (ILI) tool. One of the objectives of the inspection was to establish the condition of the pipeline sections with a known history of stress-corrosion cracking (SCC). Under test was the practicability of inspecting a gas line using a liquid coupled ILI tool, specifically its ability to detect and size defects deeper than 1 mm and distinguish cracks and crack-like defects from other types of anomalies, such as inclusions and laminations. In order to assess the confidence level of the tool, both sections were inspected in two independent runs and the repeatability of inspection was assessed. Cracks and crack-like defects with depths greater than 12.5% of the wall thickness from both runs were compared and correlation was established to assess repeatability. The accuracy of tool predictions was verified in excavations in both sections. 40 reported features, varying in depths up to over 40% were examined with respect to location, type, and size. Examples of defect patterns are shown to demonstrate the accuracy of the inspection method.Copyright © 2000 by ASM