Showing papers on "Time-of-flight diffraction ultrasonics published in 2001"

Ultrasonic testing system for tubulars

Abstract: A comprehensive system for the cleaning, inspection, and testing of tubulars, particularly riser pipes, is provided. In a first aspect, a method of inspecting a tubular comprises cleaning, visually inspecting, corrosion mapping, and TOFD testing the tubular. In another aspect, a specially designed or adapted tool is provided for each of the steps of the method.

Automatic ultrasonic flaw detection method and device

Abstract: PROBLEM TO BE SOLVED: To obtain an automatic ultrasonic flaw-detecting device for simultaneously detecting the flaw of a base material welded part and a padding welded part. SOLUTION: Ultrasonic fly detection by TOFD method and that by PA method are simultaneously conducted on a welded joint part 10. In the PA method, an array probe 21 where a number of vibrators for receiving ultrasonic waves are arranged linearly in the width direction of the welded joint part 10 is used for detecting the flaw of a padding welded part 11 and a base material welded part 12. In the TOFD method, two pairs of transmission and reception probes provided adjacent to the array probe 21 and across the padding welded part are used for performing the ultrasonic flaw detection of the base material welded part.

Method for evaluating life of metallic material

Abstract: PROBLEM TO BE SOLVED: To provide a method by which the life of a metallic material can be evaluated easily. SOLUTION: This method is constituted to find the life consuming rate of a high-temperature pipeline 10 based on the correlation between the life consuming rate of the pipeline 10 found in advance from the number and density of creep voids of the pipeline 10 and the generating rates of A flaws (dense flaws) by finding the generating rate of the A flaws by the TOFD method.

Laser ultrasonic TOFD method

Abstract: We applied laser ultrasound for the time of flight diffraction (TOFD) measurement. To find an effective testing condition of TOFD method, laser ultrasonic transmission around the slit in glass specimens was observed using the photoelastic ultrasonic visualization system. After the observation we constructed the laser TOFD system and applied to the slit depth measurement of aluminum plate, and then, obtained highly accurate results.

Ultrasonic inspection of risers: a simple and affordable alternative to self- contained pigging

Abstract: A riser forms the connection between the topside of an offshore platform and a pipeline on the sea bed. Increasingly, offshore operators are committed to protect the environment. Pipeline pigging and riser inspection will assist in determining the integrity ofthe line and the riser, in particular. In this article, a new approach for a full-coverage ultrasonic inspection of the riser only is described, based on the application of a compact umbilical-cable, tether-operated, tool. This requires the riser to be shut down and filled with a liquid. The inspection tool provides an on-line presentation of results, for immediate evaluation. The system uses straight-beam ultrasonic sensors for a general corrosion survey of the pipe material, and the TOFD (time of flight diffraction) technique for additional inspection of the circumferential weld area.

The simulation of ultrasonic imaging in the case of the objects with a complex geometry

Abstract: The main objective of the ultrasonic non-destructive testing (NDT) applications is to detect dangerous defects in the various constructions. The parameters and geometry of defects is very important information determining lifetime of constructions or components. In conventional ultrasonic NDT methods, based on the measurement of the amplitude and delay time of reflected signal are used. Such an approach enables evaluate size and position of defects only approximately. Most accurate is time – of the flight diffraction (TOFD) technique, which allows measuring depth of defects. Additional application of the SAFT or tomographic algorithms enables to increase accuracy even more [1,2,3]. Nevertheless, practical applications of these methods usually are complicated due to a lack of a sufficiently accurate information about ultrasound propagation conditions, such as the propagation velocity, angle, wave fronts and etc. Additional problem arises due to the fact that basic algorithms of these techniques are developed for the direct reflections only [1,2,3]. On the other hand, due to the object geometry or limited access very widely the signals reflected from the bottom or mode conversion signals are used. The successful application of all these signals in tomographic processing may increase the accuracy essentially. The development of such algorithms using only experimental data is very complicated because it is impossible to determine sensitivity of the technique to the uncertainty of the input parameters. This problem can be solved developing special method and software that enables to simulate NDT data acquisition process, taking into account material parameters, transducer characteristics, diffraction and refraction phenomena. Such models are used in other institutions like CEA (France), BAM (German) and others. Usually they are based on complicated numerical approach, which requires essential computer resources [4,5,6]. The objectives of this work was to develop relatively fast NDT simulation model, which enables to take into account not only direct reflection from defects, but specular reflection from object boundaries also. This task may be divided in some parts:

Reliability of AUT systems for the inspection of girth welds during pipeline construction

Abstract: AS AN ALTERNATIVE to radiography, a state-of-the-art system for mechaniaed ultrasonic nspection (more recently also called AUT - automated-ultrasonic testing), for pipeline girth welds is discussed. Called RTD Rotoscan, this system has been developed for inspection of girth welds during construction of long-distance pipelines, both on- and offshore. The system is characterized by a high inspection speed and instant recording of results. Unlike radiography, it provides immediate back to the weiders. Progress in flaw sizing and recording allowed the application of rejection/acceptance criteria for weld defects based on fracture mechanics. The development and actual use of such modern acceptance criteria, first in Canada and later also in other countries, supported the introduction of AUT. RTD, after having been the first company to offer these services, was soon followed by other providers. World-wide applications proved that, contrary to expectations, ultrasonic inspection does not lead to higher weld repair rates than radiography. Between early 1989 and the present, over 5,000km of pipeline (representing 300,000 welds) have been inspected with the RTD Rotoscan alone The introduction of transit-distance C-scan mapping enabled the system to cope with most existing ultrasonic procedures and acceptance criteria, because of its capability to show and, to a certain extent, quantify volumetric defects. Moreover, the integrated time-of-flight diffraction (TOFD) function, together with the amplitude-based, software-aided, sizing capability provides accurate, state-of-the-art data on defect through-thickness height. The present system is capable of achieving a very high probability of detection (POD), togethe with a low false-call rate (FCR). Despite the lack of international standards, RTD's system has been qualified in various countries for different individual customers and for a variety of weld processes, pipe diameters, and wall thicknesses, and has demonstrated its on- and offshore capabilities as an alternative to high-speed radiography, even under harsh field conditions. Development work continues to increase sizing accuracy even further, and to consider phased-array-controlled systems, enabling even better sizing and more versatile probe systems to enhance reliability and inspection speed.