In Russia, a large number of industrial potentially hazardous facilities are operated in petrochemical production, energy and, first of all, nuclear, pipeline transport, defense equipment and many other industries. Accidents that occur lead to human casualties, environmental disasters, and significant material losses. In order to improve operational safety and reduce accidents, more and more attention is being paid to equipment diagnostics, which makes it possible to assess their operability at an early stage, prevent the occurrence of emergencies and, if possible, extend the service life of facilities. Abroad, they produce and offer for sale a large range of diagnostic devices that allow solving many diagnostic tasks. However, they are quite expensive, as a rule, they are not adapted to the Russian market, they are not equipped with methods of application to various objects, they do not allow creating a complex technology that includes the use of several methods and devices and gives the most objective and complete information about the object. In this paper, a comprehensive technology for diagnosing a wide range of potentially dangerous objects is analyzed, ensuring their safe operation even when they exhaust their resource by applying new and improving known methods and devices for non-destructive evaluation of the technical condition of the object.
The problem of obtaining an image of defects from echo signals repeatedly reflected from the boundaries of the object of control is considered. A modification of the PSP and SAFT algorithm for obtaining an image of defects in a control object with plane-parallel boundaries is considered. The reason why it is impossible to obtain information about the depth of the defect by a converter operating on transverse waves in a combined mode is indicated. It is shown that recording signals in the double scanning mode, obtaining a set of partial images by the SAFT method and combining them into a final image allows us to solve this problem. To obtain a combined image, the addition of partial image modules and the calculation of their median were used. Due to problems with the accuracy of determining the speed of sound and the thickness of a particular object of control, coherent addition is potentially the most effective of the above methods of combining, did not allow to obtain a high-quality image. The results of numerical simulation of obtaining an image of point defects are presented. The results of model experiments on obtaining an image of a groove with a height of 1 mm in a metal plate with a thickness of 20 mm are presented. It is shown that the measurement of echo signals in the double scanning mode and the acquisition of an image by the DS-M-SAFT method makes it possible to determine the depth of the defect.
The general principles of the formation of tomographic images, which are formed by systems with coherent data processing, are considered; their characteristic features are analyzed. It is shown that the evaluation of the real parameters of defects based on their acoustic images consists of several stages: the selection of image elements belonging to the discontinuity in the three-dimensional image of the internal volume of the controlled object, determining the type of the identified discontinuity, measuring the parameters of the discontinuity: its length, profile (height in various sections along the length), localization. The individual stages of evaluating the parameters of defects are analyzed in detail and a number of common features that are used when performing these stages are formulated. Tables describing the features of acoustic images for various types of defects are given. The tables are illustrated with typical images of various types of defects in the welds of pipelines of various diameters. The reasons for the weak influence of the amplitude of defect images are analyzed to determine their type and real parameters.
A generalized sequence of actions for automated ultrasonic inspection of welded joints with measurement of defect sizes using the AUGUR system is considered. The main features of each control stage are described. It is shown that the effective application of the measurement mode requires calibration of acoustic transducers, analysis of surface irregularities, coherent data processing and detailed analysis of the images obtained.
An algorithm for obtaining an image of defects by double scanning for use in ultrasonic non-destructive testing, when the emitter and receiver move independently of each other along straight parallel lines, is considered. A formula for restoring the image of defects is presented. The advantages of the double scanning method and its disadvantages in comparison with the spectral space projection method (PSP), which is also used for coherent image reconstruction of defects, are discussed. Numerical and model experiments have shown the effectiveness of using the double scanning method to suppress parasitic images formed by transformed and over-scattered pulses. The stability of the method to distortions introduced by an uneven recording surface and higher noise immunity in comparison with the PSP method are also demonstrated.
The possibility of using homomorphic filtering of ultrasonic echoes as a method of data preprocessing to improve the quality of defect images obtained during coherent processing of echoes is considered. Homomorphic filtering makes it possible to reduce the influence of multiplicative interference, such as changes in acoustic contact or uneven surface of the object of control occurring during data recording. Image acquisition consists of the following stages: calculation of holograms from measured echo signals, logarithm of calculated holograms, finding the spectrum of holograms, projection operations in spectral space and Fourier transform. The results of the practical application of homomorphic filtration in the expert assessment of the size of defects in austenitic welds of stainless steel pipelines with a diameter of 325x15 mm2 are presented.
The complex technology of control of welded joints is considered, which allows the analysis of the quality of welds through the analysis of the effect of defects on the strength of the seam. This technology consists of three stages. The first stage: manual or automated ultrasonic testing according to standard control methods in order to search for defects. The second stage: automated expert ultrasound using Augur series systems in order to determine the type and size of defects. The third stage: strength calculation of the working life of the weld, taking into account information about the parameters of defects and other characteristics that affect the resource. The features of Augur series systems that use coherent processing (FT-SAFT type) of recorded pulse ultrasonic field data are briefly considered. An example of an image of a crack in a pipeline with a diameter of 890 mm is given. It is noted that the use of systems with coherent data processing of the Augur series makes it possible to carry out periodic monitoring of welds during their operation. An example of periodic monitoring of a defect in a welded seam of a stainless steel pipeline with a diameter of 325 mm is given. The results of expert control of welds of pipelines of various types in the nuclear power industry and control of oil pipelines are presented. It is shown that the use of the above-described technology of comprehensive assessment of the state of welds can significantly reduce the amount of unjustified repair of seams due to knowledge of the degree of their danger and, thereby, reduce repair costs; increase the operational reliability of industrial products by eliminating the most dangerous defects missed during routine inspection. The use of automated Augur systems makes it possible to minimize the disadvantages inherent in manual control by ensuring 100% control volume, to ensure documentation of the results; to monitor the defect, analyze its development during operation and prepare seam repairs on a planned basis.
The results of the analysis of the influence of practical control parameters (acoustic contact instability, PEP parameters, etc.) on the image quality of defects, the error and accuracy of determining their parameters: coordinates of occurrence, height and length of defects are presented. The error in determining the parameters of defects during primary and repeated control differs. It is shown that with repeated control, the error decreases. The results of comparing the data obtained during destructive testing and non-destructive testing of austenitic welded seams of stainless steel pipelines with a diameter of 325x15 mm2 are presented.
The handbook is intended for specialists in narrow-field engineering with qualifications of at least the second level, developing inspection methods and converters. The main focus is on physical control issues. Of the methods, the echometode is considered in detail, since it finds the greatest application.The values are expressed in SI. In space-time problems, more convenient derived units are used: for time – mks, for frequency – MHz, for distances – mm.
The reference book is intended for specialists in narrow-field engineering with qualifications not lower than the second level, developing control methods and converters. The main attention is paid to physical control issues. Of the methods, the echometode is considered in detail, since it finds the greatest use.The values are expressed in SI. In space-time problems, more convenient derived units are used: for time – mks, for frequency – MHz, for distances – mm.