Estimation of the losses of energy of acoustic vibrations in the course of ultrasonic testing in the atmosphere of natur
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ESTIMATION OF THE LOSSES OF ENERGY OF ACOUSTIC VIBRATIONS IN THE COURSE OF ULTRASONIC TESTING IN THE ATMOSPHERE OF NATURAL GAS М. О. Karpash1 and Т. Т. Koturbash1, 2
UDC 620.179
We propose a method for the evaluation of the losses of ultrasound vibrations in the course of contactless ultrasonic testing in an atmosphere of natural gas taking into account the physical and geometric parameters of the medium of propagation of ultrasound and tested objects for the choice of the materials of piezoelectric transducers and matching layers. This method enables us to estimate the influence of the physical parameters of the medium and tested object (temperature, pressure, composition, material, and thickness) on the losses of ultrasonic signals for the choice of their optimal values. The losses of ultrasonic signals are estimated for the case of unilateral monitoring of the thickness of the wall in a pipeline aimed at the transportation of natural gas with given composition under pressure. The results of our analyses make it possible to conclude that, in the case of application of matching layers chosen with regard for the parameters of the medium and contemporary algorithms for processing of the data of measurements, it becomes possible to realize flaw detection and monitor the thickness of the main pipeline in an atmosphere of natural gas under the action of working pressure. Keywords: ultrasonic control, natural gas, attenuation of ultrasound.
The problems of guaranteeing the reliability and safety of the delivery of natural gas by main pipelines become more and more urgent due to a significant degree of wear and aging of the equipment of domestic oil-andgas complex. For about 60% of the main pipelines, the period of their operation exceeds 30 yr [1]. These metallic structures are replaced and modernized with much lower intensity than necessary for their safe operation. The role of the main cause of failures of main pipelines is played by the inner and outer corrosion defects (28.9%) (for comparison, in the countries of the European Union, these defects are responsible for 15% of failures) [2]. To determine the actual engineering state of pipelines and predict its changes, the procedure of engineering diagnostics should be periodically performed. As one of the problems of the engineering diagnostics of pipelines, we can mention the determination of the actual thickness of pipeline walls. As a rule, the rejection criterion can be formulated as the decrease in the actual thickness of the pipe wall by more than 12.5% of its nominal value. At present, the in-tube diagnostics based on the use of autonomous projectile flaw detectors (pistons) with magnetic sensors moving inside the pipes under the pressure of the transported products is used especially extensively as the method aimed at the determination of the current state of gas mains [3]. However, the indicated instruments are characterized by the number of serious disadvantages, namely, the accuracy of determination of the sizes of defects and geometric parameters of the p
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