RU2653955C1 - Method for determining voltage supply and coordinates in heat-affected zones of pipelines by the method for measuring velocity of passage of ultrasonic wave - Google Patents

Abstract

FIELD: defectoscopy.

SUBSTANCE: use to determine voltage supply and coordinates in heat-affected zones of pipelines. Essence of invention is cleaning the surface of the heat-affected zone, determining the defects, device adjustment, determining the speed of passage of an ultrasonic wave through a metal without load, loading with periodic measurement of the speed of passage of an ultrasonic wave with and determining stress points and recording their location, loading before the formation of cracks with recording ultrasonic wave velocity measurement data, reviewing the occurrence of a crack by means of an electron microscope, fixing the coordinates of defect formation and comparing with the coordinates of the stress zone.

EFFECT: providing the possibility of determining and predicting the points of future defects in the heat-affected zone by determining the coordinates of stress points.

1 cl, 12 dwg

Description

The present invention is intended for non-contact non-tube diagnostics of the technical condition of ferromagnetic gas and oil pipes.

From the patent RU 2568808 C2 a method and device for non-contact diagnostics of the technical condition of underground pipelines is known. The method includes measuring the components of a constant magnetic field above the pipeline when moving the sensors of a constant magnetic field along the pipeline, compensating for the effect on the results of measurements of the constant magnetic field of the Earth and mathematical processing of the measurement based on the sum and difference of the components of the gradient matrix. In this case, at least seven three-component permanent magnetic field sensors with central symmetry and the location of one sensor in the center of symmetry are used. The sums and differences of the same components of the constant magnetic field are determined based on the components measured by sensors located at the extreme points from the center of symmetry and the differences of the same components measured by the sensor located at the center of symmetry and the sensors located at the extreme points from the center of symmetry along each of three orthogonal coordinate axes. After determining the components of the constant magnetic field, tensor processing of the gradient matrices is used to calculate the matrix of the first derivatives of magnetic induction and the matrix of the second derivatives of magnetic induction, while the parameters of the second derivatives of the signals of the magnetic fields of interference, the magnetic field of the pipe and the magnetic fields of defects are compared and the geometric characteristics of anomalous objects are calculated in the pipeline. The result of the technical solution is to increase the accuracy and sensitivity of the method and device for diagnosing the technical condition of steel gas and oil pipelines. This allows you to increase the reliability of diagnostic results, but not identifying zones of stress concentration in the metal. The method also requires subsequent complex processing of the results, such as tensor processing of matrices, calculation of matrices of the first and second derivatives of magnetic induction, which is a rather complicated process. The method involves comparing the parameters of the second derived signals of the magnetic fields of interference, the magnetic field of the pipe and the magnetic fields of the defects to calculate the geometric characteristics of anomalous objects (defects). The disadvantage of this method is the error of the method due to the presence of magnetic fields of interference, the exact value (value) of which cannot be determined. The reliability of the results depends on the magnetization of the pipeline, which is inevitable during operation and has a varying degree and magnitude depending on the occurrence conditions, which is also a disadvantage. The method involves complex mathematical processing of a measurement based on the sum and difference of the components of the gradient matrix, which is a disadvantage. Also, this method is directly dependent on the presence of stray currents at the site of the pipeline (the intersection of the pipeline with the railway, the occurrence of the pipeline near power lines), which is also a disadvantage of the method.

From the document CN 103018326 A, an invention is known which relates to ultrasonic non-destructive testing of direct linear automatic scanning. The device is mainly used to automatically detect a defect in a direct welding line and residual welding voltage. A magnetic type base can be used to conveniently adsorb the detection device in the area of the welding line to be detected; the transverse beam of the detection device is formed by an engine and a direct guide rail; an electric motor controls the sliding unit to install a detection sensor for moving along a straight guide; the sensor may be a residual voltage detection sensor, a TOFD (Time of Flight Diffraction) sensor, and a surface defect detection sensor; and the detected location information is recorded and fed back by the photoelectric sensor. The device can be applied to automatic detection in the area of the welding line of a plate welding component, can automatically detect on the welding line of a welding component with a curved surface, including a pipe and the like, and improves detection efficiency. The disadvantage of this method is the use of additional equipment, such as an engine and a direct guide rail. In this case, it is necessary to carry out installation and assembly of the structure. The method involves the use of a magnetic type base, which inevitably entails additional magnetization of the pipeline, which is highly undesirable. The application of the invention is impossible in highway conditions both during construction and during overhaul of the pipeline.

From patent RU 2212030 C2 a method for detecting lack of fusion is known. The invention relates to non-destructive testing and can be used to control the presence of lack of penetration during welding of the product using acoustic emission signals. Improving the reliability of the results of the identification and registration of lack of penetration during the welding process is achieved due to the fact that acoustic emission signals arising in the welded joint during the welding of parts are received, an informative parameter is selected, by changing which the quality of the weld is judged. As an informative parameter, the amplitude distribution of AE signals arising from the vibration of atoms at the mouth of a lack of fusion is chosen, the width of the energy spectrum of which is determined from a certain ratio. One of the parts to be welded is mounted in the fixture with the ability to move along the vertical axis, and the other is stationary, while the AE signals from the processes of lack of penetration and crack formation recorded in the same channel of the amplitude analyzer are separated by the number of AE pulses. The disadvantage of this method is that the method provides only for finding a defect such as lack of fusion in the weld. Not only lack of penetration of the welded joint is an unacceptable defect in the operation of the pipeline. The method does not determine the presence and characteristics of other defects in the welded joint. The surrounding area is not controlled by this method. With this control method, the amplitude distribution of AE signals arising from the vibration of atoms at the mouth of a lack of fusion is chosen as an informative parameter. This fluctuation is very insignificant, which does not allow to determine with high accuracy the geometric dimensions of lack of penetration.

The invention is aimed at eliminating the disadvantages of the above analogues, as well as to solve the problem of determining and predicting the places of future defects in the heat-affected zone by determining the coordinates of the stress concentration.

The parameter that determines the stress-strain state of the gas pipeline is the magnitude of the stresses in its walls. One of the methods for determining the magnitude of stresses in the wall of an operated pipeline is ultrasonic. Non-destructive testing of the base metal and welded joints is one of the important stages in the manufacture, repair and technical diagnosis of products for various applications. Moreover, issues related to the admissibility of various defects acquire a special role. The use of ultrasonic vibrations to detect defects is based on the reflection of elastic waves from discontinuities, on which defect detection is based. Since by their acoustic properties discontinuities (pores, slag inclusions, lack of penetration) differ from the main material. When ultrasonic waves fall on a defect, an acoustic scattering field arises containing a whole spectrum of waves of various types scattered according to the laws of geometric acoustics and diffraction theory. We can conclude that under load the speed of the ultrasonic wave passing through the heat-affected zone decreases. The heterogeneity of the structure is also the cause of the attenuation of ultrasonic waves. The appearance of heterogeneity of the metal structure and, as a consequence, the stress concentration zone is one of the main factors in the appearance of a defect during operation of the pipeline.

The speed of sound propagation (ultrasound) is the most important informative characteristic of acoustic methods for monitoring and diagnosing structural materials. It is established that the relationship between the operating voltage and the ultrasound speed is linear, and this regularity is characteristic of all the materials considered.

The analysis shows that the propagation velocity of subsurface longitudinal acoustic waves in the direction of uniaxial stresses has an unambiguous dependence on them. When the sample is loaded, the speed of the ultrasonic wave passing through the heat-affected zone will decrease. The heterogeneity of the structure is the cause of the attenuation of ultrasonic waves when the sample is loaded. The appearance of heterogeneity of the metal structure and, as a consequence, the stress concentration zone is the main factor in the appearance of a defect under load. It was also found that the speed of ultrasound increases with a decrease in internal stresses in materials and decreases with an increase in them, which is associated with the appearance of double acoustic refraction in stressed volumes of the material and the formation of crystal lattice defects, which leads to the appearance of a defect in elastic modules. For a polycrystalline material, the relationship between the speed of ultrasound and internal stresses can be explained by the fact that, at low degrees of deformation, stress relaxation occurs due to local rotations of individual volumes of material.

Ultrasonic thickness gauging is the only effective control method in cases where the structural features of the parts do not allow them to be controlled by conventional methods, since access to the inner wall of the product is difficult or impossible. Ultrasonic thickness gauge makes it possible to obtain with high accuracy data on the thickness of the controlled object without any damage. Ultrasonic thickness gauges measure the thickness of products from most structural materials, such as metals, plastics, ceramics, composites, epoxy and glass, as well as the thickness of a liquid layer or biological samples.

Ultrasonic thickness metering has been most widely used in the field of monitoring the residual wall thickness of pipelines, diagnosing defects in pipes, water pipes and heating mains that are subject to corrosion from the inside without decommissioning. Thickness measurement is the process of measuring the thickness and integrity of a material using a special apparatus - a thickness gauge.

Ultrasonic thickness gauges not only measure the thickness of the test object, but also measure the time it takes the ultrasonic pulse to travel to the opposite surface of the test object, reflection from it and return to the transducer. For such measurements, access to the opposite surface of the object of control is not required. Due to this, if the opposite surface of the control object is difficult to access or completely inaccessible, there is no need to cut the control object (which is required when using a micrometer or vernier caliper). Using ultrasonic thickness gauges, the thickness of products from most structural materials, such as metals, plastics, ceramics, composites, epoxy resin and glass, as well as the thickness of a layer of liquid or biological samples can be measured.

The proposed methodology is as follows: 1) cleaning the surface of the heat-affected zone; 2) determination of the presence of defects; 3) the use of lubricant for the sensor between the pipe and the sensor; 4) instrument setup; 5) determination of the speed of passage of the ultrasonic wave through the metal of the heat-affected zone; 6) the gradual creation of a load with periodic measurement of the speed of passage of the ultrasonic wave with the determination of places of stress concentration and registration of their location; 7) the creation of a load before the formation of cracks with the registration of the data of measuring the speed of the ultrasonic wave; 8) an overview of the appearance of a crack using an electron microscope; 9) fixing the coordinates of the defect formation and comparison with the coordinates of the stress concentration zone.

The studies and the proposed methodology, according to the author, will allow to determine and predict the places of future defects in the heat-affected zone. It was also proved on a dynamic machine that defects in the heat-affected zone are formed under load in places with the highest voltage.

The following figures show the following:

FIG. 1 - Setting the ultrasonic thickness gauge A1208.

FIG. 2 - Measurement of ultrasonic wave velocity using a transducer.

S3567 thickness gauge A 1208.

FIG. 3 - Points of measurement of the speed of passage of the ultrasonic wave through the heat-affected zone of the welded joint.

FIG. 4 - Visualization of thickness gauge data A 1208.

FIG. 5 - Universal testing machine.

FIG. 6 - Scheme of the load on the sample. Bending test: 1 - fragment of a welded joint; 2 - tip; 3 - supports; 4 - load indicator.

FIG. 7 - The speed of the ultrasonic wave passing through the sample under the action of a load: 40 kN.

FIG. 8 - Velocity of an ultrasonic wave passing through a sample under load: 70 kN.

FIG. 9 - The speed of the ultrasonic wave passing through the sample under the action of a load: 120 kN.

FIG. 10 - The results of the study of the sample by the method of magnetic memory of the metal at a load of 40 kN.

FIG. 11 - The results of the study of the sample by the method of magnetic memory of the metal at a load of 70 kN.

FIG. 12 - The results of the study of the sample by the method of magnetic memory of the metal at a load of 110 kN.

To conduct the results of the study used: ultrasonic thickness gauge A1208; tripod holder electron microscope; universal testing machine.

The setting of the ultrasonic thickness gauge A1208 (Fig. 1) is as follows:

activation of the radiation / capture configuration;

connection of the wearproof combined S3567 converter;

performing thickness measurement of the sample and calibrating the device for the resulting thickness δ = 19 mm;

discreteness of indication of measurements of 0.01 mm;

inclusion of the selection device in the scan area;

the inclusion of the function of automatically determining the speed of ultrasound at an object of known thickness;

setting the “NORMA” operating mode for calibration measurement;

setting the “MEMORY” operating mode for subsequent measurements.

This mode allows you to perform correction of stored records by conducting repeated measurements with the subsequent recording of new data in the corrected memory cells. Any questionable result may be overwritten.

The operation of this device is based on the reflection of an ultrasonic pulse from the opposite surface of the test object. The advantage of thickness measurement is the high accuracy of measurement without destroying the object being examined.

There are three types of tasks when measuring thickness:

1) Manual control of products with smooth, equally spaced surfaces, for example, products after their manufacture.

2) Manual control of products with rough non-parallel surfaces, for example products whose inner surface is affected by corrosion.

3) Automatic flow control (usually pipes, sheets).

Initially, in the model fragment of the welded joint of the DU1420 gas main, δ = 19 mm, the surface of the heat-affected zone was prepared for non-destructive testing. All loose particles, dust, dirt, and corrosion products were removed from the surface. After that, non-destructive X-ray inspection was performed. As a result of the inspection of the heat-affected zone, an X-ray film was installed, installed on the outside of the fragment of the welded joint of the main pipeline. The analysis of the blackening density of the X-ray film installed behind the object in the controlled area indicated the absence of defects. Then, the speed of ultrasonic waves passing through the heat-affected zone of the fragment of the welded joint of the main pipeline was measured.

The thickness gauge A 1208 has the function of measuring the speed of passage of the ultrasonic wave during the thickness gauge (Fig. 2).

After preliminary thickness measurement of the heat-affected zone of the fragment of the welded joint of the main pipeline, the device was calibrated for the obtained thickness value. Calibration is necessary to accurately measure the speed of an ultrasonic wave through a given thickness. Ultrasonic waves passing through the metal body are reflected from its inner surface (bottom signal).

The thickness gauge A 1208 automatically measures the reflection time of the ultrasonic wave, and comparing it with the thickness of the sample, calculates the speed of passage of the ultrasonic wave through the experimental sample. The ultrasonic wave velocity was measured at three points in the root zone of the fragment of the welded joint of the MG (Fig. 3), 3 times at each point for higher reliability of the result.

From the results of measuring the speed of the ultrasonic wave during passage through the body of the fragment (Table 1), it can be seen that at all three points of measurement, the velocity had a constant value.

Visualization of the result of measuring the speed of the ultrasonic wave, made by a thickness gauge A 1208, is shown in FIG. 4. The conditional value of the thickness gauge was taken as the norm, since X-ray inspection showed the absence of defects in the weld zone near the weld.

To simulate the internal radial load on the wall of the gas pipeline (internal pressure), a universal testing machine was used (Fig. 5).

The load in the sample was created smoothly, according to RD 26-11-08-86 “Welded joints. Mechanical tests ”until a surface crack is formed in the weld zone, but not in the weld itself. The load on the bend, emitting the load of the operation of the gas pipeline, was carried out according to the scheme shown in FIG. 6.

So, the pressure of the tip was produced directly on the heat-affected zone of the welded joint at point 2. The load was applied until cracks formed in the heat-affected zone.

The measurement of the speed of the ultrasonic wave passing through the heat-affected zone was performed at point 2 (Fig. 6) after each increase in the load created by the universal testing machine. To save and compare the results on the thickness gauge, the MEMORY mode was selected.

Studies on the effect of the duration of static bending of the material on the propagation velocity of ultrasonic longitudinal waves showed that during the first 20 days a decrease in speed was observed, after a further 10 days of exposure, the speed stabilized. Measurements carried out at different levels of deformation showed that in the first periods (20 days) a chaotic change in the velocity of ultrasonic longitudinal waves was noted, and after 20-30 days of exposure, the situation stabilized. In this case, in the initial period of deformation, a slight decrease in speed or almost its absence was observed, and when the degree of deformation corresponding to the working state of the sample, the ultrasound speed decreased, with a further increase in deformation, a speed increase was again observed.

The results of measuring the speed of the ultrasonic wave at point 2 using a thickness gauge A 1208 are summarized in table 2. Images of the informative screen of the thickness gauge with the values of the speed of transmission of the ultrasonic wave at different load on the sample are shown in FIG. 7, 8, 9.

The determination of the magnitude and coordinates of the stresses was performed using the magnetic memory of the metal (IMMP). The results of the MMPM are shown in FIG. 10, 11 and 12.

As a visualization of the test result of the sample by the magnetic magnetic memory of the metal, we presented a magnetogram of the distribution of the normal component of the intrinsic scattering magnetic field Hp and its gradient dHp / dx, recorded in the stress concentration zone when the sensor scanned the device along the line of the weld (along the weld zone).

The control was carried out by the device IKN-1M. On the upper part of the magnetogram, the distribution of the normal component of the magnetic field recorded during control is shown. On the bottom of the magnetogram is the maximum value of the gradient dH / dx. A stress concentration zone is noted, characterized by local changes in the field gradient in this zone. The control result shows that the defective zones of stress concentration at all those control points are located in areas from 370 to 440 mm of the test sample.

The uneven distribution of the magnetic field, expressed by a sharp change in the dHp / dx gradient in the zone from 382 to 423 mm, indicates the presence of a stress concentration in the heat-affected zone in all three cases.

It should be noted that the magnetogram at point 2, obtained at a load of 40 kN, shows the maximum permissible value of the voltage for the operation of the gas pipeline, equal to 10 A / m. From the bottom of the magnetogram it can be seen that a sharp change in the value of the gradient dH / dx is in the coordinates of 380-417 mm. The distribution of the normal component of the magnetic field in these coordinates also has a sharp change. Based on the results of the MMMPM study, it can be concluded that the studied area of the OZHZ is acceptable for use in accordance with the “Instructions for the assessment of defects in pipes and fittings during repair and diagnostics of gas pipelines approved by Gazprom on November 18, 2005. When analyzing the magnetogram obtained during the study After applying a load of 70 kN, it can be seen that the maximum gradient dH / dx exceeded the permissible value for operation, equal to 10 A / m. The result of the study of the sample at a load of 70 kN shows that the magnitude of the stresses, as well as the distribution of the normal component of the magnetic field, increased significantly in the same coordinates. In other words, the maximum value of the dH / dx gradient at a load of 70 kN in the coordinates of 380-419 mm significantly increased in comparison with the result of the IMFM at the same point at a load of 30 kN. At a given value of the gradient dH / dx, the section of the OSHZ is unacceptable for operation. When analyzing the fragment magnetogram at point 2, obtained with a sample load of 110 kN, a strong change in the maximum gradient dH / dx in coordinates of 380–422 mm is noticeable. Also, the distribution of the normal component of the magnetic field in these coordinates has a sharp change relative to previous results. It can be noted that at a load of 110 kN, the magnitude of the stresses in the coordinates of 380-420 mm is of the highest value relative to studies of the IMF of the same sample at 30 kN and 70 kN loads. This fragment is unacceptable for operation, since it has a maximum gradient dH / dx of more than 10 A / m. This indicates the presence of an unacceptable defect (crack) in the area of the longitudinal seam. Further, with an increase in load at point 2, a crack formed.

Analyzing the results of magnetograms at loads of 30 kN, 70 kN and 110 kN, we can see a directly proportional dependence of the change in the values of the gradient dH / dx on the magnitude of the applied load. As the load on the pipeline fragment increases, the maximum gradient dH / dx and the distribution of the normal component of the magnetic field also increase and have a sharper change in the coordinates of 380-423 mm. The result of the control of the MMPM sample shows a change in the magnitude of the A / m stresses with increasing load. At a load of 30 kN, the stress value at point 2 of the sample was 37 A / m, with a load of 70 kN, the stress value was 48 A / m, at a load of 110 kN, the stress value was 69 A / m. Analyzing the change in the value of the applied load on the sample with a change in the magnitude of the stresses, we can conclude that there is a direct proportional dependence of these values.

When analyzing the change in the velocity of the ultrasonic wave passing through point 2 of the sample, and the results of the IMFM, we can conclude that the higher the stress value in the body of the OZHZ metal (gradient value dH / dx), the lower the speed of the ultrasonic wave through the stress concentration zone. The results of the passage of the velocity of the ultrasonic wave through point 2 and the results of the IMFM at point 2 for different values of the load are summarized in table 3.

Comparing the values of the velocity of the ultrasonic wave and the magnitude of the stresses, we can conclude that with an increase in the load on the sample, the magnitude of the stress gradient also increases. The theoretical substantiation of the dependence of the change in the speed of passage of the ultrasonic wave through the body of the metal OShZ on the magnitude of the stresses is practically proved.

As a result of the experiment, it was revealed that when the load on the sample, the speed of the ultrasonic wave passing through the SWD decreased. The heterogeneity of the structure is the cause of the attenuation of ultrasonic waves when the sample is loaded. The appearance of heterogeneity of the metal structure and, as a consequence, the stress concentration zone is the main factor in the appearance of a defect at a load of 114 kN - a visible crack formed on the surface of the fragment. A crack was formed in coordinates with the lowest ultrasound velocity of the body of the metal of the OSh and with the largest gradient dH / dx, that is, the largest stress value. The applicability and reliability of the method, based on the passage of the change in the speed of passage of the ultrasonic wave, is confirmed not only theoretically, but also practically. The reliability of the method is confirmed by the IMF method and the coincidence of the coordinates of the attenuation of the waves with the coordinates of the crack.

Claims (1)

The method for determining the presence and coordinates of stresses in the heat-affected zones of pipelines by measuring the speed of passage of an ultrasonic wave, which consists in cleaning the surface of the heat-affected zone, determining the presence of defects, adjusting the device, determining the speed of passage of an ultrasonic wave through a metal without load, and providing a gradual load with periodic measurement of the speed of the ultrasonic wave with the determination of the concentration of stresses and registration of their location, about they ensure the creation of a load before the formation of cracks with the recording of ultrasonic wave velocity measurement data, conduct an overview of the appearance of a crack using an electron microscope, fix the coordinates of the defect formation and compare with the coordinates of the stress concentration zone.

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