RU2506581C2 - Method of remote magnetometry for diagnostics of pipelines and device for its realisation - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to non-contact diagnostics of metal tubes during operation. The inventive method comprises determining the location and depth of the pipeline at the test site, installation along the pipeline of at least two identical sensors for measuring tension (tangential component) of the magnetic field, synchronous recording of changes in the magnetic field caused by stray currents, comparative information processing from all sensors and diagnostic conclusion. The apparatus comprises at least two identical sensors for installation along a pipeline axis, determining the magnetic field, means for linkage at the location, means for determining the depth of the pipeline, a facility of synchronisation of switching and sensor means for recording the magnetic field change caused by stray currents and data processing.

EFFECT: simplification of searching for locations of pipeline corrosion, improving accuracy of fault location.

13 cl, 8 dwg

Description

The invention relates to the oil and gas industry, utilities and other fields of science and technology using underground metal pipelines. In particular, the present invention relates to non-contact diagnostics of the integrity of metal pipes during operation.

Metal pipelines laid in the ground are exposed to various physical and chemical factors. Violations of insulation, soil pressure, the influence of stray currents, significant changes in temperature and internal pressure lead to a significant reduction in their service life. Corrosion of metal pipes is one of the main reasons for their depressurization and technological disasters in pipelines. Due to the heterogeneity of the pipe metal and the heterogeneity of the soil (in physical properties and chemical composition), areas with different electronic potential arise, which leads to the formation of galvanic corrosion elements.

The corrosion situation in which the metal pipeline is located in the soil depends on many circumstances associated with soil and climatic conditions, features of the route, and operating conditions. Stray currents in the earth caused by electrified direct current rail transport have the greatest negative effect on the electro-corrosive destruction of pipelines. From practice it is known that the value of stray currents can reach 400 A, and the corrosion caused by them - up to 10 mm per year.

Methods of protecting underground metal pipelines from corrosion are divided into passive and active.

The passive method of corrosion protection involves the creation of an impermeable barrier between the pipeline metal and the surrounding soil. This is achieved by applying special protective coatings to the pipe: bitumen, coal tar pitch, polymers, epoxy resins, etc.

However, in practice it is not possible to achieve the necessary integrity of the insulation coating. Its various types have different diffusion permeabilities, and during construction and operation, cracks, scratches, dents and other defects occur in it. The most dangerous are through damage to the protective coating, where soil corrosion is observed.

Since passive methods do not provide absolute protection for the pipeline, active protection associated with the control of electrochemical processes occurring at the boundary of the pipe metal and soil electrolyte is usually used at the same time. The active method of corrosion protection is carried out by cathodic polarization and is based on a decrease in the dissolution rate of the metal as its corrosion potential shifts to a region of more negative values.

The cathodic protection of pipelines is carried out in two ways: galvanic - using sacrificial anode protectors, and electric - using external DC sources, minus which connects to the pipe, and plus - with anode grounding.

The use of cathodic protection with the help of protectors is effective only in low-resistance soils (up to 50 Ohm / m) and is limited in terms of life. Cathodic protection by external sources depends little on the resistivity of the soil, but is more complex, time-consuming and requires a lot of energy. In addition, the protective current applied to the pipe and creating a potential difference "pipe-to-ground" is distributed unevenly along the length of the pipeline. As you move farther from the connection point, the protection efficiency decreases. Excessive overestimation of the potential difference negatively affects the adhesion of the coating and can cause structural changes in the pipe metal and lead to cracking. Moreover, with a high density of communications under cathodic protection, corrosion processes can be amplified in some of them due to redistribution of potentials.

Thus, both passive and active protection methods have a number of limitations and do not provide complete safety of pipelines. Therefore, it is necessary to regularly monitor the integrity of the pipes during operation.

Flaw detectors for internal inspection of pipes are known (for example: RF patent No. 2102652; US 6,917,176; US 7,154,264; WO 2007/130723). However, their use in many sections of the pipeline is limited by the need to install special reception and launch chambers, the design features of the pipeline (the presence of bends, the connection of pipes of various diameters, etc.). In addition, for the duration of the examination, it is necessary to introduce restrictions into the operation mode of the pipeline. Therefore, in practice, on the main sections, such measurements are taken every two to three years, and significant corrosion damage caused by stray currents can form in a shorter time.

Widespread methods for monitoring pipelines based on electrical measurements. In the patent of the Russian Federation No. 224297 a method for detecting corrosion damage is described by evaluating the specific resistance of the pipe metal. In the studied area, pits are dug and a contact measurement of electrical resistance and pipe parameters is carried out. In general, this method is characterized by high labor costs, low efficiency and effectiveness of predictions. In addition, it has significant limitations on the size of the surveyed area.

Another way to determine the location and area of defects in the insulation coating and the depth of corrosion damage to the outer surfaces of underground and underwater pipelines (RF patent No. 2 319 139) is based on measuring the polarization potential after removing the polarization. This method also has low diagnostic accuracy and requires a change in the operating mode of the pipeline during the examination.

Currently, the most commonly used technique is the determination of dangerous sections of the pipeline in operation by the presence of stray currents ("Typical Instructions for the Protection of Pipes of Heat Networks from External Corrosion" No. RD 153-34.0-20.518-2003 of November 29, 2002). However, it provides only indirect information about the presence of a threatening factor, but does not indicate the exact location and nature of the defect. For accurate diagnosis, significant excavation work is required to open hazardous areas and visual or other contact inspection of pipes.

Contactless methods for finding defects are based on measuring the components of the magnetic field around the pipeline. A known method of inspection of the pipeline (US 4,430,613), associated with the movement of the magnetometer along the axis of the pipeline and identifying places with a deviation of magnetic characteristics. However, in this way only significant heterogeneities can be determined under ideal conditions. Natural heterogeneities of the Earth’s magnetic field, different depths of pipes, high density communications, etc. limit the possibilities of practical application of this method.

To increase the accuracy of measurements, the magnetic field tensor is determined (RF patent No. 2264617), direction and nature of its change, component ratio (RF patent No. 2246742; RF patent 2062394; RF patent No. 225 155 943; RF patents for PM No. 11608, No. 88453 ) The presence of defects in the pipe and their dimensions are determined by the deviation from the background value. However, the background value can vary along the line of the pipeline, depending on the nature and condition of the soil, as well as on the depth and technical features of the pipe. An additional measurement error is introduced by the presence of extraneous metal objects near the pipeline.

The limitations of the magnetometry methods described above are due to a low level of change in the desired signal and a large number of difficult to take into account artifacts that introduce distortion into the measurements. This leads to relatively low accuracy of localization of hazardous areas, low reliability of assessing the level of damage (corrosion value) and difficulty in interpreting the results associated with taking into account soil properties, weather conditions, etc.

The present invention is directed to measuring changes in the magnetic field due to the presence of stray currents and the localization of places of their runoff to the ground. The magnitude of the changes determines the nature and degree of threat of defects for the pipeline.

This method: firstly, allows you to directly localize a dangerous place and, secondly, to determine the nature of this danger - to conduct an estimated calculation of the amount of corrosion.

The aim of the present invention is to develop a method and create technical means for determining sections of the pipeline with a maximum change in the value of stray current appearing on the pipe, localization and assessment of the magnitude of the corrosion damage caused by it.

The technical result consists in simplifying the method of searching for places of corrosion on a pipeline while improving the accuracy of localization of damage and assessing their scale.

The claimed technical result is achieved by the fact that the method of remote magnetometry to determine the location and magnitude of the corrosion damage of underground metal pipelines by stray currents includes the following steps:

- determination of the location and depth of the pipeline in the study area;

- installation along the axis of the pipeline of at least two identical sensors for measuring the magnetic field strength (tangential component);

- synchronous recording of changes in the magnetic field due to stray currents;

- comparative processing of information from all sensors;

- diagnostic conclusion.

The diagnostic report may contain both information about the hazardous area with the greatest change in the magnitude of the magnetic field caused by stray current, and an assessment of the degree of danger presented.

The distances between the sensors are selected depending on the specific task, the source data and the conditions on the track. Usually this distance is between 1 and 10,000 meters. The deviation of the sensor installation site from the vertical passing through the axis of the pipeline usually does not exceed 10% of the depth of the pipe.

The number of sensors used depends on the tasks. If the location of the insulation damage is known and it is necessary to assess the degree of danger of this damage by stray currents, then two sensors are sufficient. They are usually located above the pipeline at a distance of 10-20 meters from each other before and after damage.

If the state of the insulating coating is unknown and the boundaries of the pipeline section subject to the influence of stray currents are not defined, then in this case use the maximum possible number of sensors. Sensors are installed above the pipeline on a plot of several kilometers on both sides of a possible source of stray currents. In practice, the railroad usually acts as such a source of stray current, and the length of the sections under investigation can reach 20 km.

At each point where the sensors are installed, the distance from the sensor to the pipeline is determined. Automatically in real time or after completion of the measurement process, the direction is determined and the stray current values are calculated. By comparing the results obtained, the area between two adjacent sensors is determined where the maximum stray current draining from the pipeline occurred. If there is information about the value of insulation damage, an estimated calculation of metal losses is carried out and a conclusion is drawn on the degree of danger of insulation damage. In the absence of data on the magnitude of insulation damage, a section is selected between adjacent sensors, where the maximum stall current of the stray current has occurred. The measurements are repeated several more times (usually 2-3 times) until the length of the selected section is commensurate with the length of the possible pit.

For the effective implementation of the method, it is preferable to obtain preliminary information about the time of occurrence of stray currents (familiarize yourself with the schedule of electric trains, the operating mode of neighboring industrial enterprises, etc.).

The claimed method is preferably carried out using a device

remote magnetometry for piping diagnostics, which contains: at least two identical sensors that determine the magnetic field strength (its tangential component), means for synchronizing the inclusion and operation of sensors, means for recording and processing data. Preferably, the device contains at least three identical sensors. Additionally, the inventive device may include a means for binding on the ground (GPS or Glonass navigator) and means for determining the depth of the pipeline. As such a device, a mechanical probe, sonar, etc. can be used. A device typically includes a communications tool that synchronizes the operation of sensors when installed at a distance of 1 to 10,000 meters from each other. Sensors after installation are controlled from a single remote control, information from them comes in real time. Signals can be transmitted over wires or over radio channels. In another embodiment of the device, each of the sensors includes means for synchronizing the inclusion and means for recording data. In this case, each of the sensors is programmed and performs the inclusion, measurement, data recording independently in automatic mode. And after the measurements are completed, all information from them is copied to the analytical unit. By means here, everywhere is meant the functional part of the device. So, for example, the means for synchronizing the inclusion and operation of sensors can be performed in the form of one unit or in the form of several units, each of which is structurally included in a stand-alone device - a sensor. The device can be performed as a combination of these two options, when the signal to turn on the recording and control the operation of the sensors is carried out from a single remote control via a communication tool, and the sensors are configured to delay recording. The transfer of information to the analytical unit and its processing is carried out after completion of measurements. Preferably, the device also further comprises means for automatically calculating the value of the stray current at each point in the measured section of the pipeline. The specific design of the remote magnetometry device for piping diagnostics depends on the challenges. When examining a small section of the pipeline (not more than 40 meters), it is preferable to use a multichannel device that controls the operation of all sensors. To study long stretches, it is preferable to use autonomous sensors with the function of delayed recording and data storage.

The essence of the present invention is illustrated by the following drawings:

Figure 1 presents a block diagram of the inventive device, with a single remote control sensors and the receipt of information in real time;

Figure 2 presents a block diagram of a radio-controlled device;

Figure 3 presents a block diagram of the inventive device, with autonomous sensors;

Figure 4 presents a block diagram of the inventive device, with combined data management;

Figure 5 shows a diagram of field measurements when localizing the place of damage to the pipeline;

Figure 6 shows a diagram of field measurements in the absence of information about the place of damage to the pipeline;

Figure 7 (a), (b), (c) shows photographs of corrosion damage detected using the proposed method;

On Fig (a), (b), (c) shows photographs of corrosion damage detected using the proposed method

Remote magnetometry device for piping diagnostics can have different design. Figure 1 presents a block diagram of the inventive device, with a single remote control sensors and the receipt of information in real time. Sensors 1 of the magnetic field are installed in a selected section of the pipeline, as described above. The operation of the sensors is carried out from the control unit 2. Data from the sensors arrive in real time in block 3 of the accumulation and storage of information. Management of data flows is carried out by means of signals from block 4 synchronization of the countdown. All received information is transmitted to block 5 data analysis. There also comes information from block 6 binding to the coordinates on the ground and block 7 measuring the depth of the pipeline. Structurally, the indicated blocks 6 and 7 can be made in the form of separate devices or be a part of each of the sensors 1. Processing of the obtained data is carried out in block 5 according to a special algorithm. The results are transmitted to monitor 8 or any other device for data visualization. As results, information is obtained: on the spatial distribution of the change in the magnetic field in the selected area, on the change in the value of the stray current, on the coordinate of the place of runoff of the stray current, on the value of corrosion in this place, etc. Communication between the blocks is carried out by wire. The directions of the control signals and data streams in figure 1 are represented by arrows.

Communication between devices can also be carried out by means of radio signals (Figure 2). Then each sensor 10 is made in the form of a separate device containing directly the magnetic field sensor 11, the block 12 to the coordinates on the ground and the block 13 measuring the depth of the pipeline. The remaining functional blocks are structurally included in a separate device 14, which is controlled by the operator. The device 14 includes a data analysis unit 15, a synchronization unit 16, an information storage and storage unit 17, there is also a control unit 18 and a data visualization unit 19.

A block diagram of another embodiment of the inventive device is presented in Fig.3. In this case, each sensor 20 is made in the form of a stand-alone device, including several functional units: directly the sensor 21 for measuring the magnetic field strength; block 22 synchronization on / off; block 23 binding to coordinates on the ground; block 24 measuring the depth of the pipeline and block 25 of the accumulation and storage of information. Each of the sensors 20 is installed in a selected location and programmed to turn on at a certain point in time. Typically, all data is recorded on a flash card, which subsequently can be used in block 16 data analysis. The result is transmitted to the monitor 27.

The device may also have a combined communication scheme between the functional blocks and the control of data flows (Figure 4). Each sensor 30 includes the following functional blocks: directly a sensor 31 for measuring the magnetic field strength; block 32 binding to coordinates on the ground; block 33 measuring the depth of the pipeline and block 34 of the accumulation and storage of information. The operation of the sensors 30 is controlled from a separate device 34, including a synchronization unit 35, a data analysis unit 36, a control unit 37, and a visualization unit 38. The data obtained at the sensor 30 can then be transferred to block 34 via any electronic medium. Communication between the functional blocks is via wires or radio signals.

Based on the long-standing practice of using various types of magnetometers for measuring stray currents, both at the test site and at existing trunk pipelines, technical requirements have been developed for sensors for measuring magnetic field strength. Preferably, these are three-coordinate sensors with a measurement range for each of the three coordinates +/- 200 MkTl and a resolution of at least 0.02 MkTl. They can be controlled in manual or automatic mode (delayed recording mode); have a programmable turn-on time from 10 to 90 minutes and a recording time from 1 to 120 minutes.

Examples of the implementation of the claimed invention.

Example 1

It was known that in one of the sections of the existing pipeline there was a damage to the insulation with a length of 5 meters. It was necessary the degree of danger of corrosion under the influence of stray currents for further operation. To solve this problem, two sensors are enough, however, in order to increase the reliability of measurements, four sensors were used in practice (Figure 5). Two sensors 41 were located at a distance of 10 and 20 meters before the damage, two sensors 42 at a distance of 10 and 20 meters after the damage. At the locations of each sensor, the distances from the sensor to the axis (or upper generatrix) of the pipeline 43 were determined. The measurements started simultaneously, the readings of all four sensors were recorded synchronously. The operation of the sensors, recording, data processing and subsequent visualization was carried out using the device 44. The data obtained are the dependence of the magnetic field strength over time for four coordinates. According to well-known algorithms, the direction and magnitude of the stray current are calculated and a conclusion is drawn about the degree of danger of insulation damage. If the damage area is known, an estimated calculation of metal losses is performed.

Example 2

If necessary, to explore an unknown section of the pipeline usually use a larger number of sensors (Fig.6). The number of sensors and the distance between them depends on the length of the plot and the diagnostic tasks involved.

Using the GPS-navigator, locator and probe, the location and depths of the pipeline 51 in the selected area are specified.

Recording devices 52 are installed over the axis of the pipeline. Structurally, the device can be made as shown in FIG. 2. The deviation of the position of the sensors 53 for measuring the magnetic field strength from the axis of the pipeline depends on the diameter of the pipe and its depth, but should not exceed 10% of the depth.

Devices program for the time of delayed recording, taking into account the time required to install them at selected points.

After recording, the data is transferred to the processing unit, analysis and storage of information (not shown in the Figure). Based on the measurement results, the area between adjacent devices is determined, on which the maximum change in the stray current occurs. The measurements are repeated several more times (usually 2-3 times) until the length of the selected section is commensurate with the length of the possible pit. The final conclusion on pipeline defects and recommendations for their elimination are given after visual inspection of the excavated pipe section (pit).

Example 3

There was a task to explore the main pipeline crosses the electrified railway at a constant current. The insulation of the pipeline is film. Pipe diameter DN 400 mm, wall thickness 8 mm. The boundaries of the area affected by stray currents are not defined. At the drainage protection station, currents of up to 200 Amperes were recorded. No other data provided. It was required to find a point (a section of the pipeline with a length of not more than 5 meters) of the maximum runoff of the stray current.

For work, five single-channel devices were used.

At the first stage, the instruments were installed on a 15 km pipeline section. Operating modes of devices: delayed recording time - 1.5 hours; recording period - 1 sec., recording time - 2 hours. The coordinates of the points of installation of devices, the depth of the pipeline at the measurement points are summarized in Table 1.

Table 1. Device number Location Description Depth, m one 1,030 m to railway 1.27 2 80 m to railway 2.63 3 2 170 m after railway 2.14 four 6,320 m after railway 1,5 5 13 900 m after railway 1.28

The calculated maximum currents for each device are as follows:

Table 2. Device number Maximum current, A one 8.4 2 18.3 3 17.6 four 14,4 5 11.3

The table shows that the maximum change in currents was observed between devices No. 1 and No. 2, therefore, for the second stage, a section was chosen between the installation points of these devices. The coordinates of the points of installation of devices, the depth of the pipeline at the measurement points are summarized in Table 3.

Table 3. Device number Location Description Depth, m one 1,030 m to railway 1.27 2 725 m to railway 1.3 3 480 m to railway 2.21 four 255 m to railway 1.45 5 80 m to railway 2.63

The calculated maximum currents for each device are as follows:

Table 4. Device number Maximum current, A one 12.3 2 13.5 3 14.2 four 9.7 5 10.1

The table shows that the maximum change in currents was observed between devices No. 3 and No. 4, therefore, for the third stage, a section was selected between the installation points of these devices. The coordinates of the installation points of the devices, the depth of the pipeline at the measurement points are summarized in Table 5.

Table 5. Device number Location Description Depth, m one 480 m to railway 2.21 2 400 m to railway 1.85 3 335 m to railway 1.77 four 290 m to railway 1,5 5 255 m to railway 1.45

The calculated maximum currents for each device are as follows:

Table 6. Device number Maximum current, A one 21.5 2 15.9 3 16.3 four 17.1 5 17.8

The table shows that the maximum change in currents was observed between devices No. 1 and No. 2, therefore, for the fourth stage, a section was chosen between the installation points of these devices. The coordinates of the installation points of the devices, the depth of the pipeline at the measurement points are summarized in Table 7.

Table 7. Device no. Location Description Depth, m one 480 meters to the railway 2.21 2 460 meters to the railway 1.95 3 440 meters to the railway 1.8 four 420 meters to the railway 1,64 5 400 meters to the railway 1.85

The calculated maximum currents for each device are as follows:

Table 8. Device number Maximum current, A one 13.6 2 9,4 3 9.8 four 9.9 5 10.1

At the last, fifth stage, the devices were installed with a step of 5 meters in the area of 450 m to the railway - 480 m to the railway.

Table 9. Device number Location Description Depth, m one 480 m to railway 2.21 2 475 m to railway 2.05 3 470 m to railway 1.93 four 465 m to railway 1.87 5 460 m to railway 1.95

The calculated maximum currents for each device are as follows:

Table 10. Device number Maximum current, A one 23.5 2 23.9 3 19,4 four 19.8 5 19.8

The coordinates of the control pit are obvious from the last table: the beginning of the pit is 475 meters to the railway, the end of the pit is 470 meters to the railway.

When examining the insulation coating and the condition of the metal in the control pit, it was found:

- The insulation coating is broken due to the "tightening" of the cable during construction when laying the pipeline in a trench (Fig. 7 (a));

- On a cut of soil in the immediate vicinity (up to 15 cm) from the pipe, in the place of insulation damage, characteristic streaks of rusty color are visible - runoff lines of stray current (Fig. 7 (b));

- After removal of the damaged insulation, corrosion was detected (Fig. 7 (c)) with signs of electrocorrosion (small defect area, shiny metal inside, significant defect depth 3.2 mm (more than 30% of wall thickness). Non-destructive testing specialists recognized this defect unacceptable, it was decided to repair the defect.

Example 4

The main pipeline is crossed by an electrified direct current railway. The insulation of the pipeline is bitumen. The diameter of the pipeline is DN 800 mm, the wall thickness is 8-10 mm. The length of the site to be examined is 350 meters. No other data provided. It was required to find the points most dangerous from the point of view of corrosion by stray currents. The length of the pits should not exceed 5 meters.

For work, a multichannel device with five sensors was used (Figure 1). A section of the pipeline was marked with pegs after 5 meters; at each point, the depth was laid. The sensors were installed as follows:

stage 1 - sensor No. 1 - 0 m, No. 2 -5 m, No. 3 - 10 m, No. 4 - 15 m, No. 5 - 20 m;

stage 2 - sensor No. 1 - 20 m, No. 2 - 25 m, No. 3 - 30 m, No. 4 - 35 m, No. 5 - 40 m;

stage 3 - sensor No. 1 - 40 m, No. 2 - 45 m, No. 3 - 50 m, No. 4 - 55 m, No. 5 - 60 m; and so on until the end of the plot.

Then the measurements were repeated in the opposite direction with the same sensor installation step, but with a shift of 2.5 meters.

Choosing sections with the maximum runoff of stray current, we determined the coordinates of the pits: the first section - 70-75 meters; the second section - 132-137 meters; third section - 165-170 meters; the fourth section is 182.5-190 meters. Survey pipeline results:

Pit # 1.

The insulation condition is satisfactory, the damage area is 5 square meters. cm, caverns up to 0.5 mm (Fig. 8 (a));

Pit No. 2.

The insulation condition is satisfactory, the damage area is 17 square meters. cm, caverns up to 0.3 mm;

Pit No. 3

The insulation condition is satisfactory, the damage area is 24.4 square meters. cm, ulcerative corrosion up to 3.2 mm deep (Fig. 8 (b));

Pit No. 4.

The insulation condition is satisfactory, the damage area is 2.8 square meters. cm, ulcerative corrosion up to 2.8 mm deep; 3 sq. cm, ulcerative corrosion up to 1.5 mm deep; 30 sq. cm, ulcerative corrosion up to 1 mm deep; 100 sqm cm, ulcerative corrosion up to 1.7 mm deep (Fig. 8 (c)).

All four pits showed signs of electrocorrosion. Non-destructive testing laboratory specialists recognized defects in pits No. 3 and No. 4 as unacceptable, a decision was made to repair (cutting a pipe section).

Example 5

To test the methodology for estimating the stray current magnitude, model experiments were performed on the existing pipeline DN 400 mm in film insulation that crossed the railway. At 500 meters from the intersection with the railway, a magnetometer sensor was installed over the axis of the pipeline. The axis Y of the sensor is oriented tangentially to the axis of the pipeline. The depth of the pipeline in this place was 1.9 meters. In automatic mode, the sensor readings were recorded for 1.5 hours with a recording period of 1 s. Peak changes in the magnetic field ranged from 3 to 24 μT and a duration of 5 to 80 seconds. All changes in the magnetic field were caused only by stray currents flowing through the pipeline. To estimate the values of magnetic induction, we proceeded from the position of identical current density over the cross section of the pipeline. Then B = µ ₀ I / 2πR, where µ ₀ is the magnetic constant of the material, I is the flowing current, R is the distance from the conductor to the measurement point. All measurements were carried out in a constant magnetic field of the Earth, deformed by the metal of the pipeline, so we can only talk about relative measurements. Measurements are taken when the sensor is stationary when the current flowing through the pipeline changes. In this case, having determined the maximum and minimum values of the magnetic field induction for the selected time interval, it is possible to determine the current value at a given point in the pipeline: I = 5 × R × (B ₁ -B ₂ ), where B ₁ is the maximum value of the magnetic field induction ( in μT); In ₂ - the minimum value of the magnetic field induction (in μT). Table 11 shows the test data, the average time interval was selected 10 sec.

Table 11 Time interval, s Max / min induction values in the range, μT Estimated current value, A Start The ending 1171 1181 -10.49 / -17.02 65.3 1186 1196 -7.33 / -9.26 19.3 1243 1253 -8.9 / -17.61 87.1 1263 1273 -10.96 / -14.06 31 1318 1328 -8.42 / -10.83 24.1 1367 1377 -6.48 / -9.14 26.6 1395 1405 -8.89 / -17.71 88.2 2123 2133 -12.78 / -17.05 42.7 2141 2151 -10.55 / -16.52 59.7 2191 2201 5.08 / -10.5 155.8 2213 2223 -0.08 / -4.72 46,4 2242 2252 -1.45 / -5.02 35.7 2256 2266 -5.72 / -17.54 118.2

The maximum value of the stray current reached 156 A. In addition, the direction of the stray current (anode or cathode) was determined by the known orientation of the sensor relative to the pipeline. For processing, storing the results and performing calculations, laptop computers with the appropriate software installed on them are usually used. Autonomous computing devices may also be used.

Example 6

Based on the present invention, field magnetometers have been designed and manufactured for operation in sections of pipelines with stray currents:

- single-channel with one three-coordinate sensor (for synchronous measurements at distances between measurement points over 20 meters);

- multi-channel with the number of three-coordinate sensors up to 5 (for synchronous measurements at distances between measurement points less than 20 meters).

Devices have the following characteristics:

the maximum number of files is 32;

recording period - from 1 to 60 s;

recording time - from 1 to 90 minutes;

delayed recording time (time sufficient to install the instruments at selected points above the pipeline before recording) - from 10 to 120 minutes;

food - 6 elements of type AA;

current consumption by one sensor in recording mode - 40 mA;

permissible ambient temperature from -15 to + 40 ° C.

The main characteristics of the sensors:

number of coordinates - 3;

measuring range ± 200 MkTl;

resolution not less than 0.05 μT;

measurement error of 0.01%.

The present invention is not limited to the above examples and includes all possible cases of the implementation of the remote magnetometry device for the diagnosis of pipelines and methods of its application.

Example 7

One of the algorithms for calculating stray current values is based on the well-known fact that the induction of the magnetic field generated by a rectilinear infinite conductor with current decreases inversely with the distance from the conductor (see, for example, Evgrafova N.N., Kagan V.L. Physics course. Textbook for preparatory departments of universities. M: Higher school, 1973 - p. 284). B = µ ₀ I / 2πR, where µ ₀ is the magnetic constant, I is the current strength, R is the distance from the conductor to the measurement point.

When passing through the pipeline stray current, a sharp change in the magnetic field. The amplitude, duration and form of such a change is significantly different from any fluctuations in the natural background. As already noted in the description of the invention, the value of stray currents can reach 400A, and the change in the magnetic field will be several orders of magnitude higher than the magnitude of the induction of the Earth's natural field. In this case, having determined the maximum and minimum value during the observation of magnetic field induction, it is possible to determine the magnitude of the current, due to the flow of which the magnetic field induction has changed from B ₁ to B ₂ . I = 2πR * (B ₁ -B ₂ ) / µ ₀ , where B ₁ is the maximum value of the magnetic field induction, B ₂ is the minimum value of the magnetic field induction. If we measure the magnetic field induction in microtesla, the distance in meters, then we get the current in amperes:

I = 2πR * (B ₁ -B ₂ ) / μ ₀ = 2πR * (B ₁ -B ₂ ) 10 ^-6 / 4π * 10 ^-7 = 1 / 2R * (B ₁ -B ₂ ) × 10 = 5 * R * (B ₁ -B ₂ )

For practical measurements, the magnetic permeability of the medium (soil and air) µ = 1, so we can talk about measuring the magnetic field strength. Then, fixing the values of the magnetic field strength, it is possible to determine its change during the observation time, and, knowing the distance to the conductor (in our case, to the axis of the pipeline), we can calculate the magnitude of the current flowing.

To carry out the work, five identical magnetometers with the function of delayed recording and synchronous start-up and one five-channel magnetometer were designed and manufactured. Three-coordinate magnetoresistive sensors HMR 2300 manufactured by Honeywell (USA): modes - manual, automatic, delayed recording; recording period - from 1 to 60 seconds; deferred recording - from 11 to 90 minutes; recording time from 1 to 120 minutes; number of files - up to 32.

Below are the results of a multi-channel magnetometer with the simultaneous connection of five sensors during field trials.

In the area with stray currents, five points were chosen above the axis of the pipeline to place sensors in increments of five meters. All sensors were installed unidirectionally, while the Y axis of each sensor was tangential to a circle lying in a plane perpendicular to the axis of the pipeline, centered on the axis of the pipeline. The coordinates of the sensors binding relative to the zero point of the surveyed area were selected as follows: sensor No. 1 - 0 m, sensor No. 2 - 5 m, sensor No. 3 - 10 m, sensor No. 4 - 15 m, sensor No. 5 - 20 m.

Prior to the measurement, the depth of the pipe in the studied area was determined. The readings of all sensors were recorded in the magnetometer memory in automatic mode. Based on experience and preliminary studies of the intensity of stray currents, the following measurement parameters were established: recording time - 20 minutes, recording period of the averaged signal -1 sec.

The obtained data were processed using Microsoft Excel software tools according to the above formulas. On the graph of the change in tension over time, intervals of the maximum change in tension were selected. According to the experience of field and bench tests, it was found that it is enough to choose 10-20 time intervals to conclude that the stray current is draining. The average value of the stray current on each of the sensors was: sensor No. 1 - 7.21 A, sensor No. 2 - 7.04 A, sensor No. 3 - 6.99 A, sensor No. 4 - 6.72 A, sensor No. 5 - 7.47 A. The largest changes in current values occurred in the area between sensors No. 3 and No. 5 (7.47 - 6.99 = 0.75A), which is caused by the stray current flowing off the pipeline.

Repeated measurements were taken at this site with a shift of their position by 2.5 m. Their coordinates relative to the steel anchor point: sensor No. 1 - 2.5 m; No. 2 - 7.5 m; No. 3 - 12.5 m; No. 4 - 17.5 m; No. 5 - 22.5 m. This time, maximum runoff was detected between the sensors by sensors No. 4 and No. 5. It was decided to carry out control drilling with a long trench of 7.5 m. As a result of the inspection of the pipeline metal in the hole, a corrosion damage was found with dimensions unacceptable for further operation of the pipeline. A decision was made to replace this section of the pipeline.

The present invention is not limited to the above examples and includes all possible cases of the implementation of the remote magnetometry device for the diagnosis of pipelines and methods of its application.

Claims (12)

1. A remote magnetometry device for pipeline diagnostics, comprising at least two identical sensors for installation along the axis of the pipeline, determining the magnetic field strength, means for locating on the ground, means for determining the depth of the pipeline, means for synchronizing the inclusion and operation of sensors, recording means changes in the magnetic field caused by stray currents, and data processing. 2. The device according to claim 1, characterized in that it contains at least three sensors. 3. The device according to claim 1, characterized in that it includes a communication tool that provides synchronization of the sensors when installing sensors at a distance of 1 to 10,000 m from each other. 4. The device according to claim 1, characterized in that each of the sensors comprises a power-on synchronization unit and a data recording unit. 5. The device according to claim 1, characterized in that it further comprises means for automatically calculating the value of the stray current at each point on the measured section of the pipeline. 6. A remote magnetometry method for piping diagnostics, comprising the following steps:
determination of the location and depth of the pipeline in the study area;
installation along the axis of the pipeline, at least two identical sensors for measuring magnetic field strength;
synchronous recording of changes in the magnetic field due to stray currents; comparative processing of information from all sensors; diagnostic conclusion. 7. The method according to claim 6, characterized in that at least three identical sensors are installed and the diagnostic conclusion comprises selecting a section between two sensors with the largest change in the magnitude of the magnetic field due to stray current. 8. The method according to claim 6, characterized in that the deviation of the sensor installation from the vertical passing through the axis of the pipeline does not exceed 10% of the depth of the pipe. 9. The method according to claim 6, characterized in that the sensors are installed at a distance of 1 to 10,000 m from each other along the axis of the pipeline. 10. The method according to claim 6, characterized in that in the area with the largest change in the magnitude of the magnetic field caused by stray currents, repeated measurements are taken with shorter distances between the sensors. 11. The method according to claim 10, characterized in that repeated measurements are carried out until the distance between the sensors is less than the length of a standard pit. 12. The method according to claim 6, characterized in that it additionally determines the time of appearance of the maximum stray currents.

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