RU2514822C2 - Method to monitor internal corrosive changes of manifold pipeline and device for its realisation - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to the field of diagnostics of a linear part of pipeline systems and may be used for diagnostics of technical condition of an inner wall of manifold pipelines. Excitation and measurement coils are placed on the outer surface of the pipeline, a harmonic test signal is generated and sent to excitation coils, voltage induced in the excitation coil is amplified, and thickness of the pipeline wall is determined on the basis of the complex amplitude. Periodically they measure thickness of the pipeline wall, the produced values are compared to previously accumulated and produced as a result of modelling. As a result of regression treatment they predict time of pipeline thinning to the limit value, and monitor variation of observation conditions and correct measured parameters. The device comprises an excitation generator, a unit of measurement converters, including excitation and measurement coils, an amplifier. The device is equipped with a band-pass filter, a digital temperature sensor, arranged in close proximity to any excitation coil on the surface of the pipeline, a digital calculator, comprising a central processor, main and permanent memories, an analogue-digital converter and an input-output port.

EFFECT: higher safety of operation of a manifold pipeline.

2 cl, 2 dwg

Description

The invention relates to the field of diagnostics of the linear part of pipeline systems and can be used to diagnose the technical condition of the inner wall of the main pipelines, monitor corrosion changes in the wall thickness of the main pipeline in the most corroded sections of the main pipeline and predict the moment of thinning of the pipeline to the pre-emergency state.

Thinning of the pipeline wall under operational conditions can lead to the formation of through holes (fistulas) and the transported product to exit the pipeline. In most cases, this poses a danger to human life and the environment. There are a large number of methods for controlling corrosion changes in the external wall of a pipeline, as well as for implementing its electrochemical protection, for example [1]. Monitoring of corrosion changes in the inner wall of the pipeline under operational conditions is complicated by the fact that main pipelines are mainly made of structural steels with conductive and magnetic properties that impede the passage of test signals to the entire thickness of the test object. Therefore, the main way to monitor internal corrosion changes in pipelines is to use flaw detectors equipped with video cameras and sensors, for example [2]. The disadvantage of this approach is the need to stop supplying the transported product along the controlled section of the pipeline and, as a consequence of this, increasing the intervals between inspections and reducing the safety of operation. Analysis of information from flaw detectors is usually carried out by the operator in manual mode. The lack of automatic processing of information reduces the responsiveness to internal corrosion changes and also affects the safety of pipelines.

The known method [3] for determining the residual metal resource of the main gas pipeline, which consists in the fact that three plates are cut out of the metal of the gas pipeline, for example, from emergency reserve pipes. One of the plates is used as a reference sample, while the others are installed inside the main gas pipeline in places accessible for periodic extraction. Then they are tested and a subsequent study, the results of which determine the residual resource of the material of the main gas pipeline.

The disadvantage of this method is the need to periodically violate the tightness of the pipeline to extract a control sample and take measurements of corrosion changes, as well as the inability to monitor corrosion changes in automatic mode.

There is a known [4] method for emergency diagnostics of a main pipeline, which consists in measuring physical quantities by several sensors located uniformly along the entire length of the pipeline from the inside and outside, designed to detect the fact of a leak and determine the coordinates of its occurrence.

The disadvantage of this method is the control of only extreme values of corrosion changes that led to the leakage of transport products, as well as the use of sensors placed inside the pipeline and in contact with the transport products.

There is a known [5] method for diagnosing the technical condition of a main pipeline, which consists in monitoring, using a linear strain sensor and acoustic emission sensor, developing pipeline defects and generating an alarm signal when the correlation coefficient of the values of both sensors reaches a threshold value determined in laboratory conditions. The disadvantage of this method is the inability to assess the wall thickness of the pipeline in the current and forecast periods.

Known [6–9] are eddy current flaw detectors for non-destructive testing of longitudinally extended cylindrical products (wire, rods, pipes, etc.), containing a straight eddy current transducer (ETC) with one or more excitation coils, one or more measuring coils, harmonic or a pulse generator of excitation signals, a receiver-converter of the secondary voltage, and a processing device. Common for eddy current flaw detectors is the extraction of information about the parameters of the test object (including its thickness) from the signal induced in the measuring coil.

The known method, which consists in the fact that on the outer part of the surface of the pipeline are placed exciting and measuring coils covering the pipeline, represent the control object (the outer part of the surface of the pipe) in the form of a magnetic circuit. The electrical and magnetic parameters of this magnetic circuit, as well as its cross-sectional area, affect the secondary voltage induced in the measuring coil. A harmonic test signal is then generated, transmitted to the exciting coils, the voltage induced in the measuring coil is amplified, and the thickness of the pipe wall is determined from the complex amplitude. This method is taken as the closest analogue [8].

The disadvantage of this method is the lack of control of changes in the parameters of the pipeline during its operation due to the fact that this method is intended for a single measurement of the parameters of the pipeline. Thus, corrosion changes in the inner wall of the pipeline are not detected, which leads to increased accident rate.

Known [8] is an eddy current flaw detector, the action of which is based on the amplitude method of extracting information, containing an exciting generator, a block of measuring transducers, including exciting and measuring coils, an amplifier and an amplitude detector.

This device is taken as the closest analogue of the claimed device.

The disadvantages of this device are the low accuracy of determining the thickness of the pipe, associated with the use of a harmonic signal of one frequency and the lack of taking into account the temperature of the test object, the inability to compare current monitoring results with previously obtained and, therefore, the ability to predict the occurrence of emergency destruction of the pipeline wall, the use of manual labor by the operator to determine the presence of a defect and its characteristics, which leads to low safety tion of the pipeline.

The objective of the claimed technical solution is to increase the safety of operation of the main pipeline.

The problem is achieved due to the fact that in the method for monitoring internal corrosion changes of the main pipeline, exciting and measuring coils are placed on the external part of the pipeline surface, covering the pipeline, generate a harmonic test signal and transmit it to the exciting coils, increase the voltage induced in the measuring coil, and determine by the complex amplitude the wall thickness of the pipeline; exciting and measuring coils are placed on the surface of the pipeline, in areas most susceptible to internal corrosion, periodically measure the wall thickness of the pipeline, the obtained values are compared with previously accumulated and obtained as a result of modeling. As a result of regression processing, the time of thinning of the pipeline to the limit value is predicted; during measurements, changes in the observation conditions are monitored and the measured parameters are adjusted.

Thus, the pipeline acts as the magnetic circuit of the transformer eddy current transducer, and the EMF induced in the measuring coil will depend on the parameters of the pipeline, including its thickness. Periodic measurement of EMF, the accumulation of measured values in the memory of a digital computer and comparison with calculated values allows you to determine the residual resource of the metal wall of the pipeline and to predict the moment of thinning of the wall to the pre-emergency state.

In contrast to the closest analogue, exciting and measuring coils are placed on the surface of the pipeline in areas most susceptible to internal corrosion, periodically measuring the wall thickness of the pipeline, the obtained values are compared with previously accumulated and obtained as a result of modeling, as a result of regression processing, the time of thinning of the pipeline to limit value, in the course of measurements control changes in the observation conditions and adjustments the measured parameters.

The task is also achieved due to the fact that the inventive device for monitoring internal corrosion changes, containing an exciting generator, a block of measuring transducers, including exciting and measuring coils, and an amplifier, is equipped with a bandpass filter, a digital temperature sensor located in the immediate vicinity of any of the excitation coils on the surface of the pipeline, with a digital computer consisting of a central processor, random access memory, permanent apominayuschego devices, analog-to-digital converter and input-output ports; the exciting generator is tunable in frequency synchronously with a bandpass filter. In this case, the first output of the exciting generator is connected to the input of the first exciting coil, the output of which is connected to the input of the second exciting coil, and its output is connected to the first input of the exciting generator, the second input of the exciting generator is connected to the first output of the central processor, frequency tuning is controlled by this input . The second output of the exciting generator is connected to the first input of the bandpass filter, the reference voltage from the exciting generator is transmitted to the bandpass filter at this input, the first input of the measuring coil is connected to the first output of the amplifier, and the first output of the measuring coil is connected to the first input of the amplifier. The second output of the amplifier is connected to the first input of the analog-to-digital converter, the output of which is connected to the first input of the central processor. The output of the digital temperature sensor is connected to the second input of the central processor, the third input of the central processor is connected by a bi-directional line to the random access memory, the fourth input of the central processor is connected to the output of the permanent memory from which commands and constants are sent to the central processor. The second output of the central processor is connected to the input-output port, through which the operator can read the monitoring results located in the random access memory. The central processor can transmit this information using any of the known communication protocols.

Unlike the closest analogue, the claimed device is equipped with a band-pass filter, a digital temperature sensor located in the immediate vicinity of any of the excitation coils on the pipeline surface, a digital computer consisting of a central processor, random access memory, read-only memory, analog-to-digital converter and port input-output; the exciting generator is tunable in frequency synchronously with a band-pass filter; wherein the first output of the exciting generator is connected to the input of the first exciting coil, the output of which is connected to the input of the second exciting coil, and its output is connected to the first input of the exciting generator, the second input of the exciting generator is connected to the first output of the central processor, frequency tuning is controlled by this input ; the second output of the tunable generator is connected to the first input of the bandpass filter, the reference voltage from the exciting generator is transmitted to the bandpass filter at this input, the first input of the measuring coil is connected to the first output of the amplifier, and the first output of the measuring coil is connected to the first input of the amplifier; the second output of the amplifier is connected to the first input of the analog-to-digital converter, the output of which is connected to the first input of the central processor; the output of the digital temperature sensor is connected to the second input of the central processor; the third input of the central processor is connected via a bi-directional line to the random access memory, the fourth input of the central processor is connected to the output of the permanent memory from which commands and constants are sent to the central processor; the second output of the central processor is connected to the input-output port, through which the operator can read the monitoring results located in the random access memory, and the central processor can transmit this information using any of the known communication protocols.

EMF induced in the measuring coil is pre-amplified by an amplifier and filtered by a band-pass filter to increase noise immunity and protection against accidental interference. The algorithm of the digital computer is based on the solution of the following expression for calculating the EMF of the measuring winding [8]:

$$\dot{E}=-\mathrm{<figure-callout\; id="0"\; label="j\; \pi \; \mu "\; filenames="00000007.png"\; state="\{\{state\}\}">j\; </figure-callout>}\pi {\mu }_{}{}_0\omega w_u\frac{\dot{I}{w}_b}{l_b}{R}_u^2\left(\mathrm{one}-\eta +\eta {\mu }_a{\stackrel{}{\dot{\mu }}}_{aff}\right),\left(\mathrm{one}\right)$$

- эффективная магнитная проницаемость, определяющая степень ослабления магнитного потока за счет вихревых токов; η=(R₁/R_u)² - коэффициент заполнения, определяемый отношением площадей поперечных сечений трубопровода и трубки магнитного потока, сцепленного с измерительной катушкой; R₁ - внешний радиус трубопровода; R_u - радиус измерительной катушки.where İ is the excitation current; l _b is the length of the exciting coil; w _u , w _b is the number of turns in the measuring coil and the excitation coil; ω is the cyclic frequency of the harmonic excitation signal; µ _{a is the} relative magnetic permeability of the steel of which the pipeline is made; $${\dot{\mu }}_{aff}$$

- effective magnetic permeability, which determines the degree of attenuation of the magnetic flux due to eddy currents; η = (R ₁ / R _u ) ² - fill factor, determined by the ratio of the cross-sectional areas of the pipeline and the magnetic flux tube, coupled to the measuring coil; R ₁ is the outer radius of the pipeline; R _u is the radius of the measuring coil.

в случае однородного трубопровода имеет вид [8]Formula for determining $${\dot{\mu }}_{aff}$$

in the case of a homogeneous pipeline has the form [8]

$${\dot{\mu }}_{aff}=\frac{2\left[F_{\mathrm{eleven}}\left(x_{21};x_{22}\right)+\frac{x_{{}_{21}}}{2{\mu }_a}{F}_{01}\left(x_{21};x_{22}\right)\right]}{x_{22}\left[F_{10}\left(x_{21};x_{22}\right)+\frac{x_{{}_{21}}}{2{\mu }_a}{F}_{00}\left(x_{21};x_{22}\right)\right]},\left(2\right)$$

where the following notation is accepted:

F ₁₁ (u; ν) = K ₁ (u) I ₁ (ν) -I ₁ (u) K ₁ (ν);

F ₀₁ (u; ν) = K ₀ (u) I ₁ (ν) -I ₀ (u) K ₁ (ν);

F ₁₀ (u; ν) = K ₁ (u) I ₀ (ν) -I ₁ (u) K ₀ (ν);

F ₀₀ (u; ν) = K ₀ (u) I ₀ (ν) -I ₀ (u) K ₀ (ν);

x ₂₁ = R ₁ k; x ₂₂ = R ₂ k = (R ₁ -h) k;

$$k=\sqrt{-j\omega {\mu }_a\sigma ;}$$

I ₀ and I ₁ - modified cylindrical functions of the first kind, respectively, of the zero and first orders; K ₀ and K ₁ - modified cylindrical functions of the second kind, respectively, zero and first orders; R ₂ is the inner radius of the pipeline; h is the wall thickness of the pipeline; σ is the specific conductivity of the material of which the pipeline is made.

After placing the measuring and exciting coils on the main pipeline (coil winding can be performed simultaneously with the insulation of the pipeline), the monitoring device is configured to supply harmonic oscillations from the exciting generator in a given frequency range (for example, from 20 to 2000 Hz). The choice of frequency range is determined by the need for magnetic field penetration to the entire depth of the pipeline wall. The frequency tuning of the harmonic test signal is controlled by the central processor. The voltage proportional to the EMF of the mutual induction of the coils is amplified and supplied to the frequency-tunable bandpass filter simultaneously with the exciting generator. Next, the current or amplitude voltage value is converted into a digital code and stored in the random access memory of a digital computer. Since the specific conductivity and magnetic permeability of the structural steel of which the pipeline is made depends on its temperature, along with the measurement of the output voltage, the temperature of the pipeline is measured by a digital sensor. The measured temperature is stored in random access memory. Next, the EMF is calculated by the formula (1) for the same frequency range for which the measured data were obtained. When performing calculations, all data except µ _a and σ are known exactly and correspond to the measurement conditions. The values of μ _a and σ are known approximately and are selected to coincide with the given accuracy of the measured and calculated graphs.

To monitor corrosive changes in the wall thickness of the pipeline, the voltage induced in the measuring winding in the same frequency range as during tuning is periodically measured. Next, the calculation is performed according to formula (1), while the value of specific conductivity σ is adjusted taking into account the temperature of the pipeline at the time of measurement. Achieve the coincidence of the measured and calculated graphs by changing the wall thickness of the pipeline in the calculation formulas. A regression model is constructed for several cycles of measuring the thickness of the pipeline, which allows predicting the thinning of the pipeline to the pre-emergency state. The results of automatic control of internal corrosion changes in the pipeline through the input-output port can be transmitted to the operator or to a radio modem.

The control of internal corrosion changes in the linear part of the main pipeline is carried out in automatic mode without depressurization of the pipeline and cutting out control samples, which provides a more rapid determination of the emergency condition of the pipeline and, as a result, increases the safety of its operation.

Through the use of a band-pass filter and an exciting generator, tunable in frequency, the accuracy of determining the wall thickness of the pipeline and predicting its emergency thinning increases. A digital temperature sensor can reduce the likelihood of false alarms, since a decrease in voltage in the measuring coil can be caused not only by thinning of the pipeline, but also by a decrease in relative magnetic permeability and an increase in the conductivity of the material of which the pipeline is made. The digital computer allows not only to compare the results of current measurements with previously obtained ones, but also to simulate the process of corrosion changes and to predict the thinning of the pipeline to the pre-emergency state. The combination of distinctive elements and their relationships provides monitoring of internal corrosion changes and the ability to predict the thinning of the pipeline wall to the pre-emergency state, thereby increasing the safety of operation of trunk pipelines.

Figure 1 shows the structural diagram of a device for monitoring internal corrosion changes of the main pipeline; figure 2 shows approximate graphs of the calculated and measured values of the EMF induced in the measuring coil. The curve "measured values" corresponds to the results of voltage measurements in the measuring coil, the curve "calculated graph" corresponds to the calculation results according to formula (1) with the initial data presented on the graph. The first measurement varies the unknown data associated with the electromagnetic properties of the pipeline. In subsequent calculations, only the thickness of the pipeline changes.

The device for monitoring internal corrosion changes in the main pipeline (Fig. 1) contains a digital computer, consisting of a central processor 1, random access memory 2, read-only memory 3, analog-to-digital converter (ADC) 4 and input / output port 5; excitation generator 6, amplifier 7, band-pass filter 8, first 11 and second 13 excitation coils, measuring coil 12 and a digital temperature sensor 9.

The first output of the exciting generator is connected to the input of the first 11 of the exciting coil, the output of which is connected to the input of the second 13 of the exciting coil, and its output is connected to the first input of the exciting generator 6. The pipe 10 acts as a magnetic circuit for organizing magnetic coupling between the measuring coil 12 and the exciting coils 11 and 13. The second input of the exciting generator 6 is connected to the first output of the central processor 1, frequency tuning is controlled at this input. The second output of the exciting generator 6 is connected to the first input of the band-pass filter 8, at this input the reference voltage is transmitted to the filter. The first input of the measuring coil 12 is connected to the first output of the amplifier 7, and the first output of the measuring coil 12 is connected to the first input of the amplifier 7. The second output of the amplifier 7 is connected to the input of the analog-to-digital converter 4, the output of which is connected to the first input of the central processor 1. In the immediate In proximity to any of the excitation coils, a digital temperature sensor 9 is located directly on the pipeline surface. The output of the digital temperature sensor is connected to the second input of the central processor. The third input of the central processor 1 is connected by a bi-directional line to the random access memory 2, and the fourth input of the central processor is connected to the output of the permanent memory 3 from which commands and constants are sent to the central processor 1. The second output of the central processor is connected to the input-output port, through which the operator can read the monitoring results located in the random access memory, and the processor can transmit this information using any of the known communication protocols. A digital computer can be implemented on a microcontroller that has built-in read-only memory and memory, a built-in analog-to-digital converter and at least three input / output ports.

Information sources

1. RF patent No. 2286558, MKI G01N 17/02, 2005, published 2006.

2. USSR author's certificate No. 1629683, MKI F17D 5/00; G01B 17/02, 1989, published 1991.

3. RF patent No. 2391601, MKI F17D 5/00, 2008, published 2010.

4. RF patent No. 2382270, MKI F17D 5/02, 2008, published 2010.

5. RF patent No. 2423644, MKI F17D 5/06, 2009, published 2011.

6. USSR author's certificate No. 1116376, MKI G01N 27/90, 1983, published 1984.

7. RF patent No. 2090882, MKI G01N 27/90, 1995, published 1997.

8. Non-Destructive Testing and Diagnostics: A Guide. / V.V. Klyuyev, F.R.Sosnin, A.V. Kovalev and others; Ed. V.V. Klyueva. 2nd ed., Rev. and add. - M.: Mechanical Engineering, 2003, p. 407-408.

9. Non-destructive testing of product quality by electromagnetic methods. / Gerasimov V.G., Ostanin Yu.A., Pokrovsky A.D. et al. - M.: Energy, 1978, p. 156.

Claims (2)

1. A method for monitoring internal corrosive changes in the main pipeline, in which exciting and measuring coils are placed on the external surface of the pipeline, covering the pipeline, generate a harmonic test signal and transmit it to the exciting coils, amplify the voltage induced in the measuring coil, and determine the complex amplitude the wall thickness of the pipeline, characterized in that the exciting and measuring coils are placed on the surface of the pipeline in areas The most susceptible to internal corrosion, periodically measure the wall thickness of the pipeline, the obtained values are compared with previously accumulated and obtained as a result of modeling, as a result of regression processing, the time of thinning of the pipeline to the limit value is predicted, during measurements, changes in the observation conditions are monitored and the measured parameters are adjusted. 2. A device for monitoring internal corrosion changes in the main pipeline, containing an exciting generator, a block of measuring transducers, including exciting and measuring coils, and an amplifier, characterized in that the device is equipped with a bandpass filter, a digital temperature sensor located in the immediate vicinity of any of the exciting coils on pipeline surface, with a digital computer consisting of a central processor, random access memory, read-only memory minal device, an analog-digital converter and input-output ports; the exciting generator is tuned in frequency synchronously with the bandpass filter, while the first output of the exciting generator is connected to the input of the first exciting coil, the output of which is connected to the input of the second exciting coil, and its output to the first. the input of the exciting generator, the second input of the exciting generator is connected to the first output of the central processor, frequency tuning is controlled at this input; the second output of the exciting generator is connected to the first input of the bandpass filter, the reference voltage from the exciting generator is transmitted to the bandpass filter at this input, the first input of the measuring coil is connected to the first output of the amplifier, and the first output of the measuring coil is connected to the first input of the amplifier; the second output of the amplifier is connected to the first input of the analog-to-digital converter, the output of which is connected to the first input of the central processor; the output of the digital temperature sensor is connected to the second input of the central processor; the third input of the central processor is connected via a bi-directional line to the random access memory, the fourth input of the central processor is connected to the output of the permanent memory from which commands and constants are sent to the central processor; the second output of the central processor is connected to the input-output port.

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