Electromagnetic detection system and detection method for PCCP pipes

Abstract

The present invention relates to an electromagnetic detection system and detection method for a PCCP pipe, comprising: an excitation source circuit for generating a high-power low-frequency AC excitation signal; an intelligent monitoring layer is arranged between the prestressed steel wire layer and the protective layer of the PCCP pipe, an excitation coil and a magnetic sensor device are encapsulated in the intelligent monitoring layer, the excitation coil is used to generate a low-frequency alternating magnetic field under the excitation of the excitation signal, the prestressed steel wire layer generates an induced magnetic field under the action of the alternating magnetic field, the magnetic sensor device is used to obtain detection signals at different positions of the PCCP pipe and transmit them to a signal processing system; the signal processing system is used to process the magnetic detection signal, convert the magnetic detection signal into a digital signal, and transmit the digital signal to a main control computer; the main control computer is used to adjust the parameters of the excitation source circuit and judge whether the prestressed steel wire layer of the PCCP pipe has a broken wire problem according to the change of the digital signal. The present invention reduces the requirements for data acquisition base stations, reduces daily monitoring costs, improves detection efficiency, and does not require water outage or pressure reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent nondestructive testing, and in particular to an electromagnetic detection system and a detection method for a PCCP pipe, which are used to realize online monitoring or regular inspection of broken wires in a prestressed steel wire layer of the PCCP pipe. Background Art

[0002] Prestressed concrete cylinder pipe (PCCP) refers to a pipe made by spirally winding high-strength steel wire on a concrete pipe core with a steel cylinder and covering it with a mortar protective layer. It has the advantages of long life and anti-leakage. It is widely used in long-spacing water transmission trunks, pressure inverted siphons, urban water supply projects, industrial pressurized water transmission pipelines, power plant circulating water project sewer pipes, pressure sewage mains, etc. The strength of PCCP depends on the high-strength steel wire. The steel wire produces uniform prestress on the pipe core, which can compensate for the tensile stress generated by internal pressure and external loads. However, during operation, various reasons can cause damage or corrosion of the steel wire, which then breaks, causing the pipeline strength to decrease, and eventually leading to accidents such as pipe bursts. Therefore, the detection technology for PCCP broken wires is very important. At present, the abnormality of PCCP steel wires is mainly evaluated by the changes in acoustic, magnetic, electrical and other reactions caused by the abnormality of the internal structure of the material or the existence of defects. Its main detection technologies include hydrophone monitoring method, distributed optical fiber monitoring method and electromagnetic detection method.

[0003] The hydrophone monitoring method can be used to monitor broken wires and leaks. This method uses hydrophones to monitor abnormal acoustic emission signals caused by broken wires or leaks, and calculates the location of the abnormality based on the time difference between the signals received by two adjacent sensors. The hydrophone monitoring method can be implemented in two ways: base station type and array type. The difference between the two lies in the sensor spacing and data transmission method. The base station type has a larger spacing and is suitable for rough estimation, while the array type is generally used for detailed monitoring; the base station type uses wireless transmission while the array type uses cable transmission. The advantages of this method are easy installation and simple construction, and it is suitable for various pipe diameters. The limitations of the hydrophone monitoring method include: (1) high operating and maintenance costs, and it is only suitable for local monitoring of key pipe sections; (2) it can only monitor newly generated broken wires.

[0004] Distributed fiber optic monitoring is mainly used for online monitoring of wire breakage. It involves laying sensor optical fibers on the inner or outer wall of PCCP. By detecting the acoustic emission signals or stress changes caused by prestressed wire breakage, only one sensor optical cable is needed to achieve continuous and seamless real-time monitoring over tens of kilometers and accurately locate wire breakage events without the need to place a large number of sensors. This method is particularly suitable for long-distance water supply projects. The limitations of distributed fiber optic monitoring include: (1) it can only monitor the occurrence of new wire breakage; and (2) in order to accurately assess the wire breakage status, other detection technologies are required to determine the pipeline baseline information in advance.

[0005] The basic principles of the above two methods are based on acoustic methods, that is, detecting the acoustic signal or stress change generated when the steel wire breaks. It is impossible to obtain the broken wire status of the pipeline before the laying of the monitoring network. This leads to the following two disadvantages: (1) The pipeline needs to be evaluated by electromagnetic monitoring method before laying the monitoring network; (2) Acoustic monitoring requires 24-hour uninterrupted operation, otherwise the new broken wire generated in the pipeline during the shutdown period of the monitoring platform cannot be re-detected, which greatly increases the daily maintenance cost of the monitoring platform.

[0006] Compared with the hydrophone monitoring method and the distributed optical fiber monitoring method, the electromagnetic detection technology can not only accurately monitor the number and location of broken wires in the pipeline, but also obtain the broken wire status of the pipeline before the laying of its monitoring network.

[0007] Electromagnetic detection technology is mainly used for broken wire detection in PCCP pipelines. Remote field current / transformer coupling technology (RFEC / TC) and polar wave detection technology (P-wave) are two commonly used electromagnetic monitoring technologies in PCCP pipeline detection. Remote field current detection technology is based on the principle of electromagnetic induction. The steel cylinder or the continuously wound prestressed steel wire is equivalent to the coil. Broken wire or steel cylinder defects will cause changes in resistance value or coil coefficient. Broken wire monitoring is achieved in the following way: a detection platform with an excitation coil and a detection coil is placed inside the pipeline. When the detection platform travels through the pipeline, the excitation coil will emit an electromagnetic signal, which passes through the prestressed steel wire and returns to the detection coil. The main control computer records and analyzes the phase and amplitude of the returned electromagnetic signal and the distance and time of the detection vehicle to obtain the number and location of broken wires. Polar wave detection technology consists of a transmitting and receiving signal device, in which the transmitting device generates an electromagnetic field and the receiving device captures the electromagnetic signal passing through the PCCP pipe. Broken wires will cause abnormal electromagnetic signals. By analyzing the abnormal signals, the number and location of broken wires in the monitored pipeline can be accurately obtained. Before testing, the size and shape of the tested pipe should be calibrated to improve the accuracy of the test. Electromagnetic detection technology is usually implemented based on two detection platforms: push-type and floating-type. The push-type detection platform is suitable for the following two situations: pipeline wire breakage risk assessment before the formal use of PCCP pipelines, and wire breakage inspection and maintenance work after the pipeline is shut down; the floating platform is suitable for the detection and inspection of wire breakage on the pipe wall and siltation in the pipe under pipeline operation conditions.

[0008] For example, the invention patent with patent number CN104297337B provides a PCCP wire break detection method, including the following steps: S1: the detection vehicle moves by automatic or manual control, during which: the displacement change is recorded and detected by the measuring device; the transmitting probe continuously receives the AC signal generated by the host, and transmits the corresponding electromagnetic wave signal, thereby inducing an eddy current signal on the PCCP pipe wall; at the same time, the host uploads the AC signal to the main control computer; the receiving probe continuously responds to the eddy current signal to generate a voltage signal; S2: when it is detected that the detection vehicle has not reached the preset position, step S1 is repeated; when it is detected that the detection vehicle has reached the preset position, it stops moving, and the data acquisition card is triggered. The data acquisition card collects the voltage signal in the receiving probe and uploads it to the main control computer for display, storage and fault judgment; S3: Restart moving, repeat steps S1 and S2 until the detection of the required pipe section is completed.

[0009] The limitations of the traditional electromagnetic detection method are: (1) the platform can only enter the PCCP pipeline for detection when there is no water or the pressure is reduced, and (2) the platform needs to travel completely inside the pipeline to obtain data for the entire pipeline. Only tens of kilometers of pipeline can be detected in one day. Therefore, the traditional electromagnetic detection method will greatly limit its scope of application and cannot achieve daily monitoring of PCCP pipe broken wire status and meet the needs of frequent detection and maintenance. Summary of the invention

[0010] The purpose of the present invention is to propose an electromagnetic detection system and method for PCCP pipes to address the problem that the traditional electromagnetic detection method has a small application scope and cannot realize daily monitoring of the broken wire status of PCCP pipes and meet the needs of frequent detection and maintenance.

[0011] In order to achieve the purpose, the technical solution provided by the present invention is:

[0012] The present invention relates to an electromagnetic detection system for PCCP pipes, comprising:

[0013] An excitation source circuit, used for generating a high-power low-frequency AC excitation signal;

[0014] The intelligent monitoring layer is arranged between the prestressed steel wire layer and the protective layer of the PCCP pipe, and an excitation coil and a magnetic sensor device are encapsulated in the intelligent monitoring layer; the excitation coil is used to generate a low-frequency alternating magnetic field under the excitation of an excitation signal, and the prestressed steel wire layer generates an induced magnetic field under the action of the alternating magnetic field; the magnetic sensor device is used to obtain the magnetic field strength of the alternating magnetic field and the induced magnetic field at different positions of the PCCP pipe after superposition, and transmit the magnetic field strength at different positions as the detection signal of each position to the signal processing system;

[0015] A signal processing system is used to process the magnetic detection signal, convert the magnetic detection signal into a digital signal, and transmit the digital signal to the main control computer;

[0016] The main control computer is used to adjust the parameters of the excitation source circuit and determine whether the prestressed steel wire layer of the PCCP pipe has broken wires based on the changes in the digital signal.

[0017] Preferably, the magnetic sensor device comprises a plurality of magnetic sensors arranged at different positions of the PCCP pipe to obtain magnetic detection signals at different positions of the PCCP pipe, forming a magnetic sensor array, and the magnetic sensors are all equipped with communication lines, which extend outside the PCCP pipe and are communicatively connected to the signal processing system through cables;

[0018] The magnetic sensors are arranged in one of the following ways: horizontal placement along the axis of the PCCP pipe, oblique placement or cross placement at different wall heights of the PCCP pipe in the horizontal direction, placement around the wall of the PCCP pipe or around part of the circumference, grid placement combining horizontal placement and circumferential placement, and grid placement combining oblique placement or cross placement and circumferential placement.

[0019] Preferably, the signal processing system is used to convert the magnetic detection signals at different positions of the PCCP tube detected by each magnetic sensor into multiple groups of digital signals, and the main control computer is used to draw an electromagnetic signal background map based on the multiple groups of digital signals, run a magnetic field inversion algorithm to extract signal singularities and infer the location and number of broken wires.

[0020] Preferably, the excitation source circuit comprises:

[0021] A signal generator, used to generate a low-frequency AC signal;

[0022] Current amplifier, used to increase the power of low frequency AC signals.

[0023] Preferably, the signal processing system comprises:

[0024] Preamplifier, used to amplify the magnetic detection signal;

[0025] Filters include bandpass filters and bandstop filters. Bandpass filters are used to select magnetic detection signals with the same frequency as the excitation signal according to the frequency band of the excitation signal to eliminate the interference of low-frequency and high-frequency noise; bandstop filters are used to filter out the influence of strong interference signals according to the environment in which the PCCP pipe is located;

[0026] The phase-locked amplifier further improves the signal-to-noise ratio of the magnetic detection signal according to the frequency and phase of the excitation source circuit;

[0027] A / D converter, used to convert magnetic detection signals into digital signals;

[0028] Data acquisition card, used to collect digital signals and input them to the main control computer.

[0029] Preferably, the excitation coil is a flexible coil wound by a metal wire, and a communication line for connecting to an excitation source circuit is provided on the excitation coil. The communication line extends outside the PCCP tube and is connected to the excitation source circuit via a cable; the excitation coil is one of a circular spiral coil, a square spiral coil, a rectangular spiral coil, an elliptical spiral coil or a diamond spiral coil.

[0030] Preferably, the excitation source circuit, signal processing system and main control computer are all arranged in a ground monitoring base station.

[0031] The present invention also relates to a detection method based on the electromagnetic detection system of the PCCP pipe, comprising the following steps:

[0032] S1. Set the parameters of the excitation source circuit through the main control computer, turn on the excitation source circuit to output a high-power low-frequency AC excitation signal to the excitation coil, and the excitation coil generates a low-frequency alternating magnetic field under the excitation of the excitation signal;

[0033] S2. The prestressed steel wire layer generates an induced current and an induced magnetic field under the action of the alternating magnetic field. The magnetic sensor device obtains the magnetic field strength of the alternating magnetic field and the induced magnetic field at different positions of the PCCP pipe after superposition, and transmits the magnetic field strength at different positions as the detection signal of each position to the signal processing system;

[0034] S3. The signal processing system amplifies the magnetic detection signal, eliminates noise interference, improves the signal-to-noise ratio, and converts the magnetic detection signal into a digital signal and transmits it to the main control computer;

[0035] S4. The main control computer determines whether there is a wire breakage problem in the prestressed steel wire layer of the PCCP pipe based on the changes in the digital signal.

[0036] Preferably, the magnetic sensor device includes a plurality of magnetic sensors arranged at different positions of the PCCP tube to obtain magnetic detection signals at different positions of the PCCP tube to form a magnetic sensor array. In the step S4, the main control computer also draws an electromagnetic signal background map, runs a magnetic field inversion algorithm to extract signal singularities, and infers the position and number of broken wires based on the digital signals and the positions of the magnetic sensors in the magnetic detection array.

[0037] Preferably, the signal processing system includes a preamplifier, a filter, a lock-in amplifier, an A / D converter and a data acquisition card, and the specific steps of converting the magnetic detection signals at various positions into corresponding digital signals in S3 include:

[0038] S3.1. The magnetic sensor connects the magnetic detection signals at each position to the preamplifier to amplify the magnetic detection signals;

[0039] S3.2. The filter selects the magnetic detection signal with the same frequency as the AC signal generated by the excitation source circuit, eliminates the interference of low-frequency and high-frequency noise, and filters out the influence of strong interference signals;

[0040] S3.3. The phase-locked amplifier further improves the signal-to-noise ratio of the magnetic detection signal according to the excitation source frequency and phase;

[0041] S3.4.A / D converter converts the magnetic detection signal into a digital signal;

[0042] S3.5. The data acquisition card collects digital signals and inputs them to the main control computer.

[0043] The waveform of the excitation current output by the excitation circuit is a periodic waveform or a pulse waveform; the periodic waveform is a sine wave, a triangle wave or a square wave, and the pulse waveform is a pulse waveform composed of one or several periods of a sine wave, a triangle wave or a square wave.

[0044] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0045] 1. The excitation coil and magnetic field sensor array of the present invention are placed in the intelligent monitoring layer, which is located as a whole between the prestressed steel wire layer and the protective layer of the PCCP pipe. Since the detection platform does not need to enter the interior of the PCCP pipe for detection, this method does not require water cutoff or pressure reduction to detect wire breakage. The wire breakage of the entire PCCP pipe can be detected while the PCCP pipe is working normally, forming a real-time PCCP wire breakage monitoring network and an early warning system for PCCP pipe wire breakage.

[0046] 2. The detection range of the sensor array in the electromagnetic detection system of the PCCP pipe involved in the present invention covers the entire length of the PCCP pipe. One detection can simultaneously collect magnetic field data at different positions of the PCCP pipe, and the number and position information of broken wires can be obtained through an inversion algorithm. Compared with the traditional electromagnetic detection technology that requires the platform to move once in the PCCP pipe, it does not need to work uninterruptedly for 24 hours, and the requirements for the data acquisition base station are greatly reduced. In addition, different detection cycles and detection methods can be implemented based on the daily maintenance of different pipe ends according to factors such as the laying environment and service life of the PCCP pipe. The means are more flexible, and the daily monitoring cost can be greatly reduced, which greatly improves the detection efficiency.

[0047] 3. Compared with the hydrophone monitoring method and the distributed optical fiber monitoring method, two broken wire detection methods based on acoustic principles, the electromagnetic detection method of PCCP pipes involved in the present invention can realize the detection and evaluation of existing broken wires. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a principle block diagram of the electromagnetic detection system of the PCCP pipe of the present invention;

[0049] Figure 2 It is a schematic diagram of the structure of the PCCP pipe;

[0050] Figure 3 It is a structural diagram of the expanded state of the intelligent monitoring layer;

[0051] Figure 4 It is the structural diagram of the ground monitoring base station;

[0052] Figure 5 It is a line graph of electromagnetic detection results when there is no broken wire and when there is one broken wire.

[0053] Labeling instructions: 1-inner concrete layer, 2-steel cylinder layer, 3-outer concrete layer, 4-prestressed steel wire layer, 5-intelligent monitoring layer, 6-protective layer, 7-excitation coil, 8-magnetic sensor, 9-ground monitoring base station, 10-PCCP pipe. DETAILED DESCRIPTION

[0054] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0055] See attached Figure 1 As shown, this embodiment relates to an electromagnetic detection system for PCCP pipes, including an excitation source circuit, an intelligent monitoring layer, a signal processing system and a main control computer.

[0056] See attached Figure 1 As shown, the excitation source circuit is used to generate a high-power low-frequency AC excitation signal, which includes a signal generator and a current amplifier connected in sequence. The signal generator is used to generate a low-frequency AC excitation signal, and the current amplifier is used to increase the power of the excitation signal.

[0057] See attached Figure 2 As shown, the structure of the PCCP pipe 10 includes an inner concrete layer 1, a steel cylinder layer 2, an outer concrete layer 3, a prestressed steel wire layer 4 and a protective layer 6 from the inside to the outside. The intelligent monitoring layer 5 is arranged between the prestressed steel wire layer 4 and the protective layer 6 of the PCCP pipe 10. The intelligent monitoring layer 5 encapsulates an excitation coil 7 and a magnetic sensor device. The excitation coil 7 is connected to the current amplifier in the excitation source circuit for communication. Figure 3As shown, the excitation coil 7 is a flexible coil wound by a metal wire. A communication line for connecting to the excitation source circuit is provided on the excitation coil 7. The communication line extends to the outside of the PCCP pipe and is connected to the excitation source circuit through a cable. The excitation coil 7 is a circular spiral coil, a square spiral coil, a rectangular spiral coil, an elliptical spiral coil or a diamond spiral coil. The present embodiment uses a circular spiral coil. The excitation coil 7 is used to generate a low-frequency alternating magnetic field under the excitation of an excitation signal. The prestressed steel wire layer generates an induced magnetic field under the action of the alternating magnetic field. The magnetic sensor device is used to obtain the magnetic field strength of the alternating magnetic field and the induced magnetic field at different positions of the PCCP pipe after superposition, and transmit the magnetic field strength at different positions as the detection signal of each position to the signal processing system. Refer to the attached Figure 3 As shown, the magnetic sensor device includes a plurality of magnetic sensors 8 arranged at different positions of the PCCP pipe to obtain magnetic detection signals at different positions of the PCCP pipe, forming a magnetic sensor array, and the magnetic sensors 8 are all equipped with communication lines, which extend outside the PCCP pipe and are communicatively connected to the signal processing system through cables; the arrangement of the magnetic sensors 8 adopts one of the following methods: horizontal placement along the axis of the PCCP pipe, oblique placement or cross placement at different wall heights of the PCCP pipe in the horizontal direction, placement around the wall of the PCCP pipe or around part of the circumference, grid placement combining horizontal placement and circumferential placement, and grid placement combining oblique placement or cross placement and circumferential placement. The present embodiment adopts the arrangement method of horizontal placement along the axis of the PCCP pipe.

[0058] See attached Figure 1 As shown, the signal processing system is communicatively connected with the magnetic sensor device. The signal processing system is used to process the magnetic detection signals of different positions of the PCCP tube detected by each magnetic sensor, convert the magnetic detection signals into digital signals, and transmit the digital signals to the main control computer. The signal processing system includes a preamplifier, a filter, a phase-locked amplifier, an A / D converter and a data acquisition card connected in sequence. The preamplifier is used to amplify the magnetic detection signal; the filter includes a bandpass filter and a bandstop filter. The bandpass filter is used to select the magnetic field signal with the same frequency as the excitation signal according to the frequency band of the excitation signal to eliminate the interference of low-frequency and high-frequency noise; the bandstop filter is used to filter out the influence of strong interference signals according to the environment in which the PCCP tube is located; the phase-locked amplifier further improves the signal-to-noise ratio of the magnetic detection signal according to the frequency and phase of the excitation source circuit; the A / D converter is used to convert the magnetic detection signal into a digital signal; the data acquisition card is used to collect the digital signal and input it to the main control computer.

[0059] See attached Figure 1As shown, the main control computer is respectively connected to the excitation source circuit and the signal processing system for communication. The main control computer is used to adjust the parameters of the excitation source circuit, determine whether the prestressed steel wire layer of the PCCP pipe has broken wires according to the changes in the digital signal, draw an electromagnetic signal background map according to multiple groups of digital signals, run the magnetic field inversion algorithm to extract signal singularities and infer the location and number of broken wires.

[0060] The electromagnetic detection system of PCCP pipe needs to be debugged before detection. The debugging steps are as follows:

[0061] 1) The part of the electromagnetic detection system of the PCCP tube installed in the ground monitoring base station is placed in a mobile monitoring vehicle to form a mobile monitoring platform, including an excitation source circuit, a signal processing system, a main control computer and its supporting connection lines; the excitation source circuit in the mobile monitoring vehicle is connected to the excitation coil 7 of the intelligent PCCP tube, and the signal processor is connected to the data acquisition lines of each magnetic sensor in the tube, and power is supplied to the system at the same time;

[0062] 2) Collect electromagnetic detection signals of unburied PCCP pipe steel wires one by one to obtain blank signal background (background signal when there is no broken wire); check the electromagnetic signal singularity (abnormal signal mutation position) to eliminate the impact of PCCP pipe production, intelligent monitoring layer packaging and device defects on subsequent electromagnetic monitoring;

[0063] 3) When burying the PCCP pipe, extend the PCCP pipe intelligent monitoring layer connection line to the ground. Repeat step 3) when the PCCP pipe is officially working to obtain the blank signal background after burial. This background includes the impact of the PCCP pipe working environment on the magnetic detection signal. After being recorded in detail, it will serve as a reference background for subsequent electromagnetic detection;

[0064] 4): Refer to the attached Figure 4 As shown, a ground monitoring base station 9 is established at an appropriate location, and an excitation source circuit, a signal processing system, a main control computer, corresponding lines and other supporting hardware equipment are installed. The base station is connected to the equipment in the monitoring layer 5 of the PCCP pipe 10 of the corresponding pipe section to complete the debugging of the corresponding equipment.

[0065] The present invention relates to a detection method based on an electromagnetic detection system for PCCP pipes, comprising the following steps:

[0066] S1. Setting the parameters of the excitation source circuit through the main control computer, turning on the excitation source circuit and outputting a stable high-power low-frequency AC excitation signal to the excitation coil, the excitation coil generates a low-frequency alternating magnetic field under the excitation of the excitation signal, the excitation signal output by the excitation circuit is an excitation current with a periodic waveform or a pulse waveform, the periodic waveform can be a sine wave, a triangular wave or a square wave, the pulse waveform can be a pulse waveform composed of one or several periods of a sine wave, a triangular wave or a square wave;

[0067] S2. The prestressed steel wire layer generates an induced current under the action of the alternating magnetic field. The magnetic sensor device obtains the magnetic field strength of the alternating magnetic field and the induced magnetic field at different positions of the PCCP pipe after superposition, and transmits the magnetic field strength at different positions as the detection signal of each position to the signal processing system;

[0068] S3. The signal processing system amplifies the magnetic detection signal, eliminates noise interference, improves the signal-to-noise ratio, and converts the magnetic detection signal into a digital signal and transmits it to the main control computer. The specific steps include:

[0069] S3.1. The magnetic sensor connects the magnetic detection signals at each position to the preamplifier to amplify the magnetic detection signals;

[0070] S3.2. The filter selects the magnetic detection signal with the same frequency as the AC signal generated by the excitation source circuit, eliminates the interference of low-frequency and high-frequency noise, and filters out the influence of strong interference signals;

[0071] S3.3. The phase-locked amplifier further improves the signal-to-noise ratio of the magnetic detection signal according to the excitation source frequency and phase;

[0072] S3.4.A / D converter converts the magnetic detection signal into a digital signal;

[0073] S3.5. The data acquisition card collects digital signals and inputs them to the main control computer;

[0074] S4. The main control computer determines whether the wire is broken according to the changes in the digital signal, and draws the electromagnetic signal background map according to each digital signal and the position of each magnetic sensor in the magnetic detection array, runs the magnetic field inversion algorithm to extract the signal singularity, and calculates the position and number of broken wires.

[0075] The electromagnetic detection system of the above-mentioned PCCP pipe can perform online monitoring of the PCCP pipe, that is, the excitation coil generates an excitation signal 24 hours a day, and the magnetic sensor device senses the detection signal 24 hours a day, thereby realizing online monitoring. When the prestressed steel wire layer breaks at a certain moment, the main control computer will promptly feedback the location and number of the broken wires, so as to facilitate timely assessment of the safety of the PCCP pipe and implementation of maintenance work on the dangerous pipe sections found.

[0076] The electromagnetic detection system of the PCCP pipe can also perform periodic detection on the PCCP pipe. The detection process includes: formulating different daily detection cycles for different pipe sections according to the service life, working years, working environment and previous broken wire detection status of the PCCP pipe to ensure the normal operation of the PCCP pipe and monitor the safety of the PCCP pipe; regularly performing electromagnetic detection on the corresponding pipe sections according to the formulated detection cycle, i.e., steps S2 to S4, recording the detection data and evaluating the safety of the PCCP pipe; and performing maintenance work on dangerous pipe sections.

[0077] In this embodiment, the model of the PCCP tube to be detected is PCCPDE-1400, and the dimensions of the excitation coil 7 are: inner diameter 23 cm, outer diameter 30 cm, number of coil turns 500, and the excitation coil 7 is located at the center of the PCCP tube axis. The excitation source circuit is set as follows: the excitation frequency is 73 Hz, the output waveform is a sine wave, and the effective value of the current output is 0.8 A. The excitation circuit is kept stable and continuously output, and the driving coil generates an alternating magnetic field. The magnetic sensor device is on the other side of the PCCP tube opposite to the excitation coil 7. The magnetic detector type is a tunnel magnetoresistive sensor (TMR), which is evenly placed horizontally along the axis of the PCCP tube. Adjacent sensors are 10 cm apart. The sensors are powered in parallel by an 8V DC power supply, and the data output line is connected to a phase-locked amplifier. The sensitivity of the phase-locked amplifier is 200, and the integration time is 500ms. The data collected by each magnetic sensor is then plotted into a graph by a computer, as shown in the attached figure. Figure 5 These are the results of electromagnetic detection when there is no broken wire and when there is one broken wire. The position of the broken wire is the horizontal coordinate 0. It can be seen that there is a specific peak at the position of the broken wire in the figure, which realizes the electromagnetic detection of the broken wire.

[0078] The present invention is described in detail above in conjunction with the embodiments, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. An electromagnetic detection system for PCCP pipes, characterized in that: It includes: An excitation source circuit, used for generating a high-power low-frequency AC excitation signal; The intelligent monitoring layer is arranged between the prestressed steel wire layer and the protective layer of the PCCP pipe, and an excitation coil and a magnetic sensor device are encapsulated in the intelligent monitoring layer; the excitation coil is used to generate a low-frequency alternating magnetic field under the excitation of an excitation signal, and the prestressed steel wire layer generates an induced magnetic field under the action of the alternating magnetic field; the magnetic sensor device is used to obtain the magnetic field strength of the alternating magnetic field and the induced magnetic field at different positions of the PCCP pipe after superposition, and transmit the magnetic field strength at different positions as the detection signal of each position to the signal processing system; The magnetic sensor device includes a plurality of magnetic sensors arranged at different positions of the PCCP pipe to obtain magnetic detection signals at different positions of the PCCP pipe, forming a magnetic sensor array. The magnetic sensors are all equipped with communication lines, which extend outside the PCCP pipe and are connected to the signal processing system through cables. The magnetic sensors are arranged in one of the following ways: horizontal placement along the PCCP pipe axis, oblique placement or cross placement at different wall heights of the PCCP pipe in the horizontal direction, placement around the PCCP pipe wall or around part of the circumference, grid placement combining horizontal placement and circumferential placement, and grid placement combining oblique placement or cross placement and circumferential placement. The signal processing system is used to process the magnetic detection signals, convert the magnetic detection signals at different positions of the PCCP tube detected by each magnetic sensor into multiple groups of digital signals, and transmit the digital signals to the main control computer; The main control computer is used to adjust the parameters of the excitation source circuit, determine whether the prestressed steel wire layer of the PCCP pipe has broken wires based on the changes in the digital signal, draw the electromagnetic signal background map based on multiple sets of digital signals, run the magnetic field inversion algorithm to extract signal singularities and calculate the location and number of broken wires.

2. The electromagnetic detection system for PCCP pipe according to claim 1, characterized in that: The excitation source circuit comprises: A signal generator, used to generate a low-frequency AC signal; Current amplifier, used to increase the power of low frequency AC signals.

3. The electromagnetic detection system for PCCP pipe according to claim 1, characterized in that: The signal processing system comprises: Preamplifier, used to amplify the magnetic detection signal; Filters include bandpass filters and bandstop filters. Bandpass filters are used to select magnetic detection signals with the same frequency as the excitation signal according to the frequency band of the excitation signal to eliminate the interference of low-frequency and high-frequency noise; bandstop filters are used to filter out the influence of strong interference signals according to the environment in which the PCCP pipe is located; The phase-locked amplifier further improves the signal-to-noise ratio of the magnetic detection signal according to the frequency and phase of the excitation source circuit; A / D converter, used to convert magnetic detection signals into digital signals; Data acquisition card, used to collect digital signals and input them to the main control computer.

4. The electromagnetic detection system for PCCP pipe according to claim 1, characterized in that: The excitation coil is a flexible coil wound by a metal wire, and a communication line for connecting to an excitation source circuit is provided on the excitation coil. The communication line extends outside the PCCP tube and is connected to the excitation source circuit through a cable; the excitation coil is one of a circular spiral coil, a square spiral coil, a rectangular spiral coil, an elliptical spiral coil or a diamond spiral coil.

5. The electromagnetic detection system for PCCP pipe according to claim 1, characterized in that: The excitation source circuit, signal processing system and main control computer are all arranged in a ground monitoring base station.

6. A detection method based on the electromagnetic detection system of PCCP pipe according to claim 1, characterized in that: It includes the following steps: S1. Set the parameters of the excitation source circuit through the main control computer, turn on the excitation source circuit to output a high-power low-frequency AC excitation signal to the excitation coil, and the excitation coil generates a low-frequency alternating magnetic field under the excitation of the excitation signal; S2. The prestressed steel wire layer generates an induced current and an induced magnetic field under the action of the alternating magnetic field. The magnetic sensor device obtains the magnetic field strength of the alternating magnetic field and the induced magnetic field at different positions of the PCCP pipe after superposition, and transmits the magnetic field strength at different positions as the detection signal of each position to the signal processing system; The magnetic sensor device includes a plurality of magnetic sensors arranged at different positions of the PCCP pipe to obtain magnetic detection signals at different positions of the PCCP pipe, forming a magnetic sensor array; S3. The signal processing system amplifies the magnetic detection signal, eliminates noise interference, improves the signal-to-noise ratio, and converts the magnetic detection signal into a digital signal and transmits it to the main control computer; S4. The main control computer determines whether there is a problem of broken wires in the prestressed steel wire layer of the PCCP pipe based on the changes in the digital signal. According to the digital signals and the positions of each magnetic sensor in the magnetic detection array, it draws the electromagnetic signal background map, runs the magnetic field inversion algorithm to extract the signal singularities, and calculates the position and number of broken wires.

7. The detection method based on the electromagnetic detection system of PCCP pipe according to claim 6 is characterized in that: The signal processing system includes a preamplifier, a filter, a lock-in amplifier, an A / D converter and a data acquisition card. The specific steps of converting the magnetic detection signals at various positions into corresponding digital signals in S3 include: S3.

1. The magnetic sensor connects the magnetic detection signals at various positions to the preamplifier to amplify the magnetic detection signals; S3.

2. The filter selects the magnetic detection signal with the same frequency as the AC signal generated by the excitation source circuit, eliminates the interference of low-frequency and high-frequency noise, and filters out the influence of strong interference signals; S3.

3. The phase-locked amplifier further improves the signal-to-noise ratio of the magnetic detection signal according to the frequency and phase of the excitation source; S3.

4. A / D converter converts the magnetic detection signal into a digital signal; S3.

5. The data acquisition card collects digital signals and inputs them to the main control computer.

Images