Acoustic emission internal detection method and equipment for corrosion of bottom plate of large liquid storage tank

Abstract

The present invention discloses an acoustic emission internal detection method and device for corrosion of the bottom plate of a large liquid-carrying storage tank, and relates to the field of tank bottom plate detection. An acoustic emission sensor and a hydroacoustic transducer are mounted on a tank robot. First, the acoustic emission sensor collects the acoustic emission signal generated by the hydroacoustic transducer, and the attenuation coefficient of the acoustic emission signal when the hydroacoustic transducer propagates through the medium is calculated, thereby determining the step distance of the tank robot. Then, after the tank robot travels a step distance on the tank bottom plate, the acoustic emission sensor collects the acoustic emission signal generated by the tank bottom plate, and finally, according to the intensity characteristic parameters and activity characteristic parameters of the acoustic emission signal collected after each step distance, the location and degree of corrosion of the tank bottom plate are determined. By mounting an acoustic emission sensor and a hydroacoustic transducer on the robot, the present invention integrates the advantages of the acoustic emission technology and the tank robot technology, and realizes comprehensive detection and evaluation of the real-time corrosion state of the tank bottom plate.

Description

Technical Field

[0001] The invention relates to the field of tank bottom plate detection, and in particular to an acoustic emission internal detection method and equipment for bottom plate corrosion of a large liquid-carrying tank. Background Art

[0002] Atmospheric pressure storage tanks are important storage and transportation equipment in the field of petroleum and chemical industry. Corrosion is the main cause of failure and damage of steel storage tanks. Due to its hidden nature, it is the least likely to be detected by management personnel. And as the service time of the storage tank increases, the degree of damage increases. In order to prevent it before it happens, it is necessary to regularly inspect the bottom plate of the storage tank.

[0003] The detection of tank bottom corrosion can be divided into open tank detection and online detection. Open tank detection is the most commonly used method for regular inspection of tank bottoms. It has the advantages of comprehensive detection, but it requires stopping production, pouring materials, cleaning tanks, replacing tanks, and then allowing people to enter. Therefore, the detection process lasts for a long time, the workload is large, and the economic cost is high. Online detection avoids the shortcomings of open tank detection. However, the commonly used online detection technologies such as acoustic emission and tank bottom detection robot technology also have certain problems.

[0004] Acoustic emission technology mainly detects the acoustic emission signals generated by corrosion of the tank bottom plate by installing a certain number of sensors at a certain distance from the tank outer wall plate to the bottom plate, and judges the severity of tank bottom corrosion and determines the location of the corrosion area based on the characteristic parameters of the acoustic emission signals. However, due to the limited propagation distance of the acoustic emission signals of tank bottom corrosion, with the development of large-scale storage tanks, the acoustic emission detection range may not be able to cover the entire bottom plate, which makes this technology face the problem of missed detection.

[0005] The existing tank bottom plate inspection robot technology uses ultrasonic, magnetic flux leakage, pulse eddy current and other sensors to measure the tank bottom plate wall thickness or metal remainder during the robot's movement, thereby quantitatively determining the degree of tank bottom plate corrosion. However, these methods can only identify areas where corrosion has occurred, but cannot determine whether these areas are still corroding or whether the corrosion is severe. Summary of the invention

[0006] The purpose of the present invention is to provide an acoustic emission internal detection method and equipment for corrosion of the bottom plate of a large liquid-carrying storage tank. By carrying an acoustic emission sensor and a hydroacoustic transducer on a tank robot, comprehensive detection and evaluation of the real-time corrosion status of the tank bottom plate can be achieved.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] An acoustic emission internal detection method for bottom plate corrosion of a large liquid storage tank comprises:

[0009] At least two acoustic emission sensors and one water acoustic transducer are installed at the bottom of the tank robot along the traveling direction of the tank robot; wherein the water acoustic transducer is adjacent to one of the acoustic emission sensors;

[0010] After the tank robot is lowered into the tank, the hydroacoustic transducer moves to the bottom plate, and the acoustic emission sensor collects the acoustic emission signal generated by the hydroacoustic transducer, and calculates the attenuation coefficient of the acoustic emission signal when it propagates from the hydroacoustic transducer through the medium according to the acoustic emission signal and the relative position of the hydroacoustic transducer and the acoustic emission sensor;

[0011] Determining the stepping distance of the tank robot according to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal;

[0012] After the tank robot travels a step distance on the tank bottom plate, all acoustic emission sensors collect the acoustic emission signals generated by the tank bottom plate;

[0013] The location and degree of corrosion on the bottom plate of the tank are determined based on the intensity characteristic parameters and activity characteristic parameters of the acoustic emission signal collected at each step distance.

[0014] Optionally, after the tank robot is lowered into the tank, the water acoustic transducer moves to the bottom plate, the acoustic emission sensor collects the acoustic emission signal generated by the water acoustic transducer, and according to the acoustic emission signal and the relative position of the water acoustic transducer and the acoustic emission sensor, calculates the attenuation coefficient of the acoustic emission signal when it propagates through the medium from the water acoustic transducer, specifically including:

[0015] The hydroacoustic transducer carried by the tank robot is moved to the bottom plate of the tank via the telescopic rod, and generates an acoustic emission signal under the excitation of the pulse voltage;

[0016] The i-th acoustic emission sensor and the j-th acoustic emission sensor adjacent to the underwater acoustic transducer receive the acoustic emission signal generated by the underwater acoustic transducer;

[0017] According to the acoustic emission signals received by the i-th acoustic emission sensor and the j-th acoustic emission sensor, and the relative position of the underwater acoustic transducer and the i-th acoustic emission sensor, the formula is used Calculate the attenuation coefficient β corresponding to the i-th acoustic emission sensor i ; In the formula, a i is the amplitude of the acoustic emission signal received by the i-th acoustic emission sensor, b j is the amplitude of the acoustic emission signal received by the jth acoustic emission sensor, x ij is the distance between the i-th acoustic emission sensor and the j-th acoustic emission sensor, y i is the vertical distance from the ith acoustic emission sensor to the underwater acoustic transducer;

[0018] The average value of the attenuation coefficients corresponding to all acoustic emission sensors is taken as the attenuation coefficient when the acoustic emission signal propagates from the tank bottom plate through the medium.

[0019] Optionally, determining the stepping distance of the tank robot according to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal specifically includes:

[0020] According to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal, the formula Determine the measurement range F of the acoustic emission sensor; where β is the attenuation coefficient of the acoustic emission signal when it propagates from the tank bottom plate through the medium, m1 is the amplitude of the corrosion acoustic emission signal, and m th is the threshold value;

[0021] A value smaller than the measuring range is selected as the step distance.

[0022] Optionally, the stepping distance of the tank robot is determined according to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal, and then the method further includes:

[0023] According to the travel route and stepping distance of the tank robot, the detection area after each stepping distance of the tank robot is marked.

[0024] Optionally, the step of determining the location and degree of corrosion of the bottom plate of the storage tank according to the intensity characteristic parameters and activity characteristic parameters of the acoustic emission signal collected at each stepping distance specifically includes:

[0025] Obtain the active characteristic parameters of the material with the same material as the tank bottom plate during the corrosion process in the laboratory, and form a corresponding table between the active characteristic parameters and the corrosion degree level;

[0026] Determine the location of the tank bottom corrosion area based on the intensity characteristic parameters of the collected acoustic emission signals;

[0027] According to the active characteristic parameters of the collected acoustic emission signals, the corrosion degree level of the corrosion area of ​​the tank bottom plate is determined by looking up the corresponding table of active characteristic parameters and corrosion degree levels.

[0028] Optionally, the intensity characteristic parameters include amplitude, energy and root mean square voltage value of the acoustic emission signal;

[0029] The activity characteristic parameters include the number of impacts and the number of ringings of the acoustic emission signal.

[0030] An acoustic emission internal detection device for bottom plate corrosion of a large liquid-carrying storage tank, comprising: a storage tank robot, an acoustic emission acquisition card, a host computer, an underwater acoustic transducer and at least two acoustic emission sensors;

[0031] At least two acoustic emission sensors are sequentially installed at the bottom of the tank robot along the traveling direction of the tank robot; the acoustic emission acquisition card is arranged inside the tank robot or outside the tank; the water acoustic transducer is mounted on the tank robot, and the water acoustic transducer is adjacent to one of the acoustic emission sensors;

[0032] The hydroacoustic transducer is used to generate acoustic emission signals under pulse voltage excitation after the tank robot is lowered into the tank;

[0033] At least two acoustic emission sensors are used to collect the acoustic emission signals and convert the acoustic emission signals into acoustic emission electrical signals;

[0034] The signal input end of the acoustic emission acquisition card is connected to at least two acoustic emission sensors, and the signal output end of the acoustic emission acquisition card is connected to the host computer; the acoustic emission acquisition card is used to collect the acoustic emission electrical signal and transmit it to the host computer;

[0035] The host computer is used to determine the stepping distance of the tank robot, the location where corrosion occurs on the tank bottom plate, and the degree of corrosion according to the acoustic emission electrical signal.

[0036] Optionally, at least two of the acoustic emission sensors are installed at the bottom of the tank robot, and at least two of the acoustic emission sensors are evenly distributed along the moving direction of the tank robot;

[0037] The water acoustic transducer is installed at the bottom of the tank robot through a telescopic rod, and the water acoustic transducer is closely adjacent to one of the acoustic emission sensors.

[0038] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0039] The present invention discloses an acoustic emission internal detection method and device for corrosion of the bottom plate of a large liquid-carrying storage tank. An acoustic emission sensor and a hydroacoustic transducer are mounted on a storage tank robot. First, the acoustic emission sensor collects the acoustic emission signal generated by the hydroacoustic transducer, and the attenuation coefficient of the acoustic emission signal when the hydroacoustic transducer propagates through a medium is calculated, thereby determining the stepping distance of the storage tank robot. Then, after the storage tank robot travels a stepping distance on the storage tank bottom plate, the acoustic emission sensor collects the acoustic emission signal generated by the storage tank bottom plate. Finally, according to the intensity characteristic parameters and activity characteristic parameters of the acoustic emission signal collected for each stepping distance, the location and degree of corrosion of the storage tank bottom plate are determined. By mounting an acoustic emission sensor on the robot, the present invention integrates the advantages of the acoustic emission technology and the storage tank robot technology, and realizes comprehensive detection and evaluation of the real-time corrosion state of the storage tank bottom plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0041] Figure 1 A flow chart of an acoustic emission internal detection method for bottom plate corrosion of a large liquid storage tank provided by an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of the installation of an acoustic emission sensor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The purpose of the present invention is to provide an acoustic emission internal detection method and equipment for corrosion of the bottom plate of a large liquid-carrying storage tank. By carrying an acoustic emission sensor and a hydroacoustic transducer on a tank robot, comprehensive detection and evaluation of the real-time corrosion status of the tank bottom plate can be achieved.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] In view of the shortcomings of acoustic emission technology and tank bottom plate detection robot technology, the present invention integrates acoustic emission technology and robot technology, and proposes an acoustic emission internal detection method for bottom plate corrosion of large liquid-carrying tanks. By installing an acoustic emission sensor on the tank bottom plate detection robot, comprehensive detection and evaluation of the real-time corrosion status of the tank bottom plate is achieved.

[0047] The embodiment of the present invention provides an acoustic emission internal detection method for corrosion of the bottom plate of a large liquid storage tank, such as Figure 1 As shown, including:

[0048] Step 1: Install at least two acoustic emission sensors and one hydroacoustic transducer on the bottom of the tank robot along the travel direction of the tank robot.

[0049] At least two acoustic emission sensors and one water acoustic transducer are installed on the bottom of the tank bottom plate detection robot (tank robot). The acoustic emission sensors are evenly distributed along the movement direction of the tank bottom plate detection robot, with their detection surfaces facing the tank bottom plate, and the water acoustic transducer is adjacent to one of the acoustic emission sensors, such as Figure 2 shown.

[0050] Step 2: After the tank robot is lowered into the tank, the acoustic emission sensor collects the acoustic emission signal generated by the hydroacoustic transducer, and calculates the attenuation coefficient of the acoustic emission signal when it propagates from the hydroacoustic transducer through the medium based on the acoustic emission signal and the relative position of the hydroacoustic transducer and the acoustic emission sensor.

[0051] After the tank bottom plate detection robot is placed on the tank bottom plate, the tank liquid level is at least higher than the detection surface of the sensor. A pulse voltage with the same amplitude and energy is applied to the hydroacoustic transducer to excite the sound wave signal. Since the hydroacoustic transducer generates a uniform acoustic emission signal within the hemispherical surface, the acoustic emission signal generated by it is received by each sensor. The attenuation coefficient β of the acoustic emission signal in the tank medium is calculated based on the amplitude of the acoustic emission signal collected by each sensor and the relative distance between the sensor and the hydroacoustic transducer. The attenuation coefficient thus measured avoids the influence of factors such as the type of medium in the tank, medium unevenness, and stratification on the attenuation coefficient.

[0052] The specific calculation method of the attenuation coefficient is:

[0053] The hydroacoustic transducer carried by the tank robot is moved to the bottom plate of the tank via the telescopic rod, and generates an acoustic emission signal under the excitation of the pulse voltage;

[0054] The i-th acoustic emission sensor and the j-th acoustic emission sensor adjacent to the underwater acoustic transducer receive the acoustic emission signal generated by the underwater acoustic transducer;

[0055] According to the acoustic emission signals received by the i-th acoustic emission sensor and the j-th acoustic emission sensor, and the relative position of the underwater acoustic transducer and the i-th acoustic emission sensor, the formula is used Calculate the attenuation coefficient β corresponding to the i-th acoustic emission sensor i ; In the formula, a i is the amplitude of the acoustic emission signal received by the i-th acoustic emission sensor, b j is the amplitude of the acoustic emission signal received by the jth acoustic emission sensor, x ij is the distance between the i-th acoustic emission sensor and the j-th acoustic emission sensor, y i is the vertical distance from the ith acoustic emission sensor to the underwater acoustic transducer;

[0056] The average value of the attenuation coefficients corresponding to all acoustic emission sensors is taken as the attenuation coefficient β when the acoustic emission signal propagates from the tank bottom plate through the medium.

[0057] Step 3: Determine the stepping distance of the tank robot according to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal.

[0058] The measurement range of the acoustic emission sensor is determined based on the attenuation coefficient of the acoustic emission signal when it propagates from the tank bottom plate through the medium and the amplitude of the tank bottom plate corrosion acoustic emission signal. Due to the acoustic emission signal collection, the tank bottom plate detection robot is in a stopped state. Based on the measurement range, the stepping distance of the tank bottom plate detection robot is determined.

[0059] Among them, the amplitude of the acoustic emission signal generated by corrosion is generally not greater than 75dB. Assuming that the amplitude of the corrosion acoustic emission signal is m1dB, the attenuation coefficient is β, and the threshold value is m th dB, the measurement range is (m1-m th ) / β. The stepping distance can be smaller than the measuring range.

[0060] Mark each detection area according to the robot's route and step. Take the robot's route as the coordinate system, and name the position when the robot stops moving for detection according to a certain rule, and use this name as a mark. For example, take the robot's starting position as the origin, and name this point "1-0". After detection at this point, the robot steps Tm, then stops moving, and starts detection at a new position. This position is named "1-1", and so on. The position after the robot moves nTm is named "1-n". When performing acoustic emission detection, when the robot is at the "0" point, the acoustic emission data is named "0" point, and when the robot is at the "1-n" point, the acoustic emission data is named "1-n". The acoustic emission signal data is named consistent with the tag name or corresponds one to one. Then the collected corrosion acoustic emission signal data is matched with the collection position.

[0061] Step 4: After the tank robot travels a step distance on the tank bottom plate, all acoustic emission sensors collect the acoustic emission signals generated by the tank bottom plate.

[0062] Step 5: Determine the location and degree of corrosion on the tank bottom plate based on the intensity characteristic parameters and activity characteristic parameters of the acoustic emission signal collected at each step distance.

[0063] The closer the sensor is to the corrosion area, the greater the intensity parameters such as the amplitude, energy, and root mean square voltage value of the collected acoustic emission signal; the larger the corrosion area of ​​the tank bottom plate and the faster the rate, the greater the active parameters such as the number of acoustic emission signal impacts and ring counts collected by the acoustic emission sensor. After the tank bottom plate inspection robot completes the inspection according to the planned path, the location of the corrosion area can be determined by comparing and analyzing the intensity characteristic parameters such as the amplitude, energy, and root mean square voltage value of the acoustic emission signal in each inspection area; the corrosion degree of each inspection area of ​​the tank bottom plate is graded according to the active characteristic parameters such as the number of impacts and ring counts.

[0064] The energy and RMS voltage are calculated based on the acoustic emission signal waveform.

[0065] Before testing the tank bottom, the laboratory obtains the characteristic values ​​of active parameters such as the number of acoustic emission impacts and ring counts during the corrosion process of the same material of the tank bottom, and forms a corresponding table between the active characteristic parameters and the corrosion degree level. The actual test is graded according to the corresponding table between the active characteristic parameters and the corrosion degree level.

[0066] The acoustic emission internal detection method for corrosion of the bottom plate of a large oil storage tank proposed by the present invention combines the advantages of acoustic emission technology and tank bottom plate detection robot technology, which not only solves the problem of limited detection range of the existing acoustic emission technology, but also makes up for the problem that the existing tank bottom plate detection robot cannot judge the corrosion state of the tank bottom plate in real time. The present invention can realize an all-round scanning of the tank bottom plate, and detect and evaluate the parts of the tank bottom plate that are corroding.

[0067] The present invention also provides an acoustic emission internal detection device for bottom plate corrosion of a large liquid-carrying storage tank, comprising: a storage tank robot, an acoustic emission acquisition card, a host computer, an underwater acoustic transducer and at least two acoustic emission sensors.

[0068] At least two acoustic emission sensors are sequentially installed on the bottom of the tank robot along the moving direction of the tank robot; and the acoustic emission acquisition card is arranged inside the tank robot or outside the tank.

[0069] The water acoustic transducer is carried on the tank robot, and the water acoustic transducer is adjacent to one of the acoustic emission sensors;

[0070] The underwater acoustic transducer is used to generate an acoustic emission signal under pulse voltage excitation after the tank robot is lowered into the tank; at least two acoustic emission sensors are used to collect the acoustic emission signal and convert the acoustic emission signal into an acoustic emission electrical signal.

[0071] The signal input end of the acoustic emission acquisition card is connected to at least two acoustic emission sensors, and the signal output end of the acoustic emission acquisition card is connected to a host computer; the acoustic emission acquisition card is used to collect the acoustic emission electrical signal and transmit it to the host computer.

[0072] The host computer is used to determine the stepping distance of the tank robot, the location where corrosion occurs on the tank bottom plate, and the degree of corrosion according to the acoustic emission electrical signal.

[0073] The host computer determines the stepping distance of the tank robot according to the acoustic emission electrical signal, and the method for determining the location and degree of corrosion of the tank bottom plate can be found in the aforementioned acoustic emission internal detection method for corrosion of the bottom plate of a large liquid-carrying tank, which will not be repeated here.

[0074] Exemplarily, at least two of the acoustic emission sensors are installed at the bottom of the tank robot, and at least two of the acoustic emission sensors are evenly distributed along the traveling direction of the tank robot. The water acoustic transducer is installed at the bottom of the tank robot through a telescopic rod, and the water acoustic transducer is closely adjacent to one of the acoustic emission sensors. The acoustic emission sensor is connected to the acoustic emission acquisition card by a cable.

[0075] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0076] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An acoustic emission internal detection method for bottom plate corrosion of a large liquid storage tank, characterized in that: include: At least two acoustic emission sensors and one water acoustic transducer are installed at the bottom of the tank robot along the traveling direction of the tank robot; wherein the water acoustic transducer is adjacent to one of the acoustic emission sensors; After the tank robot is lowered into the tank, the hydroacoustic transducer moves to the bottom plate, and the acoustic emission sensor collects the acoustic emission signal generated by the hydroacoustic transducer, and calculates the attenuation coefficient of the acoustic emission signal when it propagates from the hydroacoustic transducer through the medium according to the acoustic emission signal and the relative position of the hydroacoustic transducer and the acoustic emission sensor; Determining the stepping distance of the tank robot according to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal; After the tank robot travels a step distance on the tank bottom plate, all acoustic emission sensors collect the acoustic emission signals generated by the tank bottom plate; According to the intensity characteristic parameters and activity characteristic parameters of the acoustic emission signal collected at each step distance, the location and degree of corrosion of the tank bottom plate are determined; After the tank robot is lowered, the water acoustic transducer moves to the bottom plate, and the acoustic emission sensor collects the acoustic emission signal generated by the water acoustic transducer, and calculates the attenuation coefficient of the acoustic emission signal when it is propagated from the water acoustic transducer through the medium according to the acoustic emission signal and the relative position of the water acoustic transducer and the acoustic emission sensor, specifically including: The hydroacoustic transducer carried by the tank robot is moved to the bottom plate of the tank via the telescopic rod, and generates an acoustic emission signal under the excitation of the pulse voltage; The i-th acoustic emission sensor and the j-th acoustic emission sensor adjacent to the underwater acoustic transducer receive the acoustic emission signal generated by the underwater acoustic transducer; According to the acoustic emission signals received by the i-th acoustic emission sensor and the j-th acoustic emission sensor, and the relative position of the underwater acoustic transducer and the i-th acoustic emission sensor, the formula is used , calculate the attenuation coefficient corresponding to the i-th acoustic emission sensor β i ; In the formula, a i is the amplitude of the acoustic emission signal received by the i-th acoustic emission sensor, b j is the amplitude of the acoustic emission signal received by the jth acoustic emission sensor, x ij is the distance between the i-th acoustic emission sensor and the j-th acoustic emission sensor, y i is the vertical distance from the ith acoustic emission sensor to the underwater acoustic transducer; Take the average value of the attenuation coefficients corresponding to all acoustic emission sensors as the attenuation coefficient of the acoustic emission signal when it propagates from the tank bottom plate through the medium; According to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal, the stepping distance of the tank robot is determined, specifically including: According to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal, the formula Determining the Measurement Range of an Acoustic Emission Sensor F ; In the formula, β is the attenuation coefficient of the acoustic emission signal when it propagates from the tank bottom through the medium, m 1 is the amplitude of the corrosion acoustic emission signal, m th is the threshold value; A value smaller than the measuring range is selected as the step distance.

2. The acoustic emission internal detection method for bottom plate corrosion of large liquid storage tanks according to claim 1 is characterized in that: According to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal, the stepping distance of the tank robot is determined, and then the method further includes: According to the travel route and stepping distance of the tank robot, the detection area after each stepping distance of the tank robot is marked.

3. The acoustic emission internal detection method for bottom plate corrosion of large liquid storage tanks according to claim 1 is characterized in that: The method of determining the location and degree of corrosion of the tank bottom plate according to the intensity characteristic parameters and activity characteristic parameters of the acoustic emission signal collected at each stepping distance specifically includes: Obtain the active characteristic parameters of the material with the same material as the tank bottom plate during the corrosion process in the laboratory, and form a corresponding table between the active characteristic parameters and the corrosion degree level; Determine the location of the tank bottom corrosion area based on the intensity characteristic parameters of the collected acoustic emission signals; According to the active characteristic parameters of the collected acoustic emission signals, the corrosion degree level of the corrosion area of ​​the tank bottom plate is determined by looking up the corresponding table of active characteristic parameters and corrosion degree levels.

4. The acoustic emission internal detection method for bottom plate corrosion of large liquid storage tanks according to claim 1 is characterized in that: The intensity characteristic parameters include the amplitude, energy and root mean square voltage value of the acoustic emission signal; The activity characteristic parameters include the number of impacts and the number of ringings of the acoustic emission signal.

5. An acoustic emission internal detection device for corrosion of the bottom plate of a large liquid storage tank, characterized in that: include: Tank robot, acoustic emission acquisition card, host computer, a hydroacoustic transducer and at least 2 acoustic emission sensors; At least two acoustic emission sensors are sequentially installed at the bottom of the tank robot along the traveling direction of the tank robot; the acoustic emission acquisition card is arranged inside the tank robot or outside the tank; the water acoustic transducer is mounted on the tank robot, and the water acoustic transducer is adjacent to one of the acoustic emission sensors; The hydroacoustic transducer is used to generate acoustic emission signals under pulse voltage excitation after the tank robot is lowered into the tank; At least two acoustic emission sensors are used to collect the acoustic emission signals and convert the acoustic emission signals into acoustic emission electrical signals; The signal input end of the acoustic emission acquisition card is connected to at least two acoustic emission sensors, and the signal output end of the acoustic emission acquisition card is connected to the host computer; the acoustic emission acquisition card is used to collect the acoustic emission electrical signal and transmit it to the host computer; The host computer is used to determine the stepping distance of the tank robot, the location where corrosion occurs on the tank bottom plate, and the degree of corrosion according to the acoustic emission electrical signal; The process of determining the stepping distance of the tank robot includes: The hydroacoustic transducer carried by the tank robot is moved to the bottom plate of the tank via the telescopic rod, and generates an acoustic emission signal under the excitation of the pulse voltage; The i-th acoustic emission sensor and the j-th acoustic emission sensor adjacent to the underwater acoustic transducer receive the acoustic emission signal generated by the underwater acoustic transducer; According to the acoustic emission signals received by the i-th acoustic emission sensor and the j-th acoustic emission sensor, and the relative position of the underwater acoustic transducer and the i-th acoustic emission sensor, the formula is used , calculate the attenuation coefficient corresponding to the i-th acoustic emission sensor β i ; In the formula, a i is the amplitude of the acoustic emission signal received by the i-th acoustic emission sensor, b j is the amplitude of the acoustic emission signal received by the jth acoustic emission sensor, x ij is the distance between the i-th acoustic emission sensor and the j-th acoustic emission sensor, y i is the vertical distance from the ith acoustic emission sensor to the underwater acoustic transducer; Take the average value of the attenuation coefficients corresponding to all acoustic emission sensors as the attenuation coefficient of the acoustic emission signal when it propagates from the tank bottom plate through the medium; According to the attenuation coefficient and the amplitude of the corrosion acoustic emission signal, the formula Determining the Measurement Range of an Acoustic Emission Sensor F ; In the formula, β is the attenuation coefficient of the acoustic emission signal when it propagates from the tank bottom through the medium, m 1 is the amplitude of the corrosion acoustic emission signal, m th is the threshold value; A value smaller than the measuring range is selected as the step distance.

6. The acoustic emission internal detection equipment for bottom plate corrosion of large liquid storage tanks according to claim 5 is characterized in that: At least two of the acoustic emission sensors are installed at the bottom of the tank robot, and at least two of the acoustic emission sensors are evenly distributed along the moving direction of the tank robot; The water acoustic transducer is installed at the bottom of the tank robot through a telescopic rod, and the water acoustic transducer is closely adjacent to one of the acoustic emission sensors.

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