CN110702778A - Oil-gas pipeline surface crack defect safety assessment method based on weak magnetic method - Google Patents
Oil-gas pipeline surface crack defect safety assessment method based on weak magnetic method Download PDFInfo
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Abstract
Based on a weak magnetic method oil and gas pipeline surface crack defect safety assessment method, firstly, a weak magnetic detection instrument runs at a constant speed, and analog signals acquired by a sensor are converted into digital signals; secondly, storing two continuous signal data (two continuous signals in the acquisition frequency) obtained by conversion into a length register and a high register respectively, carrying out filtering processing, and then storing the data subjected to filtering processing in different directions into different registers; thirdly, judging whether cracks exist on the surface of the oil-gas pipeline or not by using the data in the register, if not, ending the program, if so, evaluating the sizes of the cracks, and entering the fourth step; and fourthly, carrying out safety evaluation on the crack size data in the third step. The invention utilizes the cooperation of the hardware filtering and amplifying circuit and the software filtering program, can effectively filter noise, amplify the detection signal and improve the detection precision.
Description
Technical Field
The invention belongs to the technical field of flaw detection monitoring and detection of metal materials, and particularly relates to a safety evaluation method for surface crack defects of an oil-gas pipeline based on a weak magnetic method.
Background
The weak magnetic detection technology is a novel nondestructive detection technology, integrates research contents in the fields of ferromagnetism, nondestructive detection, metal histology and the like, and is widely applied to industrial production due to the advantages that the technology supports non-contact online detection, materials do not need to be pretreated before detection, the performance of the materials is not influenced after detection, detection signals are obvious, and the like. At present, the method has been successfully applied to the aspect of detection in a pipeline stress concentration area, and has a great application potential in the aspect of online detection of pipeline surface cracks; however, the crack defect characteristics are directly judged based on weak magnetic signals, and a crack safety evaluation method lacks system research, and relevant achievement reports are not found yet.
Disclosure of Invention
The purpose of the invention is as follows:
the invention aims to solve the problems and provides a weak magnetic method-based oil and gas pipeline surface crack defect safety assessment method.
The technical scheme is as follows:
in order to achieve the purpose, the invention adopts the following technical scheme,
a weak magnetic method-based oil and gas pipeline surface crack defect safety assessment method comprises the following steps:
firstly, enabling a weak magnetic detection instrument to run at a constant speed, and converting an analog signal acquired by a sensor into a digital signal;
secondly, storing two continuous signal data (two continuous signals in the acquisition frequency) obtained by conversion into a length register and a high register respectively, carrying out filtering processing, and then storing the data subjected to filtering processing in different directions into different registers;
thirdly, judging whether cracks exist on the surface of the oil-gas pipeline or not by using the data in the register, if not, ending the program, if so, evaluating the sizes of the cracks, and entering the fourth step;
and fourthly, carrying out safety evaluation on the crack size data in the third step.
The system comprises a system calling and data processing main program, a stepping motor driving program, a data acquisition subprogram, a filtering subprogram, an ADC conversion program, a tangential data maximum value judgment program, a normal data zero crossing point judgment program, a crack size judgment program and a safety assessment subprogram.
The system calling and data processing main program firstly sets a stepping motor driving program to enable the instrument to run at a constant speed, and calls a data acquisition subprogram, namely analog signals acquired by a sensor are converted into digital signals by AD conversion; then, the collected two continuous data are respectively stored in a length register and a high register through a filtering wave subprogram, the collected data in different directions are stored in different registers after filtering treatment, namely tangential data are respectively stored in a storage area with an ADTURN1 (defined data register name) as a first address, and normal data are stored in a storage area with an ADTURN2 as a first address; then the system calls a tangential data maximum value judgment program and a normal data zero crossing point judgment program to judge whether cracks exist, if not, the program is ended, and if cracks exist, a crack size judgment program is called to evaluate the sizes of the cracks; finally, sending the collected crack size data to a safety evaluation program so as to obtain the safety evaluation of the detected cracks, and displaying the safety evaluation through a display program;
the stepping motor driving program is used for adjusting the advancing speed of the instrument by adjusting a pulse signal of the stepping motor, and the rotating speed of the stepping motor is in direct proportion to the frequency of the pulse, so that the motor driving is used for adjusting the pulse frequency of the stepping motor by using a delay function (namely the speed of the instrument is controlled by the delay function, and the speed and the frequency can be combined to obtain the length of a crack by using weak magnetic data) so as to realize the uniform motion of the instrument;
and the data acquisition subprogram performs analog-to-digital conversion on the analog signals acquired by the sensor through ADC conversion. Enabling ADC interruption after ADC initialization, starting AD conversion, stopping AD conversion after an ADC interruption mark is cleared, and sending converted data to a filtering subprogram;
the software filtering subprogram firstly reads data in an ADC register, then respectively stores the front and rear sampling data into a length register and a high register, determines the maximum deviation value A allowed by two times of sampling, and judges when a new value is detected each time: if the difference between the current value and the previous value is greater than A, the current value is invalid, the current value is abandoned, the previous value is used for replacing the current value, and interference signals are filtered; if the difference between the current value and the previous value is less than or equal to A, the current value is valid, and then tangential data of the detected piece is respectively stored in the ADTURN1, and normal data is stored in the ADTURN 2;
the tangential data maximum judgment program firstly defines the occurrence frequency of an initial maximum as 0, and points R0 to the first address ADTURN1 of the acquired data storage area; r1 is pointed to the acquisition data storage area first address ADTURN1+ 1; putting an R0 pointing value into a register 2CH, putting an R1 pointing value into a register 3CH, circularly summing the results of R0 and 2CH, storing the results into a @2C register, then circulating for 10 times, calculating the mean value, giving the mean value to A1, circularly taking the next 10 data mean values to A2, continuously circularly taking the next 10 data mean values to A3, comparing A1, A2 and A3, judging whether A2 is the maximum value, if yes, adding one to the maximum value recording time, continuously acquiring data until the maximum value appears again, calling a normal data zero crossing point judgment program, and if data meets the requirement value, determining that a crack exists and calling a crack size judgment program; if not, sending the A2 data to A1, sending the A3 data to A2, circularly taking the average value A3 of the next N data, and judging the average value A3 again;
the normal data zero crossing point judgment routine assigns data in the address ADTURN2 to R2, calculates the absolute value of the R2 register value, and judges whether the absolute value is smaller than the required value M. If not, continuing to acquire and convert data and modifying the pointer; if yes, recording and storing the data;
the crack size decision program first defines the initial acquisition peak number of times to be 0 and points R2 to the acquisition data storage area first address ADTURN2, i.e., points the normal component data address to R2; pointing R3 to the temporary calculated memory bank first address ADTURN2+1, pointing R4 to the temporary calculated memory bank first address ADTURN2+2, putting the R2 pointing value into register 4CH, putting the R3 pointing value into register 5CH, and putting the R4 pointing value into register 6 CH; the data in the first addresses ADTURN2, ADTURN2+1 and ADTURN2+2 of the data storage area are sent to registers 4CH, 5CH and 6CH, the previous data is added with the following data by [ R2 ] + @4CH, and the next data is sent to an @4C register, ten times of circulation are carried out, the continuous ten data in the 4CH are added, then the data are averaged, and the average value is put into an AL1 register; the data in the 5CH register is also averaged, and the average value is put into AL 2; and then, continuously calculating the average value of the next ten data, storing the average value into an AL3 register, comparing the data sizes of AL1, AL2 and AL3 to judge whether a peak value exists in the normal direction, and if the peak value does not exist, continuously and circularly collecting the data. And if so, storing the data in an @7C register, and adding 1 to the number of peak values until a second peak value is acquired. Because the sampling frequency is 10Hz, the instrument speed is 1cm/s, the crack length c can be obtained by measuring the sampling point times a between two peak values (the instrument speed is 1cm/s, a point is acquired by adopting the frequency of 10Hz, namely 0.1 second, the unit of the number of the sampling points between the two peak values is MM, namely how many sampling points, and how many MM the crack length is), the crack normal peak value data has a linear relation with the crack depth, and the crack normal peak value data is divided by 8.2 after subtracting 13A/MM (A/MM is the unit of the magnetic field intensity and has no other meanings) to obtain the crack depth d;
the safety evaluation program firstly needs to assign the parameters required by calculation, namely setting the Poisson's ratio, Young's modulus and yield strength sigma of the material1Tensile Strength σ2And fracture toughness Kmat, pipe parameters such as wall thickness B and pipe radius R, and pipe working pressure P, and calculating corresponding fracture ratio K1 and load ratio Lr according to crack depth d and crack length c, the calculation formula is:
o＝(1+1.464*(d/c)^1.65)^0.5 (1)
x1＝1.13-0.09*(d/c) (2)
x2＝(0.89/(0.2+(d/c)))-0.54 (3)
x3＝0.5-1/(0.65+(d/c))+14*(1-(d/c))^24 (4)
K1＝P1*sqrt(3.14*d)*(x1+x2*(d/B)^2+x3*(d/B)^4)/(o*Kmat) (5)
Lr＝P*(3.14*(1-d/c)+2*(d/c)*sin(c/R))/(σ2*((1-d/c)*(3.1-(c/R)*(d/c)))) (6)
the critical fracture ratio was calculated as:
Kr＝((1+0.5*Lr^2)^-0.5)*(0.3+0.7*exp(-0.38*Lr^6)) (7)
comparing the calculated fracture ratio K1 with the critical fracture ratio Kr obtained according to the load ratio, and further obtaining the safety evaluation of the cracks; (unsafe if K1 is greater than Kr), where P1 is the calculated maximum crack-free pressure of the pipe, and P is the internal pressure of the pipe. (X1, X2, X3 are too long to be signed, and are omitted).
The display program firstly defines a port to determine a data transmission port, then sets a display mode and an input mode of the display, then initializes the display, and then displays the safety evaluation result of the crack by inputting a command, and simultaneously displays the detected crack depth d and the crack length c.
As another preferable aspect, in the crack size determination program according to the present invention, regarding the determination of the crack depth, a linear relationship exists between the normal peak signal at the crack and the crack depth, and the relationship formula is that the crack normal peak signal is the crack depth multiplied by 8.2 plus 13A/M; as another preferable scheme, regarding the crack length determination in the crack size determination program of the present invention, the sampling frequency is set to 10Hz, and the detector advancing speed is set to 1 cm/s; the crack length can be effectively obtained by utilizing the parameters;
as another preferable mode, the maximum deviation value is set to 50 uT.
In another preferred embodiment, N in the present invention is 10.
As another preferred scheme, the method for judging whether the normal data of the program meets the requirement value at the zero crossing point of the normal data comprises the following steps: if the normal component value M is less than 300nT, the desired value is deemed to be satisfied.
As another preferred embodiment, the stepping angle of the stepping motor used in the present invention is 20 degrees, so that one rotation is 360 degrees, and 18 pulses are required to complete the rotation.
As another preferred scheme, the advancing speed of the instrument is directly proportional to the pulse frequency, and the speed of the instrument can be effectively controlled to be constant 1cm/s by adjusting the pulse frequency.
A weak magnetic method-based oil and gas pipeline surface crack defect safety evaluation system comprises a signal acquisition module, a signal processing and registering module, a crack size evaluation module and a safety evaluation module;
the signal acquisition module enables the instrument to run at a constant speed and converts the acquired analog signals into digital signals;
the signal processing and registering module respectively stores two continuous data acquired by the signal acquisition module into a length register and a high register, performs filtering processing, and then stores the data acquired in different directions into different registers;
the crack size evaluation module judges whether cracks exist on the surface of the oil-gas pipeline or not by utilizing data in the signal processing and register module register, if not, the program is ended, and if the cracks exist, the crack size is evaluated and the safety evaluation module is entered;
and the safety evaluation module carries out safety evaluation on the crack size data in the crack size evaluation module.
The advantages and effects are as follows:
the invention has the following specific effects:
the invention solves the problem that the existing detector cannot specifically analyze the cracks in real time.
The invention can detect the crack and judge the size of the crack, and can judge the safety of the crack.
The invention utilizes the cooperation of the hardware filtering and amplifying circuit and the software filtering program, can effectively filter noise, amplify the detection signal and improve the detection precision.
The invention uses the singlechip to control and assemble the language programming, so that the experimental facility is smaller and is easy to adapt to the requirements of various experimental environments.
Drawings
The invention is further described with reference to the following figures and detailed description. The scope of the invention is not limited to the following expressions.
Fig. 1 is a block diagram of the process of the present invention.
Fig. 2 is a flowchart of a stepping motor driving procedure.
FIG. 3 is a flowchart of a data collection subroutine of the present invention.
FIG. 4 is a flow chart of the filtering subroutine of the present invention.
FIG. 5 is a flowchart of the maximum tangential data value determination process of the present invention.
FIG. 6 is a flow chart for determining normal data zero crossings in accordance with the present invention.
Fig. 7 is a flowchart of crack size determination according to the present invention.
FIG. 8 is a flowchart of a security evaluation procedure of the present invention.
Fig. 9 is a block diagram of a display process flow of the present invention.
Detailed Description
A weak magnetic method-based oil and gas pipeline surface crack defect safety assessment method comprises the following steps:
firstly, enabling an instrument to run at a constant speed, and converting an acquired analog signal into a digital signal;
secondly, storing the two continuous collected data into a length register and a high register respectively, carrying out filtering processing, and then storing the data collected in different directions into different registers;
thirdly, judging whether cracks exist on the surface of the oil-gas pipeline or not by using the data in the register, if not, ending the program, if so, evaluating the sizes of the cracks, and entering the fourth step;
and fourthly, carrying out safety evaluation on the crack size data in the third step.
The method specifically comprises the following steps: the method comprises a system calling and data processing main program, a data acquisition subprogram, a filtering subprogram, an ADC conversion program, a tangential data maximum value judgment program, a normal data zero crossing point judgment program, a crack normal data peak value acquisition program, a crack depth judgment program, a safety evaluation program and a display program;
as shown in fig. 1, the main system calling and data processing program first sets a stepper motor driver to drive the instrument at a constant speed, and calls a data acquisition subroutine, that is, converts an analog signal acquired by a sensor into a digital signal by using AD conversion; then, storing the two continuous collected data into a length register and a high register respectively through a filtering wave subprogram, storing the collected data in different directions into different registers after filtering treatment, namely storing the detected tangential data into a storage area with an ADTURN1 as a first address and storing the normal data into a storage area with an ADTURN2 as a first address; then the system calls a tangential data maximum value judgment program and a normal zero crossing point judgment program to judge whether cracks exist, if not, the program is ended, and if so, a crack size judgment program is called to evaluate the size of the cracks; finally, sending the collected crack size data to a safety evaluation program, thereby obtaining the safety evaluation of crack detection; and the detection result is sent to a display module for displaying.
As shown in fig. 2, the driving program of the stepping motor firstly defines the port of the stepping motor, then defines the working mode of the stepping motor by initializing the serial port and the timer, and adjusts the pulse frequency of the stepping motor by using the delay function, since the rotating speed of the stepping motor is in direct proportion to the pulse frequency, the instrument moves at a constant speed, and stops the trolley moving by interrupting the pulse frequency output when the instrument is finished;
as shown in fig. 3, the data collection subroutine reads the analog signal received by the sensor through the port P1 of the single chip microcomputer, and performs analog-to-digital conversion on the analog signal collected by the sensor by using ADC conversion, that is, the ADC is initialized first, then the ADC is enabled to be interrupted, AD conversion is started, the ADC interruption flag is cleared when the work is stopped to stop AD conversion, and the converted data is stored in the ADC register;
as shown in fig. 4, the filtering subroutine first reads the data in the ADC register, then stores the two previous and next sample data in the length and high registers, respectively, determines the maximum deviation value a allowed by two sampling operations, and determines when a new value is detected each time: if the difference between the current value and the previous value is greater than A, the current value is invalid, the current value is abandoned, the previous value is used for replacing the current value, and interference signals are filtered; if the difference between the current value and the previous value is less than or equal to A, the current value is valid, and then tangential data of the detected piece is respectively stored in the ADTURN1, and normal data is stored in the ADTURN 2;
as shown in fig. 5, the tangential data maximum judgment program first defines the initial maximum occurrence number as 0, and points R0 to the acquired data storage area first address ADTURN 1; r1 is pointed to the acquisition data storage area first address ADTURN1+ 1; putting an R0 pointing value into a register 2CH, putting an R1 pointing value into a register 3CH, circularly summing the results of R0 and 2CH, storing the results into a @2C register, then circulating for 10 times, calculating the mean value, giving the mean value to A1, circularly taking the next 10 data mean values to A2, continuously circularly taking the next 10 data mean values to A3, comparing A1, A2 and A3, judging whether A2 is the maximum value, if yes, adding one to the maximum value recording time, continuously acquiring data until the maximum value appears again, calling a normal data zero crossing point judgment program, and if data meets the requirement value, determining that a crack exists and calling a crack size judgment program; if not, sending the A2 data to A1, sending the A3 data to A2, circularly taking the average value A3 of the next N data, and judging the average value A3 again;
as shown in fig. 6, the normal data zero crossing point judgment stores the normal data in the ADTURN2 register, assigns the data in the address ADTURN2 to R2, calculates the absolute value of the R2 data, and judges whether the absolute value is less than M, if not, continues to perform data acquisition and conversion and modifies the pointer, and if yes, records and stores the data;
as shown in fig. 7, the crack size determination program first defines the initial acquisition peak number of times to be 0 and points R2 to the acquisition data storage area first address ADTURN2, i.e., points the normal component data address to R2; pointing R3 to the temporary calculated memory bank first address ADTURN2+1, pointing R4 to the temporary calculated memory bank first address ADTURN2+2, putting the R2 pointing value into register 4CH, putting the R3 pointing value into register 5CH, and putting the R4 pointing value into register 6 CH; the data in the first addresses ADTURN2, ADTURN2+1 and ADTURN2+2 of the data storage area are sent to registers 4CH, 5CH and 6CH, the previous data is added with the following data by [ R2 ] + @4CH, and the next data is sent to an @4C register, ten times of circulation are carried out, the continuous ten data in the 4CH are added, then the data are averaged, and the average value is put into an AL1 register; the data in the 5CH register is also averaged, and the average value is put into AL 2; and then, continuously calculating the average value of the next ten data, storing the average value into an AL3 register, comparing the data sizes of AL1, AL2 and AL3 to judge whether a peak value exists in the normal direction, and if the peak value does not exist, continuously and circularly collecting the data. And if so, storing the data in an @7C register, and adding 1 to the number of peak values until a second peak value is acquired. Because the sampling frequency is 10Hz, and the instrument speed is 1cm/s, the crack length c can be obtained by measuring the sampling point times a between two peak values, the crack normal peak value data and the crack depth have a linear relation, and the crack normal peak value data is divided by 8.2 after subtracting 13A/MM to obtain the crack depth d;
as shown in fig. 8, the safety evaluation program first needs to assign values to parameters required for calculation, i.e. to set the poisson's ratio, young's modulus and yield strength σ of the material1Tensile Strength σ2And fracture toughness Kmat, parameters of the pipeline such as wall thickness B and pipeline radius R, and pipeline working pressure P and maximum main stress P1, and according to corresponding parameters of a formula such as o, x1, x2 and x3, further calculating a fracture ratio K1 and a load ratio Lr corresponding to the crack size, wherein the calculation formula is as follows:
o＝(1+1.464*(d/c)^1.65)^0.5 (8)
x1＝1.13-0.09*(d/c) (9)
x2＝(0.89/(0.2+(d/c)))-0.54 (10)
x3＝0.5-1/(0.65+(d/c))+14*(1-(d/c))^24 (11)
K1＝P1*sqrt(3.14*d)*(x1+x2*(d/B)^2+x3*(d/B)^4)/(o*Kmat) (12)
Lr＝P*(3.14*(1-d/c)+2*(d/c)*sin(c/R))/(584*((1-d/c)*(3.1-(c/R)*(d/c)))) (13)
the critical fracture ratio was calculated as:
Kr＝((1+0.5*Lr^2)^-0.5)*(0.3+0.7*exp(-0.38*Lr^6)) (14)
comparing the calculated fracture ratio K1 with the critical fracture ratio Kr obtained according to the load ratio, and further obtaining the safety evaluation of the cracks;
as shown in fig. 9, the display program firstly defines a port to determine a data transmission port, then sets a display mode and an input mode of the display, and then displays the safety evaluation result of the crack by inputting a command after initializing the display, and simultaneously displays the detected crack depth d and the crack length c.
The maximum deviation value is set to a 50 uT.
And N is 10.
The method for judging whether the requirement value is met comprises the following steps: if the normal component value M is less than 300nT, the desired value is deemed to be satisfied. The sampling frequency is 10 Hz. The instrument speed was 1 cm/s.
A weak magnetic method-based oil and gas pipeline surface crack defect safety evaluation system comprises a signal acquisition module, a signal processing and registering module, a crack size evaluation module and a safety evaluation module;
the signal acquisition module enables the instrument to run at a constant speed and converts the acquired analog signals into digital signals;
the signal processing and registering module respectively stores two continuous data acquired by the signal acquisition module into a length register and a high register, performs filtering processing, and then stores the data acquired in different directions into different registers;
the crack size evaluation module judges whether cracks exist on the surface of the oil-gas pipeline or not by utilizing data in the signal processing and register module register, if not, the program is ended, and if the cracks exist, the crack size is evaluated and the safety evaluation module is entered; and the safety evaluation module carries out safety evaluation on the crack size data in the crack size evaluation module.
It should be understood that the detailed description of the present invention is only for illustrating the present invention and is not limited by the technical solutions described in the embodiments of the present invention, and those skilled in the art should understand that the present invention can be modified or substituted equally to achieve the same technical effects; as long as the use requirements are met, the method is within the protection scope of the invention.
Claims (10)
1. A weak magnetic method-based oil and gas pipeline surface crack defect safety assessment method is characterized by comprising the following steps: the method comprises the following steps:
firstly, enabling a weak magnetic detection instrument to run at a constant speed, and converting an analog signal acquired by a sensor into a digital signal;
secondly, storing two continuous signal data obtained by conversion into a length register and a high register respectively, carrying out filtering processing, and then storing the data subjected to filtering processing in different directions into different registers;
thirdly, judging whether cracks exist on the surface of the oil-gas pipeline or not by using the data in the register, if not, ending the program, if so, evaluating the sizes of the cracks, and entering the fourth step;
and fourthly, carrying out safety evaluation on the crack size data in the third step.
2. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized in that: in the first step, the uniform running of the instrument is realized by setting a stepping motor driving program, wherein the stepping motor driving program is used for adjusting the advancing speed of the instrument by adjusting a pulse signal of a stepping motor, and the motor driving is used for adjusting the pulse frequency of the stepping motor by using a time delay function so as to realize the uniform motion of the instrument.
3. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized in that: in the first step, analog-to-digital conversion is carried out on analog signals collected by a sensor through ADC conversion; the ADC is enabled to be interrupted after the ADC is initialized, the AD conversion is started, the AD conversion is stopped after an ADC interruption mark is cleared, and the converted data is sent to the second step.
4. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized in that:
in the second step, the data collected in different directions are stored in different registers, that is, tangential data are respectively stored in a storage area with an ADTURN1 as a first address, and normal data are respectively stored in a storage area with an ADTURN2 as a first address;
in the second step, firstly receiving the digital signal data in the first step, then respectively storing the front and back sampling data into a length register and a high register, determining the maximum deviation value A allowed by two times of sampling, and judging when a new value is detected each time: if the difference between the current value and the previous value is greater than A, the current value is invalid, the current value is abandoned, the previous value is used for replacing the current value, and interference signals are filtered; if the difference between the current value and the previous value is less than or equal to A, the current value is valid, and then the tangential data of the detected piece is respectively stored in the ADTURN1, and the normal data is stored in the ADTURN 2.
5. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized by comprising the following steps of: judging whether cracks exist by using a tangential data maximum value judgment program and a normal data zero crossing point judgment program in the third step;
the tangential data maximum value judgment program firstly defines the occurrence frequency of an initial maximum value as 0, and points R0 to the first address ADTURN1 of the acquisition data storage area; r1 is pointed to the acquisition data storage area first address ADTURN1+ 1; putting an R0 pointing value into a register 2CH, putting an R1 pointing value into a register 3CH, circularly summing the results of R0 and 2CH, storing the results into a @2C register, then circulating for 10 times, calculating the mean value, giving the mean value to A1, circularly taking the next 10 data mean values to A2, continuously circularly taking the next 10 data mean values to A3, comparing A1, A2 and A3, judging whether A2 is the maximum value, if yes, adding one to the maximum value recording time, continuously acquiring data until the maximum value appears again, calling a normal data zero crossing point judgment program, and if data meets the requirement value, determining that a crack exists and calling a crack size judgment program; if not, sending the A2 data to A1, sending the A3 data to A2, circularly taking the average value A3 of the next N data, and judging the average value A3 again;
the normal data zero crossing point judging program gives the data in the address ADTURN2 to R2, calculates the absolute value of the R2 register value and judges whether the absolute value is smaller than the required value M; if not, continuing to acquire and convert data and modifying the pointer; if yes, recording and storing the data.
6. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized by comprising the following steps of: in the third step, the crack size is evaluated by a crack size judging program, wherein the crack size judging program firstly defines the initial acquisition peak frequency as 0 and points R2 to the initial address ADTURN2 of the acquired data storage area, namely points the normal component data address to R2; pointing R3 to the temporary calculated memory bank first address ADTURN2+1, pointing R4 to the temporary calculated memory bank first address ADTURN2+2, putting the R2 pointing value into register 4CH, putting the R3 pointing value into register 5CH, and putting the R4 pointing value into register 6 CH; the data in the first addresses ADTURN2, ADTURN2+1 and ADTURN2+2 of the data storage area are sent to registers 4CH, 5CH and 6CH, the previous data is added with the following data by [ R2 ] + @4CH, and the next data is sent to an @4C register, ten times of circulation are carried out, the continuous ten data in the 4CH are added, then the data are averaged, and the average value is put into an AL1 register; the data in the 5CH register is also averaged, and the average value is put into AL 2; and then, continuously calculating the average value of the next ten data, storing the average value into an AL3 register, comparing the data sizes of AL1, AL2 and AL3 to judge whether a peak value exists in the normal direction, and if the peak value does not exist, continuously and circularly collecting the data. And if so, storing the data in an @7C register, and adding 1 to the number of peak values until a second peak value is acquired. The sampling frequency is known, the instrument speed is known, the crack length c can be obtained by measuring the sampling point times a between two peak values, the crack normal peak value data and the crack depth have a linear relation, and the crack normal peak value data minus 13A/MM is divided by 8.2 to obtain the crack depth d.
7. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized by comprising the following steps of: and step four, performing safety evaluation in a safety evaluation procedure, wherein the safety evaluation procedure firstly needs to assign values to parameters required by calculation, namely the Poisson's ratio, the Young's modulus and the yield strength sigma of the material are set1Tensile Strength σ2And fracture toughness Kmat, pipe parameters such as wall thickness B and pipe radius R, and pipe operating pressure P, and calculating corresponding fracture ratio K1 and load ratio Lr according to crack depth and crack length c, the calculation formula being:
o＝(1+1.464*(d/c)^1.65)^0.5 (1)
x1＝1.13-0.09*(d/c) (2)
x2＝(0.89/(0.2+(d/c)))-0.54 (3)
x3＝0.5-1/(0.65+(d/c))+14*(1-(d/c))^24 (4)
K1＝P1*sqrt(3.14*d)*(x1+x2*(d/B)^2+x3*(d/B)^4)/(o*Kmat) (5)
Lr＝P*(3.14*(1-d/c)+2*(d/c)*sin(c/R))/(σ2*((1-d/c)*(3.1-(c/R)*(d/c)))) (6)
the critical fracture ratio was calculated as:
Kr＝((1+0.5*Lr^2)^-0.5)*(0.3+0.7*exp(-0.38*Lr^6)) (7)
and comparing the calculated fracture ratio K1 with the critical fracture ratio Kr obtained according to the load ratio to further obtain the safety evaluation of the crack, wherein P1 is the calculated maximum pressure of the pipeline without the crack, and P is the internal pressure of the pipeline.
8. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized by comprising the following steps of: when data is collected, the sampling frequency is set to be 10Hz, and the instrument speed is 1 cm/s.
9. The weak magnetic method based safety evaluation method for the surface crack defects of the oil and gas pipeline is characterized in that: before the normal data is filtered, the absolute value needs to be obtained.
10. The utility model provides a based on weak magnetism method oil gas pipeline surface crack defect safety assessment system which characterized in that: the system comprises a signal acquisition module, a signal processing and registering module, a crack size evaluation module and a safety evaluation module;
the signal acquisition module enables the instrument to run at a constant speed and converts the acquired analog signals into digital signals;
the signal processing and registering module respectively stores two continuous data acquired by the signal acquisition module into a length register and a high register, performs filtering processing, and then stores the data acquired in different directions into different registers;
the crack size evaluation module judges whether cracks exist on the surface of the oil-gas pipeline or not by utilizing data in the signal processing and register module register, if not, the program is ended, and if the cracks exist, the crack size is evaluated and the safety evaluation module is entered;
and the safety evaluation module carries out safety evaluation on the crack size data in the crack size evaluation module.
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