CN113375846A

CN113375846A - Device and method for quickly detecting axial stress of pipeline

Info

Publication number: CN113375846A
Application number: CN202110537235.4A
Authority: CN
Inventors: 廖德琛; 廖柯熹; 何腾蛟; 何国玺; 赵建华; 石能灿; 林梓薇
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2021-05-17
Filing date: 2021-05-17
Publication date: 2021-09-10
Anticipated expiration: 2041-05-17
Also published as: CN113375846B

Abstract

The invention discloses a device and a method for quickly detecting axial stress of a pipeline, belongs to the field of pipeline stress detection, and particularly relates to a device and a method for detecting the stress of the pipeline. The invention aims to provide a pipeline stress detection device based on a force-magnetic relationship and a use method thereof, wherein the pipeline stress level is determined through the quantitative relationship between the pipeline magnetic induction intensity and the pipeline axial stress, and the purpose of rapidly detecting the pipeline stress is achieved. The overall stress level of the pipeline is directly determined by the detection device and the using method thereof.

Description

Device and method for quickly detecting axial stress of pipeline

The technical field is as follows:

the invention belongs to the field of pipeline stress detection, and particularly relates to a pipeline stress detection device and method.

Secondly, background art:

2.1 background of the invention

The total length of the built oil and gas pipelines in China breaks through 9.5 kilometers, and the pipeline transportation and transportation volume is large, continuous and rapid. Meanwhile, accidents of oil and gas pipelines occur frequently in recent years, most accidents are pipeline body stress overrun, so that the pipeline weak part is broken, leaked, ignited or exploded, immeasurable economic loss, environmental damage or casualties are possibly caused, and the life and property safety of people is directly threatened.

At present, the stress state of a pipeline is mostly detected by adopting an ultrasonic detection means in China, and the stress of a detected medium is calculated through the change of the propagation speed of the ultrasonic critical refraction longitudinal wave. The ultrasonic stress detection of the pipeline mainly aims at carrying out stress detection on a certain random position of an excavated pipeline section, and cannot carry out stress detection on the whole pipe section, an elbow and an irregular pipe body.

2.2 prior art relating to the invention

2.2.1 technical solution of the prior art one

1. Stripping of corrosion resistant layer on pipeline surface

And stripping an anticorrosive layer on the surface of the pipeline at the upstream of the welding line in the excavation pit, stripping the anticorrosive layer by 30cm along the axial direction, preliminarily polishing the surface of the pipeline body by using a polishing machine, and removing the viscoelastic body on the surface until the pipeline body is exposed, wherein the polishing width is 10cm along the annular direction.

2. Measuring point polishing

And (3) polishing the preliminarily polished measuring points along the axis direction of the pipeline by using a polishing machine, wherein during polishing, firstly, 80-mesh abrasive paper is used for rough polishing until corrosion pits on the surface of the pipeline are removed, and then, 240-mesh fine abrasive paper is used for polishing until a plane appears at the position of the measuring points of the pipeline, and the area of the plane is not less than 30 multiplied by 10 cm.

3. Environmental temperature calibration and measurement point stress measurement

After polishing, a test block made of the same steel as the pipeline to be tested is placed on the surface of a pipeline measuring point, standing is carried out for at least 3 minutes, and when the temperature and the zero stress sound of the test block start to be calibrated, the temperature and the sound are not changed until the temperature and the sound are measured for 3 times continuously, so that the influence of heat generated by friction in the polishing process on stress coefficient calibration is avoided. And after calibration is finished, measuring the stress of the 0-point, 3-point and 9-point clock measuring points in sequence, and recording data in the measuring process in a table.

4. Evaluation of measurement results

(1) And giving the safety level of the pipeline in the running state according to the test result and the mechanical parameters of the pipeline.

(2) And describing the stress state and whether the test point is bent or not near the test point according to the test result.

(3) And analyzing the load state of the pipeline according to the terrain environment of the buried pipeline and the deformation history of the buried pipeline and primarily giving a mechanism for generating abnormal load to the measuring points with the stress values exceeding the safety range.

(4) Reporting the abnormal point of the measurement result to the contact person of the party A at the first time, and providing the preliminary analysis and judgment for the party B.

5. Generating an ultrasonic stress detection report

And the field engineer sends the related data to a data processing center of a service provider by the original data on the detection tool through a network, a mailing optical disc and the like, and the related personnel of the service provider can analyze the data and generate an ultrasonic stress detection report to be provided for a pipeline operator.

2.2.2 disadvantages of the first prior art

1. The ultrasonic stress detection on the surface of a pipe section of 300 square centimeters takes more than two hours, the detection time is long, only the random surface point positions of the excavated pipe section can be selected for testing, and the full-aspect rapid stress detection on the whole excavated pipe section cannot be performed.

2. The ultrasonic stress detection is used for detecting the pipe section, so that only the residual stress value of the detection part can be detected, and the real stress value of the detection part cannot be detected.

3. The stress detection technology is limited by the basic principle of the ultrasonic stress detection technology, can only be applied to straight pipe sections, and cannot detect the stress of the pipeline elbows and irregular pipe bodies.

Thirdly, the invention content:

the invention aims to provide a pipeline stress detection method based on magnetic induction intensity, which determines the stress level of a pipeline through the quantitative relation between a pipeline magnetic signal and the stress level of the pipeline so as to achieve the aim of quickly detecting the pipeline. The overall stress level of the pipeline is directly determined through the detection device and the using method thereof.

Fourthly, explanation of the attached drawings:

in order to show the embodiments and technical solutions of the present invention more clearly, the embodiments or the prior art will be briefly described below with reference to the accompanying drawings, which are only some embodiments of the present invention.

FIG. 1 is a schematic diagram of magnetic induction intensity detection of a tensile test piece;

FIG. 2 is a front view of the in situ test apparatus;

FIG. 3 is a left side view of the in situ test apparatus;

FIG. 4 is a top view of the in situ test device.

The magnetic signal probe 1 is connected with the data processor 2, the data processor is connected with the back-end processor 3 through a data transmission line, and the magnetic signal data detected by the magnetic signal probe 1 is displayed in the back-end processor 3 after being processed. 4 the pipeline body test piece is the biaxial tension test piece that the material is the same with the pipeline. The 4 pipeline body test pieces are connected with a biaxial stretching device through 5 chucks, and the 4 pipeline body test pieces are respectively subjected to biaxial stretching through 6 stretching arms. And scanning a test piece magnetic signal under the biaxial stress above the 4-pipeline-body test piece by using a 1-magnetic-signal probe.

The field detection device consists of a 7-axis magnetic signal detector, an 8-ring-shaped metal shell, a 9 nut and a 10 pulley, wherein the 7-axis magnetic signal detector is arranged and fixed in the 8-ring-shaped metal shell at every 45 degrees along the circumferential direction of the device. The 8 annular metal shell has two parts, and is connected through a 9 nut. The on-site detection device wraps the detection pipeline inside, and the detection pipeline moves along the pipeline through the 10 electronic pulleys, and the 10 electronic pulleys can control the moving speed and record mileage.

Sixthly, detailed description (emphasis):

example (c): step 1: survey and research of data of detection pipeline

The information about the detected section of the pipeline is collected, and mainly comprises the starting position and the end position of the detected section of the pipeline, the length, the category and the peripheral description information.

Step 2: making biaxial tensile test piece

A test pipe section which is the same as the field pipe is taken from a pipeline company, and a pipe wall with the arc length of 1m and the axial length of 1m is cut out from the test pipe section by a grinding wheel cutting machine. The cut tube wall was machined into a standard biaxial tensile specimen with a specimen cutter.

And step 3: demagnetization of tensile test piece

And (3) demagnetizing the manufactured standard tensile test piece by using a metal demagnetizer, wherein the demagnetizing time is 10min, after the test piece is demagnetized, detecting a magnetic signal of the test piece by using a three-dimensional magnetic signal detection device, and putting the test piece into a Faraday shielding box for standby after the detection is qualified.

And 4, step 4: testing background magnetic field

The method comprises the steps of testing a background magnetic field at a tensile testing machine, starting a detection device to detect geomagnetic field information, keeping no external disturbance in the detection process, and controlling the detection time to be 5 minutes, so that the accuracy of background magnetic field data is ensured, the method is used for eliminating background magnetic field interference and improving the calculation precision.

And 5: set the test protocol

There is a quantitative relationship between the axial stress, the hoop stress and the axial magnetic induction intensity, the hoop magnetic induction intensity

σ_a-σ_h＝k(B_a-B_h)

B_a＝B_at-B_ag

B_h＝B_ht-B_hg

In the formula sigma_aIs the axial stress value, MPa; sigma_hThe value is the hoop stress value, MPa; k is a test coefficient, and is measured by a test, namely MPa/T; b is_aTo calculate the axial magnetic induction, T; b is_hCalculating the circumferential magnetic induction intensity T; b is_atTo test axial magnetic induction, T; b is_agIs the background axial magnetic induction, T; b is_htTo test the circumferential magnetic induction, T; b is_hgAs background ring magnetic induction, T.

Determining pipeline hoop stress sigma according to operating pressure P of target pipeline_h

σ_h＝Pd/2δ

Wherein P is the pipeline operating pressure, MPa; d is the inner diameter of the pipeline, mm; delta is the pipe wall thickness, mm.

According to experience, the range of the experimental axial stress value is set to be 0-5 MPa, the interval of the experimental axial stress is set to be 0.5MPa, and 11 axial stress values are taken. The experimental conditions were:

and carrying out a biaxial tensile test according to the upper table, testing the axial magnetic induction intensity and the circumferential magnetic induction intensity of the test piece with the biaxial stress by using a magnetic induction intensity detection device, and calculating a test coefficient k suitable for the target pipe section according to a formula.

Step 6: axial and toroidal magnetic induction measurement

And after the tensile testing machine is adjusted to a proper position, clamping the test piece to the chuck. And (5) after the test piece is fixed, checking and trial run are carried out to check whether the testing machine works normally. And after the test is finished, setting test parameters for testing, and slowly increasing the tensile force of the test piece by the tensile testing machine until the tensile force reaches the set value so as to keep the test piece in a stable tensile state. And opening the magnetic signal detection device, placing the magnetic signal probe at a position 1cm above one end of the test piece in a stretching state, moving the magnetic signal probe along the stretching test piece until the magnetic signal probe is separated from the range of the stretching test piece, and storing the data of the stretching test piece to a computer end.

And 7: repeat the experiment

The experimental parameters were varied and 11 sets of experiments were repeated, see

steps

6 and 7.

And 8: data processing

(1) And determining k values of 11 groups of experiments, processing each group of experimental data, calculating three k values under each experimental condition, and then averaging. The k values under 11 different conditions were repeatedly calculated and recorded.

k＝((B_a-B_h)+σ_h)/σ_a

(2) Determining a true value k of k_rThrough 11 experimentsDetermining k value by using true value calculation formula_r。

In the formula k_rIs the true value of a correction coefficient k, MPa/T; k is a radical of_iThe k value is the value of MPa/T tested by the i group of experiments; e (k) is a point value correction of k, MPa/T.

And step 9: in situ applications

(1) And (3) detecting a background magnetic field, namely cleaning a 3M multiplied by 3M flat area in an area more than 10 meters away from the pipeline, and ensuring that no metal and other substances influencing the magnetic field exist in the area. The detection device is started to detect the geomagnetic field information, no external disturbance is kept in the detection process, and the detection time needs to be controlled within 10-15 minutes, so that the accuracy of the geomagnetic field data is ensured, the geomagnetic field data is used for eliminating the interference of a background magnetic field on pipeline magnetic signals, and the calculation precision of the defect stress is improved.

(2) And (3) installing the on-site detection device, respectively fixing two parts of the on-site detection device above the pipeline, and connecting the two parts through nuts after the position is fixed.

(3) And (3) detecting the pipeline, namely opening a detection switch of the field detection device, keeping the detection for 1min, testing after the data to be detected is stable, and detecting along the pipeline by the detection device after setting the detection speed.

(4) And data processing, namely calculating the axial stress of each position of the pipeline by combining the calculated hoop stress through a k true value determined by experiments based on the axial and hoop magnetic induction intensity of the pipeline detected on site.

Seventhly, the technical effects are as follows:

1. the axial stress value of the pipeline can be measured by detecting the axial magnetic induction intensity and the circumferential magnetic induction intensity on the surface of the pipeline and combining an axial stress calculation model.

2. Compared with the traditional ultrasonic stress detection mode, the method can detect the real stress value of all the positions of the target pipe section instead of the residual stress value.

3. The invention only needs to detect the magnetic field of the pipeline without performing contact detection on the pipeline, and can detect pipeline parts such as pipeline elbows, irregular structures and the like which cannot be detected by traditional ultrasonic waves.

Claims

1. A device and a method for rapidly detecting axial stress of a pipeline are used for detecting the stress of the pipeline and are characterized by comprising the following steps:

step 1, collecting information about a detection section pipeline, wherein the information mainly comprises a starting point position and an end point position of the detection section pipeline, length, category and peripheral description information;

step 2, cutting a pipe wall with the arc length of 1m and the axial length of 1m from a pipe section which is made of the same material as the site material by using a grinding wheel cutting machine, and processing the cut pipe wall into a standard biaxial tension test piece by using a test piece cutting machine;

step 3, demagnetizing the manufactured standard tensile test piece by using a metal demagnetizer, wherein the demagnetizing time is 10min, detecting the magnetic signal of the test piece by using a three-dimensional magnetic signal detection device after the test piece is demagnetized, and placing the test piece into a Faraday shielding box for standby after the detection is qualified;

step 4, detecting background magnetic field information, keeping no external disturbance in the detection process, and controlling the detection time to be 5 minutes, so as to ensure the accuracy of background magnetic field data, eliminate background magnetic field interference and improve calculation precision;

step 5, designing a biaxial tension test according to the operation condition of the pipeline on site;

step 6, performing a tensile test to keep the test piece in a stable tensile state; opening a magnetic signal detection device, and detecting the magnetic induction intensity of the tensile test piece pipeline;

step 7, changing test parameters and repeating the test;

step 8, processing the experimental data to determine a true value of K;

and 9, detecting the axial stress on site by using a novel detection device.

2. The device and the method for rapidly detecting the axial stress of the pipeline according to claim 1, wherein in the step 5, the following quantitative relations exist among the axial stress, the hoop stress, the axial magnetic induction and the hoop magnetic induction:

σ_a-σ_h＝k(B_a-B_h)

B_a＝B_at-B_ag

B_h＝B_ht-B_hg

3. The device and the method for rapidly detecting the axial stress of the pipeline according to claim 1, wherein in the step 6, the magnetic induction intensity detection of the tensile test piece comprises the following steps:

step a, after adjusting a tensile testing machine to a proper position, clamping a test piece on a chuck; after the test piece is fixed, checking and trial run are carried out to check whether the testing machine works normally; after the test is finished, setting test parameters for testing, and slowly increasing the tensile force of the test piece by the tensile testing machine until the tensile force reaches the set value so as to keep the test piece in a stable tensile state;

and b, opening the magnetic signal detection device, placing the magnetic signal probe at a position 1cm above one end of the test piece in a stretching state, moving the magnetic signal probe along the stretching test piece until the magnetic signal probe is separated from the range of the stretching test piece, and storing the data of the stretching test piece to a computer end.

4. The device and the method for rapidly detecting the axial stress of the pipeline according to claim 1, wherein in the step 9, the novel detection device comprises the following components:

the field detection device consists of a double-shaft magnetic signal detector, an annular metal shell, a nut and a pulley, wherein the double-shaft magnetic signal detector is arranged and fixed in the annular metal shell every 45 degrees along the annular direction of the device, and the annular metal shell comprises two parts which are connected through the nut; the on-site detection device wraps the detection pipeline and moves along the pipeline through the electronic pulley, and the electronic pulley can control the moving speed and record mileage.