CN210322889U - Based on low frequency magnetic leakage sleeve pipe type pipeline appearance of detecting a flaw - Google Patents

Abstract

The utility model discloses a based on low frequency magnetic leakage sleeve pipe type pipeline appearance of detecting a flaw comprises FL sensor, magnetism shielding ware, magnetizing coil, signal processor, power module, singlechip, accurate potentiometre, LCD screen, detection shell, plastic sleeve, computer. Sleeving a plastic sleeve on a detected pipeline, collecting a background magnetic field outside the detected pipeline through a magnetic shielding device and guiding the background magnetic field to form a local magnetic vacuum leakage environment, enabling magnetic flux in the detected pipeline to be leaked to a created magnetic vacuum area most thoroughly without reverse background magnetic pressure at a defect position, magnetizing the inner surface of the detected pipeline through a magnetizing coil to form a leakage magnetic field and inducing the leakage magnetic field by an FL sensor arranged in the area, transmitting a signal to a signal processor, converting the signal into a digital signal through filtering amplification and A/D conversion, transmitting the digital signal to a computer, and processing the digital signal by MATLAB to form an image; the invention has the advantages of long detectable distance, high signal-to-noise ratio and high sensitivity, and is an innovation of the traditional magnetic flux leakage detection principle.

Description

Based on low frequency magnetic leakage sleeve pipe type pipeline appearance of detecting a flaw

Technical Field

The invention belongs to the technical field of instruments and meters for non-contact metal detection, and particularly relates to a nondestructive detection technology based on low-frequency magnetic flux leakage detection.

Background

Since the discovery of the prototype of the magnetic flux leakage detection principle, namely magnetic particle detection, by hokes of americans in 1922, the magnetic flux leakage detection theory and its engineering application have been widely studied.

The corresponding theoretical research includes the magnetic field static distribution solving problem of magnetic dipole and finite element method, the magnetic leakage inverse inversion problem of AMEET, the mutual influence relationship analysis between the defect geometrical parameters of MUKHOPADHYAY, etc. and the leakage field and scanning speed.

The magnetic flux leakage detection principle based on the physical characteristics of high magnetic permeability and magnetic refraction of ferromagnetic materials is used up to now, but the application mainly comprises qualitative detection.

The assumption of the magnetic flux leakage detection technology has been made internationally long. In 1933 Zuschlug firstly proposed the idea of using magnetic sensitive element to detect the leakage magnetic field. In 1975, Hwang and Lord performed the analysis of the leakage magnetic field by relating the internal field strength and permeability of the ferromagnetic material to the magnitude of the leakage magnetic field for the first time. In 1976, KrankKitZinger et al, norada mining ltd, canada, first utilized a hall element as a magnetosensitive element with the addition of an axial yoke comprised of permanent magnets to impart axial magnetization to a steel tube. In 1988, Atherton improved the research results of predecessors, utilized a two-dimensional finite element analysis method, combined with the influence of pipeline pressure on pipeline permeability, and conducted specific analysis on the distribution of the leakage magnetic field by developing a specific detection device, so as to obtain the corresponding relation between the leakage magnetic signal and the crack set parameters. Eduardo alsthcuper proposed in 1995 a non-linear defect detection model for pipe inspection. In 2006, Germany nondestructive testing and service company and U.S. Tuboscope pipeline service company collaborate to research the reliability problem of reconstructing the size of the magnetic flux leakage detection defect. In 2009, Sushant m.dutta and fathih. ghurbel et al self-built magnetic dipole models analyze the distribution of three-dimensional leakage magnetic fields. A.a.carvalho, j.m.a.rebello et al can identify defective and non-defective signals in the detection results using an Artificial Neural Network (ANN) algorithm.

The expert scholars in China begin to research the pipeline magnetic flux leakage detection from the last 80 th century, and related instrument development is advanced. Beginning in the nineties, a great number of foreign advanced pipeline magnetic flux leakage detection instruments are introduced in China, and most of the instruments are internal detectors. At present, the technology is always stabilized by other developed countries.

Disclosure of Invention

Aiming at the defects of the prior art, the invention adopts a new theory: under the guidance of the magnetic vacuum leakage principle, a magnetic shielding device is adopted to generate a local magnetic vacuum environment, so that the inner surface of the sleeve can form a maximized defect leakage magnetic field, and the maximum defect leakage magnetic field is picked up by the FL sensor.

1. The invention is realized by the following technical scheme: the utility model provides a based on low frequency magnetic leakage sleeve pipe type pipeline appearance of detecting a flaw, by FL sensor (1), magnetism shielding ware (2), magnetizing coil (3), signal processor (4), power module (5), singlechip (6), accurate potentiometre (7), LCD screen (8), button (9), switch (10), survey shell (11), plastic sleeve pipe (one side direction has belt formula discount) (12), computer (13) and constitute, its characterized in that: the power module (5) supplies power to all parts, the singlechip (6) generates adjustable square waves, the amplitude is adjusted through the precision potentiometer (7), the frequency is adjusted through the key (9), the adjustable square waves are displayed on the liquid crystal screen (8), the adjustable square waves are sent to the magnetizing coil (3) to generate a magnetic field, and the pipeline in the plastic sleeve (12) is magnetized; the magnetic shield (2) and the pipeline form a vacuum sealing area, so that an external magnetic field of the magnetizing coil (3) is shielded outside, and the FL sensor (1) is only influenced by a pipeline leakage magnetic field in the sleeve; after the surface of the pipeline is saturated and magnetized, when the magnetic shield (2) moves together with the plastic sleeve (12), the generated leakage magnetic field can be detected by the FL sensor (1) and is transmitted to the signal processor (4) to be filtered, amplified and A/D converted into a digital signal which can be processed by the computer (13); by the computer (13) using MATLAB processing, the magnetic field change curve chart can be obtained, thereby determining the damage position and the damage condition.

The magnetizing coil (3) is made of ferrite and is arc-shaped, the opening angle is 270 degrees, the thickness is 2cm, the radius is 10cm, and the length is 7 cm.

The working principle of the invention is that the magnetic field has diffusion and concentration characteristics, and the diffusion and concentration transfer of the magnetic field at the interface of the medium follows continuous conditions of equal ① tangential magnetic field strength, equal ② normal magnetic induction strength, namely:

where e is a unit vector perpendicular to the interface and directed from medium 1 to medium 2, B1(H1) and B2(H2) are the magnetic induction (magnetic field strength) in medium 1 (permeability μ 1) and medium 2 (permeability μ 2), respectively, and their included angles with the normal line e in media 1 and 2 are α 1 and α 2, respectively, from equation (1):

in the formula (2), B_ne(H_ne) And B_nτ(H_nτ) Normal and tangential components of the magnetic induction (magnetic field strength) in the medium n (n ═ 1,2), respectively, i.e.:

equation (3) constitutes the magnetic refraction and diffusion rule, the direction of magnetic refraction and deflection is related to the incident angle and the permeability of the medium, and the direction of the magnetic field and the geometry of the medium surface constitute the incident angle α₁Due to α₁0 ° or α₁A magnetic angle of incidence of 90 ° only occurs with ideal medium surface geometry, so that the actual magnetic angle of incidence range 0 is combined<α₁<Equation (3) is discussed below at 90 °.

(1) When mu is₂＝μ₁When, there is α₂＝α₁The magnetic induction lines directly pass through the interface without refraction. Under the same magnetization field H, B is known from B ═ muH₂＝B₁At this time, the magnetic pressures of the two are equal, and no magnetic leakage occurs when the magnetic pressure difference is zero.

(2) When mu is₂≤μ₁When, there is α₂≤α₁，μ₂The magnetic induction lines in the medium are refracted and folded to the normal n to form magnetic flux of mu₁Dielectric direction mu₂The leakage of the medium spreads.

At this time, since B₂＝μ₂H≤μ₁H＝B₁There is a reaction of₁Dielectric direction mu₂The magnetic pressure difference of the medium forms a magnetic leakage diffusion from the former to the latter when the magnetic pressure difference is mu₁The medium being a magnetically conductive member, mu₂When the medium is air, magnetic leakage from the magnetic conductive member to the air is finally formed. Due to abrupt defects, i.e. 0, at the interface of the media<α₁<The 90-degree condition is adopted, so that the defect magnetic air leakage principle and the corresponding magnetic leakage detection method are adopted.

But anyway, because mu₂(μ_air1) is greater than or equal to 1, so

It can be seen that due to mu₂(μ_airThe presence of ≧ 1) results in a maximum deflection leakage angle of 90 ° - α₂。

(3) From the analysis (1) and (2), it is further assumed that a certain mediator μ is present₂→ 0 or μ₂When 0, then:

or

Thus, the refracted rays of the magnetic flux lines are more deflected toward and coincide with the mid-normal, and the most severe extreme refraction occurs, resulting in eventual magnetic leakage.

At this time, since B₂＝μ₂H＝0，μ₂Without magnetic induction lines in the medium, i.e. for mu₁The medium, the background magnetic field of which is in the shape of magnetic vacuum, forms mu₂Dielectric to mu₁Magnetic attraction tendency of the media, or mu₁When the magnetic flux in the medium leaks, the reverse magnetic pressure effect is avoided, so that the leakage magnetic field generated by the defects is the most thorough, and the maximization is achieved. This magnetic leakage is referred to as magnetic vacuum leakage.

Artificially removing a strong background magnetic field, and allowing the magnetic flux in the magnetized magnetic conduction member to be detected to maximally leak to the created magnetic vacuum area at the defect without reverse magnetic pressure to form a maximized defect leakage magnetic field; at the same time, the FL sensor is placed within the formed magnetic vacuum region, picking up the maximized defect leakage field.

The invention has the beneficial effects that: in the design of the invention, the low-frequency magnetic leakage detection is used as a detection method, and the nondestructive detection is carried out on the damage of the inner surface of the sleeve on the basis of the function relation between the magnetic field intensity change and the damage position and the damage condition. The method eliminates signal distortion caused by an external strong magnetic field, can realize non-contact detection, has higher measurement accuracy, strong innovativeness and practical value, and has good application prospect.

Drawings

Fig. 1 is a flow chart of the work of a low-frequency leakage bushing-based pipeline flaw detector.

Fig. 2 is a schematic diagram of a detection structure of a low-frequency leakage sleeve type pipeline flaw detector.

Detailed Description

2. The utility model provides a based on low frequency magnetic leakage sleeve pipe type pipeline appearance of detecting a flaw, by FL sensor (1), magnetism shielding ware (2), magnetizing coil (3), signal processor (4), power module (5), singlechip (6), accurate potentiometre (7), LCD screen (8), button (9), switch (10), survey shell (11), plastic casing (one side direction has belt formula discount) (12), computer (13) and constitute its characterized in that: the power module (5) supplies power to all parts, the singlechip (6) generates adjustable square waves, the amplitude is adjusted through the precision potentiometer (7), the frequency is adjusted through the key (9), the adjustable square waves are displayed on the liquid crystal screen (8), the adjustable square waves are sent to the magnetizing coil (3) to generate a magnetic field, and the pipeline in the plastic sleeve (12) is magnetized; the magnetic shield (2) and the pipeline form a vacuum sealing area, so that an external magnetic field of the magnetizing coil (3) is shielded outside, and the FL sensor (1) is only influenced by a pipeline leakage magnetic field in the sleeve; after the surface of the pipeline is saturated and magnetized, when the magnetic shield (2) moves together with the plastic sleeve (12), the generated leakage magnetic field can be detected by the FL sensor (1) and is transmitted to the signal processor (4) to be filtered, amplified and A/D converted into a digital signal which can be processed by the computer (13); by the computer (13) using MATLAB processing, the magnetic field change curve chart can be obtained, thereby determining the damage position and the damage condition.

Claims (3)

1. The utility model provides a based on low frequency magnetic leakage sleeve pipe type pipeline flaw detector comprises FL sensor (1), magnetism shielding ware (2), magnetizing coil (3), signal processor (4), power module (5), singlechip (6), accurate potentiometre (7), LCD screen (8), button (9), switch (10), detection shell (11), plastic sleeve pipe (12), computer (13), its characterized in that: the power module (5) supplies power to all parts, the singlechip (6) generates adjustable square waves, the amplitude is adjusted through the precision potentiometer (7), the frequency is adjusted through the key (9), the adjustable square waves are displayed on the liquid crystal screen (8), the adjustable square waves are sent to the magnetizing coil (3) to generate a magnetic field, and the pipeline in the plastic sleeve (12) is magnetized; the magnetic shield (2) and the pipeline form a vacuum sealing area, so that an external magnetic field of the magnetizing coil (3) is shielded outside, and the FL sensor (1) is only influenced by a pipeline leakage magnetic field in the sleeve; after the surface of the pipeline is saturated and magnetized, when the magnetic shield (2) moves together with the plastic sleeve (12), the generated leakage magnetic field can be detected by the FL sensor (1) and is transmitted to the signal processor (4) to be filtered, amplified and A/D converted into a digital signal which can be processed by the computer (13); the FL sensor (1) is spaced from a component to be measured by 1mm-2 mm; the plastic sleeve (12) can be sleeved on the pipeline and is provided with a buckle head which can be stretched to adapt to pipelines with different sizes; by the computer (13) using MATLAB processing, the magnetic field change curve chart can be obtained, thereby determining the damage position and the damage condition.

2. The pipeline flaw detector based on the low-frequency leakage casing pipe type is characterized in that the magnetizing coil (3) is made of ferrite and is in the shape of an arc, the opening angle is 270 degrees, the thickness is 2cm, the radius is 10cm, and the length is 7 cm.

3. The pipeline flaw detector based on the low-frequency leakage sleeve is characterized in that the square wave frequency generated by the single chip microcomputer (6) is adjustable in steps from 10Hz to 1kHz, and the amplitude is adjustable from 1V to 3.3V.

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