RU2717902C1 - Transverse magnetisation system for an in-tube flaw detector - Google Patents

Abstract

FIELD: monitoring and measuring equipment.

SUBSTANCE: invention relates to instrumentation and particularly to magnetic flaw detection. Essence of the invention is that the transverse magnetisation system for the in-tube flaw detector comprises magnetic brushes, wherein the non-attached ends of the bristles of the magnetic brushes form a surface, which bending radius is equal to the pipeline inner surface radius, and each of the brush plates, on which one of the brushes of the magnetic brushes is fixed, is bent, wherein the ratio of the radius of the inner surface of the pipeline to the radius of the outer surface of the base of the brush plate is selected from range of 1.15–1.7.

EFFECT: high accuracy of diagnosing thick-wall pipelines of small diameter.

1 cl, 2 dwg

Description

Technical field

The invention relates to the field of instrumentation, in particular to magnetic flaw detection, and can be used in the development of devices for non-destructive testing of pipelines, namely the magnetic system of an in-line flaw detector.

State of the art

The prior art patent RU 111299 U1 “Intra-pipe magnetic flaw detector with transverse magnetization (options)” (Patentee: ZAO Scientific and Production Association "Spectrum", ZAO "Scientific and Production Association" Spetsneftegaz "(RU)), published on 12/10/2011, in which a useful model is disclosed relating to devices for monitoring the state of long pipelines, namely, to identify defects in main oil and gas products pipelines by passing diagnostically shell, recording data on-board computer and then determining the parameters of pipeline defects from the accumulated data.

An in-tube magnetic flaw detector with transverse magnetization, made in the form of a section, contains a housing (yoke), at the ends of which there are supporting-motor elements, a magnetizing system made in the form of two magnetizing belts mounted on the housing from radially magnetized permanent magnets, the poles of which are magnetically fixed soft magnetic brushes, each of the magnetizing belts is divided into magnetic modules of transverse magnetization, formed by two bipolar blocks (pole ami), moreover, a hole is made inside the magnetic module - the pole space, which forms the measuring zone. Magnetic modules are evenly spaced around the perimeter of the magnetizing belt, and the magnetization in adjacent magnetic modules is multidirectional. The magnetic modules of one magnetizing belt are offset relative to the magnetic modules of the other magnetizing belt by an angle π / n, where n is the number of magnetic modules in the magnetizing belt. In the measuring zone, magnetic field sensors spring-loaded to the pipe walls are installed, which measure the magnetic field component H _{at the} perpendicular to the pipe generatrix.

Additionally, magnetic field direction sensors are introduced into the device, which measure the angle α between the direction of the magnetic field vector and the direction perpendicular to the generatrix of the pipe, and the magnetic field direction sensors alternate in the measuring zone with the magnetic field sensors. Thin-film magnetoresistive sensors or other sensors measuring the direction of the magnetic field vector are used as sensors for the direction of the magnetic field.

Also known is the patent RU 40804 U1 “In-tube magnetic flaw detector (options)” (Patentee: LLC “Scientific and Technical Center“ Neftegazspetsproekt ”(RU)), published September 27, 2004, which refers to a utility model that relates to in-line magnetic inspection the state of the walls of oil and gas pipelines.

Known flaw detector contains sections for both longitudinal and transverse magnetization. Each of these sections contains a magnetization system with permanent magnets and elastic brushes made of steel wire. These magnetization systems create a saturation magnetic field in the pipe wall, which is scattered by the continuity defects of the pipe walls. Scattering fields are recorded by magnetic field converters, which are made on the basis of Hall elements. Hall converters are attached to runners sliding along the inner surface of the pipe and pressed by elastic levers to it. The transducers located on the section of longitudinal magnetization measure the longitudinal, and on the section of the transverse magnetization, respectively, the transverse component of the magnetic field. In addition, the flaw detector contains a ring of magnetic field transducers that measure the radial component of the magnetic field.

After analog-to-digital conversion, data from magnetic field converters are recorded on a data carrier together with information from odometric sensors, pressure and temperature sensors.

The closest analogue of the claimed invention is a “Magnetic transverse magnetization system with fixed magnetic modules for an in-tube flaw detector” disclosed in the patent for utility model RU 147368 U1 (Patentee: Transneft PJSC, Transneft Diascan JSC (RU)), published on 10.11 .2014, IPC: G01N 27/83.

A well-known utility model relates to the field of magnetic flaw detection, to devices for non-destructive testing of pipelines and relates to the magnetic system of an in-line flaw detector.

The transverse magnetization magnetic system with fixed magnetic modules for an in-line flaw detector consists of two main and four additional magnetic module belts mounted on two magnetic circuits connected by a non-magnetic insert. Each magnetic module consists of permanent magnets and elements of ferromagnetic material that transmit magnetic flux to the pipe wall. The magnetic modules adjacent to the belt have the opposite direction of the magnetic field in the interpolar space. The main poles of the magnetic modules are located with an angular displacement relative to each other by an angle cp: ϕ = 180 ° / N, where N is the number of magnetic modules in one belt. Between the magnetic poles along the entire circumference of the pipeline installed sensors that record any change in magnetic induction caused by a change in the wall thickness of the pipeline.

On the edges of the main belts of the magnetic modules, additional belts of the magnetic modules are installed, while two additional belts of the magnetic modules are located between the main belts of the magnetic modules and serve to compensate for the mutual influence of the magnetic field of the main belts of the magnetic modules and to reduce the asymmetry of the magnetic field, which is caused by the proximity of the main belts magnetic modules. Each additional belt of magnetic modules, in order to correct the asymmetry of the field, has an angular displacement relative to the main magnetic belt by an angle α <90 °.

To reduce the error, the pipeline material is magnetized to a state of technical saturation, since with an increase in magnetization, the intrinsic noise of the pipeline material and the sensitivity of the flaw detector measuring system to the pipeline material are reduced.

In the development of a utility model, a magnetic transverse magnetization system with fixed magnetic modules for an in-line flaw detector can be performed both single-section and multi-section, while it consists of two main and more, and four or more additional magnetic module belts installed on two or more magnetic circuits, while the non-magnetic insert is replaced by a cardan joint.

The magnetic system of transverse magnetization in the closest analogue consists of a solid magnetic circuit, on which are fixed permanent magnets and brushes made of steel wire. The magnetic flux of permanent magnets is closed on the one hand by the magnetic circuit and brushes, on the other hand by the wall of the diagnosed pipe. Because with transverse magnetization there is no axial symmetry, then the field from the pole gap tends to spread. This leads to a decrease in tension and an increase in field heterogeneity, which negatively affects the accuracy and quality of diagnostics. To reduce the spreading along with the main magnets, additional (alignment, closing) magnets are used. Additional magnets do not allow the field to spread, so the field strength increases and uniformity increases. The disadvantage of this system is the high magnetic resistance of the bristles of the brushes, which limits the magnetic flux transmitted to the pipe. Such a solution is suitable for large-diameter pipelines, and is not applicable for the diagnosis of thick-walled small-diameter pipelines.

Disclosure of the invention

The objective of the invention is to develop a transverse magnetization system for an in-line flaw detector, which allows the flaw detector to make turns and narrowings in thick-walled pipelines of small diameter, while at the same time creating the required magnetic field strength in the diagnosed area of the pipe wall.

The technical result of the invention is to increase the accuracy of diagnosis of a thick-walled pipeline of small diameter.

The set of essential features sufficient to achieve the indicated technical result and defining the scope of legal protection of the invention includes a transverse magnetization system for an in-line flaw detector containing a magnetic unit including a protective housing with a permanent magnet installed in it, pole mounted on opposite ends of the protective housing lugs with magnetic brushes mounted on brush plates mounted in an interpole simple anstve magnetic field sensors mounted on the ends of the container body locomotor elements. Each of the magnetic brushes contains a main part in the central region of the magnetic brush, and additional parts along the longitudinally opposite edges of the magnetic brush. In this case, the loose ends of the magnetic brush bristles form a surface whose bending radius is equal to the radius of the inner surface of the pipeline, and each of the brush plates, on which one of the ends of the magnetic brush bristles is fixed, is made curved, and the ratio of the bending radius of the brush plate to the radius of the inner surface of the pipeline is selected from the range of 1.15-1.7.

The claimed transverse magnetization system for an in-line flaw detector is illustrated by drawings (Fig. 1-2), which show: Fig. 1 (a, b, c, d) - magnetic system of transverse magnetization, FIG. 2 - a magnetic system as part of a transverse magnetization section.

In FIG. 1, 2 positions marked:

1 - pole tip;

2 - permanent magnet;

3 - the base of the brush plate;

4 - magnetic field sensors;

5 - a protective housing of the magnetic unit;

6 - direction of magnetization;

7 - magnetic brushes;

8 - the main part of the magnetic brush;

9 - an additional part of the magnetic brush;

10 - interpolar space;

11 - musculoskeletal elements;

12 - gimbal connection.

The claimed invention describes a transverse magnetization system for an in-line flaw detector, and is intended to diagnose the condition of thick-walled pipelines of small diameter for transporting gas, oil and oil products, the pipe wall thickness of which is in the range from 8 to 15 mm, and the outer diameter is from 159 to 377 mm. The transverse magnetization system (Fig. 1) contains a magnetic unit with a permanent magnet 2, pole pieces 1 with magnetic brushes 7 and magnetic field sensors 4.

The magnetic unit includes a protective housing 5 with a radially magnetized permanent magnet 2 of an H-shape in horizontal projection installed in it. The protective housing 5 covers the permanent magnet 2 from the sides parallel to the direction of magnetization 6 and is made of non-magnetic material. The proposed design of the magnetic unit, unlike the closest analogue, does not have a magnetic circuit, and the main and additional magnets of both poles are replaced by a single permanent magnet 2, the dimensions and configuration of which make it possible to provide a saturation magnetic field in the wall of the diagnosed thick-walled pipeline of small diameter, the magnitude of which is in the sensor region magnetic field not less than 6 kA / m.

At the opposite ends of the protective housing 5 in the transverse direction relative to the axis of the pipeline, pole pieces 1 are fixed with magnetic brushes 7 made of soft magnetic material, in an advantageous embodiment of the invention steel. Magnetic brushes 7 are fixed to the base of the brush plates 3. Each of the magnetic brushes 7 contains a main part 8 in the central part of the magnetic brush 7, and additional parts 9 along opposite edges of the magnetic brush 7 in a direction longitudinal to the axis of the pipeline. Magnetic brushes 7 are made elastic due to the fact that their bristles are a rope-like twisted bundle of wire segments, mainly steel.

The brush plates in horizontal projection have an H-shape, repeating the shape of a permanent magnet 2. Each of the brush plates, on which one of the ends of the bristles of the magnetic brushes 7 is fixed, is made curved. Moreover, the loose ends of the bristles of the magnetic brushes 7 of each of the brush plates form a surface whose bending radius is equal to the radius of the inner surface of the pipeline. Moreover, the ratio of the radius of the inner surface of the pipeline to the radius of the outer surface of the base of the brush plate 3 to is selected from the range of 1.15-1.7. When the radius ratio is less than 1.15, the significant stiffness of the bristles in the main part 8 of the magnetic brush, associated with a decrease in their length in this area, will increase the resistance to movement of the transverse magnetization section during the passage of the constrictions and turns of the pipeline. In addition, the ratio of the radii less than 1.15 will result in a structurally caused decrease in the width of the permanent magnet 2 in the region of the additional part 9 of the magnetic brushes, which will not allow creating the required magnetic field strength in the pipe wall.

With a radius ratio of more than 1.7, a significant length of the bristles in the main part 8 of the magnetic brush will create significant resistance to magnetic flux, and as a result will not allow you to create the required magnetic field strength in the pipe wall. Moreover, in the range 1.15-1.7, the ratio of the lengths of the bristles in the main 8 and additional parts 9 of the magnetic brushes will be optimal to achieve the claimed technical result.

Thus, the length of the bristles of the magnetic brushes 7, mounted on the brush plates, in the main part 8 of the magnetic brush is longer than in the additional parts 9 of the magnetic brushes, which is necessary to facilitate the passage of the constrictions and turns of the pipeline. The aforementioned configuration of the brush plates and differences in the length of the bristles prevent the spreading of the magnetic field and ensure optimal stiffness of the bristles during passage of contractions and turns in thick-walled pipelines of small diameter. This makes it possible to increase the accuracy of diagnostics of a thick-walled pipeline of small diameter.

In the interpolar space 10 (Fig. 2), which forms the measuring zone, magnetic field sensors 4 are installed elastically pressed against the walls of the pipeline by spring-loaded levers that measure the magnetic field induction. In an advantageous embodiment of the invention, magnetic field transducers based on Hall elements are used as sensors 4 of the magnetic field. At the front and rear ends of the protective housing 5 are installed musculoskeletal elements 11, which in the particular case of execution can be polyurethane cuffs equipped with a gimbal connection device 12.

The claimed system operates as follows.

The claimed transverse magnetization system is used to magnetize the pipeline wall in the direction transverse to the axis of the pipeline, in order to identify defects in the pipeline by changing (leakage) the magnetic field in the area of defects in the pipeline wall. This system is part of a magnetic flaw detector and can work both in conjunction with a longitudinal magnetization magnetic system, and separately, provided that it is equipped with an information collection unit. The flaw detector is stored in the diagnosed pipeline and, under the influence of the pressure of the pumping product, similarly to the piston, moves along the pipeline. The magnetic field sensors 4, located in the interpolar space 10 of the transverse magnetization system, measure the value of electromagnetic induction near the inner surface of the pipe wall and record the change in the magnetic field in the region of defects.

Unlike the longitudinal magnetization system, the transverse magnetization system is designed primarily to detect defects elongated along the axis of the pipeline (cracks, risks). For diagnostics in a full circle, two identical magnetic transverse magnetization systems are used, rotated 90 ° relative to each other around the axis. The proposed system due to the magnets of larger volume allows you to create sufficient magnetic field strength in the pipe wall, which in turn allows you to diagnose defects in thick-walled pipelines of small diameter (159-377 mm). Diagnostics of such pipelines by transverse magnetization systems of the prior art has not been identified.

The technical result of the invention is to increase the accuracy of diagnosis of a thick-walled pipeline of small diameter by creating a transverse magnetization system for an in-line flaw detector that provides the required magnetic field strength in the pipe wall.

Claims (1)

A transverse magnetization system for an in-line flaw detector, characterized in that it comprises a magnetic unit including a protective housing with a permanent magnet installed in it, pole tips with magnetic brushes mounted on brush plates mounted in opposite spaces in the transverse opposite ends of the protective housing, mounted in the interpolar space magnetic field sensors mounted on the ends of the protective housing of the musculoskeletal elements, each of the magnetic brushes contains the main part in the central region of the magnetic brush and the additional parts along the longitudinally opposite edges of the magnetic brush, while the loose ends of the brushes of the magnetic brushes form a surface whose bending radius is equal to the radius of the inner surface of the pipeline, and each of the brush plates on which one of the ends is attached the bristles of the magnetic brushes are made curved, and the ratio of the radius of the inner surface of the pipeline to the radius of the outer surface of the base of the brush plate is selected from azone 1,15-1,7.

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