RU2293314C1 - Intratube flaw detector's magnetic system - Google Patents

Abstract

FIELD: magnetic flaw detection.

SUBSTANCE: magnetic system can be used for carrying out flaw detection of steel pipelines due to inspection of dissipation magnetic fields due to probes being moved inside pipe. Magnetic system has permanent magnetic field source in form of two permanent magnets disposed coaxially. Poles of magnets, turned to meet each other, have opposite polarities. External poles of magnets are connected with magnetic circuit, which are made in form of discs. There are brushes on side surfaces of magnetic circuits, which brushes are fastened for mechanical contact with inner surface of pipe. There are devices for adjusting strength of magnetic field, which devices belong to magnetic circuits at side of poles of magnets. Elastic magnetic-permeable member is mounted between opposite poles of permanent magnets, which member serves for pressing of any magnet against corresponding device for adjusting strength of magnetic field.

EFFECT: improved uniformity of magnetic field of dissipation; higher sensitivity.

7 cl, 4 dwg

Description

The invention relates to the field of magnetic flaw detection of steel pipelines by examining the scattering magnetic fields using probes moving inside the pipe.

Various types of magnetic systems with permanent magnets are known that create a scattering magnetic field in the wall of a ferromagnetic pipe, by the changes of which, using sensors, they are judged on the presence of defects.

When using permanent magnets in in-tube flaw detectors, they are usually installed along the generatrix of the cylinder in a row, forming a ring magnet. One ring magnet is oriented toward the walls of the pipe by the N pole, the other by the S pole, while ring magnets of different polarity are spaced along the length of the pipe. Between the ring magnets in the pipe wall, a scattering field is created. A magnetic field can enter the pipe wall through the air gap between the pipe magnets and the wall or with the help of ferromagnetic elements in contact with the pipe wall.

In US Pat. No. 6,198,277, “Sensor Module for Use in a Gas Distribution Inspection System,” IPC G 01 N 27/82, published March 6, 2001, a magnetic field is generated by two rows of conical magnets mounted closely to each other along a circular generatrix of the cylinder. There is an air gap between the magnets and the pipe wall.

In patent EP 0051344 "Advanced magnetic system for conveyor inspection vehicles", IPC G 01 N 27/82, publication 05/12/1982, a magnetic field is created using two rows of magnets mounted by groups on a magnetic circuit connecting these groups of magnets. Flexible magnets or foils are installed on the magnets, having mechanical contact with the inner surface of the pipe under study.

The closest in design is the magnetic system of an in-line flaw detector described in Russian patent 2133032 "Method of magnetic flaw detection and device for implementing this method", IPC G 01 N 27/83, publication 10.07.1999. The magnetic system of the device contains an annular magnetic circuit, permanent magnets located on both ends of the magnetic circuit and annular brush pole pieces in contact with the inner surface of the pipeline.

All the solutions considered have a common drawback - the magnetic system used in these devices, consisting of several permanent magnets, creates an uneven magnetic field of scattering, since the permanent magnets cannot be selected the same. And the unevenness of the scattering magnetic field can lead to inaccurate determination of the size of the defect and a decrease in sensitivity.

The inventive magnetic system of the in-tube flaw detector in both embodiments allows you to adjust the magnetic field in the magnetic circuit, which increases the uniformity of the magnetic field scattering in the test pipe, which increases the sensitivity of the flaw detector and allows you to evaluate the emerging defects of the pipe.

The magnetic system of the in-tube flaw detector includes a source of a constant magnetic field in the form of two permanent magnets located axially, the poles of which are opposite to each other have opposite polarity. The outer poles of the magnets are connected to the magnetic cores, including, on the side of the poles of the said magnets, devices for adjusting the magnetic field strength. Magnetic cores are made in the form of disks, on the lateral surface of which brushes are fixed with the possibility of their mechanical contact with the inner surface of the studied pipe. Between the opposite poles of the permanent magnets, an elastic magnetically permeable element is installed, which serves to press each of the aforementioned magnet to the corresponding device for adjusting the magnetic field strength and the latter to the disk.

The poles of the permanent magnets are connected to devices for adjusting the magnetic field strength, which in special cases can be in the form of washers with holes or recesses. The area and distribution of holes or recesses in the devices for adjusting the magnetic field strength is selected so that the tension in the magnetic disk drives is the same, despite the fact that each of the magnets can have a different level of magnetic field strength.

The device for adjusting the magnetic field strength can be performed in the body of the magnetic circuit, in particular, in the form of recesses in the disk from the side of the pole of the permanent magnet.

To create a uniform magnetic field during the operation of the flaw detector, an elastic magnetically permeable element is also important, which serves to press each magnet to the corresponding device for adjusting the magnetic field strength, and if the device for adjusting the magnetic field strength is made in the form of a separate element, for example, a washer, then it is to the disk. It allows you to maintain tight contact between them and prevents the occurrence of gaps due to shocks or vibrations that occur when the flaw detector moves. It is also important that the magnetic cores are made in the form of disks with many brushes located on the side surface of the disks, which also allows you to create a uniform field in the entire circular segment of the pipe that the brushes touch.

Permanent magnets are most appropriate to perform cylindrical. In addition, permanent magnets can be installed in a housing made of non-magnetic material. In this case, they can be separated from the housing by damping elements.

The invention is illustrated by drawings.

Figure 1 shows a section of the magnetic system according to the first embodiment, in Figure 2 the system is shown in side view.

Figure 3 shows an embodiment of the device for adjusting the magnetic field in the form of a washer with holes, and Figure 4 is a device for adjusting the magnetic field in the form of recesses in the disk.

The magnetic system of an in-line flaw detector in the best embodiment (FIG. 1 and FIG. 2) includes a constant magnetic field source 1 in the form of two cylindrical permanent magnets 2 located axially. The outer poles of the magnets 2 (N and S) through the device 3 for adjusting the magnetic field in the form of washers 9 are connected to the disks 4. On the side surface of the disks 4 there are many brushes 5 fixed, which have mechanical contact with the inner surface of the pipe 12. Brushes 5 can be installed on disks 4 with the necessary frequency. Brushes can also be mounted on the side, end surface of the disc. Between the opposite poles (S and N) of the permanent magnets 2, an elastic magnetically permeable element 6 is installed, which serves to press each magnet 2 to the washer 9 and it to the disk 4. Magnets 2 are installed in the housing 7 from non-magnetic material, located between the wall of the housing 7 and the magnets 2 damping elements 8. Sensors 13 of the magnetic field of dispersion are installed between the rows of brushes 5 mounted on the disks 4.

One of the embodiments of the device 3 for adjusting the magnetic field strength, shown in FIG. 3, is a washer 9 with holes 10. The holes 10 or recesses in the soft magnetic material of the washer 9 are so thick as to provide the necessary magnetic field strength in the disk 4 of the magnetic circuit. The holes 10, as a rule, are performed symmetrically with respect to the axis of the washer 9 in order to ensure a uniform and symmetrical dispersion field in the walls of the pipe 12.

The device for adjusting the magnetic field strength can be performed directly in the part of the magnetic circuit, that is, in the disk 4, as shown in Fig.4. At the end of the disk 4, which is in direct contact with the pole of the magnet 2, a number of recesses 11 are performed, which act as a regulator of the magnetic flux intensity. However, this embodiment of the adjustment element requires changing the entire disk 4, and not a relatively small part, washers 9.

The magnetic system of the in-line flaw detector operates as follows.

In the process of preparing the flaw detector for operation, the magnetic field is checked at each of the disks 4 or at the ends of the brushes 5 of each of the disks 4. By selecting washers 9 with a different number of holes 10, a uniform magnetic field in the disks 4 and, therefore, the scattering field in the pipe are achieved. It should be borne in mind that with permanent magnets, the magnetic force can change during operation, so that the adjustment operation may be required repeatedly.

During operation, the permanent magnets 2 are protected from vibrations and shocks by the presence of an elastic magnetically permeable element 6 and damping elements 8.

The proposed system for adjusting the magnetic field strength can be used in magnetic systems of an in-tube flaw detector with an air gap.

The entire design of the magnetic system of the in-line flaw detector is simple and symmetrical, which allows you to create a fairly powerful symmetric scattering field. In the system, the magnetic flux is created by only two powerful permanent magnets that are connected to the magnetic circuit so that the magnetic flux losses are minimal and the scattering magnetic field is symmetrical.

Claims (7)

1. The magnetic system of the in-tube flaw detector, comprising a source of a constant magnetic field in the form of two permanent magnets located axially, the poles of which are opposite to each other have opposite polarity, and the outer poles of the magnets are connected to magnetic circuits, including magnetic field intensity adjustment devices from the poles of the said magnets , the mentioned magnetic cores are made in the form of disks, on the side surface of which brushes are fixed with the possibility of their mechanical contact with the inside renney surface of the tubular, wherein between the opposed poles of said permanent magnets is mounted a resilient magnetically permeable element serving for pressing each of said magnet to the corresponding adjustment unit magnetic field intensity. 2. The magnetic system according to claim 1, characterized in that the said permanent magnets are cylindrical. 3. The magnetic system according to claim 1, characterized in that the permanent magnets are installed in a housing of non-magnetic material. 4. The magnetic system according to claim 3, characterized in that the permanent magnets are separated from the housing by damping elements. 5. The magnetic system according to claim 1, characterized in that the said device for adjusting the magnetic field is made in the form of a washer with holes. 6. The magnetic system according to claim 1, characterized in that the said device for adjusting the magnetic field is made in the form of a washer with recesses. 7. The magnetic system according to claim 1, characterized in that the said device for adjusting the magnetic field is made in the form of recesses in the said disk.

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