RU2404471C1 - Device for local demagnetisation of pipelines - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device for local demagnetisation of pipeline elements consists of a demagnetising cable powered by direct current from a welding rectifier and designed in the form of a multiturn coil connected by connectors lying in a metal framework, on which sensors of magnetic field magnitude and direction are mounted on both sides of a weldable seam, and current is fed through a control unit which is incorporated in a system for feedback coupling with said magnetic field sensors, the metal framework consists of an open ferromagnetic magnetic circuit with a coil inside, pole-pieces and nonmagnetic plates in form of pipes, alternately situated with respect to the magnetic circuit, wherein said pole-pieces are in form of a five-star mechanism on hinges with control of the diametre of the lower cylindrical surface in the range from 325 to 1420 mm and on supports with a magnet lock which can be made in form of magnetic wheels with axial direction of magnetisation.

EFFECT: enhanced operation of the device for pipes with different diametres while providing good quality of local demagnetisation.

2 cl, 3 dwg

Description

The present invention relates to techniques for the demagnetization of pipes, pipe joints of field and main gas pipelines of all categories and other magnetized products. When conducting magnetic inspection of an in-pipe or external inspection of a pipeline, significant residual magnetization occurs.

In particular, when repairing pipelines by replacing damaged pipe sections, residual magnetization not only significantly complicates the process of electric welding, but sometimes makes it impossible due to the influence of the known effect of “magnetic blast”.

The closest in technical essence to the proposed invention is a device for compensating for the magnetic field of the pipeline (utility model certificate No. 13271, IPC H01F 13/00), consisting of a demagnetizing cable wound around a pipe and fed by direct current from a welding rectifier, the demagnetizing module is performed in in the form of split rings containing multi-turn coils connected using multi-pin connectors located in a non-magnetic metal frame with sensors pivotally mounted on it elichiny and direction of the magnetic field in the welded seam area, and it is applied on both sides of a welded seam and a demagnetizing current compensation unit is fed through an electronic control unit included in a feedback system with sensors of the magnetic field.

The disadvantage of this technical solution is the use of only one pipe diameter due to split rings with the same diameter.

A device for local demagnetization of pipelines (patent for software No. 70778),

characterized by:

- the composition of the main elements: a housing with supports and a handle, a measuring device, magnetic clips, connecting cable;

- a solution in the form of a U-shaped composition formed by a horizontally oriented body and two supports oriented along the sides of the body;

- the decision of the shape of the body in the form of a horizontally oriented half-cylinder, paired with a rectangular parallelepiped;

- the decision of the upper wall of the housing in the form of a removable cover;

- the location of the connectors for connecting cables on the cover;

- the location of the handle on the rear wall of the housing at an obtuse angle to its surface, protruding beyond the level of the upper wall of the housing;

- the location on the front wall of the casing of the digital display;

- the implementation of each support in the form of legs attached at an angle to the center of the base;

- the implementation of the base with a trapezoidal upper surface and an arcuate lower;

- the location of the magnetic clips at the junction of the legs and base;

- the implementation of the measuring device L-shaped with an explicit separation into the handle of the measuring device and the sensor holder;

- by performing a power button on the handle of the measuring device.

This device is designed to demagnetize pipes of the same diameter due to the base (pole piece) with a constant shape of the lower surface.

A device for local demagnetization of pipeline elements (patent RU No. 2331945 dated 05/23/2007), consisting of a demagnetizing cable supplied with direct current from a welding rectifier and made in the form of a multi-turn coil connected using connectors located in a metal frame with magnitude sensors mounted on it and the direction of the magnetic field in the area of the welded seam, is imposed on both sides of the welded seam, and the current is supplied through the control unit included in the feedback system with magnetic sensors total field, the frame is made of composite open ferromagnetic magnetic circuit with a coil located inside, pole pieces and non-magnetic plates of rectangular shape with a lower cylindrical diameter surface equal to the outer diameter of the pipe, which are alternated relative to the sides of the magnetic circuit, and coated with fire-resistant material.

This device is applicable for the demagnetization of pipes of the same diameter during welding.

The objective of the invention is to expand the capabilities of the device for the nomenclature of pipes of various diameters.

The problem is achieved in that the device of local demagnetization of pipeline elements, consisting of a demagnetizing cable, supplied with direct current from a welding rectifier and made in the form of a multi-turn coil connected using connectors located in a metal frame with sensors mounted on it for the magnitude and direction of the magnetic field in zone of the welded seam, imposed on both sides of the welded seam, and the current is supplied through the control unit included in the feedback system with the sensor magnetic field, the frame is made up of an open ferromagnetic magnetic circuit with a coil located inside, pole pieces and non-magnetic plates of the pipe shape, which are arranged alternately relative to the sides of the magnetic circuit, the tip is made in the form of a five-link mechanism on hinges with adjustment of the diameter of the lower cylindrical surface ranging from 325 up to 1420 mm and supports with magnetic lock. In this case, the supports are made in the form of magnetic wheels with an axial direction of magnetization.

The proposed device is a local demagnetization is illustrated by drawings. Figure 1 presents the demagnetization circuit, figure 2, figure 3 is a section and General view of the device of local demagnetization.

The device for local demagnetization of pipelines contains a frame 1, on the inside of which a multi-turn coil 2 of a demagnetizing cable 3 is wound. The frame 1 is made of a ferromagnetic magnetic circuit 4, two alternating non-magnetic plates 5 of a rectangular shape and pole pieces 6 in the form of a five-link mechanism 7 on hinges 8 and on supports 9 with a magnetic lock 10. A magnetic field sensor 11 is mounted on the frame 1, which is connected to the control unit 13 through the connector 12 to the control unit 13. The frame 1 with the coil 2 and the sensor 7 is installed oval in the area of the welded joint 14 of the elements of the pipeline 15, where the electrode 16 is located, which is connected to the welding rectifier 17. The pole tip 6 due to the bending of the five link tip 7 on the joints 8 is installed in the shape of the pipe 15.

The device operates as follows. The frame 1 with the coil 2 of the demagnetizing cable 3 is placed in an open magnetic circuit 4 and, when installed on the pipe to be welded, closes the magnetic circuit so that a predetermined magnetic flux passes in the pipe wall in the direction perpendicular to the welded joint 10.

Removable ferromagnetic pole pieces 6 allow the passage of magnetic flux through the welding joint, and removable non-magnetic plates 5 establish the necessary air gap 14 with the cylindrical surface of the pipe of any diameter. Thus, the demagnetizable pipe section becomes part of the magnetic circuit of the coil with an adjustable magnetic flux both in magnitude and direction.

Using the DC power source of the control unit 13, the coil current required in magnitude and direction is set, the field of which compensates for the residual magnetic induction in the area of the weld joint 14. After the device is turned on by the magnitude and direction of the magnetic field sensors in the area of the weld being welded, such as Hall sensors 11, the current direction is determined through coil 2, and a coil 2 is created by a field directed towards the field in the pipe with a minimum magnetic gap of weld 14. Change in the magnitude of the magnetic field in the welding zone due to s causes controlled by a sensor 11, and unit 13 automatically changes the current through the coil 2.

Upon reaching the magnitude of the magnetic induction to values of 20 Gs≥V≥-20Gs, it is allowed to conduct electric welding.

In operating mode, the device is magnetized by a compensating flow to the section to be welded and is firmly held on the pipe in any position, and in the off state it is easily moved to any section of the pipe. In the idle state, the device is held on any part of the pipe by two magnetic locks 10, each of which is two permanent magnets with a set of steel plates installed between them 3. The magnetic flux of permanent magnets, closing through the plates and the pipe wall, keeps the device on the pipe inoperative condition. Magnetic wheels mounted on the ends of the ferrules allow the device to move along the pipe weld. The magnetic wheel consists of a permanent magnet with a magnetization direction along the axis of the wheel and two rollers made of steel 3. A closed magnetic circuit allows demagnetization of pipe sections with uneven ring magnetization. Made a prototype of the inventive device (figure 3). To test a device with a five-link tip, the demagnetization of welded joints was carried out in the repair and restoration of gas pipelines with a diameter of 325 mm (wall thickness 6.5 mm) and 1420 mm (wall thickness 17.5 mm).

The initial value of the magnetic field induction in the joint gap was 35 mT. A demagnetizing coil was used, containing a total of 330 turns. The total installation time was 2 minutes. After switching on the electronic control unit, minimization of the magnetic field was achieved at a current <4 A with an output voltage of the welding rectifier of 18 V. The control measurements of the magnetic field in the weld gap gave values less than 1.5 mT. A weld of the weld carried out under these conditions according to the criteria of fractography, microanalysis of the weld sections along the length and cross-section (property indices as required by Table 12 RD 03-614-03) and magnetic flaw detection data (GOST 3.242-79. Welded joints. Quality control methods.) showed its good quality.

Claims (2)

1. A device for local demagnetization of pipeline elements, consisting of a demagnetizing cable, supplied with direct current from a welding rectifier and made in the form of a multi-turn coil connected using connectors located in a metal frame with sensors for magnitude and direction of the magnetic field in the area of the weld being welded, impose on both sides of the weld, and the current is supplied through the control unit included in the feedback system with magnetic field sensors, the frame is made with identical from an open ferromagnetic magnetic circuit with a coil located inside, pole pieces and non-magnetic plates of pipe shape, which are arranged alternately relative to the sides of the magnetic circuit, characterized in that the tip is made in the form of a five-link mechanism on hinges with adjustable diameter of the lower cylindrical surface ranging from 325 to 1420 mm and supports with magnetic lock. 2. The device of local demagnetization of pipeline elements according to claim 1, characterized in that the supports are made in the form of magnetic wheels with an axial direction of magnetization.

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