RU13271U1 - PIPELINE MAGNETIC FIELD COMPENSATION DEVICE - Google Patents

Abstract

A device for compensating for the magnetic field of a pipeline, consisting of a demagnetizing cable wound around a pipe and supplied with direct current from a welding rectifier, characterized in that the demagnetizing module is made in the form of split rings containing multi-turn coils connected by multi-pin connectors located in a non-magnetic metal frame with sensors of magnitude and direction of the magnetic field pivotally mounted on it in the area of the weld being welded, and impose it on both sides of the weld th joint, and the compensation current to the demagnetizing module is fed through an electronic control unit included in a feedback system with sensors of the magnetic field.

Description

Device for compensating the magnetic field of the pipeline

The utility model relates to electrical engineering, namely, devices for demagnetization and compensation of magnetic fields of large-sized pipelines from magnetic materials in the process of electric arc welding, in particular, during repair work.

With the magnetization of welding objects, welding processes using an electric arc become unstable and the likelihood of defects in the welded joint increases. To remove magnetization, the method of demagnetization of ferromagnetic bodies is widely known. consisting in magnetization reversal by their alternating magnetic field with an amplitudes decreasing to zero (for example. 1). However, the method is unsuitable for the demagnetization of long thick-walled pipes due to the impossibility of fully demagnetizing them and the occurrence of vibrations of the demagnetized object when applying non-saturated frequencies of an alternating field. In addition, the electric power needed to carry out such demagnetization cannot be obtained from mobile power plants.

For pipelines, a device is known for compensating for magnetization by creating local magnetic fields of the opposite direction by several turns of a welding wire wound around one pipe at a distance of 200-400 mm from the welding site, by applying a direct current of 50-200 A so. so that when the current increases, the field in the gap decreases, and at the start point of welding it is minimum 2. At the same time, the magnetic field in the gap of the weld being welded is controlled by a portable magnetic probe, and direct current is supplied from the welding rectifier with discrete adjustment.

IPC H01F13 / 00

The main disadvantage 2. taken for prototin. lies in the fact that it does not provide the necessary reduction in the level of magnetic zero to a level of less than 2 mT in the gap of the weld. This is explained by the fact that the field induction in the gap observed for pipes with a diameter of the order of 1000 mm reaches values of more than 100 mT. and to neutralize it requires currents of not less than 500 A at the really possible number of turns (i.e., about 10). Such currents cannot be issued by mobile power sources for a sufficiently long time necessary for welding. In addition, the adjustment of the current value of the welding rectifier can only be stepwise, which often does not allow obtaining the necessary magnetization reduction. A significant drawback is. that during repair work in the field, the installation of the device, measurements of the magnetic field, often inhomogeneous, and the selection of the necessary compensation current are quite long (at least 0.5 hours).

The technical problem to be solved is to reduce the magnetic field induction in the gap of the welded pipe joint to a level below 2 mT with initial values of about 200 mT, to reduce the current consumption and reduce labor costs for preparing magnetized large pipelines for welding.

The problem is solved as follows. The proposed device for compensating for the magnetic field of the pipeline consists of a demagnetizing module placed on the pipe, magnetic field sensors, and an electronic control unit. The device is powered by direct current from a welding rectifier. The demagnetizing module is made in the form of hollow detachable non-magnetic metal rings containing multi-turn coils connected with the help of multi-pin connectors, equipped with sensors for magnitude and direction of magnetic zero pivotally mounted in the zone of the weld. When the device is operating, the demagnetizing module is applied on both sides of the welded seam, and the compensation current is supplied to the demagnetizing module through the electronic control unit, which is included in the feedback system with magnetic field sensors.

The manufacture of a demagnetizing module in a detachable metal casing reduces the time of mounting and dismounting it on the pipeline several times. The use of a non-magnetic metal frame for coils protects them from damage by splashes of molten metal and, in comparison with the prototype, allows them to be placed at a shorter distance from the weld being welded. In addition, the rigid frame allows you to associate with it and magnetic field sensors. The increase in the number of turns of the demagnetizing coil allows, in comparison with the prototype, to reduce the amount of current consumed while maintaining the number of ampere turns necessary for demagnetization, and the separation of the demagnetizing coil into two. superimposed from different sides of the weld prepared for welding leads to a decrease in the required number of ampere-turns.

The utility model is illustrated as follows. Pa fig. A longitudinal section of a welded pipe 1 with a clearance for welding 2. ) exceeding the width of the seam 2. This avoids the effect of the dependence of the measured magnetic induction on the width of the gap 2. To ensure the possibility of continuous operation, several sensors are installed on the seam 4. They are pivotally mounted on a rigid frame of a multi-turn compensating coil, which allows the welder to easily deflect them from the welding zone when creating interference to the welding process. Sensors of the magnetic field of the device are located directly in the area of the welded seam and constantly monitor the level of magnetic

fields. A change in the magnetic state in the weld gap during the welding process is monitored by sensors, and the control unit automatically changes the compensating current. In the case of magnetic field inhomogeneity along the length of the welded seam. exceeding 4 mT, the control unit 6 can be switched to manual mode in order to set the magnetic field induction at the anomalous point of gap 2 to a minimum.

After turning on the device, the sensors 4 determine the direction of the field, and the electronic unit 6 selects the direction of the current through the coils 3 so. so that the field created by them is directed towards the field in the pipe, and a current value is set through the coils 3. which minimizes the magnetic field in the joint gap 2. A change in the magnetic field in the weld zone of this joint 2, for various reasons, is monitored by sensors 4 , and, accordingly, block b automatically changes the current through the coils 3.

Made a prototype of the claimed device. Its tests were carried out during repair work on the 01220 mm oil pipeline with a pipe wall thickness of 13 mm. The initial value of the magnetic field induction in the gap gap. prepared for welding, amounted to 165 MT. Demagnetizing coils were used. containing a total of 150 turns. The total installation time of the compensating coils was 10 minutes. After switching on the electronic unit, minimization of the magnetic field was achieved at a current of 18 A with an output voltage of the welding rectifier of 70 V. The control measurements of the magnetic field in the joint gap gave values less than 1.5 mH. Conducted under these conditions, the weld of the seam according to x-ray inspection showed its good quality.

A comparative analysis with the prototype shows that the inventive device is characterized by a reduction in current consumption by 10 times. 3 times reduction in labor costs and allows you to fully compensate for the magnetic field with an initial induction of about 200 mT. Comparison of the claimed technical solution with the prototype made it possible to establish that the claimed device is distinguished by the presence of new units: split coils and electronic control unit for compensation current. working in feedback mode with magnetic field sensors. Thus, the claimed technical solution meets the criterion of "novelty. The introduction of automatically controlled compensation of the magnetic field of the pipeline leads to an increase in the reliability of demagnetization and. accordingly, to improve the quality of welding, and therefore it provides the claimed technical solution according to the criterion of "significant differences. The industrial applicability of the technical solution is shown above.

Sources of Information

1.A.S. USSR No. 1734126, H01F13 / 00. Bull. .№ 18.1992.

2.Korolkov P.M. Installation, and special. work in the building, 1993. No. 2. p.22-26.

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Ivoilov I.G.

 Halabuda U.E. U Khripunov D.M. (Khuzin R.A.

Kamenskikh S.V. L Akhmetshin R.T.

Mirgasimov P.M.

Claims (1)

A device for compensating for the magnetic field of a pipeline, consisting of a demagnetizing cable wound around a pipe and supplied with direct current from a welding rectifier, characterized in that the demagnetizing module is made in the form of split rings containing multi-turn coils connected by multi-pin connectors located in a non-magnetic metal frame with sensors of magnitude and direction of the magnetic field pivotally mounted on it in the area of the weld being welded, and impose it on both sides of the weld th joint, and the compensation current to the demagnetizing module is fed through an electronic control unit included in a feedback system with sensors of the magnetic field.