Device for reducing friction forces of a magnetising device

Abstract

The present invention relates to a device for non-destructively testing pipelines. In order to prevent a magnetisation device from being damaged on the wall of the pipeline due to attractive forces between the magnetisation device and the wall of the pipeline when testing pipelines, the device has a compensation unit which movably connects the support device to the magnetisation device via an adjustment unit, wherein the adjustment unit is supported on the device via a force-storing means.

Description

[0001] Device for reducing the frictional forces of a magnetizing device

[0002] The present invention relates to a device for the non-destructive testing of pipelines with at least one measuring unit for recording measured values ​​of the pipeline, wherein the measuring unit has at least one magnet, in particular designed as a permanent magnet, which is preferably arranged in a magnetizing device and which, when the device is in use, generates attractive forces between the magnetizing device and the wall of the pipeline, wherein the magnetizing device is connected to a support device which supports the magnetizing device against the wall of the pipeline when the device is in use, and wherein the device is designed to move along the pipeline.

[0003] Examples of magnetic methods for inspecting pipelines include the MFL and EMAT methods. When inspecting a pipeline, or even a metal storage tank, using the MFL and EMAT methods, a stronger magnetization of the metal wall must be generated. The MFL and EMAT methods are used to evaluate the quality of metal walls and, in particular, to identify defects such as corrosion or cracks. In the inline method, sensors are moved through a pipeline to be inspected in order to draw conclusions about the quality of the wall being inspected from the sensor data of the measuring unit. The inspection can also be carried out from the outside, and when inspecting storage tanks, the sensors can be moved along the inside and outside of the wall of the storage tank.If the following refers to pipelines or a pipe, the statements also apply to storage containers. In the MFL or magnetic flux leakage method, a magnetic field is induced in the pipe wall. Material defects, such as corrosion or other forms of material erosion, can be detected by measuring the deviating magnetic field that partially escapes from the pipe wall using appropriate sensors. The magnetization of the pipe wall has a significant influence on the accuracy of the information. If the pipe wall is not sufficiently magnetized, anomalies cannot be detected. The EMAT method - Electro Magnetic Acoustic Transducer - is an ultrasonic testing technology in which ultrasonic waves are generated and received electromagnetically.In this method, a magnet is used to generate a static or quasi-static magnetic field, which is superimposed on alternating magnetic fields generated by a coil. An EMAT induces ultrasonic waves into a test object through magnetostriction, the strength of which depends on the magnetic field induced by the magnets. Here, too, the quality of the pipe inspection is influenced by the strength of the applied magnetic field.

[0004] In most cases of non-destructive testing of pipelines, the magnetic field is generated using one or more permanent magnets that are part of the fixture. However, these magnets exert strong forces of attraction on the wall. The fixture containing the magnet(s) moves along the pipe wall with increased friction due to these forces of attraction.

[0005] Pipeline inspection equipment is moved by the internal transport of the pipeline medium or on or by a crawler. This often becomes a challenge in pipelines with low internal pressure. Due to the high friction, the crawlers also consume more energy and require a complex design to pull themselves and the equipment. When inspecting metal walls from the outside, increased frictional resistance must also be overcome because the magnets press the magnetizing device against the wall.

[0006] In a gas line, reducing friction is often desirable to ensure smooth operation of the device. Higher friction can cause the device to stop. As a result, the pressure behind the device increases due to the continuous gas flow. When the pressure reaches a sufficient level, the device often suddenly begins to move at a very high speed. This speed can exceed a critical level at which reliable measurement is no longer possible.

[0007] Friction reduction also plays a major role in portable testing devices and enables a significant improvement in user-friendliness.

[0008] In addition, the higher friction causes increased wear of the yoke brushes in a magnetizing device, which can lead to higher maintenance costs.

[0009] Friction reduction is also very important for other devices where magnetization of the pipe wall is required and high friction is not desired.

[0010] To reduce the friction of the device, weaker magnets are used, but this leads to a deterioration in the measurement results. Another option is to attach wheels to the brushes. An example of a generic device can be found in the document DE 10 2007 058 043 A1 . In this device, the magnetizing device is firmly connected to a support roller as one version of a support device, although the magnetizing device is pivotally connected to the rest of the device. The low coefficient of rolling friction of the support roller greatly reduces the friction caused by adhesive forces. To allow the wheels to run freely, there is a gap between the wall and the brush of the yoke, which, however, greatly weakens the magnetic field.

[0011] Furthermore, a device for testing pipelines is known from US Pat. No. 5,565,633 A. The device comprises a cylindrical device body with a magnetizing device to be arranged in the pipeline. The device body is centered in a pipeline via spring-loaded support arms and supported on an inner pipeline wall. The distance between the magnetizing device and the inner pipeline wall depends on the centering of the device body by means of the centering units. This is detrimental to uniform magnetization of the pipeline and / or reliable detection of the magnetic field.

[0012] It is the object of the present invention to develop a device for reducing friction while maintaining the strength of the magnetic flux.

[0013] The problem is solved for a generic device in that the device has a compensation unit that movably connects the support device to the magnetizing device via an adjustment unit, wherein the adjustment unit is supported on the device via a force accumulator. The compensation unit is preferably supported on the magnetizing device. The adjustment unit is preferably supported on the magnetizing device via a force accumulator. The magnetizing device comprises, in particular, the measuring unit and the magnet.

[0014] The compensation unit makes it possible to support the magnetizing device in such a way that the magnetic force of the permanent magnet(s) acts to a high degree on the pipe wall during operation of the device, while at least reducing the friction of the magnetizing device on the pipe wall or, if there is a small gap between the pipe wall and the adjacent surface of the magnetizing device, eliminating it altogether. The adjustment unit is connected to the rest of the device, in particular to the magnetizing device, in such a way that it is supported on another part of the device, in particular on the magnetizing device, via the force storage device. The adjustment unit is part of the compensation unit, and the compensation unit is part of the device, in particular the magnetizing device.The compensation unit is used to at least partially or completely compensate for the attractive forces with which the permanent magnet(s) are drawn to the surface of the pipe wall. The compensation unit generates a force component opposite to the magnetic force via the energy storage device and transfers it to the pipe wall on which it rests.

[0015] While the support roller known from the prior art keeps the magnetizing device at a constant distance from the pipeline wall, the compensation unit allows the magnetizing device to continue gliding along the pipeline wall so that the magnetic force acting on it can be fully utilized for signal evaluation. As the magnetizing device approaches the wall, the compensation unit is pressed in. There is only a small gap, or no gap at all, between the brush and the wall, and at the same time, the compensation unit generates an opposing force. The contact pressure with which the magnetizing device is held on the surface of the wall is reduced by the amount of the counterforce generated by the compensation unit, so that the frictional force with which the magnetizing device glides over the pipeline wall is also reduced.The adjustment unit has the function of adjusting the support device in relation to the magnetizing device, in particular a distance between the support device and the magnetizing device, whereby a counterforce to the magnetic force acting on the magnetizing device is generated via the energy storage device.

[0016] The compensation unit can also compensate for the magnetic force to such an extent that the magnetizing device is kept at a small distance from the pipeline wall. Since an adjustment unit movably connects the support device to the rest of the magnetizing device, relative movements between the rest of the magnetizing device and the support device are possible. For example, the support device resting on the pipeline wall can deflect if there are inward-facing unevenness on the wall, such as those caused by weld seams, without the magnetizing device itself moving inward. As a result, the signal quality of the measurement signal is fully maintained, especially in such critical areas, or at least it does not collapse to such an extent that the quality of the measurement performed in the affected area is limited or completely rendered unsuitable.An advantage of supporting the magnetizing device by a compensation unit is that the distance at which the magnetizing device is kept away from the wall of the pipeline does not necessarily have to remain the same, but is variable and, in particular, can be zero, because the support device is relatively movable in relation to the magnetizing device via the compensation unit.

[0017] The magnetizing device is connected to the rest of the device in a particularly movable, and furthermore in particular pivotable, manner. The support device supports the magnetizing device independently of the rest of the device, in particular independently of a distance of the rest of the device from the pipeline wall. The variable distance of the magnetizing device from the pipeline wall is thus independent of any support and / or centering of the rest of the device on the pipeline wall, for example via support arms, centering units, cups, disks, or the like. The relative movement between the magnetizing device and the support device by means of the compensation unit and the adjustment unit is independent of the rest of the device, in particular independent of a distance of the rest of the device from the pipeline wall.For example, if the distance between the remaining device and the pipeline wall remains constant, a relative movement can occur between the magnetizing device and the support device.

[0018] The compensation unit allows the device to move through the pipeline with less drive power. The lower sliding friction forces in the area of ​​the permanent magnets reduce the drive power required to move the device through the pipeline. The movement is also more consistent. This is especially true when the device is conveyed through the pipeline with a gaseous medium that has a low flow velocity. The compensation unit can be completely compressed by the magnetic force while traveling through the pipeline, reducing the load on the compensation unit from possible irregularities on the pipe wall, such as weld seams, dents, and the like.

[0019] Because the attractive force on the magnetizing device is reduced, passage over irregular areas on the pipe wall, such as welds, dents, etc., is facilitated, resulting in smoother device operation, reduced mechanical impacts on the entire structure, and also reduced measurement distortions. Preferably, the strength of the pressure force of the compensation unit is designed such that the magnetic attractive forces attract the magnetizing device to the wall without a gap, allowing the magnetizing device to adhere to the pipeline wall, while simultaneously compensating for as much of the magnetic attractive force as possible by the compensation unit.

[0020] The present solution makes it possible to reduce the friction of the device, in particular of the magnetizing device that induces the magnetization, while minimizing any disturbing influence on the magnetic flux.

[0021] According to one embodiment of the invention, the support device has at least one support roller. In order to reduce the friction between the compensation unit and the pipe wall, one or more wheels can be mounted on the compensation unit so that the unit travels over the wall surface on at least one wheel. However, the support device can also consist of a conveyor belt, a caterpillar track, or other rotating or revolving actively or passively driven elements that roll on the surface of the pipe wall. However, the support device can also consist of one or more sliding elements with one or more sliding surfaces that are passively guided in a sliding movement over the surface of the wall. The sliding surfaces can, in particular, be made of a material with low sliding friction coefficients, such as PTFE or suitable elastomers.

[0022] According to one embodiment of the invention, a counterforce generated by the compensation unit via an energy storage device is variable. The counterforce generated in the energy storage device is variable if the adjustment unit, via which the support device is connected to the magnetizing device, is supported on an energy storage device that generates a counterforce of varying magnitude in different positions of the adjustment unit. For example, mechanical springs have a different restoring force depending on how far they are extended. A different pressure level of a pneumatic cylinder also results in different restoring forces. An actuator can also be set to a different support force. Such changes alter the counterforce acting from the compensation unit on the magnetizing device.In the case of variable counterforces, this can be particularly greater the further the compensation unit deflects against the magnetizing device and the force accumulator used.

[0023] According to one embodiment of the invention, the compensation unit is supported by a mechanical spring as a force accumulator. When the compensation unit is pressed in, the spring generates a force that counteracts the magnetic forces of attraction on the wall. A mechanical spring, for example, can be used as a force accumulator, the spring's spring characteristic showing an increasing force the further it is retracted or extended. The spring characteristic can have a progressive, linear, degressive, very soft, pre-tensioned, or linear course with a kink. When a spring acts as a force accumulator, advantageous restoring forces build up during a spring movement, which move the adjustment unit back to its original position after a compression or rebound movement when the force impulse that caused the compression or rebound movement disappears.This generally keeps the adjustment unit in its normal position, which provides the desired level of support for the magnetizing device on the pipe wall. The spring force of the mechanical spring is selected based on the spring travel used so that the magnetic force acting on the magnetizing device is at least partially compensated when the compensation unit is in the compressed position.

[0024] According to one embodiment of the invention, the compensation unit is supported by a pneumatic cylinder as a force accumulator. Pneumatic cylinders also enable compression and rebound of the adjustment unit via a gas bladder, whereby advantageous restoring forces are also generated in pneumatic cylinders during compression or rebound. If the compensation unit is pneumatically sprung, the gas cushion located therein generates a force when the compensation unit is pressed into the pneumatic cylinder, which acts as a counterforce against the magnetic forces of attraction.

[0025] According to one embodiment of the invention, the compensation unit is supported by a support drive. Instead of mechanical springs or pneumatic cylinders, a support drive with adjustable force can also be used. Electric motors, particularly in the form of servomotors, with a variable counterforce can be used as the support drive, or other suitable motor-driven components with a variable counterforce generated by them can be used. In this way, a support drive also serves as a force storage device that counteracts the magnetic force.

[0026] According to one embodiment of the invention, the counterforce generated by the compensation unit is adjustable. To adjust the counterforce, mechanical springs can be provided with an adjustable tensioning device, which allows the springs to be preloaded or relaxed, thus resulting in a modified spring characteristic. Similarly, the counterforces generated by gas bubbles in pneumatic cylinders can be adjusted by introducing additional gas into the pneumatic cylinder or releasing it from it. Actuators can also be designed with adjustable drive forces.

[0027] According to one embodiment of the invention, the compensation unit is connected to an electrical control system, via which the counterforce can be adjusted. The electrical control system allows the counterforce to be adapted, in particular, to the strength of the magnetic force. For example, a Hall sensor can be used to measure the magnetic field, and based on the measured value, the spring force of the compensation unit is changed via a motorized system. Such an adjustment via the electrical control system can be automated during operation of the device, for example, controlled by software that forms part of the electrical control system.

[0028] According to one embodiment of the invention, a plurality of compensation units are arranged on a magnetizing device, wherein the support devices are arranged at a distance from one another in the direction of movement of the device. Since a magnetizing device extends over a certain length in the direction of movement of the device, it is advantageous to support the magnetizing device at several spaced-apart locations. Advantageously, the magnetizing device is supported in its front part and in its rear part, so that at least approximately equal support against the magnetic force is achieved across its length.

[0029] Further advantages and details of the invention will become apparent from the following figures. The schematically illustrated figures 1-13 show possible embodiments of the invention. They show:

[0030] Fig. 1 is a view of a device in a pipeline,

[0031] Fig. 1a: an enlarged view of the zone in which the magnetizing device with the measuring unit is located,

[0032] Fig. 2 is a view of a magnetizing device with a compensation unit,

[0033] Fig. 3 - 14: further embodiments of the magnetizing device shown in Fig. 2 with differently designed compensation units.

[0034] Individual technical features of the objects described below can be the subject of the invention on their own, in combination with the features already described above and / or with one another, and can be advantageous thereto. Parts of the devices that act identically or similarly are provided with identical reference numerals where appropriate. Fig. 1 shows a pipeline 1 to be examined, with an inner wall 2, along which the device 3 - here in the form of a pig - is guided through the pipeline 1. The measuring units 4 each generate a magnetic field with at least one magnet 5 arranged in the corresponding measuring unit 4, by which they are held on the surface of the inner wall 2. The magnets 5 are arranged on a magnetizing device 6, which in the exemplary embodiment is designed as a magnetic yoke and is guided along the inner side of the wall 2 for measuring purposes.From its illustrated first position, the magnetizing device 6, which is pivotably arranged on the remaining device 3, can pivot or be pivoted into a second position (illustrated with dashed lines).

[0035] The magnetic field generated by the measuring unit 4 generates an attractive force directed towards the surface of the wall 2 of the pipeline 1 to be measured. This attractive force holds the measuring units 4 pressed against the inside of the pipeline 1. The device 1 is moved through the pipeline 1 in the direction of the arrow in order to measure properties of the wall 2 using the measuring units 4. To reduce the frictional forces with which the measuring units 4 are moved across the surface of the pipeline 1, the measuring units 4 have a compensation unit 9, which generates a counterforce on the measuring unit 4 that opposes the magnetic attractive force of the permanent magnets 5.

[0036] Fig. 1a shows an enlarged view of the zone in which the magnetizing device 6 with the measuring unit 4 is located. In contrast to the merely sketchy representation in Fig. 1, the magnetic yoke shown in Fig. 1a in the magnetizing device 6 is larger. Fig. 2 shows an embodiment of a compensation unit 9. The compensation unit 9 has an adjustment unit 7, which is pivotally mounted on a rotational axis 8, in particular on the magnetizing device 6.While a support roller 12a is mounted at a first end of the adjustment unit 7 as an exemplary embodiment of a support device 12, an energy accumulator 11—in the exemplary embodiment in the form of a mechanical spring—engages the opposite end of the adjustment unit 7. The compensation unit 9, via the restoring force generated by a compression movement, supports the device 3, in particular the magnetizing device 6, against the acting magnetic force. The adjustment unit 7, which can be mounted on a rotational axis 8 and is in any case movably supported on the energy accumulator 11, forms a compensation unit 9 with the energy accumulator 11, which is connected to the support device 12 attached to the adjustment unit 7.

[0037] On its side facing the wall 2, the magnetizing device 6 in the illustrated embodiment has a brush 13. Since the support roller 12a projects beyond the circumferential shape of the brush 13 in the direction of the wall 2 to be examined, the support roller 12a would press the arm of the adjustment unit 7 connected to it below the wall-side upper edge of the brush 13 when the measuring unit 4 with the brush 13 rests against the wall 2 of the pipeline 1, if it is attracted thereto by the magnetic force of the permanent magnet 5. However, if the arm of the adjustment unit 7 provided with the support roller 12a is pressed downwards, the opposite arm of the adjustment unit 7 moves upwards around the rotation axis 8, whereby the mechanical spring of the energy accumulator 11 is extended.The mechanical spring, extended from its rest position, generates a torque around the rotational axis 8 as a counterforce during the extension movement, which counteracts the attractive force of the permanent magnet 5. In this way, the contact pressure with which the magnetizing device 6 is held on the wall 2 is reduced.

[0038] Fig. 3 shows a modified embodiment in which the force of the energy accumulator 11 acts on the wall 2 not in a lateral direction, but in a vertical direction. When the part of the adjustment unit 7 provided with the support roller 12a is pressed in, the arm opposite the rotation axis 8 compresses the energy accumulator 11, resulting in the counterforce.

[0039] In Fig. 4, the support roller 12a is mounted in the adjustment unit 7, which in turn is mounted on a spring assembly acting as an energy storage device 11. When the support rollers 12a are pressed downward, the spring assemblies of the energy storage devices 11 generate a counterforce to the magnetic force from the permanent magnet 5 during a compression movement. This design does not require a rotational axis around which the adjustment unit pivots. Instead, the adjustment unit 7 is pressed directly into the energy storage device 11 during a compression movement of the support device 12.

[0040] In Fig. 5, a toggle lever linkage is shown in which the pressing force with which the support roller 12a is pressed downwards is transmitted to the energy accumulator 11, which generates the counterforce against the magnetic force.

[0041] In the embodiment shown in Fig. 6, the support rollers 12a are located next to the brushes 13. However, they are each mounted on a compression spring as an energy accumulator 11 with the adjustment unit 7 as a bearing. In Fig. 7, the adjustment units 7 are arranged laterally next to the magnetizing device 6. The rotational axis 8 is fixedly arranged on the magnetizing device 6. The adjustment units 7 rotate as rocker arms about the respective rotational axis 8 when the associated support roller 12a is pressed downward. The end of the adjustment unit 7 facing away from the support roller 12a is pressed against the energy accumulator 11 during a tilting movement, in which a counterforce builds up.

[0042] Fig. 8 shows an embodiment in which a support roller 12a is located at one end of the adjustment unit 7 and the rotational axis 8 is located at the other end. The energy accumulator 11 is arranged between the support roller 12a and the rotational axis 8. During a compression movement of the adjustment unit 7, the energy accumulator 11 is compressed, thereby generating the counterforce.

[0043] In Fig. 9, the support rollers 12a are arranged at opposite ends of the magnetizing device 6. The support rollers 12a are each mounted in an adjustment unit 7, which in turn is supported on a force accumulator 11. When the support rollers 12a are pressed down, the force accumulators 11 are compressed, thereby generating the counterforce.

[0044] The embodiment shown in Fig. 10 corresponds to the embodiment shown in Fig. 9, however, two additional compensation units 9 are arranged in the central region of the magnetizing device 6, with which additional counterforces can be generated. Figures 11, 12, and 13 each show a modified embodiment of the embodiment shown in Fig. 8, wherein the rotation axes 8 are arranged at different positions and the adjustment units 7 are of different lengths or have a different shape.

[0045] Fig. 14 shows an embodiment with four compensation units 9, two of which are arranged in the area of ​​a brush 13.

[0046] List of reference symbols Pipeline Wall Device Measuring unit Permanent magnet Magnetizing device Adjustment unit Rotary axis Compensation unit Energy storage Supporting device Brush

Claims

Patent claims 1. A device (3) for non-destructive testing of pipelines (1) comprising at least one measuring unit (4) for recording measured values ​​of the pipeline (1), wherein the measuring unit (4) comprises at least one magnet (5), in particular designed as a permanent magnet, which is preferably arranged in a magnetizing device (6) and which, when the device (3) is in use, generates attractive forces between the magnetizing device (6) and the wall (2) of the pipeline (1), wherein the magnetizing device (6) is connected to a support device (12) which supports the magnetizing device (6) against the wall of the pipeline (1) when the device (3) is in use, and wherein the device (3) is designed to move along the pipeline (1), characterized in that the device (3) comprises a compensation unit (9) which movably connects the support device (12) to the magnetizing device (6) via an adjustment unit (7),wherein the adjusting unit (7) is supported on the device (3) via a force accumulator (11).

2. Device (3) according to claim 1, characterized in that the support device (12) has at least one support roller (12a).

3. Device (3) according to claim 1 or 2, characterized in that a counterforce generated by the compensation unit (9) is variable.

4. Device (3) according to claim 3, characterized in that the compensation unit (9) is supported by a mechanical spring as an energy accumulator (11).

5. Device (3) according to claim 3, characterized in that the compensation unit (9) is supported by a pneumatic cylinder as an energy accumulator (11).

6. Device (3) according to claim 3, characterized in that the compensation unit (9) is supported by a support drive as a force accumulator (11).

7. Device (3) according to one of the preceding claims 3 to 6, characterized in that the counterforce generated by the compensation unit (9) is adjustable.

8. Device (3) according to one of the preceding claims, characterized in that the compensation unit (9) is connected to an electrical control via which the counterforce can be adjusted.

9. Device (3) according to one of the preceding claims, characterized in that a plurality of compensation units (9) are arranged on a magnetizing device (6), wherein the support devices (12) are arranged at a distance from one another in the direction of movement of the device.

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