INSPECTION OR CLEANING PIG

Abstract

A pig is provided for passing through a pipeline having a pipeline wall. The pig comprises at least one functional unit for cleaning the pipeline and/or for receiving pipeline information. The pig also comprises at least one magnet unit which is provided for magnetizing the pipeline wall, and which has a plurality of magnets. The magnet unit has a plurality of segments each with at least one magnet. The magnetizing devices of mutually adjacent segments are angled at least by approximately 90° to one another.

Claims

1. A pig for passing through a pipeline having a pipeline wall, the pig comprising: at least one functional unit for cleaning the pipeline and/or recording pipeline information; at least one magnet unit for magnetizing the pipeline wall, the at least one magnet unit having a plurality of magnets, wherein the magnet unit further includes a plurality of segments each with at least one magnet, wherein the magnetization directions of mutually adjacent segments are angled at least by approximately 90° to one another.

2. The pig as claimed in claim 1, wherein the magnet unit has magnets formed as permanent magnets, wherein the poles (N, S) of first and third segments which are directed toward each other, and which are separated by a further second segment, have an identical polarity.

3. The pig as claimed in claim 2, wherein second segment is a vertical segment with a magnetization direction directed in the direction of the pipeline wall in operation.

4. The pig as claimed in claim 3, wherein the second segment, viewed from a longitudinal central axis, is bounded radially on an outside by a focusing element.

5. The pig as claimed in claim 4, wherein the focusing element is bounded by a magnet on at least three sides, wherein the poles of the magnets located on said sides have an identical polarity.

6. The pig as claimed in claim 1, wherein the magnet unit has in the longitudinal direction at least one enclosure at least also formed of a magnetizable material, which bounds the magnets of the magnet unit.

7. The pig as claimed in claim 1, wherein the magnet unit has a sensor for recording inspection data.

8. The pig as claimed in claim 4, wherein the sensor is arranged in the focusing element, in a recess in the same and/or on the focusing element.

9. The pig as claimed in claim 1, wherein the magnet unit co-forms an eddy current braking unit.

10. The pig as claimed in claim 1, wherein the magnet unit has at least three magnets arranged one after another in its longitudinal direction.

11. The pig as claimed in claim 1, wherein a plurality of magnet units are arranged beside one another in the circumferential direction of the pig.

12. The pig as claimed in claim 1, further including at least one spacer, via which the magnet unit is positioned at a distance from the pipeline wall.

13. The pig as claimed in claim 1, wherein a length of the magnet unit, including any enclosures, is less than 0.5*D.sub.Pipe, where D.sub.Pipe=diameter of the pipeline [m].

14. The pig as claimed in claim 1, wherein at a speed of 2 m/s in the pipeline, the magnet unit generates a braking force F as a function of the pipeline diameter of at least F=m*D.sub.Pipe, where D.sub.Pipe=the diameter of the pipeline [m] and m=7000 N/m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Reference is now made more particularly to the drawings, which illustrate the best presently known mode of carrying out the invention and wherein similar reference characters indicate the same parts throughout the views.

[0028] FIG. 1 shows a spacer with a magnet unit of a pig according to the invention in a perspective illustration.

[0029] FIG. 2 shows the article according to FIG. 1 in a partly sectioned view.

[0030] FIG. 3 shows part of a pig according to the invention comprising a plurality of magnet units in a side view.

[0031] FIG. 4 shows a pig according to the invention in a partly sectioned view.

[0032] FIG. 5 shows a simplified view of a magnet unit in a partly sectioned illustration.

[0033] FIG. 6 shows a magnet unit of a further article according to the invention.

[0034] FIG. 7 shows a view of an article according to the invention in an operating position in a sectional illustration.

[0035] FIG. 8 shows magnetic field lines in a magnet unit of an article according to the invention and an adjacent pipeline wall.

[0036] FIGS. 9-11 show further variants of a magnet unit.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Individual technical features of the exemplary embodiments described below can also be combined in combination with previously described exemplary embodiments and the features of the independent claim and, if appropriate, further claims to form articles according to the invention. If expedient, functionally identical elements are provided with identical designations.

[0038] A spacer 1 having a magnet unit of a pig according to the invention is illustrated perspectively in FIG. 1. The spacer 1 comprises a housing 2, in which a magnet unit 3 that can be seen in FIG. 3 is housed. The housing 2 is depicted with its side directed towards the pipeline wall illustrated from above in FIG. 1. Via a wheel 4, which is rotatably mounted in a fork 6, a distance to the pipeline wall is set. Illustrated on the opposite end of the spacer 1 is a further fork 8, which is mounted on a supporting frame of the pig and/or can possibly be provided with a further wheel.

[0039] The magnet unit 3 has two magnets 10, of which the magnetization directions (direction North-South) extend parallel or at least approximately parallel to the longitudinal central axis of the pig and of which the North-pole sides 12 face toward each other (FIG. 2). At the same time, both North-pole sides 12 rest on a focusing element 14. On its radial side relative to the longitudinal central axis 24 of the pig, to be characterized in more detail below, a further magnet rests with its North-pole side 16 (cf. FIG. 3). This magnet 18 has a magnetization direction which is tilted or angled by 90° relative to the magnetization direction of the magnets 10.

[0040] In the longitudinal direction of the pig, the magnet unit has enclosures 20, which are made of a magnetizable material, preferably a steel comprising cobalt and iron, wherein the enclosures 20 bound the magnets of the magnet unit in such a way that they adjoin the latter at the front and back in the longitudinal direction.

[0041] The focusing element 14 is also made of a steel comprising cobalt and iron. As a result of the arrangement radially outward from a longitudinal central axis 24, the focusing element achieves flux densities of preferably 2 to 3 Tesla. The magnetic flux is compressed by the magnets 18 through the focusing element 14 formed as a steel element such that focusing of the magnetic field lines toward the pipeline results. While standard Halbach arrays are limited in their maximum introduction of the magnetic field by the saturation flux density, as a result of the design of the pig according to the invention, the attraction force is enlarged by a factor of at least 3 as previously described. Therefore, weight and costs can be kept correspondingly low. The segments of the magnet units in the exemplary embodiments of the figures are each formed by a magnet, which then also predefines the magnetization direction of the respective segment.

[0042] On the inner side of the magnet unit 3, directed toward the longitudinal central axis 24 of the pig, there is an internal enclosure 22, which additionally shields the magnetic field from the magnet unit, which is in any case already virtually negligible, toward the inside.

[0043] A pig segment of a pig according to the invention is illustrated in FIG. 3, a multiplicity of magnet units 3 being arranged beside one another in the circumferential direction about a longitudinal axis 24. Furthermore, two rings of magnet units 3 are arranged one after another relative to the longitudinal central axis 24 of the pig. Magnet units 3 located one behind another in the longitudinal direction parallel to the longitudinal central axis 24 are attached to one another in an articulated manner, so that the result is very good pipe bend mobility of the eddy current braking unit illustrated in FIG. 3. The spacers 1 themselves are in turn mounted movably on a supporting frame 26.

[0044] According to FIG. 4, a pig according to the invention has a pulling segment 28, illustrated on the left in FIG. 4, which ensures forward drive in the direction F. In addition, sensors 30, illustrated only partly and schematically, are introduced into the focusing elements 14. The sensors 30 are in particular EMAT-WT sensors, i.e. sensors for the electromagnetic-acoustic measurement of the wall thicknesses of the pipeline wall 32. The pig segment on the right in the figure is thus designed firstly as an eddy current braking unit and secondly as a functional unit for recording inspection data or pipeline information. The magnet unit can also be part of the functional unit.

[0045] A magnet unit of a further pig according to the invention having a higher number than three magnets is illustrated in FIG. 5. Focusing elements 14 are respectively arranged on the North-pole sides of the adjacent magnets 10 and 18 in the present case. A further focusing element 14′ is correspondingly bounded by South-pole sides of the adjacent magnets. In addition to this, a magnet unit can have the enclosure 20 illustrated in FIG. 6, as already described.

[0046] FIG. 7 discloses, in the two depictions there, an alternative design of a magnet unit 3. The depiction on the top right in FIG. 7 shows a perspective illustration, while a matching cross section is illustrated on the bottom left in FIG. 7. A hemispherical focusing element

[0047] 14 is bounded by a one-piece or multi-part magnet 10 which is ring-shaped in cross section and which is in turn arranged within an enclosure 20.

[0048] The magnetic field lines arising in a magnet unit 3 and in a pipeline wall 32 arranged closely beside the latter during operation are symbolized in FIG. 8 by black, acute-angled triangles. In FIG. 8, these are located in the cells of a triangular grid, produced on the basis of the simulation, both of the magnet unit 3 and of the pipeline wall 32. The more intense the gradients of the magnetic field lines in relation to direction and/or amplitude, the finer the resolution and the smaller the cells of the grid. The magnetic flux densities present in the focusing elements 14, 14′ are particularly high, symbolized by correspondingly large triangles.

[0049] According to a further exemplary embodiment of the invention, the magnet unit is designed as part of a functional unit for recording inspection data or pipeline information (FIG. 9). Here, the magnet unit is arranged to be housed in a similar way to that in FIG. 2, wherein in addition, on that side of the focusing element 14 which is directed toward the pipeline wall or the metal surface to be inspected, said focusing element being illustrated only dashed because of the housing, two sensors 30 are fitted, which can in particular be EMAT-WT sensors. Further parts of the magnet unit are magnets 10 and 18, likewise illustrated only dashed because of the housing. This functional unit uses the magnetic field generated by the focusing of the Halbach array and intensified as a result to excite acoustic waves with the aid of electromagnetic force transmission, for example, as a result of which the non-destructive testing of sheet metals of any type in relation to the remaining wall thickness becomes possible.

[0050] In a further variant of a pig according to the invention, having a once more similarly constructed magnet unit, additional magnets are attached to the sides of the magnet unit, which continue to focus and thus further intensify the magnetic field onto the focusing element 14 in an identical way (FIG. 10). Here, too, once more a sensor 30 is arranged, which permits the recording of inspection data. As a result of the variant of the focusing element, now enclosed on four sides and in particular rectangular in a top view, a magnetic field that is virtually directed maximally in the direction of the surface to be inspected, and therefore an optimal magnetic bias, is generated. Here, the viewing direction B is indicated by means of an arrow B. The direction B is also the direction of the magnetic field in the direction of the surface. For example, two, three or four of the magnet units according to FIG. 10 distributed uniformly in the circumferential direction around a pig longitudinal axis can be used for the wall thickness measurement by means of the associated functional unit.

[0051] A maximally optimized variant is also disclosed in FIG. 11, in which the magnet 10 is arranged in the form of a spherical shell around the central focusing element. A bottom view is shown in the bottom left part of FIG. 11, while a perspective illustration is illustrated in the top right part in FIG. 11. Around the hemispherical shell of the magnet 10 there is a further hemispherical shell made of steel as a magnetic circuit closure of the focused magnetic field. Here, too, once more sensors 30 are arranged in order to obtain information about the inspected surface.

[0052] In general, the magnet units of a pig according to the invention can be used to form eddy current braking units in which, because of a multiplicity of magnet units arranged in the circumferential direction around a longitudinal axis of the pig, a ring-shaped current running around in the circumferential direction can be formed in the pipeline wall.