IE44113B1 - Device for the magnetization of elongated regions of curved surface areas - Google Patents

Abstract

1516055 Magnetographic inspection M FORSTER 19 Jan 1977 [28 April 1976] 02154/77 Heading G1N [Also in Division H1] A device for the magnetization of regions of curved surfaces of ferromagnetic bodies for magnetic defect inspection comprises a core 13 of ferromagnetic material and a flexible electrical conductor 15 through which in use current is passed to establish a magnetic flux in the core and the body being inspected. The core consists in a series of members 13a, b, c held together by joints 14 which permit swivelling of adjacent members relative to one another in two planes within an angular spread which is limited at least in one plane, each joint allowing no more than a small twisting motion of the members relative to one another about their longitudinal axes. The joints permit magnetographic inspection of weld seams between tubes of different diameters and at acute or obtuse angles to each other whereby the weld seam does not lie within a single plane. Magnetic storage tape is used to detect the faults. In an alternative construction, Figs. 3a-c (not shown), coils (26) for generating magnetic flux are wound around core members (27) and inter-connected by pairs of stranded wires (28).

Description

The present invention relates to a device for tlie magnetization of elongated regions of curved surface areas of ferromagnetic bodies for magnetic defect inspection, comprising a core of ferromagnetic mater5 ial and a conductor arrangement for the excitation of a magnetic flux through the core, the core consisting of a serie.s of flexible linked members of ferromagnetic material..

British Patent Specification No. 1,366,287 dos10 crihes such a device, in which tlie core consists of a plurality of U-shaped bridge-pieces of ferromagnetic material which are interconnected by means of a flexible strip to form a belt. The open sides of the bridge pieces rest on either side of a weld seam on a tube surface. A ribbon-shaped flexible electrical conductor establishes a magnetic flux through the bridge-pieces and through the. subjacent tube surface when connected to a current source. The stray magnetic flux emerging from the tube surface at defects can be stored in a magnetic storage tape located on the tube surface underneath the conductor and be interpreted in a known manner by subsequent inspection of the magnetic storage tape.

The described device has proved successful in the inspection of weld seams extending circumferentially around a tube. However, the application of the device to weld seams connecting tubes of the same or different diameter at an angle relative to one another has hitherto not been possible. The intersection lines of such tubes which are connected by weld, seams are generally not located in one plane. To allow the band to accomm5 odate to such a weld seam, the strip connecting the bridge-pieces would have to be flexible in more than one plane. However, such lability of the strip can cause difficulties in the use of the device described. Strips which are flexible within a plane formed by the If* flat side of the .strip tend to iieavy torsional distortion and the bridge-pieces tend to become entangled with each other. This is all the more the case, the longer the strip.

According to the present: invention there is provided a device for the magnetization of elongated regions of curved surface areas of ferromagnetic bodies for magnetic defect inspection, comprising a tore of ferromagnetic material, and an elongated conductor arrangement to carry electric current for the excitation of a 21* magnetic flux through the core, the core consisting of a row of members of ferromagnetic material spaced along the conductor arrangement and connected to one another by joints which permit swivelling of adjacent members relative to one another in two planes within an angular spread which is limited at least in one plane, each joint allowing no more than a small twisting motion of the members relative to one another about their longitudinal axes, the conductor arrangement being such as to allow flexing of the joints.

As compared lu the prior art, this deviee has various advantages, the introduction of the use of joints for tile connection of tin: members constituting tile yoke core, among one another, enables a defined - 4 deflection of the members relative to one another- to be achieved within two given planes on the one hand and within a limited angular spread, on the other· hand.

Thus, a magnetization device is obtained which is very well capable of alignment itself to the curvatures of weld seams of any tube connections, which, however, shows a good stability against undesired distortion about the longitudinal axis of the device. This Is still the case even if the device has a considerable number of members or length of the yoke core extension. Further developments of the invention are described in the subelaiins.

The invention will be described in more, detail, by way of example, with reference to the accompanying drawings, wherein:Plgure 1 shows tube joints on which the magnetization device is used; Figures 2a to 2c show various views of a magnetization device, Figure 2c being a section on the line A-A of Figure 2b; and Figures 3a to 3c show various views of a further magnetization device, Figure 3c being a section on the line B-B of Figure 3b.

Figure 1 represents a tube structure 1 with weld 25 seams 2 and 3 between a large-diameter tube 4 and two smaller tubes 5 and 6 attached at acute and right angles respectively to the tube 4, as well as a weld seam 7 between two sections of the tube 4. The tube structure 1 may be part of a mobile drilling platform the weld seams of which are to be inspected for defects. The Inspection of such weld seams - no matter whether during construction or during operation, whether below or above the water surface - is accompanied by great difficulties 4113 and can be best, effected by means of magnetography. The positioning of magnetic storage tapes on the weld seams 2 and 3 is not to be explained in more detail here but can, for example, be effected by sticking the tapes on.

The magnetization of the weld seam areas will, however, be explained. it is clear that, out of the weld seams represented, only the weld seam 7 extends within one plane. Moreover, in the case of the weld seams 2 and 3, in particular, in the case of the first weld seam, ]() Lhe angles formed by the interconnected tube walls vary considerably. ill tills case the extremes of an acuteangled area S and of an obtuse-angled area 9 are obtained figure 2 shows a magnetization device 11 embodying the invention on an enlarged scale as compared to Figure 1, namely Figure 2a is a partially sectioned side view, Figure 2b is a front view and Figure 2c is a section taken along the line A-A. The core 13 is composed of a row of yoke members 13a, 13b, 13c which are held together by .joints 14- For the excitation of the. magnetic flux a flexible electrical conductor 15 is provided which may consist of a ribbon-shaped braid of copper Wires cue J used by an insulating sleeve 16. I'he yoke members have approximately U-shaped sections with lugs 17 retaining the conductor 15. The outer flanks 18 of the section are curved and thus optimally adapt themselves to the tube walls of the weld seams 2 and 3 meeting one another at various angles. In addition, the (J-shaped section is of course also suited for the magnetization of the fiat weld seam 730 I'he joints 14 make use of a clevis 20 which is pivoted to the yoke member 13b by means of bolt 21 and to the yoke? member 13a by means of bolt 22 which is perpendicular to the bolt 21. The angular spreads within whicli the clevis 20 can be swivelled are limited by a stop flank 23 on the yoke member 13b, on the one hand, and by the flanks 24 of a cutout 35 in the yoke member 13a, on the other hand. To achieve good stability, the bolts 21 and 22 can be tight in their holes but loose enough to ensure that, under the influence of the magnetic flux provided for the magnetization, the yoke members automatically bear against the tube surface.

Figure 3 shows another magnetization device 25, namely Figure 3a is a side view, Figure 3b is a front view and Figure 3c is a section taken along the line B-B, In contrast to the device 11 according to Figure 2, for the generation of the magnetic flux, coils 26 are wound around each individual core member 27, the coils being electrically connected to one another by pairs of stranded wire 28. For the electrical connection of c.oils 26 a series connection is provided. For the sake of simplicity, in the present embodiment core members 27 having a flat profile are represented, such core members being particularly suited for the magnetization of the acute-angled zones 8 of weld seam 2 in Figure 1, as illustrated by the broken lines in Figure 3c.

The joints 29 are of a very simple design. A pin 31 which is rigidly inserted into the lower end 30 of each core member 27 connects the core member with a fork-shaped upper end 32 of the adjacent core member.

At the same time, the pin 31 can move in elongated holes 33 provided in the ends 32, the elongated holes enabling the adjacent core members to perform not only a swivelling motion relative to one another about the pin axis but also a limited swivelling motion within the drawing plane A twisting motion of the yoke! members 27 relative to one another about Choirlongitudirial axes is precluded in this case as in the first embodiment.

The joints may, however, allow a small amount of twisting motion, preferably no more: than will permit the total twist along the whole length of the device to reach l80°.

Claims (10)

1. A device for the magnetization of elongated regions of curved surface areas of ferromagnetic bodies for magnetic defect inspection, comprising

2. A device according to Claim 1, wherein each joint allows substantially no twisting motion of adjacent 20 members relative to one another about their longitudinal axes.

3. A device according Lo Claim 1, wherein each joint allows such a small twisting motion of adjacent members relative to one another about their longitudinal axes 25 that the total twist permitted along the whole length of the device does not exceed lS0°.

4. A device according to Claim 1, 2 or 3, wherein each joint has a clevis which is pivoted to the two adjacent members about axes transverse to each other. 30 5. A device according to Claim 4, wherein the swivelling motion about both pivotal axes Ls limited by stops.

5. Claims, wherein each member has apertures in the vicinity of its joints and a coil wound on the member through the apertures. 5 a core of ferromagnetic material and an elongated conductor arrangement to carry electric current for the excitation of a magnetic flux through the core, the core consisting of a row of members of ferromagnetic material spaced along the conductor arrange10 ment and connected to one another by joints which permit swivelling of adjacent members relative to one another in two planes within an angular spread which is limited at least in one plane, each joint allowing no more than a small twisting motion of tho members rel15 ative to one another about their longitudinal axes, the conductor arrangement being such as allow flexing of the joints.

6. A device according to Claim I, 2 or 3, wherein each joint, comprises a pin and slot connection allowing pivotal movement, about, the axis of the pin and about, an axis perpend i cul at- to tlie pin.

7. A device according to any one of the preceding

8. A device according to any one of the preceding claims, wherein tlie flanks of the profile of the members It) are of a curved shape in cross-section.

9. Λ device according to Claim 1 substantially as hereinbefore described with reft rein e to, and as illustrated in I-i gores 2a, 2b and 2< of tho accompanying drawings. iς

10. A device according to Claim 1 substantially as hereinbefore described with reference to, and as illust rated in Figures ,7a, 3b and 3c of the accompanying drawi ngs.