GB2396419A

GB2396419A - Method and device for detecting seam offset of welded sheets or pipes

Info

Publication number: GB2396419A
Application number: GB0327152A
Authority: GB
Inventors: Hans-Juergen Fischer; Bernd Michelbrink; Bernd Kleinjans; Thomas Kersting; Ludwig Oesterlein
Original assignee: Mannesmannroehren Werke AG
Current assignee: Vodafone GmbH
Priority date: 2002-11-27
Filing date: 2003-11-21
Publication date: 2004-06-23
Anticipated expiration: 2023-11-21
Also published as: GB0327152D0; DE10255898B4; DE10255898A1; GB2396419B; ITMI20032308A1

Abstract

In a first step of the method the transition points 4, 5, 6, 7 of the seams 2, 3 are marked visually and visibly on the end face of the sheet or pipe. Then these marked points are located in contactless manner with a measuring device (fig.2) starting from a selected starting point and the distances traversed are related to one another and the seam offset is determined therefrom. The measuring device includes a digitally operated measuring slide (12) having a sighting device (13, 14) which consists of an open frame (13) in which a sighting wire (14) is mounted for exact positioning.

Description

- 1 239641 9

Method and device for detecting the seam offset of welded sheets or pipes The invention relates to a method of detecting the seam offset of buttwelded sheets and pipes.

Pipes, especially longitudinally welded large pipes, are 10 produced by forming sheets into a circle and providing in each case an outer and an inner seam at their longitudinal edges. Pipes which are produced from helically formed steel strips are likewise welded with outer and inner seams at the longitudinal edges of the strip. To produce larger 15 sheet metal plates, the individual plates are likewise welded with outer and inner seams at a longitudinal edge.

When producing these weld seams for example by submerged arc welding, it is possible for the seam centres of the 20 inner and outer beads not to lie in the ideal position one above the other. Standards and customer specifications set

a degree of tolerance for this seam offset which has to be complied with.

25 In order to ensure that customer requirements are complied with with regard to seam offset, it must be possible to determine this reproducibly with sufficient accuracy.

The seam offset between the outer and inner seams, 30 especially at the pipe or sheet ends, has hitherto been made visible by means of extensive radiographic images and determined by measuring the seam centre distances.

- 2 - If the seam offset is close to a critical value, i.e. the tolerance value, an additional verification test is performed. In this test, etching is used to make the seam area visible at the end edge of the sheet or pipe and the 5 seam offset is measured manually by means of a ruler by visual marking of the seam centres.

These methods of determining seam offset have several disadvantages, however.

X-ray testing is performed during final inspection and thus only at a relatively late point in the manufacturing process, such that corrective measures in the welding process can only be performed at that very late point. For 15 economic reasons, it would therefore be desirable to effect detection and correction of a seam offset which may be too large at the earliest possible time after welding.

A further disadvantage is that the seam offset determined 20 by the radiographic test is too imprecise, since different seam widths are incorrectly interpreted as seam offset.

Carrying out an additional test, which may be necessary, by etching the weld seam and manually measuring seam offset is relatively time-consuming and expensive. A prerequisite for 25 etching is a precision-ground, flattened surface of the weld seam area at the end face, which likewise entails expense. A weld seam measuring gauge, which serves inter alla to 30 determine the width of a weld seam, is known from patent no. CH 203464.

- 3 This measuring gauge consists of a Y-shaped holder, in which a measuring tongue is guided in the longitudinal direction. Two rulers are arranged displaceably on the two legs of the holder at right angles to one another. The 5 holder with the measuring tongue is located at an angle of 45 between the two legs.

To measure seam width, the displaceable rulers are pushed up against the transition points from weld seam to the 10 adjacent body, which points function as reference points, and the seam width may then be read off relative to a set calibration point from the measuring scale on the ruler.

This measuring gauge has several disadvantages. Since it 15 operates purely mechanically, precise measurement is impossible unless pronounced steps are provided at the points of weld seam transition to the adjacent body for exact positioning of the rulers.

20 However, these measurement steps conflict with the - requirement for the smoothest possible seam transition, in order to keep the notch effect as small as possible. On the other hand, without these steps it is impossible to perform precise measurement, since there are no stops for the 25 rulers.

An object of the invention is to provide a method and device with which the seam offset in the front and back beads of butt-welded sheets or pipes may be reproducibly 30 determined in a simple and economic manner.

According to the invention, a method is used which determines the seam offset by sighting of the previously

- 4 - marked weld seam transition points of the outer and inner seams, and detection of the distances traversed from a starting point. The weld seam transition points are those locations at which the weld seam contour, starting from a 5 raised portion, merges generally in sharp-edged manner with the adjacent body.

Prior to actual measurement, the readily visible, generally sharp-edged outer and inner seam transition points from the 10 weld seam to the body are firstly marked visually at the end face, such that altogether four measuring points are present. A device for performing the method comprises a U-shaped 15 holding yoke with sighting means displaceable perpendicularly to the weld seam, which means is provided with a measuring device for detecting the distance traversed by the sighting means.

20 In order to be able to fix the holding yoke temporarily to the sheet or pipe, magnets are preferably arranged at the ends of the legs of the holding yoke. For adaptation to different pipe curvatures, they are attached swivellably to the legs.

A parallel guide is attached to the longitudinal beam of the holding yoke, on which guide a direction-finding device and an electronic displacement measuring device are arranged so as to be displaceable perpendicularly to the 30 weld seam. The guide may take the form of a straddle seat, a Tslot or a separate bar. The measuring device comprises elements complementary thereto, to allow unhindered displacement.

The sighting device consists of a frame and a sighting or positionfinding wire attached and pretensioned therein for exact sighting of the weld seam transition points. For measurement, the holding yoke is fixed with the aid of 5 magnets to the outside of the pipe or the sheet at the respective end in such a way that the direction-finding device may be moved directly in front of the weld seam of the sheet or pipe at the end face and the previously marked weld seam transition points may be sighted using the wire.

The starting point may lie to the right or left of the weld seam. The seam offset X may accordingly have a positive or negative value.

15 The seam offset X is determined by means of an analysis unit, which also displays the value. A prerequisite for application of this method is, however, that the weld seams are approximately symmetrical in form, such that it may be assumed that the sought weld seam centre does indeed lie 20 centrally between the two weld seam transition points.

The proposed method has the advantage that only four measuring points which are easily located visually are required for determination of the seam offset.

Analysis of a time-consuming, cost-intensive, extensive representation of the weld seam by X-ray or etching is thus no longer necessary.

30 In addition, this measuring method has the advantage that it may be used directly after completion of welding, such that any corrections may be performed without any great delay.

- 6 In addition, the proposed measuring method is more objective than the previously known manual measurement with a ruler.

The invention will now be further described by way of example with reference to the accompanying drawings in which: 10 Figure 1 is a schematic representation of a weld joint with seam offset on a sheet or pipe with outer and inner seam, Figure 2 is a schematic front view of the weld seam 15 measuring device according to the invention.

Figure 1 shows a weld joint with a seam offset (X) on a sheet or pipe (1, 1'), having an outer seam (2) and an inner seam (3). In order to clarify the interrelationships, 20 the seam offset (X) is exaggerated here. The locations of the weld seam transition points (4, 5, 6, 7), starting from the seam portion raised relative to the basic body (1, 1'), identify the measuring points to be sighted for the method according to the invention for detecting the seam offset 25 (X).

The device according to Figure 2 consists of a U-shaped holding yoke (8, 8', 9), at the free leg ends (8, 8') of which there are attached movably arranged magnets (10, 30 10'). A parallel guide (11), here in the form of a bar, is attached to the longitudinal beam (9) of the holding yoke, to which guide a digitally operating measuring slide (12) displaceable perpendicularly to the weld seam is attached.

- 7 The measuring slide (12) is connected with a sighting device (13, 14) extending perpendicularly to the longitudinal beam (9). This sighting device (13, 14) 5 consists of an open frame (13), in which a sighting wire (14) is mounted for exact positioning.

In addition, the device comprises an electronic analysis unit (15) for determining the seam offset (X). The analysis 10 unit (15) is connected electrically with the measuring slide (12).

Starting from a selected starting point, the marked locations are sighted using the wire (14)and the distances 15 traversed are measured and the seam offset X is determined according to the formula: ( VIA + V2A) /2 ( V3A + V4A) /2 = X

20 In this formula: VIA = distance traversed to point 5 - outer seam V2A = distance traversed to point 4 - outer seam V3A = distance traversed to point 7 - inner seam 25 V4A = distance traversed to point 6 - inner seam

Claims

- 8 - Claims

1. A method for detecting the seam offset in the inner and outer beads of butt-welded sheets or pipes, in 5 which the transition points of the weld seam to the adjacent body portion of the sheet or pipe are used as reference points, wherein, firstly, the transition points of the outer and inner seams are marked visibly on the end face of the sheet or pipe and, secondly, 10 the distance of the marked points from a selected starting point are determined in contactless manner with a measuring device and the distances are related to one another and the seam offset is determined therefrom.

2. A device for performing the method according to claim 1, comprising a frame arranged displaceably on a substantially U- shaped holding yoke having a beam and two legs attached to the ends thereof, a tensioned 20 position-finding wire attached in the frame and a measuring device for detecting the displacement of the frame.

3. A device according to claim 2, wherein one end of at 25 least one leg is provided with a fastening means for temporarily fixing the holding yoke to the sheet or pipe.

4. A device according to claim 3, wherein the fastening 30 element comprises a swivellably arranged magnet.

5. A device according to any one of claims 2 to 4, wherein the beam is provided with a parallel guide, on

- 9 - which the position-finding wire and the measuring device are displaceably arranged.

6. A device according to any one of claims 2 to 5, 5 wherein the measuring device comprises a measuring slide.

7. A device according to claim 6, wherein the measuring slide has a visually readable digital display for 10 displaying the distance travelled.

8. A device according to one of claims 2 to 7, wherein the measuring slide is connected to an analysis unit.

15

9. A method for detecting the seam offset in the inner and outer beads of butt-welded sheets or pipes, substantially as described herein and illustrated in the accompanying drawings.

20

10. A device for detecting the seam offset in the inner and outer beads of butt-welded sheets or pipes, substantially as described herein and illustrated in the accompanying drawings.