GB2111628A

GB2111628A - Bellows expansion joint for pipe lines

Info

Publication number: GB2111628A
Application number: GB08225542A
Authority: GB
Inventors: Roland Helfricht; Heinz Hammer; Herbert Schweigert
Original assignee: Witzenmann GmbH
Current assignee: Witzenmann GmbH
Priority date: 1981-12-15
Filing date: 1982-09-08
Publication date: 1983-07-06
Also published as: DE3149553C2; FR2518214A1; IT1201951B; CH657908A5; DE3149553A1; IT8222740A0; GB2111628B; FR2518214B1

Abstract

<IMAGE> <H0> Bellows expansion joint for pipe linese

Description

SPECIFICATION Bellows expansion joint for pipe lines The present invention relates to a bellows expansion joint for pipe lines, in particular of the type comprising at least one multilayer bellows device, which is formed in the manner of a screwthread or with annular corrugations, and at least one bellows connecting part in the form of, for example, a connecting branch or connecting flange, in which at least one intermediate layer, which is spirally wound from a thin-walled sheet or formed from closed, co-axial sheet metal cylinders, is arranged between outer and inner bellows layers, the bellows edge being welded in a leakproof manner to the bellows connecting part, including all the bellows layers, and a bore, which extends as far as the intermediate layer, being provided to indicate leakage.

In bellows expansion joints of this type the bellows comprises at least one outer and one inner sealing layer and an intermediate layer. There are, however, numerous examples in which a plurality of sealing layers are distributed over the radial cross section and an intermediate layer is in each case provided, for example in the centre or between two respective sealing layers. A structural design of this type is arranged according to the respective requirements of the particular installation.

In this connection the respective intermediate layer serves to enable leakage in one or more of the sealing layers, adjacent the intermediate layer on the pressure side of the bellows expansion joint, to be indicated, in that the leaking medium can reach the end of the bellows expansion joint, where it can then be used to indicate a leakage via the above-mentioned bore. If the intermediate layer is spirally wound, the leaking medium can pass through the gaps of the windings, reach the end of the bellows and thus the bore, while if the intermediate layer is formed from closed sheet metal cylinders, the gaps between these have to be suitably connected together, for example by a radial bore in the sheet metal cylinders. The number of windings or cylinders of the intermediate layers usually ranges between 1 and 30.

In known cases the bore is formed from outside in the bellows wall or plurality of bellows walls as a radial bore at one or at both ends of the bellows.

However this solution, which is adequate and has proved satisfactory for normal cases, in which the simple discharge of the leaking medium out of the bore represents the indication of leakage, is not suitable if the leaking medium is, for example, poisonous or radioactive. In such cases it is necessary to contain the leakage or the leaking medium and, without the possibility of damage occurring, to convey it, for example, to a quantitative indicator. It will be appreciated that not every leakage necessarily entails the immediate replacement of the bellows expansion joint. On the contrary, it is sufficient in many cases to replace the bellows expansion joint at the next opportunity which arises.In known cases the leakage is contained by welding to the bore a tube through which the leaking medium can be conveyed, for example to a container for the purpose of indicating the quantity of the leaked medium. However, this known solution entails problems, in that the additional welding of a tube in the connecting region between the bellows and the bellows connecting part creates a stress concentration in this region, the reliable detection of which, based on calculations, is difficult or almost impossible. In this respect it should be considered that the bellows expansion joint, which is usually acted upon by pressure and temperature, undergoes expansions which, in the case of irregularities over the circumference in the connecting region of the bellows, as are caused by the above-mentioned welded pipe, lead to varying loads over the circumference.

These irregularities also have an adverse effect in that they at least hinder a possibly repeated, non destructive material test of the connecting weld seam, in the form, for example, of a radiation test.

A further disadvantage lies in that, although in the case of a specified external or internal pressure load, the bore can accordingly be provided at the side distant from the pressure, a bore of this type is not suitable in the case of an alternating internal and external pressure load. This could only be achieved by providing both a radially outwardly directed and a radially inwardly directed bore and by containing the overflowing, leaking medium in a suitable manner.

However this increases the above-mentioned problems.

The present invention therefore aims to modify a bellows expansion joint of the above-mentioned type such that it can be produced in a normal, simple manner, i.e. by welding the bellows edges to the bellows connecting parts in a simple and rotationally symmetric manner, without the necessity of impairing its walls in order to provide the leakage indication. Furthermore, for those cases in which it is not necessary to contain the leakage, and for those in which the leaking medium should or must be contained, means are described by which the leakage can be simply indicated for both externally pressure loaded and internally pressure loaded bellows expansion joints, particularly with respect to an alternating external and internal pressure load.

Finally, a repeated non-destructive material test of the connecting weld seam between the bellows and the bellows connecting parts should not be impaired.

The present invention provides a bellows expansion joint for pipe lines, comprising at least one multilayer bellows device which is formed in the manner of a screw thread or with annular corrugations, and at least one bellows connecting part, in which at least one intermediate layer is arranged between outer and inner bellows layers, the bellows edge being welded in a leakproof manner to the bellows connecting part, including all the bellows layers, wherein a bore which extends as far as the said intermediate layer to indicate leakage is arranged in the weld seam so as to contact the intermediate layer.

By means of the present invention, access is provided, in a particularly simple manner, to the intermediate layer and thus to the leakage, which leaves the bellows completely unaffected as regards shape and installation method, and at the same time it is unimportant whether the bellows expansion joint is externally or internally pressure loaded and, finally, a non-destructive material test in the region of the weld seam and the other parts of the bellows expansion joint is not impaired. In this connection the intermediate layer is preferably formed as a spirally wound intermediate layer, as this makes it particularly easy for the bore to contact the intermediate layer.

However, it is also important to enable the weld joint between the bellows and the bellows connecting part to be provided is a simple, rotationally symmetric form and for the structural part in the region of the weld jointto be rotationally symmetric.

In the case of a bellows edge which is butt-welded to the bellows connecting part, it is preferable to arrange the bore so that it passes through the bellows connecting part in an axially parallel manner, in which case access to this bore can be provided on the outside by forming in the bellows connecting part a radial bore which meets this bore.

It is however also possible for the bellows end to be flanged at an angle in the region of 30 to 60 degrees, more preferably in the region of 45 degrees, with respect to the bellows axis and welded to the bellows connecting part so as to form a V-seam, and for the bore also to form an angle in the region of 30 to 60 degrees, more preferably in the region of 45 degrees, with the bellows axis. It has been shown that both the transmission of force between the bellows and the bellows connecting part and the non-destructive material testing are favoured in the case of this design, which also provides the possibil ity of connecting together two bellows, arranged one behind the other in the axial direction, by means of a bellows connecting part, without impeding the means for indicating leakage.

It is also preferable for each bellows edge to be surrounded by an outer ring and for this ring to be welded, together with the bellows edge, to the bellows connecting part.

The weld seam can be enclosed in an annular chamber, formed by the bellows connecting part, and the outer wall of the annular chamber can then have at least one radial bore.

As has been shown, the arrangement of the bore in the weld seam so as to contact the intermediate layer is suitable for all conceivable connections between a bellows and a bellows connecting part which are produced by welding, irrespective of whether, for example, a butt weld is provided or, in the other extreme, a flange butt-welding joint, which is produced when the bellows edge is flanged radially outwards and then welded to the bellows connecting part, is provided.

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a radial section showing a connection between a bellows and a bellows connecting flange by means of a lap seam; Figure 2 is a view similar to Figure 1, with an annular chamber enclosing the weld seam on all sides; Figure 3 is a radial section showing a butt joint between a bellows and a bellows connecting part; Figure 4 is a radial section showing a flange butt-welding joint between a bellows and a bellows connecting part; Figure 5 shows a variant of the connection according to Figure 3; and Figure 6 is a radial section showing the connection of two bellows, arranged one behind the other in the axial direction, by means of a bellows connecting part.

Figure 1 shows a multilayer bellows 1 with an outer layer 2, an intermediate layer 4 and an inner layer 5, which is connected by a lap seam 6 to a connecting part 7, and in the present case an outer ring 8 and an inner ring 9, which is mounted on the connecting part 7, are also welded in order to reinforce the bellows edge.

The weld seam 6, which embraces all the layers of the bellows 1, contains an axially parallel bore 10, which meets the intermediate layer 4, which is formed by winding a thin-walled sheet in a spiral or helical manner. If the inner layer 5 becomes pervious owing to a crack, the leaking medium passes, under the internal pressure load of the bellows, via the intermediate layer 4 to reach the bore 10, where it is discharged, thus serving as a leakage indication, before the entire bellows expansion joint becomes pervious. The possibility is thus provided of replacing the damaged bellows expansion joint by a new structural part, without the pipe connection, which is provided with the bellows expansion joint, having failed entirely.In this case, however, as also in the case of the following embodiments, the bellows expansion joint is entirely unimpaired, as regards its design and manner of installation, by the additional means for indicating leakage. Although the weld seam is penetrated by a bore, it should be noted that this bore need only have a very small cross section and the weld seam is produced with a safety factor which guarantees a low stress load, so that the bore does not impair the weld seam.

Figure 2 shows a bellows expansion joint in which the bellows comprises an outer sealing layer 11 and an inner sealing layer 16, as well as an intermediate layer which is arranged between the layers 11 and 16 and is formed bya plurality of layers 12,13,14,15, 17. The intermediate layer is reached via a weld seam 18 through an axially parallel bore 19. The weld seam is enclosed over the entire circumference by a chamber 20, which is formed by a ring 21 having an L-shaped cross section and welded to a connecting part 22 as illustrated.

The ring 21 has a radial bore, into which a pipe 23 is welded, to which pipe a device for containing the leaking medium or a pressure indicating device can be connected.

Figure 3 shows multilayer bellows 24 of the type described above, which is butt-joined via a weld seam 25 to a connecting flange 26 such that the bellows is supported internally on an extension 27 of the connecting part and surrounded externally by a ring 28, the weld seam 25 embracing both the extension 27 and the ring 28, as well as all the layers of the bellows 24.

The connecting flange 26 is penetrated by an axially parallel bore 29, which also passes through the weld seam 25 and meets the intermediate layer, which is not indicated in detail, in the manner described above. Since the connecting part 26 is in this case a weld flange, the bore 29 is accessible radially from the outside through a bore 30, through which the leaking medium can be contained or indicated in the manner described above.

Figure 4 shows a bellows 31 flanged radially outwards at the end, where all the layers thereof are secured between a connecting part 32 and a retaining ring 33 by a flange butt-welding joint 34. As in the embodiment of Figure 2, a ring 35 which surrounds the weld seam 34, forms a chamber 36 which is accessible through a radial bore 37 for observation purposes.

Figure 5 shows a bellows 38 butt-welded to a connecting part 39, in which the end of the bellows 38 is held by an inner prop ring 40 and an outer prop ring 41, which are also butt-welded via a weld seam 42, together with all the layers of the bellows 38, to the connecting part 39. A bore 43, which passes through the connecting part 39 in an axially parallel manner, extends to the intermediate layer of the bellows 38. A radial bore 44 provides access to the outside, and a further connecting piece 45 is pre welded to the radial bore 44 for the purpose of screwing a further connection in place.

Figure 6 shows two bellows 46 and 47 in tandem arrangement with a common connecting part 48, which internally supports the bellows 46 and 47.

Prop rings 49 and 50 are mounted radially outside on the bellows 46 and 47 and are in each case welded to the bellows ends, which are flanged at an angle of approximately 45 degrees with respect to the bellows axis, by means of a V-shaped weld seam 51, 52, in which bores 53, 54 are also arranged at an angle of approximately 45 degrees. The weld seams 51 and 52 are surrounded by a chamber 55, which is formed by a ring 56, which shuts off the space over the weld seams owing to its leakproof connection with the prop rings 49 and 50. A bore 57, through which leaking medium can be contained, is provided in the ring 50.

While only one bore, which extends to the bellows intermediate layer, is mentioned in all the illustrated embodiments, it is of course possible to provide a plurality of such bores distributed circumferentially.

In the same way, only one intermediate layer of one bellows device is referred to. In the case of multilayer bellows, however, it is also possible to provide a plurality of intermediate layers distributed radially and arranged between outer and inner layers, which intermediate layers can then in each case be tested via one of several bores.

Claims

1. A bellows expansion joint for pipe lines, comprising at least one multilayer bellows device which is formed in the manner of a screw thread or with annular corrugations, and at least one bellows connecting part, in which at least one intermediate layer is arranged between outer and inner bellows layers, the bellows edge being welded in a leakproof manner to the bellows connecting part, including all the bellows layers, wherein a bore which extends as far as the said intermediate layer to indicate leakage is arranged in the weld seam so as to contact the intermediate layer.

2. A bellows expansion joint as claimed in Claim 1, wherein a bellows edge is butt-welded to the bellows connecting part, and wherein the bore passes through the bellows connecting part in an axially parallel manner.

3. A bellows expansion joint as claimed in Claim 2, wherein a radial bore which meets the said first-mentioned bore is provided in the bellows connecting part.

4. A bellows expansion joint as claimed in Claim 1, wherein the bellows end is flanged at an angle of 30 to 60 degrees with respect to the bellows axis and welded to the bellows connecting part so as to form a V-seam, and wherein the bore also forms an angle of 30 to 60 degrees with the bellows axis.

5. A bellows expansion joint as claimed in any of Claims 1 to 4, wherein the bellows edge is surrounded by an outer ring and wherein the said outer ring, together with the bellows edge, is welded to the bellows connecting part.

6. A bellows expansion joint as claimed in any of Claims 1 to 5, wherein the weld seam is enclosed in an annular chamber formed by the bellows connecting part, and wherein the outer wall of the annular chamber has at least one radial bore.

7. A bellows expansion joint as claimed in any of Claims 1 to 6, wherein the said at least one intermediate layer is spirally wound from a thin-walled sheet.

8. A bellows expansion joint as claimed in any of Claims 1 to 6, wherein the said at least one intermediate layer is formed from closed, coaxial sheet metal cylinders.

9. A bellows expansion joint according to Claim 1, substantially as herein described with reference to, and as shown in, any of Figures 1 to 6 of the accompanying drawings.