DE102010014287A1 - Longitudinal seam-welded multi-layer pipe is made of metal, particularly steel, where pipe has solid, pressure-resistant outer layer and thin, corrosion-resistant inner layer - Google Patents

Abstract

The longitudinal seam-welded multi-layer pipe is made of metal, particularly steel, where the pipe has a solid, pressure-resistant outer layer (1) and a thin, corrosion-resistant inner layer (2). The inner layer is connected with the outer layer by an adhesive layer in holohedral manner. The outer layer and the inner layer are connected by multiple spot-welded joints that are arranged on the entire surface in a distributed manner. An independent claim is also included for a method for manufacturing a multi-layer pipe.

Description

The invention relates firstly to a longitudinally welded multilayer pipe having the features of the preamble of claim 1. On the other hand, the invention relates to a method for producing a longitudinally welded multilayer pipe of the type in question according to the preamble of claim 8.

The known longitudinally welded multilayer pipe, from which the invention proceeds ( DE-A1-10 2008 024 009 ), is based on the assignee of the present patent application itself. In the present case, reference is made in its entirety to the entire disclosure content of the previously cited prior published document, which is hereby incorporated by reference in its entirety into the disclosure content of the present patent application.

For the technological background of longitudinally welded multilayer pipes of the type in question and their manufacturing process, it is first possible to refer to sections [0002] to [0016] of the DE 10 2008 024 009 A1 to get expelled.

As can be seen from the aforementioned prior art, it has been shown that the hitherto used metallurgical and mechanical production methods for longitudinally welded multi-layer pipes both have their quirks. Correspondingly produced multilayer pipes have specific advantages and disadvantages that do not allow their use under all circumstances.

Accordingly, the above-mentioned development was based on the problem of specifying a longitudinally welded multi-layer pipe and a method for producing a longitudinally welded multi-layer pipe, which combines the advantages of the two above-explained, fundamentally different production methods, but avoids their respective disadvantages as far as possible.

The above-indicated problem has been solved in the prior art, characterized in that the inner layer has been connected to the outer layer of the longitudinal seam welded Mehrlagenrohrs by means of an adhesive layer on shear claimable substantially over the entire surface.

In the longitudinal seam-welded multilayer pipe described there, the two layers are connected to each other neither by a full-surface metallurgical bond nor by a purely mechanical bond. Rather, the two layers are bonded to each other over the entire surface by means of an adhesive layer. This adhesive layer is designed in terms of their composition and their layer thickness ago that they can be sufficiently stressed on shear.

The longitudinally welded multi-layer pipe with bonded layers described therein has an adhesive layer whose elasticity withstands the mechanical deformation during the shaping of the multilayer pipe on a bending device, even at the smallest practical diameter of the multilayer pipe of 406 mm (16 "). In this case, the adhesive layer has such an elasticity that it is able to withstand the bending of the pipeline as a whole (pipe laying method, S-Lay) in further practice when laying corresponding pipelines.

The multilayer pipe described therein, in which the layers are glued substantially over the entire surface, has a sufficiently high tensile and shear strength. A collapse of the inner layer in a negative pressure state in the tube does not practically take place here. Seen in this way, it is clearly superior to a multilayer tube (lined pipe) produced by a mechanical manufacturing process. From the production costs, the multi-layer pipe described there is significantly cheaper than the multilayer pipe produced by a metallurgical process.

The core of the multilayer pipe described there is the adhesive layer. Their properties are crucial. It is of decisive importance for the quality of the finished longitudinally welded multilayer pipe. The most important property of the adhesive layer is its bonding property. The adhesive layer must bring about an intimate connection of the metallic inner layer with the metallic outer layer. Tensile strength, elongation, hardness, shear strength and peel strength are important parameters that must be adapted to the adhesive layer used there.

Furthermore, the cited reference describes a variety of variants for the adhesive layer and other components of the longitudinally welded multilayer pipe. I can here again expressly refer to these explanations.

The object of the above-described disclosure is also a corresponding method for producing a longitudinally welded multi-layer pipe made of metal with corresponding method steps, which are also explained in the citation. This may also be referred to in full.

It has been shown in practice that the requirements for the adhesive layer in the known longitudinally welded multi-layer pipe or at the known manufacturing process are relatively high and can not be met under all conditions. Accordingly, the teaching of the present invention is based on the problem to optimize the known longitudinally welded multi-layer pipe so that the dependence on the quality of the adhesive layer is slightly lower. The same applies to the manufacturing method proposed here.

The above-indicated problem is solved in a longitudinally welded multi-layer pipe according to the invention by the features of the characterizing part of claim 1.

In terms of the method, the object indicated above solves the characterizing part of claim 8.

In addition, in the longitudinal seam-welded multilayer pipe according to the invention, in addition to the adhesive layer, spot welds are distributed over the entire surface, which metallurgically connect the outer layer and the inner layer in addition to the adhesive layer. The spot welds in the surface serve to achieve a full-surface compression of the outer layer with the inner layer without external force application during the bonding process and during the curing of the adhesive.

Even the contact pressure of the spot welding gun leads to an increase in the contact pressure on the adhesive layer in this area. Once the spot welded connection has been made, the adhesive has been displaced at this point. The metal at this point cools and contracts slightly. This increases the pressure on the adhesive layer. With this system, an optimal connection of adhesive layer and outer layer or inner layer is achieved.

In the edge regions adjacent to the region of the weld, the spot welds, which are preferably narrower, additionally act to largely protect the heat-affected zone of adhesive and also to absorb the shear and tensile forces encountered in molding to aid in the action of the adhesive layer.

In principle, it is recommended to arrange the spot welded joints substantially evenly distributed, with a grid-like arrangement is particularly recommended.

However, it is also advisable to provide a higher density in the edge regions, also preferably uniform distribution of the spot welds.

According to a preferred teaching of the invention, it is recommended that the edge regions each have a width of about 50 mm to 150 mm, preferably of about 100 mm.

While in the large central region lateral distances of the spot welded joints of about 150 mm to 300 mm, preferably from about 200 mm to 250 mm recommend, has a narrower grid of 20 mm to 60 mm, preferably from about 25 mm to 50 in each edge region mm, as practically proven.

According to a preferred teaching, the spot welded joints lie in rows one behind the other in the direction of the longitudinal axis of the multilayer pipe. The transverse to the longitudinal axis adjacent rows of spot welds, however, may conveniently be arranged offset from each other. The above-mentioned distance dimensions are understood as grid dimensions, ie not as distances of the spot welds of adjacent rows but staggered rows as distances of the rows themselves to each other.

As far as the manufacturing method is concerned, claim 8 teaches that expediently the outer layer and the inner layer are glued together by the adhesive layer substantially over the entire surface as flat sheets and that the outer layer and the inner layer with the adhesive layer therebetween then by a plurality of on the entire surface distributed spot welded joints are additionally metallurgically connected.

In a first process variant, the adhesive of the adhesive layer can then be cured directly under the action of heat and then follows the bending of the multilayer material to the multilayer pipe and the longitudinal seam welding (claim 9). This is a particularly preferred procedure in which the full effect of the adhesive layer is achieved even before the multilayer material is bent. The stable pressure distribution in the adhesive layer is maintained by the spot weld joints. The further handling of the multilayer material does not have to be in a hot press, but can be done in a normal shuttle kiln or the like.

In another variant, when the adhesive layer has not yet hardened but fixed spot welded joints, the bending of the multilayer material to the multilayer pipe follows. This then follows only the curing of the adhesive layer under the action of heat and finally the Längsnahtverschweißung (claim 10).

In a third variant then follows first bending to multilayer pipe, then the Längsnahtverschweißung and only at the very end the curing of the adhesive layer under the action of heat (claim 11).

Finally, there is also a variant with an adhesive layer of a chemically curable two-component adhesive. This will begin to chemically harden during the production of the additional spot welds. In this method, the multi-layered material thus formed is then formed by means of a bending device to the multilayer pipe and then longitudinally welded (claim 12).

Incidentally, all special proposals of the publication of the starting point for teaching also apply to the teaching of the present patent application DE 10 2008 024 009 A1 , in particular the features of the claims 2 to 14, 16, 17 and 23 to 30, which is expressly referred to again here.

In the following, the invention will now be explained with reference to a purely schematically exemplary embodiment of a drawing. In the drawing shows

1 an end view of a finished longitudinally welded multilayer pipe according to the invention,

2 an exploded view of a precursor for producing a multilayer pipe according to the invention, schematically,

3 the precursor produced by a particularly preferred method of a multilayer pipe according to the invention.

This in 1 shown multilayer pipe is a longitudinally welded multi-layer pipe made of metal, here steel. In principle, however, the teaching of the invention is also applicable to multilayer pipes of other metals, in particular of aluminum. Of particular importance, however, is the teaching of multi-layer pipes made of steel, in particular large pipes as they are needed for plants of the petrochemical industry, in particular petroleum pipelines, gas pipelines or construction elements of production platforms.

In detail, reference may be made to the introductory citations from the prior art.

The multilayer pipe according to the invention has a solid, pressure-resistant outer layer 1 , which absorbs pressure and tension, and a thin inner layer 2 with certain corrosion and possibly abrasion properties. In the illustrated and preferred embodiment, the outer layer 1 made of carbon steel, the inner layer 2 made of stainless steel. The aggressive petrochemical fluids, which can flow in the longitudinally welded multi-layer pipe, grip the stainless steel of the inner layer 2 not, but would the carbon steel of the outer layer 1 to destroy. Except stainless steel come for the inner layer 2 Other iron or non-ferrous alloys in question.

The multilayer pipe shown is on the outer layer 1 by means of a usual, chamfered pipe weld 3 welded, with a welding method corresponding to the material used. In contrast, the inner layer 2 by means of a hardfacing 4 welded, so that the inner layer 2 completely closed corrosion resistant.

Essential for the teaching of the invention is here that the outer layer 1 and the inner layer 2 on the one hand by means of an adhesive layer 5 are essentially connected over the entire surface, but that the outer layer 1 and the inner layer 2 also by a plurality of distributed over the entire surface arranged spot welded joints 6 additionally metallurgically connected.

2 schematically shows in an exploded view, the three "layers" of the multilayer pipe according to the invention, namely the outer layer 1 , the inner layer 2 and in between the glue layer 5 , This does not have to be physically coherent, like that 2 suggests. Is in 2 just for the sake of clarity.

3 shows the sheets for the outer layer 1 and the inner layer 2 merged with the intervening, in 3 no longer visible adhesive layer 5 , Through the arcuate double arrow at the top in 3 is hinted how the in 3 shown planar precursor for producing the multilayer pipe is bent.

Overall, results from the interaction of the adhesive layer 5 with the spot welded joints 6 a permanently solid and shear stressable full-surface connection of the outer layer 1 with the inner layer 2 ,

In 3 are the spot welded joints 6 schematically entered. It can be seen that the spot welds 6 here substantially evenly distributed, in particular arranged grid-like.

3 shows a particularly preferred embodiment insofar as it is provided that the spot welded joints 6 in the at the Area of the weld 4 adjacent edge regions are arranged more closely adjacent than in the intermediate large central region.

It is recommended according to a particularly preferred teaching that the edge regions each have a width of about 50 mm to 150 mm, preferably of about 100 mm.

A particularly preferred example of a suitable distribution of spot welded joints 6 states that the spot welds 6 in the large central region lateral distances of about 150 mm to 300 mm, preferably from about 200 mm to 250 mm.

In contrast, in the previously explained, in 3 schematically illustrated embodiment be provided at the edge, that the spot welds 6 in the respective edge region laterally 3 distances of about 20 mm to 60 mm, preferably from about 25 mm to 50 mm.

How one 3 For the illustrated and preferred exemplary embodiment, for the sake of a pressure distribution which is as uniform as possible, it can be readily assumed that the spot-welded connections 6 are arranged in rows in the direction of the longitudinal axis of the multilayer pipe and that the spot welded joints 6 are arranged offset from each other in rows transverse to the longitudinal axis.

In the illustrated and preferred embodiment, it is provided that the adhesive layer 5 consists of an epoxy resin adhesive. This is curable under heat and can withstand temperatures of at least about 200 ° C, preferably at least about 250 ° C for a short time in the cured state. As an alternative, it is also possible to use a phenolic resin adhesive, preferably with appropriate temperature resistance, or a chemically curing two-component adhesive. Other types of adhesives may be developed in the future. For the teaching of the invention is particularly significant that the adhesive layer 5 should not have excessive thickness.

The illustrated and preferred embodiment shows that the adhesive layer 5 having a low in the initial state layer thickness of preferably 10 .mu.m to about 100 microns.

Indicated in 2 with the local dimensions that the glue layer 5 from the area of the weld 4 the inner layer 2 is set back slightly laterally, preferably by 3 mm to 50 mm, in particular by at least 5 mm, at most 30 mm.

The multilayer pipe with the smallest outer diameter in the petroleum industry is one with an outer diameter of 16 '', which corresponds to about 406 mm. If the glue layer 5 For such a small multi-layer pipe has the necessary shear strength, it has this, of course, for multi-layer pipes with a larger diameter anyway.

In the illustrated and preferred embodiment can be understood based on the size ratios that here the outer layer 1 a thickness of at least 8, preferably at least 10 to 15 mm, while the inner layer 2 has a thickness of at least 1 mm and at most 12 mm, preferably from 2 to 4 mm.

As has already been disclosed in the general part of the description, it is also possible according to the invention to turn the layer sequence exactly over, ie to use the thin, corrosion-resistant layer as the outer layer.

This in 2 and 3 illustrated embodiment also reveals a preferred manufacturing method, which corresponds to the method of claim 9 or, in a two-component adhesive, the method of claim 12.

In particular one recognizes in 3 the basically uniform, but with edge narrower grid than distributed in the large central area arranged spot welded joints 6 ,

When displayed in 3 you can see that the lower flat, preferably the outer layer 1 forming sheet metal transverse to the bending axis (= longitudinal axis of the finished multilayer pipe) relative to the upper flat, preferably the inner layer 2 forming sheet protrudes marginally slightly on both sides. The bending axis is indicated above the circular arc-shaped double arrow with the sign "+" and you can see right and left on the flat precursor the narrow marginal projections of the lower, here the outer layer 1 forming sheet. Thus one has the final form, which in 1 can be seen, so that for the surfacing weld 4 a sufficient space is available and the welding of the outer layer 1 at the pipe weld 3 the inner layer 2 not negatively affected. The longitudinal slightly slight overhang of the outer layer 1 opposite the inner layer 2 but ultimately must only be done when resetting the inner layer 2 can not or should not be done in a subsequent milling process for weld preparation.

For the production of the multilayer pipe according to the invention, it is recommended that the outer layer 1 with a conventional method of pipe welding according to the material used and the inner layer 2 is longitudinally welded with a conventional method for build-up welding according to the material used and that the molding of the multilayer material to the multilayer pipe by means of a bending roll arrangement or by means of a bending press.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008024009 A1 [0002, 0003, 0029]

Claims (12)

Longitudinally welded multilayer pipe made of metal, in particular of steel, with a firm, pressure-resistant outer layer ( 1 ) and a thin, corrosion-resistant inner layer ( 2 ), wherein the inner layer ( 2 ) with the outer layer ( 1 ) by means of an adhesive layer ( 5 ) is connected substantially over the entire surface, characterized in that the outer layer ( 1 ) and the inner layer ( 2 ) by a plurality of distributed over the entire surface arranged spot welds ( 6 ) are additionally metallurgically connected. Multilayer pipe according to claim 1, characterized in that the spot welded joints ( 6 ) are distributed substantially uniformly, in particular arranged like a grid. Multilayer pipe according to claim 1 or 2, characterized in that the spot welded joints ( 6 ) in the at the area of the weld ( 4 ) are juxtaposed adjacent edge regions than in the intermediate middle region therebetween. Multi-layer pipe according to claim 3, characterized in that the edge regions each have a width of about 50 mm to 150 mm, preferably of about 100 mm. Multilayer pipe according to one of claims 1 to 4, characterized in that the spot welded joints ( 6 ) in the large central region lateral distances of about 150 mm to 300 mm, preferably from about 200 mm to 250 mm. Multilayer pipe according to one of claims 1 to 5, characterized in that the spot welded joints ( 6 ) in the respective edge region lateral distances of about 20 mm to 60 mm, preferably from about 25 mm to 50 mm. Multi-layer pipe according to one of claims 1 to 6, characterized in that the spot welded joints ( 6 ) are arranged in rows in the direction of the longitudinal axis of the multilayer pipe and in that the spot welded joints ( 6 ) are arranged offset in relation to each other in rows adjacent to the longitudinal axis. Method for producing a longitudinally welded multi-layer pipe made of metal, in particular of steel, which has a solid, pressure-resistant outer layer ( 1 ) and a thin, corrosion-resistant inner layer ( 2 ) and in which the inner layer ( 2 ) with the outer layer ( 1 ) permanently connected and stressable on shear, characterized in that the outer layer ( 1 ) and the inner layer ( 2 ) by means of the adhesive layer ( 5 ) are glued together as flat sheets substantially over the entire surface and that the outer layer ( 1 ) and the inner layer ( 2 ) with the adhesive layer ( 5 ) by a plurality of distributed over the entire surface arranged spot welds ( 6 ) are also metallurgically connected. A method according to claim 8, characterized in that the adhesive of the adhesive layer ( 5 ) after attaching the spot welds ( 6 ) is cured under heat and that the thus formed, bonded, multilayer material is formed by means of a bending device to the multilayer pipe and longitudinally welded by means of a welding device. A method according to claim 8, characterized in that after attaching the spot welds ( 6 ) the multilayer material thus formed is formed by means of a bending device to the multilayer pipe, that the adhesive of the adhesive layer ( 5 ) is cured under heat and that the multilayer pipe is finally longitudinally welded by means of a welding device. A method according to claim 8, characterized in that after attaching the spot welds ( 6 ) the multilayer material thus formed is shaped by means of a bending device to the multilayer pipe, that the multilayer pipe is longitudinally welded by means of a welding device and that finally the adhesive of the adhesive layer ( 5 ) is cured under heat. A method according to claim 8, characterized in that for the formation of the adhesive layer ( 5 ) a chemically curable two-component adhesive is used, which preferably also in the cured state for a short time temperatures up to at least about 200 ° C, preferably to at least about 250 ° C, withstands that after attaching the spot welds ( 6 ) the two-component adhesive of the adhesive layer ( 5 ) is chemically cured and that the thus formed, bonded, multilayer material by means of a bending device to the Molded multilayer pipe and longitudinally welded by means of a welding device.

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