JOINT BETWEEN TWO TUBULAR ELEMENTS, PREFERABLY MADE OF METAL, AND METHODS FOR THE MANUFACTURE OF SUCH A JOINT

Abstract: A joint between tubular elements, wherein a tubular element (1) is provided with an extension-piece (13) and the other tubular element (6) is fitted into one or more recesses (12) of the extension-piece (13) by explosive plastic deformation. A method for making such a joint comprises the use of an explosive charge with a detonation speed which is substantially smaller than required for creating a joint by explosive welding.

Description: Joint between two tubular elements, preferably made of metal, and methods for the manufacture of such a joint. The invention relates to a joint between two tubular elementa, preferably made of metal, and methods for the manufacture of such a joint. In Dutch Patent Application No.8304053 the disadvantages are described of welding pipes, especially pipes with a large diameter, such as those used for pipe lines for gas, oil and other industrial products. High demands are set to such pipe lines with respect to tight¬ ness. In the above-mentioned patent application a joint between two pipes is realized by an interior peripheral part and an exterior peripheral part, positioned at the location of the joint place, whereby the interior peripheral part is brought in its position by means of explosive welding and the outer peripheral part may be displaced in the longitudinal direction as a consequence of the deformation caused by this explosive welding. However, this joint has the disadvantage of not allowing for welding pipes provided with an interior covering, as these show an interruption of the covering, whereas with the power of the explosion required for explosive welding forces may occur to such an extent in pipes, pipe lines, control means present therein, and all fitting and suspension means, that damages may be inflicted therein. In addition it is not easy to bring and to keep both peripheral parts in the proper position accurately. These and other disadvantages are avoided according to the invention, which provides a joint which meets the requirements with respect to tightness and strength, in addition to crack stopping capacity, while repair remains simple. The joint according to the invention is formed by pushing together two tubular elements, one of which is provided with an extension-piece with larger internal diameter. The tubular element introduced into the enlarged extension-piece, is provided with an explosive charge of limited power. As the charge is detonated, a joint is obtained with the extension-piece at the exterior of the tubular element introduced, by explosive plastic deforma¬ tion of the material in the extension-piece whereby only this extension-piece is deformed elastically. In this manner an elasto-plastic joint is obtained, whereby the contacting faces of the tubular elements form an additinal metallic packing. The elasto-plastic joint provides a reliable strength and tightness, whereby the said tightness may be enhanced by applying a gasket, that if desired may be subjected to explosive welding, in which case an easily weldable material is used for the gasket. However, it will be understood, that the elasto-plastic joint is the most important one. The explosive charge is tubular and is provided with an ignition charge to cause ignition in a manner known as such, so that it will propagate in an axial direction. The thickness of the wall of the extension-piece is only., slightly larger than those of the tubular elements. An anvil consisting of one, two or more parts is positioned around this extension-piece; it may be reomoved after the explosion has been realized, though it is also possible to work with a lost anvil. If desired the tubular elements may be provided with a protective layer internally, such as for example a corrosion resistant layer, so that with a joint in accor¬ dance with the invention an uninterrupted layer is obtained over the full length of mutually connected tubular elements. Though it is preferable that the tubular elements are all of the same material or strification respectively, it may be desirable from practical considerations that one or more of a series of tubular elements consist of differing materials, or one or more are provided with a protective layer and the remaining ones are not. It is also possible to realize the joint under water. To that purpose the area comprising the extension- piece and the tubular element inserted therein, is sealed off with rings at the location of the joint place, so that this area may be mmade free of water and possible other undesired media. The medium present in the inserted tubular element is separated from the joint place by positioning of an annular disc or inflatable plug at some distance from the joint place upstream with respect to the joint place. On the other hand a free expansion volume is obtained at the free outer end ot the tubular element, provided with an extension-piece, by the positioning of a container, whether inflatable or not. This volume, together with an appropriately selected ignition device, will ensure that the occurring Shockwave will remain within controllable limits, so that nowhere critical values of the material will be exceeded. The explosive power required for the elasto-plastic joint is an order of magnitude smaller than the power required for explosive welding. The joint according to the invention may be used for bedding of piping, if desired also under water, as well as for repairing pipe lines. For this latter application the tubular element, provided with an extension-piece, is provided at its other outer end with a flange, which may be secured on another flange of another tubular element by bolts in a manner known in itslef. The damaged part of the pipe line is removed, the surfaces of fractures created are smoothed, whereafter a tubular element, provided with an extension-piece with flange, is mountedon each one of both free outer ends, or if the distance of the damage is large, one or more tubular elements without a flange are inserted first at one or both sides. Another solution for that is to mount a tubular element as described above with flange on both free outer ends, and to insert therebetween an accurately fitting intermediate piece with a flange at both outer ends, and to secure it subsequently. It goes without saying that all variants therebetween are useful as well and that the selection in practice will be governed by the local conditions, for example whether the pipe line is embedded into a gully or is freely accessible in which latter case a larger freedom of movement is present. The invention is illustrated in detail herein- below with reference to the accompanying drawings. In the drawings shows: figure 1 a joint before detonating an explosive charge, for simple tubular elements, figure 2 a joint as in figure 1 for tubular elements provided with an interior covering, figure 3 a joint according to figure 1 with all accessories used for the explosion, with a flange, figure 4 a joint as for repair of a damaged pipe line with flange-fitting for simple tube elements, figure 4A a joint as in figure 4 for tubular elements with an interior covering, figure 5 a joint as in figure 4, but for repair over a larger length, with intermediate piece with two flanges for simple tubular elements, figure 5A a joint as in figure 5 for tubular elements with an interior covering, figure 6 a joint according to figure 1 after the detonation of the explosive charge. In figure 1 are shown two mutually connected tubular elements to know tubular element 1 with extension- piece 13 and tubular element 6. Gaskets 2 and 3 are positioned in the extension-piece of tubular element 1 at both sides of one or more recesses in the extension-piece. The expanded extension-piece of tubular element 1 is surrounded by an anvil 4, consisting of one or more, preferably three parts. The explosive charge with ignition is shown schematically at 5. For the blasting charge a detonation speed is selected which is smaller than for explosive welding. Usually a speed of 300 m/s to 1000.m/s is used. The expanded extension-piece of tubular element 1 is only deformed elastically by the presence of the anvil 4, while the other tubular element is plastically deformed at the exterior and intrudes into the above-mentioned recesses between the gaskets 2 and 3, whereby a joint with high tightness is obtained. The material for gasket 2 may be selected, if desired, as easily flowable material, that will create a weld at that location after the explosion at the relatively small detonation speed. Figure 2 shows a joint as in figure 1 , with as only difference that the two tubular elements 1 and 6 are provided with an internal covering 7 and all other reference figures agree with those in figure 1. In figure 3 is shown a joint according to figure 1 with the same reference figures as in figure 1 and also a sealing element 8 in tubular element 6 upstream from the joint and an expansion vessel 9 connected to the free outer end of tubular element 1 downstream from the joint. Sealing element 8 prevents penetration of the detonation wave further upstream into tubular element 6 and thus damage of parts located further upstream, or of the tubular element itself, while the expansion vessel serves for one thing for providing a seal, so that the explosive charge remains dry, and for another thing for allowing adequate pressure built-up. In figures 4 and 4A joints are represented for repair of damaged pipe lines for tubular elements without (figure 4) and with (figure 4A) interior covering. Here as well the same parts are shown with the same reference figures as in figure 1. In addition 10 represents a flange whereby the mutually contacting flanges may be secured up to adequate tightness with bolts. This construction may be used for repair of pipe lines with adequate flexibility after positioning, to allow the outer ends of both tubular elements 6 to be adequately displaced mutually to allow mounting of the tubular elements 1 with flange 10. In the figures 5 and 5A joints are shown for repair of damaged pipe lines for tightly fastened pipe lines for tubular elements without (figure 5) and with (figure 5A) interior covering, in any way. This embodiment deviates from that in figures 4 and 4A in that between the flanges 10 of both tubular elements is positioned an intermediate piece 11 , provided at both outer ends with flanges 10, whereby the flanges may be fastened with bolts or another fastening technology, known as such. In figure 6 is shown the joint according to figure 1 after detonation of the explosive charge. The reference figures are as in figure 1. The tubular element 6 has intruded in a plastic manner into the recess 12 between the gaskets 2 and 3 and rests completely or substantially completely tight against the roughed surface of recess 12. Gasket 2 in figure 6 is of copper and is 5 welded to tubular element 6 on the one hand and to tubular element 1 on the other hand after the explosion as represented in the detail drawing 6A. It is possible to make the joint under water, as mentioned earlier, whereby the environment of the joint 10 place is made free of water and/or other undesirable media. This is done in a manner known as such and does not make part of the invention. Finally it should be observed that instead of the flange 10, represented in the drawings, other V51 coupling elements may be used as well, such as a screw- thread; or a mechanical coupling. Moreover flange 10 may be welded on or may be forged as an integral part. If tubular element 1 is used exclusively as an extension-piece of a pipe line or part of an intermediate 20 piece 11, the flange 10 should be omitted. 25. " 30 35

Claims: Claims: 1. A joint between two tubular elements, characterized in that a tubular element ( 1 ) is provided with an extension-piece (13) and the other tubular element (6) is fitted into the recess(es) (12) of the extension- piece (13) by explosive plastic deformation. 2. A joint according to claim 1, characterized in that the tubular elements (1) and (6) are provided with an interior covering. 3. A joint according to claim 1 or 2, characterized in that the tubular element ( 1 ) at the outer end turned away from the extension-piece (13) is provided with a coupling element. 4. A joint according to claim 3, characterized in that the coupling element is a flange, a screw-thread or a mechanical coupling. 5. A method for the manufacture of joints according to one or more of the preceding claims , characterized in that an explosive charge is used with a detonation speed of 300 m/s to 1000 m/s, below the value required for the relevant material to create a joint by explosion. 6. A method according to claim 5, characterized in that prior to the explosion a sealing element (8) is positioned into tubular element (6) upstream from an explosive charge (5) and tubular element (1) is connected with an expansion vessel (9). 7. A method according to claim 5 or 6 , characterized in that the extension-piece (13) of the tubular element (1) is provided with gaskets (2) and (3) prior to the explosion. 8. A method according to claim 7 , characterized in that gasket (2) consists of an easily flowable material. 9. A method for repairing pipe lines, characterized 5 in that after removal of the damaged part and smoothing of the remaining outer ends a tubular element ( 1 ) with a flange (10) is mounted on each one thereof and the flanges (10) are interconnected with bolts. 10 10. A modification of the method according to claim 9, characterized in that an intermediate piece (11), provided with flanges (10) is inserted between both flanges (10). T5 1 T . A method according to one or more of claims 5-10 ■ - characterized in that an anvil (4) consisting of one or more parts is positioned around the extension-piece (13) prior to the ignition of the explosive charge, which if desired may be removed after the explosion. 20 12. A method according to one or more of claims 5-11 characterized in that it is carried out in an area with controlled atmosphere. 25 30 35

Inventors: ZONDAG NICOLAAS ABRAHAM, ZONDAG, NICOLAAS, ABRAHAM
Applicants: SMT SHOCKWAVE METALWORK TECH
Application year: 1986
Main classification: F16L13
IPC codes: B21D39, F16L13, F16L55