Method of constructing a cylindrical metal storage tank, and device for implementing this method

0001The invention relates to the production of large cylindrical metal casing. It relates more specifically to the manufacture of tanks of such dimensions, used in the food, agrochemical, chemical, petrochemical fields as well as in the environment field (effluent treatment).

0002The dimensions in question are typically greater than ten meters high and fifteen meters in diameter, therefore much greater than the road gauge. In doing so, the production of such tanks must be carried out on site.

0003Document FR-A-2 551 370 describes a process for producing large size tanks on site by welding successive ferrules. This process essentially consists of:<ul id="ul0001" list-style="bullet" compact="compact"><li>to unroll continuously and at regular speed a metal strip from a reel;</li><li>depositing simultaneously and continuously said strip thus unwound on a merry-go-round comprising a turntable, the speed of rotation of which corresponds to the speed of advance of the strip, and the radius of which corresponds to the radius of the shell to be produced;</li><li>to stop the unwinding of the strip and to cut it once the length corresponding to the development of the shell has been reached;</li><li>bringing the work in progress above this shell, and carrying out docking and horizontal welding of the upper edge of this shell with the lower edge of said structure, the carousel being in rotation at a controlled speed;</li><li>to carry out the vertical welding for closing said shell by stopping the carousel.</li></ul>

0004If this process has made it possible to greatly simplify the production of relatively large tanks on site, typically three to ten meters in height and diameter, on the other hand, it quickly presents limits, as soon as one wishes to build tanks of larger dimensions. This limit is mainly inherent in the mass represented by the work in progress, which may require the use of very large capacity lifting devices, often incompatible with the space available on the site in question.

0005The object of the present invention is to provide a solution to this problem, so that it becomes possible to produce tanks, and generally cylindrical metal enclosures of very large capacity, for example having a height greater than fifteen meters. , and a diameter greater than twenty meters.

0006This process for the production of a large cylindrical metal casing by welding of successive ferrules, in which:<ul id="ul0002" list-style="none" compact="compact"><li>◆ a metal strip is continuously unwound from a reel, which is cut when the desired length, corresponding to the desired development of the shell, is reached;</li><li>◆ the part of the work already carried out is brought above this shell, and docking and horizontal welding are carried out continuously from the upper edge of this shell with the lower edge of said work, by means of a welding machine , then the vertical weld closing of said ferrule is stopped;</li></ul> consists of:<ul id="ul0003" list-style="none" compact="compact"><li>◆ to receive each metal strip during unwinding on a plurality of motorized unwinding tables, substantially regularly distributed around the periphery of the metal casing to be produced, and intended to ensure, according to a determined plane, the progression of said strip according to a cylindrical profile ;</li><li>◆ to fasten a circumferential ring, also called a belt, to the periphery of at least part of the ferrules thus produced;</li><li>◆ to carry out the lifting of the part of the structure thus produced by means of lifting mats, also substantially regularly distributed around the periphery of the metal casing to be produced, said mats being simultaneously hooked at the same circumferential ring;</li><li>◆ to repeat these operations until reaching the desired height of the envelope to be produced;</li><li>◆ and, when this height is reached, to lift the assembly by means of said lifting masts, in order to allow the evacuation of said rolling tables and of the welding machine, and the deposition of said assembly on the bottom of the envelope , previously established and implemented.</li></ul>

0007In other words, the invention basically consists of no longer using a rotary carousel, as in the case of the document of the prior art cited above, but using a plurality of unwinding tables and lifting masts. , making it possible to distribute the forces, and therefore to handle elements of significantly greater mass.

0008Advantageously, and according to the invention, the lifting mats are assembled at the unwinding tables. These two organs are therefore in equal number.

0009According to another advantageous characteristic of the invention, the circumferential lifting rings are not secured to each of the ferrules, but at periodic intervals, depending in particular on the possible lifting height conferred on said lifting masts.

0010The invention also relates to an installation for implementing this method. This installation includes:<ul id="ul0004" list-style="bullet" compact="compact"><li>a device for unwinding the metal strip, stored in the form of a reel;</li><li>a fixed welding station, capable of carrying out both horizontal and vertical welding;</li><li>a plurality of unwinding tables, substantially regularly distributed around the periphery of the metal casing to be produced, and intended to ensure, along a determined plane, the progression of the metal strip coming from the unwinding device according to a cylindrical profile;</li><li>a plurality of lifting masts, substantially regularly distributed around the periphery of the metal casing to be produced, and intended to ensure the lifting of the first ferrule produced or the part of the structure already produced, as well as their descent in contact with the shell in progress or from the bottom of said enclosure.</li></ul>

0011According to the invention, the unwinding tables include:<ul id="ul0005" list-style="bullet" compact="compact"><li>a base, which is fixed to the ground, at the periphery of the zone intended to receive the cylindrical envelope to be produced;</li><li>a mobile structure in horizontal translation on the base, and provided with:<ul id="ul0006" list-style="none" compact="compact"><li><img file="EP1464418A1_D0001.tif" /> a first roller, said motorized roller, motorized and with a vertical axis of revolution,</li><li><img file="EP1464418A1_D0002.tif" /> a second roller, called a pressure roller, with an axis of revolution parallel to that of the first</li><li>drive roller, and mounted free in rotation on a base which is itself mobile in translation</li><li>horizontal under the action of a means of translation integral with the mobile structure,</li><li>so as to allow pressure to be exerted by the generator of said roller, against the</li><li>drive roller, and thus to ensure the progression of the metal strip;</li><li><img file="EP1464418A1_D0003.tif" /> a roller with a horizontal axis of rotation, positioned between the two motor rollers and</li><li>presser and substantially flush with the lower edge of the generators of said</li><li>rollers, and intended to receive the lower edge of the shell in progress.</li></ul></li></ul>

0012According to the invention, the mobile structure is movable between an operational position, in which it receives the metal strip and a retracted position under the action of an electric or pneumatic jack or any other equivalent member.

0013Advantageously, the roller with a horizontal axis of rotation receiving the lower edge of the ferrule being produced is made of a material with structural hardening.

0014According to the invention, the unwinding tables each extend by a lifting mast. Thus, the assembly consisting of an unwinding table and a lifting mast is in one piece.

0015The manner in which the invention can be implemented and the advantages which ensue therefrom will emerge more clearly from the example of embodiment which follows, given by way of indication and without limitation in support of the appended figures. Figure 1 is a schematic plan view of the bottom of the tank to be produced according to the invention. FIG. 2 is a diagrammatic representation in cross section of FIG. 1. Figure 3 is a schematic plan view of the installation according to the invention. Figure 4 is a schematic representation of an unwinding table provided with its lifting mast. Figure 5 is a schematic detail view of the actual unwinding table. Figure 6 is a schematic representation of the welding machine according to the invention. Figure 7 is a schematic representation of the machine for unwinding the metal strip, according to the invention. Figure 8 illustrates in schematic perspective the unwinding operation according to the invention. FIG. 9 illustrates the operation of placing the dome of the tank on the first ferrule produced, in accordance with the invention. FIG. 10 illustrates the unwinding of the second ferrule, in accordance with the invention. FIG. 11 illustrates the unwinding of the fourth ferrule, in accordance with the invention. FIG. 12 illustrates in summary the different stages for the production of a tank made up of ten ferrules.

0016The following description relates to the production of a large capacity tank in accordance with the invention. However, the invention is not limited to this single application, and any envelope or cylindrical enclosure is also targeted by it.

0017The first step in the process for producing the tank according to the invention consists in making the bottom (1) of the latter. To this end, a concrete slab (2) is produced, within which are positioned a number of rods (4) in the shape of a carp tail, intended to be embedded in the concrete, and the upper end of which is welded. to a metallic structure serving as anchoring to the metallic plates constituting the bottom proper. The latter is advantageously inclined, in order to allow the operations of emptying the final tank.

0018In Figure 2, the bottom (1) is inclined from one of its peripheral edges, towards the diametrically opposite edge. However, it is also possible to envisage making a bottom, the highest or lowest point of which is situated in its center.

0019At the periphery of this circular bottom (1), a certain number of reservations (3) in the concrete are arranged, regularly distributed. These reservations (3) are intended to serve as an anchor and attachment point for as many unwinding tables and lifting masts, as will be clear from the description which follows.

0020It can be observed in FIG. 1, that the reservation situated at the bottom of the latter is not positioned with the same angular deviation with respect to the two reservations which are immediately adjacent to it. This configuration is dictated by the convenience of installing the device for unwinding the metal strips, constituting the ferrules forming part of the tank.

0021FIG. 3 shows a general view of the installation for producing the tank, in accordance with the invention. Within it, the unwinding tables associated with their lifting mast (8) have been positioned at the aforementioned reservations (3). As a corollary, the unwinding device (6) for the metal strips has also been symbolized, in the vicinity of the lowest unwinding table in said figure. Similarly, the machine for welding (7) the ferrules together has also been shown. This is mounted in a fixed position, so that to ensure the welding of two adjacent ferrules between them, it is important that said ferrules are driven in a circular translational movement at the level of said welding machine. These translation operations will be described in relation to the description of the various members making it possible to ensure this translation.

0022The unwinding tables (8) according to the invention will thus be described, in relation to FIGS. 4 and 5. As already indicated, these tables are fixed to the periphery of the bottom of the tank on a concrete slab within reservations (3) provided for this purpose.

0023Given the large dimensions of the ferrules, in particular in diameter, it is important that all the unwinding tables have a support surface for the metal strip (5) positioned at the same level. To do this, they each have a base (9) which can be fixed within the reservations (3) by means of a foot (10) provided with height adjustment members. This level adjustment is advantageously carried out by laser telemetry, well known for this application, so there is no need to describe it here in more detail.

0024The base (9) receives a structure (11) movable in horizontal translation, between an operational position, in which the table receives a ferrule in progress or already produced, and then protruding towards the center of the tank, and a retracted position in which said movable structure is somehow retracted into a housing provided for this purpose within the table, then eliminating the aforementioned projection.

0025The transition between these two positions is achieved by means of an electric or pneumatic cylinder, the cylinder (13) of which is secured to the base, and the free end of the piston (14) of which is secured to a wall of said movable structure or vice versa.

0026Said movable structure comprises a first roller (15), acting as a drive roller, and whose axis of revolution (21) is vertical.

0027This roller (15) is motorized, by means of a motor assembly secured to said mobile structure, and comprising an electric motor (16), whose motor axis cooperates with a bevel gear (17), actuating an axis vertical (18). The upper end of this vertical axis is provided with a toothed pinion, cooperating with a chain (19), cooperating in turn with a toothed pinion positioned in the vicinity of the upper end of the axis (21) of said drive roller. (15).

0028As a corollary, the mobile structure comprises a second roller (22), called the pressure roller, with an axis of revolution (23) parallel to that of the first drive roller (15). This pressure roller (22) is mounted to rotate freely on a base (24), itself movable in horizontal translation under the action of a translational means secured to the movable structure, so as to allow a pressure by the generator of said roller, against the drive roller. Typically, this means of translation consists of an electric or pneumatic cylinder, the cylinder (25) of which is secured to the movable structure, and the end of the piston (26) of which is secured to said base (24).

0029In doing so, as the two rollers, respectively motor (15) and presser (22) are parallel and have the same height and are located at the same level, the actuation of the jack (25, 26) causes the displacement of the base (24 ) on the right (in FIG. 5) and as a corollary the pressure of the roller (22) against the roller (15) by interposed generatrices, thus making it possible to ensure the progression of the metal strip.

0030The mobile structure finally comprises a roller (27) with a horizontal axis of rotation, positioned between the two drive rollers (15) and presser (22), and substantially flush with the lower edge of the generators of said rollers. This roller (27), mounted madly in rotation, is intended to receive the lower edge of the ferrule (5) in progress.

0031This planar element (27) is typically made of a material with structural hardening, in order to avoid the punching likely to be generated by the metal strip in contact with it.

0032The jack (13, 14) ensuring the displacement in horizontal translation of the mobile structure (11) is mounted and chosen so that in maximum extension, the generator of the drive roller (15) corresponds substantially to the desired diameter (28) of the shell to be produced, and therefore as a corollary of the final tank.

0033According to the invention, this unwinding table (8) is extended at its upper part by a lifting mast, secured to the base (9) of said table. In the example described, this mast rises from a height close to 4.25 meters. It is provided with a gripping hook or shoe (52), capable of being moved in height by means of an electric or pneumatic jack, or even by another device ensuring the same function (not shown).

0034In practice, the number of lifting masts, therefore of unwinding tables, is large enough, so that in the event of failure of one of them, the corresponding load can be distributed without damage over the two masts which are immediately adjacent.

0035Schematically illustrated in Figure 6 the welding machine (7) used in the installation of the invention. This is fixedly mounted for the duration of the tank mounting operations. It basically comprises a base (30), the level of which is adjusted by means of jacks (37, 38), bearing respectively on the bottom (1) and on the raft (2). From this base (30) extend two vertical columns (31, 32), on which are mounted the actual welding heads (33, 34) of an appropriate type depending on the nature of the metal to be welded. These welding heads are adjustable in height and in relation to each other by means of suitable translation members (35, 36, 39).

0036Is shown in relation to Figure 7 the unwinding machine (6) of the invention. It also includes a base or frame (46), leveled according to the level of the unwinding tables by means of a plurality of jacks (45). It further comprises a freely rotating turntable (41), intended to receive a coil (40) of metal strip (or "coil"). In this case, this metal is made of stainless steel. It could also be made of aluminum. The metal strip (5) from the coil (40) is then taken up by a pair of motor-presser rollers (42, 43), in addition to another roller (not shown) motorized by an electric motor (44), in order to ensuring the unwinding of said strip from the reel at a chosen and determined speed.

0037FIG. 8 thus illustrates the start of the unwinding of the metal strip (5) within the installation.

0038A description will now be given in more detail, in relation to FIGS. 9 to 12, of the various stages of production of the tank in accordance with the invention. In the example described, this tank is provided with a dome (50). We proceed in fact to assemble it, sector by sector with respect to a central chimney (51), ensuring the lifting and handling of said sectors by means of a crane (not shown).

0039When the dome is made, it is suspended by the lifting masts (8), the lifting hooks or shoes (52) of which are hooked by means of a link or equivalent (54) to the lifting points (53) provided for this purpose. The dome is thus raised by a height slightly greater than the width of the metal strip (5). This can then be unrolled from the unrolling machine (6) at the unwinding tables, where it is taken up, the pressure roller (22) of each of said tables tightening the strip against the motor roller (22). Obviously, the speed of rotation of the motor rollers is synchronized with the speed of unwinding of the strip (5) by the unrolling machine (6) (FIG. 9 - left part).

0040When the developed band (5) is sufficient for the realization of a continuous and complete shell, the progression thereof is stopped, then it is cut by means of a plasma torch or sectioned. Then the dome is lowered by means of said lifting masts, until it can dock with the upper edge of the shell thus formed. The different lifting points of the dome are then removed, so that it no longer rests on the upper edge of said ferrule. One then proceeds to the continuous welding of said upper edge of the ferrule on the dome, by means of the welding machine (7), the rotation of the ferrule + dome assembly then being effected by the cooperation of the motor and pressure rollers, to allow continuous passage of the area to be welded directly above the welding heads of the stationary welding machine (figure 9 - right part). Then, a pickling of the weld is carried out manually, still ensuring the ferrule + dome rotation, then constituting a single assembly. Finally, the welding bead is laminated and polished, the assembly continuing to rotate.

0041The lifting points are then put back in place at the dome, and the assembly then monobloc dome + ferrule is mounted at a sufficient height, to allow the unwinding of a second metal strip, in order to constitute the second ferrule (61 ) (Figure 10 - left part), like the first ferrule (60).

0042When the ferrule (61) is in place, the dome + first ferrule assembly (60) is lowered, in order to achieve docking of the lower edge of said assembly on the upper edge of said second ferrule (62). The lifting points are removed from said first assembly, and as for the first assembly, the latter is welded with the second ferrule by rotation at the level of the welding machine.

0043Once this operation has been completed, a circumferential ring or belt (55) is put in place, in particular by welding, at the periphery of the second ferrule, approximately halfway up the latter. This ring firstly has the function of reinforcing the ferrule in question. It is also intended to provide stability against buckling of the final tank. It also guarantees its roundness during its various construction phases. Finally, it is also intended to serve as a gripping member during successive lifting phases. It thus allows the load forces to be distributed, and in addition to avoid punching phenomena during lifting.

0044This ring typically consists of a metal angle, open towards the bottom.

0045The means for lifting the masts are then repositioned on this ring (55), and the dome + ferrule (60) + ferrule (61) assembly is lifted, and the operations of restarting are thus continued. unwinding of the metal strip and welding, with the installation of a circumferential ring or belt every two ferrules (see Figure 11).

0046The operation is thus repeated until it reaches the desired height of the tank.

0047It is thus observed, that by the establishment of a circumferential ring every two ferrules, the necessary height of the lifting masts is reduced, thereby reducing their size and the costs relating thereto.

0048When the desired height of the tank is reached, that is to say when the number of ferrules to be put in place is obtained, a new lifting operation is carried out, like what has been described above, to allow remove the welding machine, and also retract the unwinding tables associated with the lifting masts. Then, the assembly is redeposited on the bottom, and finally the welding operations are carried out from the lower edge of the lower ferrule to the peripheral edge of the bottom already in place, as specified.

0049Is shown in relation to Figure 12 the illustration of the main stages of production of the tank in question.

0050It is easy to understand the advantage of the process and of the installation according to the invention.

0051First of all, they allow the production of large capacity speakers reliably and safely, which we could not do to date.

0052Furthermore, the use of members ensuring the double function of lifting and rotating the ferrules makes it possible to reduce the power of the tools usually used for the production of such enclosures. At the same time, they make it possible to overcome cranes and other scaffolding, usually used for the construction of such enclosures. They also make it possible to avoid the work of personnel at height, a source of time loss in addition to accidents.

0053Finally, the invention makes it possible to optimize the quality of finish of the welds, and the maintenance of the appearance of the surfaces of the metal strips used, thereby favoring the conformity of the final tank with the sanitary and food requirements, when those - these are required.