FR3024841A1 - DOUBLE WALL TANK FOR STORAGE OF LIQUID CHEMICALS. - Google Patents

Abstract

The subject of the invention is a method for manufacturing a liquid-chemical storage tank of the double wall type, which tank is composed of an outer tank (2) which is capped by an upper part (23). provided with a manhole (24), and - an inner vessel (3) having an upper part (33) also provided with a manhole (34) which is sealingly connected to the manhole (24) of said outer vessel (2), which method comprises the steps of: - completely shaping the outer vessel (2), so as to obtain a one-piece vessel, - cutting the upper part (23) ) of the outer vessel (2) previously shaped, - inserting said inner vessel (3) in the free internal volume of said outer vessel (2), - recomposing the upper portion (23) of the outer vessel (2) by coinciding , in particular, its manhole (24) with that of said inner vessel (3), - assembling by welding the upper part (23) of said outer vessel (2) to said outer vessel (2) and / or to said inner vessel (3).

Description

TECHNICAL FIELD OF THE INVENTION

The subject of the invention is a method of manufacturing a double-walled tank for the storage of liquid chemicals which are liable to generate disturbances in their environment in the event of accidental leakage and in particular storage tanks for products such as liquid fertilizers, molasses or other products of the agricultural world or various industries. It also relates to a double-walled tank for chemical storage. It relates to the technical field of receptacles for the storage or transport of materials and more specifically of liquid chemical. State of the art Many tanks exist and can store liquid products like fertilizer, molasses or other. They are generally made of metal, thermoplastic material or others. Despite their robust design and their anti-UV treatment, these tanks may, over time, present risks of leakage, due for example to aggression of any kind, accidental or not, and / or because of their 3024 84 1 2 aging, and / or because of connections at the bottom of the tank or on the side of the tank which can deteriorate with time. These tanks have storage capacities ranging, for example, from 4,000 liters to 85,000 liters. As a result, a leak can quickly take a catastrophic turn for the immediate environment. The damage created by this type of leakage is difficult to repair given the enormous quantities of products that can escape as well as their speed to spread in the soil, around and / or under the tank.

The current constraints for these products, related to the protection of the environment, make it necessary to have effective means of retention to prevent leaks and avoid their disastrous consequences.

The document EP 2.754.623 (DURAPLAS) proposes a cistern which makes it possible to remedy the aforementioned drawbacks by proposing a storage tank in the form of a cylindrical double-walled tank, composed of a rigid tank and a flexible bag that can be integrated in the tank. rigid.

Although the tank shown in document EP 2.754.623 (DURAPLAS) makes it possible to overcome a number of disadvantages, such as the use of a retention tank, it remains rather complicated to install and does not allow cleaning. easy in case of change of product to store.

The invention aims to remedy this state of affairs. More particularly, the invention aims to provide a manufacturing process that facilitates the installation of the tank. Another object of the invention is to provide a technique for improving the stability of the inner vessel after installation. 3024841 - 3 - Yet another goal is to improve the tightness of the tank after are filling.

Disclosure of the invention. The solution proposed by the invention is a method for manufacturing a liquid chemical storage tank of the double wall type, which tank consists of an outer tank which is capped by an upper part 10 provided with a manhole, and - an inner vessel having an upper portion also provided with a manhole which is sealingly connected to the manhole of said outer vessel. The process is remarkable in that it comprises the steps of: - completely shaping the outer vessel, so as to obtain a monobloc tank, - cutting the upper part of the outer tank previously shaped, - inserting said inner vessel in the free internal volume of said outer vessel, 20 - recomposing the upper part of the outer vessel, making it coincide, in particular, with its manhole with that of said inner vessel, - assembling by welding the upper part of said outer vessel to said outer vessel and / or said inner vessel.

This method provides a simple method for making sealed tanks for storing large quantities of chemicals while avoiding the use of holding tanks. Other advantageous features of the invention are listed below. Each of these features may be considered alone or in combination with the remarkable features defined above, which characteristics are not essential as such for solving technical problems that the following features propose to solve: the weld may be a polyethylene weld, the outer vessel may be shaped, at the level of the cutting zone of the upper part, with a frustoconical ferrule which makes it possible to reduce the diameter of the edge of said upper part with respect to that of the upper rim of said tank so, after cutting and removal of this ferrule, to insert the rim of said upper part between the outer wall of the inner vessel and the inner wall of the outer vessel, - the outer vessel can be shaped, at the level of the cutting area of the upper part, with a frustoconical ferrule which allows to increase the diameter of the rim of said upper portion relative to that of the upper rim of said vessel; the method may comprise a step of shaping the upper portion of the outer vessel and the upper portion of the inner vessel with protruding forms, of the male-female type, which constitute centering means for positioning the inner vessel with respect to said outer vessel; the method may comprise a step of shaping the cylindrical wall of the outer vessel and the wall; cylindrical inner vessel with protruding forms, of the male-female type, which constitute centering means for positioning the inner vessel relative to said outer vessel. Another aspect of the invention is a liquid chemical storage tank of the double wall type obtained by the method described above. Other advantageous features of the invention are listed below. Each of these features may be considered alone or in combination with the remarkable features defined above, which remarkable features are not indispensable as such for the resolution of technical problems that the features below are proposed. to solve: - the lower part of the tank, between the inner surface of said outer vessel and the outer surface of said inner vessel, may comprise a leak detection device 5, which device is connected to an alert device, - the tank may have a welded and / or glued pipe, said pipe being installed between the outer wall of the inner tank and the inner wall of the outer tank, so as to be able to slide the leak detection device, the tank may comprise a pumping system between the inner wall of the outer vessel and the outer wall of the inner vessel, the tank may comprise, at the level of the lateral ends of the centering means of the upper part of each tank, the tank may comprise calluses located between the inner wall of the outer tank and the outer wall of the inner tank; the storage volume of the tank; internal tank can have a volume of between 200 liters and 200,000 liters, preferably between 10,000 and 200,000 liters. Description of the figures.

Other advantages and features of the invention will appear better on reading the description of a preferred embodiment which will follow, with reference to the appended drawings, carried out as indicative and non-limiting examples and in which: FIG. 1 is a diagrammatic cross-sectional view of a tank according to the invention, FIGS. 2 and 4 are diagrammatic sectional views of an outer tank that can be used to implement the invention; FIG. 3 is a diagrammatic cross-sectional view of an internal vessel that can be used to implement the invention, FIGS. 5, 6a and 6b are examples of cutting zones for implementing the invention. FIGS. 7a, 7b, 8a, 8b, 9a and 9b are examples of techniques for reassembling an inner vessel, FIG. 10 is a diagrammatic sectional view of a centering means according to the invention, FIGS. 11a, 11b, 11c and 11d are examples centering means according to the invention.

Preferred embodiments of the invention Figure 1 shows a large capacity tank 1 for the storage of liquid chemical such as liquid fertilizer, molasses or any other product. This cistern 1, of the double wall type, comprises a rigid cylindrical outer shell 2 with a vertical axis 2a, and a rigid inner vessel 3 having a vertical axis 3a parallel to the axis 2a.

The volume of the tank 1 can be between 200 liters and 200,000 liters. Regarding large capacity tanks, it is preferably between 10,000 liters and 200,000 liters.

A first step of the manufacturing process consists of shaping the outer vessel 2. It is monobloc, and can be made for example by a rotational molding operation. This characteristic makes it possible to limit as much as possible the possible presence of leakage. It may be made of a material such as a thermoplastic polymer, a polyethylene, or any other plastics material suitable for those skilled in the art. It can also be made in another type of rigid material such as a metal or an armed resin. In the case of the use of a plastic material, the outer vessel preferably undergoes an anti-UV treatment to prevent any denaturation of the chemical or any possible chemical reaction that can make the storage of the dangerous product.

The volume of the outer tank 2 is similar to that described above for the tank 1. It has a height H1 which can vary from 1 meter to 15 meters and a diameter D1 ranging from 1 meter to 10 meters. The outer vessel 2 illustrated in FIGS. 1 and 2 comprises a circular base 21, a vertical wall 22 attached to an upper part 23 provided with a manhole 24. The manhole 24 is preferably closed by a hatch equipped with suitable fittings allowing the installation of drain and / or filling pipes. It can have any position at the top 23 of the tank 2. This manhole can have different shapes, it is preferably circular to allow easy insertion of the drain pipes and / or filling, but may be of any other form known to those skilled in the art. The upper part 23 of the outer vessel 2 may be in the form of a dome, a cap, a disk, or a cylindrical shape. The diameter D11 of the upper portion 23 is similar to the diameter D1 described above and can therefore be between 1 meter and 10 meters depending on the size of the tank I. The next step of the manufacturing process consists in cutting the upper part 23 2. The FIG. 4 shows the axis 25 along which the top portion 23 is cut. The cutting technique may be in various forms such as cutting with the grinder, the jet high pressure water, laser, or any other industrial machining process known to those skilled in the art. This step separates the upper part 23 from its cylindrical wall 22.

FIG. 5 represents the normal case where no cutting guide has been provided on the cutting zone 25. In this case, a cutting line is preferably designed before cutting so as to obtain the most effective result. regular possible.

The outer vessel 2 may have a cutting zone 25 which facilitates cutting and which was provided during the shaping of the vessel 2. In FIG. 6a, the upper part 23 and the cylindrical wall 22 are connected by a zone 25 which is in the form of a frustoconical shell 10 allowing the upper portion 23 to have a smaller diameter D11 than that D1 of the inside of the tank 2. In Figure 6b, the upper part 23 and the cylindrical wall 22 are connected by a cutting zone 25 which is in the form of a frustoconical shell allowing the upper portion 23 to have a larger diameter D11 than that D1 of the inside of the tank 2. The tank 2 can Also have any other kind of cutting zone 25, such as a pre-cutting zone composed of a thinner material than the rest of the tank 2, or any other form suitable to the skilled person. The next step is to insert the inner vessel 3 inside the outer vessel 2, the upper portion 23 has been cut. The inner vessel 3 is similar to the outer vessel 2 described above. It is illustrated in Figures 1 and 3 and comprises a circular bottom 31, a vertical wall 32 on which is an upper portion 33 with a manhole 34. This manhole can have different shapes, it is preferably circular to allow the pipes to be inserted, but may be of any other form known to those skilled in the art. Whatever its shape, the manhole 34 of the inner vessel 3 is identical in shape to that chosen for the manhole 24 of the outer vessel so that the two so-called manholes can correspond during installation. Preferably, the manhole 24 of the outer vessel 2 has a diameter slightly smaller than the diameter of the manhole 34. In this way, the manhole 24 can fit into the manhole 34 during the reassembly step described below. The periphery of the manhole 34 may comprise a seal 36 making it possible to improve the tightness of the tank 1. The upper part 33 of the inner tank 3 is also of a shape identical to that 23 of the the outer vessel 2 and can be in the form of a dome, a cap, a disk, or even cylindrical. The diameter D2 of the inner vessel 3 is slightly smaller than the diameter D1 of the outer vessel 2 so that the inner vessel 3 can be inserted into the outer vessel 2. When the inner vessel 3 is inserted into the the outer tank 2, the bottom 31 can land directly on the bottom 21. The inner vessel 3 may also comprise 15 calli to enhance the stability of the tank 1 after the installation is complete. When the inner tank 3 is installed in the outer tank 2, the next step is then to close the outer tank 2 so that the tank 1 is sealed and does not present a risk of leakage. FIGS. 7a and 7b show one of the possible embodiments concerning the reassembly of the upper part 23. In the case represented, the upper part 23 is inserted into the gap formed by the cylindrical walls 22, 32 of the two tanks 2, 3. This mode only works when the diameter D11 of the upper part 23 is slightly smaller than the diameter D1 of the inside of the outer vessel 2. This characteristic is obtained by using, for example, the cutting zone 25 described. previously and shown in Figure 6a. After insertion of the upper part 23 into the interstices, a weld 4 is made so that the tank is sealed. This weld is made between the upper part 23 and the cylindrical wall 22 of the outer vessel 2. The weld 4 used will depend on the material used to shape the tanks 2, 3.

It can be in the form of a conventional weld or a polyethylene weld, or any other technique known to those skilled in the art. FIGS. 8a and 8b show an embodiment consisting of having the upper part 23 which closes the outer tank 2. In this case, the diameter D11 of the upper part 23 is slightly greater than the diameter D1 of the inside of the outer vessel 2. This characteristic is obtained by using, for example, the cutting zone 25 described above and shown in FIG. 6b. The welding will then be performed between the outer wall of the tank 2 and the rim of the upper part 23.

Figures 9a and 9b show another embodiment of welding the rim of the upper portion 23 to the rim of the cylindrical wall 22 so as to reform the outer vessel 2 as it was before the cutting step. To facilitate the placement of the upper part 23, calluses 20 can be used so as to center the inner vessel 3 and prevent it from moving during the use of the tank I. These calluses 5 can be manufactured in any material suitable to those skilled in the art, such as a plastic or metal material. In addition to facilitating the placement of the inner vessel 3, these calluses 5 allow to fix its position and thus prevent it from moving during transport (whether in a vertical or horizontal position). In order to be able to center the tank 3 and to facilitate the reassembly of the upper part 23 of the outer tank 2, the tank 1 may have centering means 6. These means 6 consist for example of complementary grooves and ribs. others. The upper part 23 may for example comprise grooves in which ribs created in the upper part 33 of the inner vessel 3 may be inserted. Thus, during reassembly, and as shown in FIG. 10, the two upper parts 23, 33 will fit into each other when the desired position is reached. In the case described, the ribs are found on the upper part 33 of the inner vessel 3 and the grooves are on the upper part 23 of the outer vessel 2. However, one of the centering means 6 having the opposite is quite conceivable, namely grooves on the inner vessel 3 and ribs on the outer vessel 2.

These centering means 6 may be in various forms. Preferably, they will have a cross shape as shown in Figure 11a, but they may however have different shapes such as a star (Figure 11b), a line (Figure 11c), spaced points (Figure 11d), or still any other form suitable to those skilled in the art. Various devices can be installed to use the tank 1. A leak detection device can, for example, be installed in the lower part of the tank 1, between the cylindrical wall 22 of the outer tank 2 and the wall 20. cylindrical 32 of the inner vessel 3. This detector uses an alert device which can be located directly on the outer wall of the tank 1, or on the contrary be deported. This warning device may be in the form of a visual or acoustic signal, mechanical or electrical.

In order to facilitate the installation of the detection system, the tank 1 may have a pipe welded or glued to the inner wall of the outer tank 2 or to the outer wall of the inner tank 3. This pipe allows the device to slide. leak detection and has a dual functionality. Indeed, it allows on the one hand to preserve the leak detection device and to maintain it and, on the other hand, repomper the liquid present in case of overflow. 3024841 - 12 - Tank 1 may also have a pumping system that makes it easier to empty when changing chemicals. This pump is preferably between the upper part 23 of the tank 2 and the upper part 33 of the tank 3 but can be between the two cylindrical walls 22, 32. In one embodiment, the upper part 33 of the tank 3 may have a housing created to accommodate the pumping system. The arrangement of the various elements and / or means and / or steps of the invention, in the embodiments described above, should not be understood as requiring such an arrangement in all implementations. In any case, it will be understood that various modifications may be made to these elements and / or means and / or steps, without departing from the spirit and scope of the invention. In particular: - the materials in which the tanks 2, 3 are shaped may vary, - the storage volumes of the tank 1 are variable, - the shape of the upper parts 23, 33 may vary, - the technique used for the cutting step can be in various forms, - the type of welding can vary, - there may be a cutting zone 25 provided or not on the tank 2, - the possible forms for the centering means 6 does not not limit to those described, - the position of the centering means 6 may vary, - the tank 1 may or may not be equipped with a leak detection system, - the tank 1 may or may not be equipped with a system of pumping.

Claims (13)

REVENDICATIONS1. A method of manufacturing a liquid chemical storage tank of the double wall type, which tank is composed of - an outer tank (2) which is capped by an upper part (23) provided with a hole man (24), and - an inner vessel (3) having an upper portion (33) also provided with a manhole (34) which is sealingly connected to the manhole (24) of said outer vessel (2), which method comprises the steps of: - completely shaping the outer vessel (2), so as to obtain a one-piece vessel, - cutting the upper part (23) of the outer vessel (2 ) previously shaped, - inserting said inner vessel (3) in the free internal volume of said outer vessel (2), - recomposing the upper portion (23) of the outer vessel (2) coinciding, in particular, its hole man (24) with that of said inner vessel (3), - assembling by welding (4) the upper part (23) of said outer vessel (2) to said outer vessel (2) and / or to said inner vessel (3). 20 2. The manufacturing method according to claim 1, wherein the weld (4) is a polyethylene weld. 3. Manufacturing process according to one of claims 1 or 2, wherein the outer vessel (2) is shaped, at the cutting zone (25) of the upper part (23), with a frustoconical ferrule which allows to reduce the diameter of the edge of said upper portion (23) relative to that of the upper rim of said tank (2) so, after cutting and removal of this ferrule, to insert the rim of said upper portion (23). between the outer wall 30 of the inner vessel (3) and the inner wall of the outer vessel (2). 3024841 - 14 - 4. Manufacturing method according to one of claims 1 or 2, wherein the outer vessel (2) is shaped at the cutting zone (25) of the upper part (23) with a frustoconical ferrule which allows to increase the diameter of the edge of said upper portion (23) relative to that of the upper rim of said bowl (2). 5. Manufacturing process according to any one of claims 1 to 4, characterized in that it consists in shaping the upper part (23) of the outer vessel (2) and the upper part (33) of the inner vessel ( 3) with protruding forms, of the male-female type, which constitute centering means (6) for positioning the inner vessel (3) with respect to said outer vessel (2). 6. Manufacturing process according to any one of claims 1 to 4, characterized in that it consists in shaping the cylindrical wall (22) of the outer vessel (2) and the cylindrical wall (32) of the inner vessel. (3) with protruding forms, of the male-female type, which constitute centering means for positioning the inner vessel (3) with respect to said outer vessel (2). 7. Liquid chemical storage tank, double wall type, characterized in that it is obtained by the method according to one of claims 1 to 4. 8. Storage tank according to claim 7, characterized in that it contains, in its lower part, between the inner surface of said outer vessel (2) and the outer surface of said inner vessel (3), a detection device leakage device, which device is connected to an alert device. 9. Storage tank according to claim 8, characterized in that it has a welded pipe and / or glued, said pipe being installed between the outer wall of the inner vessel (3) and the inner wall of the outer vessel (2). ), so that the leak detection device can slide. 3024841 - 15 - 10. Storage tank according to one of claims 7 to 9, characterized in that it contains a pumping system between the inner wall of said outer vessel (2) and the outer wall of said inner vessel (3). 5 11. Storage tank according to one of claims 7 to 10, characterized in that it comprises, at the lateral ends of the centering means (6) of the upper part of each vessel (2, 3). 12. Storage tank according to one of claims 7 to 11, characterized in that it comprises calli (5) between the inner wall of the outer vessel (2) and the outer wall of the inner vessel (3). ). 13. Storage tank according to any one of claims 7 to 12, characterized in that the storage volume of the inner vessel (3) has a volume of between 200 liters and 200,000 liters, preferably between 10,000 and 200,000 liters.