WO2002090101A2 - Method for producing a double wall by laminating an initial wall - Google Patents

Abstract

The invention concerns a method for producing a double wall by laminating an existing wall (10) of a tank. Said method is characterised in that it comprises steps which consist in: fixing by bonding on the tank existing wall (10) a spacer (12), then fixing a layer (12) of sealed composite material on the free surface of the spacer.

Description

PROCESS FOR PRODUCING A DOUBLE WALL BY LAMINATION FROM AN INITIAL WALL

The present invention relates to a method for producing a double wall by lamination from an initial wall. It applies in particular, but not exclusively, to tanks, vats or cisterns intended for storing dangerous materials, for example combustible and / or toxic for the environment.

Almost the entire European fleet of reservoirs, cisterns or vats, is made up of reservoirs having only a single wall.

However, single-walled tanks have the disadvantage of not offering great security with respect to the risk of leaks. Of course, these risks of leakage are particularly worrying in the case of tanks intended for the storage and / or transport of materials which are dangerous or toxic for the environment.

To overcome this drawback, double-walled tanks have been proposed; it being understood that when one of the walls leaks, the liquid is contained by the second wall and does not escape to the outside. In addition, thanks to the double wall, the leak can be detected, before any nuisance, thanks to the insertion of sensors between the two walls. At present, there are double-walled metal tanks on the market. These are conventionally constituted by a rigid tank body made of a thick sheet metal to which is fixed, by means of shims, an envelope, generally made of thinner sheet metal, located a short distance from the body of the tank. The space between the tank body and said envelope is commonly filled with a thermal insulation material.

It turns out that changing tanks or tanks due to their age, or to satisfy future European legislation requiring the use of double-walled tanks, represents a considerable cost for individuals, as well as for businesses.

The object of the invention is more particularly to eliminate this drawback by means of a process which makes it possible both to strengthen the tightness of the existing tank and to produce a second wall spaced from the first, and this at a lower cost than that of the purchase and installation of a double-walled tank.

To this end, it proposes a process for producing a double wall by stratification from an existing wall of a tank, this process consisting in fixing by bonding to the existing wall of the tank an assembly comprising a spacer and a composite material watertight secured to the spacer.

According to the invention, this method is characterized in that said assembly comprises at least one prefabricated lining in the form of a strip or a flexible plate, this lining comprising at least one central layer of crosslinked material constituting the aforementioned spacer into which a liquid can be injected, a first permeable textile lateral layer capable of sticking to the wall of the reservoir, this textile layer being fixed to one of the walls of the central layer and a second side layer which may consist of a permeable material to which an impermeable covering or an impermeable composite material may be attached.

Advantageously, the fixing step may include: - the production of a first layer of composite material, by application, after cleaning of the existing wall, of a resin in which a reinforcement will be injected, this first layer of composite making it possible to consolidate the initial wall of the tank, - then, deposit a thin layer of resin, not yet polymerized, which will be used to bond the filling.

The composite material could, for example, comprise a polyester or epoxy resin matrix, depending on the desired chemical resistance, and a reinforcement constituted by a mat of glass fibers.

The lining may include a central mesh element of polyethylene to which will be fixed, for example, by heat-sealing, respectively on each of its faces, two layers of nonwoven fibers of propylene filaments, the space delimited by these two layers forming a volume partially empty.

In addition, the partially empty volume of the spacer may include one or more leakage warning systems constituted, for example, by sensors advantageously placed at the lowest point.

According to a possibility offered by the invention, the empty volume authorized by the spacer will be filled with an antifreeze liquid whose level inevitably varies in the event of infiltration or exfiltration, that is to say leaks at the level of the initial wall or of the wall formed by stratification, the variation being easily detected by means of at least one sensor "monitoring" the level from a column of fluid. According to another possibility, the liquid injected into this empty volume is capable of reacting with the liquid contained in the tank so as to ensure self-sealing of any leak that may occur.

Advantageously, the above-mentioned assembly may comprise two linings, the respective central layers of which are filled respectively with a liquid used for detecting fluids and a reactive liquid used for self-sealing.

An embodiment of the invention will be described below, by way of nonlimiting example, with reference to the accompanying drawings in which:

FIG. 1 is a view in vertical section of a tank buried in the basement,

FIG. 2 is a side sectional view of the tank according to the invention,

FIG. 3 is a sectional view of the initial wall of the tank as well as of the elements constituting the second wall according to the invention,

FIG. 4 is a sectional view of a spacer according to the invention,

Figure 5 is a schematic sectional view of an assembly comprising two seals.

In FIGS. 1 to 5, the tank 1 chosen to illustrate the invention is a cylindrical tank used to contain petrol 2 and used to supply, thanks to a supply line 3, a pump from a service station 4.

This tank 1 is arranged in the basement in a parallelepipedic chamber 5 with dimensions slightly larger than those of tank 1. Tank 1 approximately comprises in its middle on its upper face a manhole 6 allowing in particular a man to access the interior of the tank 1. This manhole 6 is, moreover, used to fill and empty the tank 1. An operator will be able to access the manhole 6 thanks to a hatch 7 located at ground level 8, vertical to said hole 6, possibly using a ladder 9, fixed to a wall of the duct connecting the hatch 7 to the manhole 6, if the distance separating the hatch 7 and the manhole 6 is relatively large.

In order to produce a second wall by stratification on the internal face of the initial wall 10 of the tank 1, it is advisable to first empty and clean the tank 1.

In the case of the realization of this second wall on the external face of the initial wall 10, it will be necessary to consider the case where the material contained in the tank is flammable or not to know if one should empty or not the tank 1 In fact, in the process according to the invention, it is necessary to polymerize a resin; this polymerization can be exothermic and lead to risks of ignition or even explosion of a fuel contained in the tank 1, if the temperature reached by the fuel exceeds the flash temperature.

The initial wall 10 is generally cleaned by sandblasting in order, in particular, to strip the wall 10 well and thus allow perfect adhesion of the resin to the wall 10.

An operator then applies a first layer 11 of resin, for example polyester or epoxy, and then injects a reinforcement, for example a glass fiber mat, into the resin. The finish consists of passing a thin layer of resin in order to thoroughly wet all of the reinforcement used, and also to present a layer of homogeneous resin, and not yet polymerized, allowing the bonding of a lining 12 thereon.

According to a variant of the method according to the invention, the lining 12 can be bonded, by means of an appropriate adhesive, directly to the wall 10 of the tank 1 without first providing for the fixing of a layer 11 of composite material.

This lining 12 can be interposed between two layers 11 and 13 of composite material produced as described above, or between the initial wall 10 of the tank 1 and a layer 13 of composite material, and to form a partially free or empty intermediate volume in which can be injected with a liquid. In this example, the lining 12 is produced in the factory and comprises a central mesh element 14, for example made of polyethylene, to which are fixed, for example, by heat-sealing on its two faces, respectively two fine coatings 15 and 16 of nonwoven fibers, for example, propylene filaments. The lining 12 thus comprises, thanks to its particular geometry, a partially empty interior volume between the two above-mentioned coverings 15 and 16 of fibers. It can be in the form of a plate or a flexible strip easily manipulated by an operator.

Once the lining 12 is fixed to the first layer 11 of composite material, the operator proceeds to the same as the aforementioned first layer 11, possibly fixed, to produce the second layer 13 of composite material, that is to say that he applies a layer of resin, for example polyester, into which he injects a reinforcement, for example a glass fiber mat, and realizes the second layer 13, in the same manner as before, by applying a thin additional layer of resin to thoroughly wet the reinforcement.

In this example, the resin as well as the reinforcement, used to constitute the composite material of the first 11 and of the second 13 layer, are identical. We can of course consider the case where the composite material of the first layer 11 will be different from that of the second layer 13.

Of course, in the case where the coating 16 of the lining is made of a waterproof composite material, the second layer 13 is not necessary. It then suffices to provide watertight junctions at the connections of the gasket.

The composite structure 11, 12 and 13, thus produced by lamination, therefore comprises a first layer 11 of composite material, in this case a resin in which a reinforcement is injected. This first layer 11 constitutes a sealing reinforcement for the existing wall 10, or initial, of the tank 1.

This structure 11, 12 and 13 then comprises a lining 12 composed of a central element 14 having a partially empty volume and two coatings 15 and 16 partially impervious to the above resin used so that the resin does not come to spread, before its polymerization / solidification, in said empty volume of the lining 12. Finally, the structure may comprise a second layer 13 of composite material, fixed to the other coating 16 of the lining 12 and forming a second sealed wall 13, if this coating 16 is not itself waterproof.

The composite structure 11, 12 and 13 will preferably be produced on the internal face of the wall 10 of the reservoir 1 so that this layer 13 serves as the first limit for the volume of fluid 2 intended to fill the tank 1. This layer 13 undergoes the pressure exerted by the fluid 2 and is retained by the lining 12, which bears on the reinforced initial wall 10.

The empty volume of the lining 12 is here filled with an antifreeze liquid 17 which allows, thanks to a column 18 of said liquid 17 opening into the manhole 6, and possibly a sensor, to detect the slightest variation in the level of this liquid 17 occurring in the event of infiltration or exfiltration, that is to say a leak at the level of the initial wall 10 or of the second layer 13.

Alternatively, the partially empty interior volume of the lining 12 may include at least one leakage warning system constituted by a sensor sensitive to the product contained in the tank 1, advantageously placed at the lowest point so that a leak is quickly identified.

The process for producing a second wall by stratification from an existing wall 10, or initial, is illustrated here with a tank 1 designed to contain fuel 2; nevertheless, it is obvious to those skilled in the art that this method is applicable to any other tank used for various functions.

In the example shown in FIG. 5, the lining comprises two layers of crosslinked material 20, 21 connected to each other by means of a tight central layer 22. On the lateral face 23 of the crosslinked layer 20 is fixed by gluing or heat-sealing a layer of textile material, for example a non-woven material 24, intended to be fixed to the wall 25 of the container by means of a layer 26 of composite material similar to layer 11.

On the lateral face 27 of the crosslinked layer 21 is fixed by gluing or heat-bonding a layer 28 of waterproof material or of a textile material, for example, nonwoven on which can be applied a layer of laminated material 30 (unbroken line). *

Advantageously, the free volume provided by the reticular material of the layer 20 will be filled with a first liquid, while the free volume relating to the layer 21 will be filled with a second liquid. These two liquids will be chosen so that they react when they are in contact with each other while ensuring self-sealing.

According to another variant, the liquid contained in one of these two layers 20, 21 will be reactive with the liquid contained in the reservoir so as to ensure self-sealing when a leak occurs.

Claims

claims 1. A method of producing a double wall by stratification from an existing wall (10) of a tank (1), this method consisting in fixing by gluing to the existing wall (10) of the tank (1) a assembly comprising a spacer and a waterproof composite material secured to the spacer, characterized in that said assembly comprises at least one prefabricated liner in the form of a flexible strip or plate, this liner comprising at least one layer central in crosslinked material (14) constituting said spacer into which a liquid can be injected, a first permeable textile side layer (15) capable of being bonded to the wall (10) of the tank, this textile layer (15) being fixed on one of the walls of the central layer (14) and a second lateral layer (16) which may consist of a permeable material, to which an impermeable covering or an impermeable composite material may be fixed maple (13), this second lateral layer (16) being fixed on the second wall of the central layer (14). 2. Method according to claim 1, characterized in that the central layer consists of a mesh network. 3. Method according to one of claims 1 and 2, characterized in that the first side layer is made of a nonwoven fabric. 4. Method according to one of the preceding claims, characterized the above liquid reacts with the fluid contained in the tank so as to ensure self-sealing in the event of a leak. 5. Method according to claim 1, characterized in that it comprises, before fixing the spacer, fixing a first layer (11) of waterproof composite material on the wall existing (10) of the tank (1), said lining (12) being fixed on this first layer (11). 6. Method according to claim 1, characterized in that it previously comprises a cleaning step, for example by sandblasting, of the face of the initial wall (10) of the reservoir (1) on which the stratification will be practiced. 7. Tank (1) produced in accordance with the method according to one of the preceding claims, this tank (1) comprising at least one wall (10), characterized in that said wall (10) is coated with a composite structure comprising: - A first layer (11) of waterproof composite material constituted by a resin matrix and a reinforcement, this layer (1 1) covering said wall (10) and adhering thereto, - a lining (12) comprising a partially empty volume, fixed on the first layer (11), this spacer comprising a mesh network (14) on the two faces of which are fixed respectively two fine coverings of nonwoven fibers (15, 16) , - a second layer (13) of composite material constituted by a resin matrix and a reinforcement, this layer (13) being fixed on said lining (12), the above coatings being partially impervious to the resin used in said first and second layers. 8. Tank according to claim 7, characterized in that the matrix of the first and / or the second composite material is a polyester or epoxy resin. 9. Tank according to claim 7, characterized in that the reinforcement of the first and / or of the second composite material is a glass fiber mat. 10. Tank according to one of claims 7 and 8, characterized in that the non-woven fiber coverings (15, 16) are fixed by heat sealing on the two faces of the mesh network (14). 11. Tank according to claim 7, characterized in that the partially empty volume of the lining (12) comprises at least one leakage warning system, for example a sensor sensitive to the product contained in the tank (1). 12. Tank according to claim 7, characterized in that the tank (1) comprises means making it possible to detect the slightest variation in the liquid level (17). 13. Tank according to claim 7, characterized in that the lining (12) comprises two layers of crosslinked material (20, 21) connected to each other by means of a tight central layer (22), in that on the lateral face (23) of the crosslinked layer (20) is fixed a layer of textile material intended to be fixed on the wall (25) of the container by means of a layer (26) of material composite, and in that on the lateral face (27) of the crosslinked layer (21) is fixed a layer of waterproof material or of textile material to which a layer of laminated material (30) can be applied. . 14. Tank according to claim 13, characterized in that the free volumes of the layers of crosslinked material (20, 21) are filled with two respective liquids reacting with each other so as to ensure self-sealing in the event of leak.