EP1373075B1 - Connecting system for fixing a flexible plastic film to the sealing coating on the inside of the tank wall of a storage tank - Google Patents

Abstract

The invention relates to a connecting system for fixing a flexible plastic film to the sealing coating on the inside of the tank wall of a tank for storing materials which are water pollutants. The aim of the invention, improving on the disadvantages of the state of the art, is the production of a connecting system for fixing a flexible plastic film to the sealing coating on the inside of the tank wall of a storage tank, which is easy to assemble and guarantees a durable and reliable sealing. Said aim is achieved, by means of a connecting system, comprising a strip-like sealing web (6) and an adapter film (5), whereby the sealing web (6) has an upper fixing section (6b), fixed to the circumference of the inner side of the tank wall (1) by means of an adhesive made from synthetic material and a lower fixing section (6c) which overlaps the adapter film (5) and is connected thereto by means of gluing or welding. The adapter film (5) is connected to the coating film (4) by welding.

Description

The invention relates to a connection system for fastening a flexible plastic film for leak protection lining on the inside of the tank wall of a tank for storing water-polluting media.

Flat-bottom tanks are made of steel or reinforced concrete and are mainly used for storing fuels, mineral oils, acids, alkalis, solvents or the like.

In practice, both single-walled and double-walled flat-bottom tanks are used. For environmental reasons, there is a need to monitor the flat-bottom tanks for leaks. To make this possible, single-walled storage tanks must be retrofitted with an additional leak protection lining. A so-called second wall or inner wall is formed by a leak protection lining and the single-walled storage tank is thereby converted into a double-walled storage tank. The leak protection lining covers at least the tank bottom and can extend to the tank fill opening according to the given requirements or can be attached to the inside of the outer wall of the tank at a certain height.

Two different systems are known as leak protection lining based on plastics. One relates to a lining with a fixed inner wall and the other to a lining with a flexible film. To form a solid inner wall, a laminate of a knobbed film, e.g. B. made of aluminum, and a plastic layer, preferably based on epoxy resin, which contains a single or multi-layer glass fiber fabric as reinforcement, used (EP 0 470 321 B1, DE 36 22 593 C2 and US Pat. No. 5,269,436). In the wall area, the glass fiber fabric and the plastic layer consisting of a reaction resin are either firmly connected to the knobbed film or to the tank wall and form a solid, stable wall after curing. The knobbed film is used exclusively to form the required leakage monitoring area and can also be replaced by a grille or another cavity-forming insert. The attachment of this lining to the inside of the tank wall is relatively unproblematic. If the knobbed film extends into the wall area, it will be made of synthetic resin and the existing glass fiber reinforcement pulled up to the tank wall and connected to it. However, such inner linings are very expensive to manufacture and assemble.

The other system consists of a pressure-stable cavity-forming insert and at least one media-resistant flexible plastic film lying on this insert, e.g. B. made of PVC, which lies loosely on the tank wall or the cavity-forming insert and is attached to the tank wall. From CH-PS 484 798 it is known to fasten the elastic film by means of a clamping device above the liquid level, a circumferential tube being pressed by means of clips against a base attached to the inside of the wall. This solution does not guarantee a permanent media and vacuum tight connection between the lining foil and the tank wall.

From DE 196 21 469 A1 an inner lining consisting of a flexible film for a gasoline tank is known. The film is held in the dome of the tank using a tension ring. Lining the entire interior of a tank to form a double wall is, however, very costly.

It is known from practice that the connection of a flexible film to the tank wall presents difficulties, since the connection points have to be media and vacuum tight. With steel storage tanks in particular, it must also be taken into account that they are outdoors and are exposed to considerable temperature fluctuations. Additionally changing fluid levels in the containers also affect the expansion behavior of the container material.

A flat-bottom tank is known from DE 298 07 285 U1, in which the flexible lining film is attached all round by means of a clamping device. The clamping device consists of bolts which are arranged at the same height and which are fixed in or on the tank wall at defined intervals and project inwards onto which the clamping rails can be attached. Elastic sealing tapes are arranged all around between the clamping rails and the film, as well as the film and the inside of the tank wall. The clamping rails are locked under pressure on the bolts.

From WO 00/58184 a liquid container with leak monitoring for the storage of water-endangering substances is known, in which various measures for attaching a foil made of metal or plastic to the inside of the tank wall are proposed. In a positive connection by means of a clamp connection tubes or strips are attached to the inside of the outer wall, on which the second floor, for. B is a flexible film that is attached by means of a spring. Another variant consists in attaching a sheet metal strip pointing upwards at an acute angle to the inside of the wall and over the edge of the film pull the edge of the sheet metal strip and glue it with it and fill the space between the inside of the wall and the sheet metal strip with a casting compound.

A leak protection lining (DE 299 18 485 U1) with a connection system for fastening a flexible plastic film to the inside of the tank wall of a storage tank is also known, the leak protection lining consisting at least of a cavity-forming insert and a media-resistant flexible lining film made of plastic lying thereon. The connection system consists of a mounting bracket which is fixed by gluing to fix the position by means of a flexible, all-round plastic bracket on the inside of the tank wall and the upper part of the leg of the mounting bracket. The lining film is connected in an overlapping manner by gluing or welding to the leg of the fastening bracket running parallel to the tank bottom. The known fastening systems are very complex to assemble.

In addition, when using flexible foils, it must be taken into account that these can generally not be laid completely wrinkle-free and, despite a sufficient cut, do not always fit smoothly against the tank wall, especially in corner areas or if there are shoulders in the tank wall area. When filling a tank, the film is subjected to an additional load and stretched, particularly at the fastening points. In this case, shear forces occur in the fastening points, which can lead to the film tearing off or, due to the stretching of the film, lead to a reduction in material thickness, which forms a weak point. It should also be borne in mind that tank systems are subject to strict technical monitoring regulations and that there are particularly high demands on tightness, especially at the fastening points on the tank wall.

The invention has for its object to provide a connection system for attaching a flexible plastic film for leak protection lining on the inside of the outer wall of a storage tank, which requires little assembly effort and ensures permanent and reliable tightness.

According to the invention the object is achieved by the features specified in claim 1. Suitable design variants are the subject of claims 2 to 14. The proposed connection system consists at least of a strip-shaped sealing membrane and an adapter film. The sealing membrane represents the actual carrier material and has an upper fastening section which is fastened all round on the inside of the tank wall by means of an adhesive based on plastic, and a lower fastening section which overlaps the adapter film and is connected to it by gluing or welding. The lower end section of the adapter film is connected to the lining film by welding. The dimensions of the lining film and the adapter film are matched to one another in such a way that the weld seam is located in the area of the floor. The height of the attachment points on the tank wall, their Distance from the tank bottom depends on the specified lining conditions. The adapter film can be connected to the lower section of the sealing membrane either by welding or gluing. However, a welded connection is only possible if this section consists of a weldable plastic. If the connection between the adapter film and the sealing membrane is made by gluing, the adapter film can also be glued to the tank wall in the area of its upper edge. This variant is used when there are particularly high demands on the tightness of the connection point. The strip-shaped sealing membrane can be formed in various ways, e.g. B. from an impregnable synthetic fiber mat or a glass fabric mat, which is placed on the prepared adhesive layers and pressed. When processing synthetic fiber mats or glass fabrics, it is advantageous for a good adhesive bond if they are provided with an outstanding fiber structure. In this case, a reaction resin based on epoxy or polyester resin is used as the adhesive, which is then finally applied to the top of the fabric or mat in order to achieve a high level of tightness at the connection points. The adapter film should be perforated in the area of the joint so that the resin can penetrate the adapter film and an improved adhesion of the film is achieved. After the resin has hardened, a stable strip-shaped sealing membrane is created, which is permanently and firmly connected to the tank wall and the adapter film. In certain applications, especially when a tank is subject to high temperature fluctuations and the resulting expansion, it is advisable to use a sealing membrane made of a polymeric or elastomeric material that has more elastic properties than the aforementioned composites. It is also possible to manufacture the actual lining film, the adapter film and the sealing membrane from the same material. However, the waterproofing membrane should be at least twice as thick as the lining film. It can also consist of a prefabricated composite material, such as a glass fiber reinforced film. The adapter film can also be reinforced, at least in the fastening area. eg by another laminated film strip or a reinforcement insert.

The adapter film can additionally be equipped in the fastening area between the tank wall and the sealing film on one or both sides with two horizontally circumferential strips, consisting of a textile fabric made of plastic fibers. The flat structure can be a fleece or a mat, which is connected to the adapter film by lamination or gluing. The textile fabric can also first on the adhesive layer applied to the tank wall put on and pressed on. Polypropylene or polyester are preferably used as plastic fibers. In order to prevent liquid from being able to reach the monitoring space via the flat structure during the operating state of the tank, an intermediate space is arranged between the two strips, at least on the outside of the adapter film, which forms a diffusion barrier. The vertical distance between the two strips to form the diffusion barrier should be a few millimeters, preferably 3 mm. The adhesive to be used and the choice of material for the adapter film and the sealing membrane must be coordinated with one another, taking into account the medium to be stored in the tank, the nature of the wall of the tank to be lined, and the expected stresses on the tank wall due to influences from temperature and / or level fluctuations. The tanks are usually made of either steel or concrete. With regard to the choice of adhesive, adhesives should be used which have good adhesion and cohesion.

Suitable adhesives are e.g. B. polyurethane adhesives, epoxy and polyester resins, anaerobic curing adhesives and adhesives based on MS polymers. Polyurethane adhesives are suitable for almost all polar materials and are very easy to adjust in terms of processing consistency and enable particularly flexible composites. Two-component adhesives based on epoxy resin can be specifically adjusted in terms of their properties and also enable curing at room temperature. Anaerobically curing adhesives consist of a mixture of dimethacrylic acid esters of certain diols with small amounts of peroxides and accelerators, the curing being carried out by polymerization. Adhesives based on MS polymers have a high elasticity and an almost universal adhesive spectrum.

In order to keep the loads on the connection system as low as possible when filling the tank, it is proposed to equip the adapter film with at least one expansion fold running in the horizontal direction. The expansion fold is already incorporated in the manufacture of the adapter film. When the tank is filled, the adapter film attached to the sealing membrane can then yield, without stressing the material. Another way of achieving expansion compensation when filling the tank is to provide the adapter film with an oversize in terms of its height dimension or width.

Below the sealing membrane, elastic expansion means are arranged circumferentially or in sections between the adapter film and the inside of the tank wall, which are compressed into a flat state during the filling of the tank. The expansion means prevent the lining film and the adapter film from wrinkling in the lower region. When filling of the tank, the adapter film can then lay against the tank wall without wrinkling, the expansion means giving way and being pressed flat against the tank wall. As an expansion agent such. B. elastic foam elements or an air-filled hose can be used, the air escapes as a result of the load occurring during filling through valves.

Compared to the known mechanical fastening systems, the proposed connection system requires considerably less material and assembly and also fulfills the requirements for high tightness.

Fig. 1

den Ausschnitt eines Tanks mit einer Leckschutzauskleidung und deren Befestigung an der Tankwandung mittels eines Verbindungssystems auf der Basis einer Synthesefasermatte und einem Reaktionsharz, in perspektivischer Darstellung,

Fig. 2

den Ausschnitt eines Tanks mit einer weiteren Ausführungsvariante zur Befestigung der Leckschutzauskleidung, als Querschnittsdarstellung und

Fig. 3

den Befestigungsabschnitt einer weiteren Ausführungsvariante, als Querschnittsdarstellung.

The invention is explained in more detail below using a few examples. Show in the accompanying drawing

Fig. 1

the section of a tank with a leak protection lining and its attachment to the tank wall by means of a connection system based on a synthetic fiber mat and a reaction resin, in a perspective view,

Fig. 2

the section of a tank with a further embodiment for fastening the leak protection lining, as a cross-sectional view and

Fig. 3

the fastening section of a further embodiment variant, as a cross-sectional representation.

The standing tank made of steel shown in Figure 1 is single-walled and consists of a cylindrical tank wall 1 and a flat tank bottom 2 and a curved cover. Such a tank is e.g. intended for the storage of heating oil and has a diameter of 20 m and a height of 17 m. The tank also has a closable opening in the form of a manhole on the cover (not shown in more detail). Before the introduction of a leak protection lining, the empty tank is cleaned and the tank bottom 2 is checked for leaks, repaired if necessary and provided with a corrosion-inhibiting paint or sealed with a hardenable liquid plastic. The wall section provided as an adhesive point for fastening the strip-shaped sealing membrane 6 is roughened, cleaned and degreased.

The leak protection lining consists of a cavity-forming insert 3, which completely covers the tank bottom 2 and extends on the inside of the tank wall 1 to the attachment point, and a flexible media-resistant lining film 4, which completely covers the cavity-forming insert 3 in the area of the tank bottom 2, and from an adapter film 5, which covers the lining film 4 in the bottom area by approximately 20 cm. The adapter film 5 is pulled up to the wall 1 to a height of approximately 1 m and is attached to the wall 1 with its upper reinforced edge section 5a all around by means of adhesive dots arranged at certain intervals. The stitching prevents the adapter film from falling down during further assembly. The adapter film 5 is provided at a height of approx. 60 cm with a circumferential expansion fold 5b, which enables compensation at a height of approx. 2 to 5 cm and is indicated in FIG. 1 by the dashed lines. The expansion fold 5b is formed by a pressure sensitive adhesive, which does not cause any damage to the adapter film 5 when the adhesive is loosened. The strip-shaped sealing membrane 6 consists of a synthetic fiber mat 6a with an upper fastening section 6b and a lower fastening section 6c with a fiber structure which projects on both sides. A two-component epoxy resin is applied as an adhesive layer 7 in a thickness of 2 to 5 mm to the edge section 5a of the adapter film 5 pointing into the tank interior and the section of the wall 1 adjoining it. The application can be done with a spray gun with a wide slot nozzle. The consistency of the epoxy resin has been adjusted in such a way that dripping or draining downwards is impossible. The width of the surrounding adhesive layer is approx. 20 to 30 cm. For a better understanding, the structure of the connection system is shown spatially offset in FIG. 1. Subsequently or already during the application of the adhesive, the strip-shaped synthetic fiber mat 6a is placed on the adhesive point 7 and pressed on by means of an offset pair of pressure rollers, the tough plastic epoxy resin penetrating the fiber structure of the synthetic fiber mat 6a in the region of the fastening sections 6b, 6c.

Finally, a second epoxy resin layer 7a is sprayed onto the outside of the synthetic fiber mat 6a as a cover layer. After a curing process of several hours at room temperature, a firm, permanent, media-tight connection is achieved between the adapter film 5 and the lower section 6c of the strip-shaped sealing sheet 6 formed and between the upper section 6b of the sealing sheet 6 and the tank wall 1.

During the curing of the epoxy resin, the lower section of the adapter film 5 is connected to the lining film 4 by welding in the overlap region. The weld seam formed is marked with position 8.

When the tank is subsequently filled, the expansion fold 5b is released, depending on the voltage that occurs, and the adapter film 5 is not subjected to any additional expansion stress.

Before the leak protection lining is installed, the necessary connecting pieces 9 for leakage monitoring are installed in the area of the tank wall 1 near the floor. A commercially available vacuum leakage indicator is connected to this. The cavity-forming insert 3 resting on the tank bottom 2 consists e.g. from a fleece-lined flexible PEHD grid that is rolled out. The actual leak protection lining can only be installed when the adapter film 5 is fastened to the tank wall 1 by means of the strip-shaped sealing membrane 6.

A further embodiment variant of the connection system is shown in FIG. 2. The floor area has not been shown, since it is designed analogously to the variant described above. The strip-shaped sealing sheet 6 consists of an approximately 4 mm thick PVC film 6d and is welded to the adapter film 5 in the area of the lower fastening section 6c. The weld seam is identified by reference number 10. The PEHD grid serving as a cavity-forming insert 3 extends analogously to the embodiment variant according to FIG. 1 to the fastening point. The upper fastening section 6b is fastened all round to the tank wall 1 by means of an adhesive layer 7 based on polyurethane. According to this example, the adapter film 5 is only connected to the sealing membrane 6 and lies loosely against the cavity-forming insert 3. A circumferential elastic expansion round profile 11 made of soft foam is arranged below the fastening point between the adapter film 5 and the tank wall 1 and is attached to the tank wall 1 by gluing. As a result, the adapter film 5, which is arranged in excess, is arched and the necessary expansion compensation is created when filling the tank. During the filling process, the adapter film lies against the insert 3 and the elastic expansion profile 11 is pressed flat.

3 shows a further embodiment variant of the connection system for a tank. On the tank wall 1, an adhesive layer 7 based on polyester is applied all around in the area of the fastening point, the width of which corresponds to the width of the strip-shaped sealing membrane 6. The adapter film 5 is applied with its upper fastening section 5a to the adhesive layer 7, offset downwards, so that the upper region of the adhesive layer remains free. The upper fastening section 6b of the sealing membrane 6, which consists of a glass fiber fabric 6a, is applied to this. The fastening section 5a of the adapter film is provided with perforations 12, so that when the adapter film 5 is pressed on, adhesive passes through the perforations 12 and the fabric layer of the glass fiber fabric 6a in the region of the lower fastening section 6c. Finally, a cover layer 7a made of polyester resin is applied to the glass fiber fabric 6a. To the curing of the polyester resin is thus a connection via the perforations 12 between the two polyester resin layers 7 and 7a, so that the fastening section 5a of the adapter film 5 is virtually embedded in a polyester resin layer. The strip-shaped sealing membrane 6 consists of the glass fiber fabric and the polyester resin.

The cavity-forming insert and the flexible lining foil can consist of the materials which are customary per se. The lining film can also consist of a multi-layer film system.

The connection system explained above is characterized by a low cost of materials and enables inexpensive installation. The possible material combinations can be optimally matched to the tank to be lined, the tank medium and the operating conditions.

Claims (14)

1. A connection system for the attachment of a flexible plastic sheet (14) as leakage protection lining to the inside of the tank wall of a storage tank, wherein this leakage protection lining comprises at least a cavitating insert (3) and a medium-resistant, flexible plastic lining sheet (4) lying on said insert, and the connection system comprises at least a strip-like sealing web (6) and an adapter sheet (5), the sealing web (6) having an upper fixing portion (6b) and a lower fixing portion (6c), wherein the upper fixing portion (6b) circumferentially affixed to the inside of the tank wall (1) by means of an adhesive based on plastic and the lower fixing portion (6c) overlapping the adapter sheet (5) and being connected to it by adhesive bonding or welding, and the adapter sheet (5) is connected with the lining sheet (4) by welding.
2. Connection system according to claim 1, characterized in that the adapter sheet (5) is additionally affixed circumferentially to the inside of the tank wall (1), by means of an adhesive (7) based on plastic, in the overlapping region.
3. Connection system according to one of the claims 1 or 2, characterized in that the sealing web (6) is made of a synthetic fibre mat which can be impregnated or a glass fibre fabric (6a), and a reaction resin (7, 7a) based on epoxy resin or unsaturated polyesters.
4. Connection system according to claim 3, characterized in that the synthetic fibre mat and the glass fibre mat (6a) are provided with a projecting fibrous structure on at least one side.
5. Connection system according to one of the claims 1 or 2, characterized in that the sealing web (6) is made of a polymeric or elastomeric material.
6. Connection system according to one of the claims 1 to 5, characterized in that the sealing web (6) is made of a precast composite material.
7. Connection system according to one of the claims 1 to 6, characterized in that the upper (6b) and the lower (6c) fixing portion of the sealing web (6) are made of different polymeric and/or elastomeric materials.
8. Connection system according to one of the claims 1 to 7, characterized in that the adapter sheet (5) is reinforced in the fixing region (5a).
9. Connection system according to one of the claims 1 to 8, characterized in that the adapter sheet (5) is perforated (12) in the fixing region (5a) and/or embossed or structured.
10. Connection system according to one of the claims 1 to 9, characterized in that the adapter sheet (5), in the fixing region (5a), is connected on at least one side by use of two horizontal, circumferential strips comprising a textile fabric of plastic fibres, wherein a space creating a diffuse barrier is arranged between both strips.
11. Connection system according to claim 10, characterized in that the strips are laminated on to the adapter sheet (5) or connected with it by adhesive bonding.
12. Connection system according to one of the claims 1 to 11, characterized in that the adapter sheet (5) is provided with at least one expansion crease (5b) running horizontally.
13. Connection system according to one of the claims 1 to 12, characterized in that the adapter sheet (5) is oversized as regards its vertical dimension and that elastic expansion means (11) are arranged below the sealing web (6) between the adapter sheet (5) and the inside of the tank wall (1) circumferentially or in sections, at a constant height, which can be compressed to a flat state during filling of the tank.
14. Connection system according to one of the claims 1 to 13, characterized in that the adhesive for connection of the sealing web (6) and the adapter sheet (5) with the tank wall (1) and of the adapter sheet (5) with the sealing web (6) is an adhesive (7, 7a) based on polyurethane or epoxy resin or polyester resin or MS polymers or is an anaerobic adhesive.