FR2499120A1 - Reinforced PVC panels for lining hydrostatic passages - assembled using welded and covered junctions - Google Patents

Abstract

An impermeable liner for water passages subjected to significant pressure variations is made from panels of thermoplastic material internally reinforced and having modular shapes which fit together to cover larger areas. Suitable for lining water transfer channels in e.g. pumped storage hydroelectric schemes. Pref. the panels are made of layers of PVC laminated to enclose perforated or expanded metal sheets which do not extend to the borders of the panels. The openings through the panels must be large enough for the thermoplastic to form transverse bridges. Pref. the reinforcement is 0.4-1.2mm. thick and enclosed by PVC 1.5-3mm. thick. Junctions between adjacent panels of e.g. square, rectangular, hexagonal shape may be welded and then covered with cross or star shaped gusset panels of PVC pref. at least 2mm. thick. The panels may be mounted by screws, nails, bolts, etc., to a framework of metal slats lining the passage walls.

Description

 The present invention relates to materials intended for continuous impermeable coatings, in particular for supply galleries of penstocks under variable pressures, piezometric wells and other installations supplying hydroelectric plants, as well as their laying.

 I1 is already known a process for producing interior coatings for galleries with predisposition of laminated elements in several layers, and a perforated metal frame. Such a material has industrial application in particular in hydroelectric power stations using turbines of the Pelton, Francis or other type operating with pressurized water through penstocks, which upstream are connected to feeding galleries connected to retention basins and necessary intake facilities. These feed galleries, subject to sometimes significant pressure variations, must be made impermeable. Depending on the nature of the rock in which these galleries are drilled, and depending on the coating with which they are lined, the variable pressures generate phenomena of wear can over time cause more or less significant cracks in the walls of these galleries, increasing when the pool is full, and closing more or less when the water level drops and with it, the acting pressure.

 During the operation of the installation, these enlarged cracks can give rise to significant leaks of pressurized water, resulting in pressure losses. In addition, these losses risk having harmful repercussions in the surrounding geological environment, with as a consequence a risk for the stability of the installation.

 The present invention proposes to improve the conditions for preserving walls subjected to a variable hydrostatic pressure, and possibly also to dynamic phenomena resulting from such variations, while improving the production and installation of the recommended waterproofing means, so as to obtain a waterproof coating practically insensitive to pressure variations.

 In this case, according to the present invention, these are prefabricated materials in several substantially planar layers, comprising a metallic laminar framework, preferably of steel, but possibly also of copper or other suitable metal or metallic alloy, this interior reinforcement. being embedded in the mass of these covering layers which are made of synthetic material such as a heat-weldable and strictly impermeable resin, for example polyvinyl chloride (known under the name "PVC" and indicated by this abbreviation below), or other equivalent substance.

 The internal metal sheet reinforcement is, in a known manner, perforated to form passages through which the covering material on either side can bond after a hot treatment under pressure. The internal reinforcement can also be formed by a large mesh fabric of high tensile strength.

 Instead of perforations, it is possible to provide bosses or other closely projecting particles on the reinforcement to ensure its adhesion to the coating which surrounds it.

 These materials, in the form of flat, square or rectangular plates, are prefabricated in standardized and predetermined dimensions, allow jointing in order to obtain complete coverage of the surface to be coated, even adapting to curvatures thanks to their flexibility. inherent.

 In addition, in these plates the internal metal frame is slightly recessed with respect to the contour of the latter, to allow an intimate connection between them by heat sealing.

 As for the dimensions of these reinforced plates, in particular with regard to their thickness, they can vary as required.

 The internal metal reinforcement can be a steel sheet with a thickness of between 0.4 and 1.2 mm, and the surrounding mass can be, for example, PUC, with a thickness of between 1.5 and 3 mm according to the required flexibility, to allow a good adaptation of the waterproof coating.

 The accompanying drawing shows, by way of non-limiting example, such a reinforced plate as well as the way in which the assembly of this type of plate takes place to form a continuous waterproof coating.

FIG. 1 is a perspective view of a section of such a plate in partial section on an amplified scale,
FIG. 2 is a plan view of it partially cut away at the level of the internal metal frame, which shows perforations of varying shapes and sizes,
FIG. 3 shows the plate in section according to its thickness,
Figures 4,5,6,7 and 8 relate to the different phases of assembly between them of plates according to the previous figures, for the formation of the waterproof coating to establish.

 Referring to Figures 1 to 3, the rectangular or square plate, having a structure having faces 10 and 12 and a thickness 14, is made of PVC completely surrounding a metal frame 16 preferably of steel.

 The mass 10, 12 and 14 of PVC is substantially homogeneous, since it is obtained by hot compression of resin, formed by extrusion or by another suitable process, this structure consisting of at least two or more layers arranged in on either side of the metal frame 16.

 The internal metal frame 16 may include bosses, frowns or other configurations ensuring good adhesion with the enveloping mass of PVC.

 It is however more advantageous to perforate this reinforcement in the manner shown in FIG. 2.

 Thus by the hot compression treatment of the PVC mass, this material penetrates through the perforations by firmly bracing the coating on either side of the frame (Fig. 3).

 The reinforcement 16 can also be a metallic lattice or of expanded metal embedded in the mass 10, 12.

 In certain cases it is conceivable to choose a textile material for the reinforcement, provided that this guarantees sufficient resistance.

 The plates reinforced under the aforementioned conditions are in a rectangular, square, or even hexagonal shape allowing by juxtaposition to completely cover a surface to be coated.

In the implementation process illustrated in FIGS. 4 to 8, the coating is produced by assembling quadrangular plates.

This assembly is carried out as follows
Referring to FIG. 4, metal strips 20 and 22 crossing each other, constitute the framework against which the reinforced PVC plates M are placed and fixed according to F. According to FIG. 5, four of these M1 plates , M2, M3 and M4 are placed on the crossing of the strips 20 and 22.

 These plates are called to be brought into direct contact with the wall to be coated, and their fixing F to the strips takes place by any useful means, such as screws, expanding bolts and the like with possible interposition of washers, according to FIGS. 4 to 7 .

Consequently, in accordance with FIG. 6, the edges of the rx 2 plates M3 and M4 thus appeared are hot welded sint'1e
4 cables at right angles 51 'S2. This welding is carried out by known means by making use of hot air and a PVC wire to perfectly fill the joints between these plates.

 According to FIG. 7, the assembly is completed by the addition of a cross-shaped gusset C welded by hot air thermofusion. This gusset C, made of PVC with a thickness not to be less than 2 mm, covers the weld beads S1, S2 at the crossing of the strips 20, 22.

 Finally, it is advantageous to apply and weld PVC N1 and N2 tapes by thermofusion (fig. 8), the width of which exceeds that of the cross-pieces C, and extending so as to cover all the welds S1 and S2 of the joins of plates M1, M2, M3 and M4. In FIG. 8, the parts covered, and therefore masked by these ribbons M1, M2, namely the strips 20, 22 and the spider C, are shown in broken lines.

 The above process makes it possible to obtain a continuous coating, impermeable and resistant to high pressures both on the lower surface and on the upper surface thereof, and the application of which is suitable in all cases where problems of impermeability and resistance, in particular for the coating of galleries under pressure.

 Thanks to the execution in different phases of the process, it is possible in particular to guarantee the mechanical resistance of the coating composed of the reinforced plates thus assembled, in particular at the level of the joints where the metallic reinforcement is interrupted. In particular, on the edges of the plates indicated by 14 in FIGS. 1 to 3, edges which are not reinforced, the bands N1, N2 prevent the escape of the PVC by possible slots towards the bottom, thus eliminating the risk of rupture. and jamming of the PVC, in case the slots in the structure have to close during a pressure decrease during the operation of the installation provided with this coating.

Another advantage of the invention is that, thanks to the sealing by hot air thermofusion or other, there is no addition of materials, neither on the coating formed by the reinforced plates, nor on the crosspieces C in
PVC covering the welds S1 and 52, that is to say in places vulnerable to maintaining the waterproofing of the coating.

 Finally, the installation by means of a similar seal, by thermofusion without addition of materials of the tapes N1 and N2 on the welds and S2 produced on the structure already covered with cross-pieces, contributes to increasing the required sealing of the coating.

 Of course, modified technical solutions can be applied to the process according to the present invention, in the areas where the impermeable coating must necessarily be interrupted, for example at the ends of the galleries. These solutions will not be described in detail, since the principles are the same as those mentioned above, and variations are always applicable.

Claims (14)

 1. Materials intended for the formation of continuous impermeable coatings, in particular for galleries and supply pipes subjected to variable hydraulic pressures, water infiltration and wear due to the exposure medium, intended in particular to hydroelectric power stations, the installation of which is carried out in the form of flat plates composed of several layers of synthetic material of heat-sealable and strictly waterproof resins, such as polyvinyl chloride (PVC), plates inside which is embedded a frame resistant to high pulls, characterized in that the reinforced plates of standardized dimensions are assembled so as to be able to adapt to their destination, thanks to their inherent flexibility.  2. Materials according to claim 1, consisting of manufactured products comprising several layers and an inner frame resistant to traction, characterized in that the frame does not extend to the edges of the plates composed of a homogeneous mass of PVC.  3. Materials according to claims 1 and 2, characterized in that, shaped in the form of plates, they are composed of prefabricated opposite layers of PVC assembled under pressure and heating, so as to completely envelop on both sides and on the contour, the reinforcing reinforcement.  4. Materials according to claim 3, characterized in that the reinforcing reinforcement shows perforations crossed by the enveloping mass of PVC.  5. Materials according to claim 3, characterized in that the surfaces of the frame show similar bosses or projecting parts, engaging in the enveloping mass of PVC so as to obtain a homogeneous structure.  6. Materials according to claim 3, characterized in that the frame of the plates is made of expanded metal.  7. Materials according to claim 6, characterized in that the metal frame is formed by a perforated steel sheet or the like having close recesses through which the mass of PVC can penetrate so as to constitute a homogeneous whole.  8. Materials according to either of claims 4 to 7, characterized in that the frame has a thickness of between 0.4 and 1.2 mm, while the outer PVC layers covering the frame, have a thickness between 1.5 and 3 mm.  9. Materials according to either of claims 1 to 8, characterized in that the plates, of standardized dimensions, have geometric shapes, for example square, rectangular, or even hexagonal, allowing their assembly to obtain a continuous coating. of the surface to be filled.  10. Laying of materials in the form of plates according to claim 9, characterized in that these plates are applied by their edges on metal strips arranged on the walls to be coated, and fixed by means passing through these edges free of reinforcement, these means which may inter alia be nails, screws, bolts and the like, possibly provided with washers.  11. Laying of materials according to either of claims 1 to 10, characterized in that the joints between the plates are hot welded using hot air and a PVC wire having a proportional diameter.  12. Laying plate-shaped materials according to either of claims 9 to 11, characterized in that the welds are protected and reinforced, where they intersect, by interposition of gussets PVC in the form of a cross or other means, prefabricated in a manner compatible with the crossing zones, these elements being welded over their entire extent by hot air thermofusion.  13. Laying plate-shaped materials according to claim 12, characterized in that the elements superimposed on the joints and applied by heat sealing have a thickness of not less than 2 mm.  14. Installation of materials in the form of plates according to one or 1? other of claims 9 to 13, characterized in that the continuous coating is completed by the application by heat sealing of PVC tapes, of width greater than that of the cross-pieces and covering these, including the weld beads over their entire extent .