METHOD FOR REPAIRING FLOW CONDUITS, SUCH AS PIPE LINES

Abstract: In a method for repairing flow conduits, such as pipe lines, the inner surface of a conduit (7) is provided with a flexible material (8) which includes a curing agent as well as a reinforcement layer (5). This is followed by hardening said curing agent. According to the invention, said reinforcement layer (5) comprises a knitted fabric, by virtue of which said material has a good compliancy.

Description: Method for repairing flow conduits, such as pipe lines The present invention relates to a method set forth in the preamble of claim 1 for repairing flow conduits, such as pipe lines, as well as to a material set forth in the preamble of claim 5 for carrying out the above method. The repair work of old, deteriorated pipe lines with a purpose of fixing cracks and fissures developed in the pipes is currently generally effected by using a flex- ible material to be laid on the inner surface of pipes, said material including a curing agent as well as a necessary reinforcement layer for providing strength. Such material is generally laid in underground pipe lines from above the ground as a long tubular sleeve in a manner that the pipes need not be dug up. Such a method is known e.g. as "Insituform" or "Palte " and it is in a wide-spread use. The material inserted inside a pipe line is required to have a particularly good flexibility, plasticity and strength and, thus, it has been difficult to find proper materials. In addition, since pipes come in varying sizes and often include sharp bends, flexibility and plasticity are particularly important factors in a lining and repair material. An object of the invention is to provide a method which is capable of achieving further improved results in pipe-line repair work. In order to carry out this meth¬ od, the invention is principally characterized by what is set forth in the characterizing clause of claim 1. By virtue of a reinforcement layer provided by a knitted fabric, the method is highly reliable as a result of the flexibility, plasticity and strength of a repair material employed. On the other hand, a material for carrying out the in- 5. vention is characterized by what is set forth in the characterizing clause of claim 5. A knitted fabric is capable of providing the above properties, which are desirable in association with pipe-line repair . materials. Furthermore, the annexed subclaims 6-10 ■ 0 disclose a few preferred embodiments for a material of the invention. The material includes a felt layer, preferably consisting of fibres and having a knitted fabric fastened thereto. Thus, the felt can be used e.g. for absorbing a curing agent into the material, " 5 A high strength, both horizontally and in depth of the material, is obtained by binding felt layer and material together by knitting. The knitting can be of any prior known type, e.g. a smooth knit, a lining knit or an interlock knit. According to one preferred embodiment, 20 such a knitted fabric includes individual filaments of a yarn forming continous knitting loops, the knitted fabric is in this case manufactured by laying-in technique. 25 The invention will now be described in more detail with reference made to the accompanying drawing, in which fig. 1 shows the principle of a method of the invention, 30 fig. 2 shows a lining material of the invention in a sectional view perpendicular to its plane, fig. 3 shows a lining material according to a second alternative, fig. 4 shows a lining material according to a third alternative, and fig. 5 shows one preferred type of knitted fabric which is manufactured by laying-in technique and which can be used in a lining material of the invention, Fig. 1 illustrates the main principle of a method of the invention. Into an underground flow conduit 7, such as e.g. a water supply line, a sewage pipe or a gas line, is inserted a tubular continuous sleeve 8 in a manner that its one open end is clamped by means of a collar or a like 9 around the mouth of a special guide tube 10. The sleeve advances through the guide tube in a manner that its outer surface to be laid against the actual pipe to be lined serves as an inner surface inside the guide tube, i.e. in a way the sleeve is turned inside out. This is followed by using a medium, such as a gas or a fluid, to advance said sleeve 8 into the interor ofa pipe 7 to be repaied and, as a result of its plasticity or compliance, the tubular sleeve presses its outer surface against the inner walls of pipe 7. Towards the final stage, the sleeve will lie over its entire length inside a pipe section of the corresponding length as a tubular member to sur¬ round the inner periphery of a pipe line in the cross- sectional direction of said pipe, whereafter said sleeve 8 is cured or hardened by applying heat thereto, e.g. by passing hot water or gas inside the sleeve. The curing into a pipe-sealing inner layer occurs by vir¬ tue of a heat-setting resin, such as e.g. epoxy resin or unsaturated polyester, contained in the sleeve. Fig. 2 illustrates the structure of a lining material of the invention. The material 8 comprises a felt 6 which is a non-woven felt consisting of fibres. The felt layer 6 and a knitted fabric 5 are fastened to¬ gether preferably by -needling, i.e. said felt layer 6 and knitted fabric 5 are fixed together mechanically during the course of needling by means of the felt layer fibres, which are attached to the fibres of knitted fabric 5. A felt layer can also be produced in a manner that the fibres are fed as a carded mat on top of the knitted fabric, followed by needling. Fig. 3 illustrates another structure, wherein a felt layer 5 lies between two knitted fabrics 5. This struc¬ ture can be manufactured as described above. Fig. 4 illustrates yet a third structure with a knitted fabric 5 inside a felt layer. This can be provided e.g. by needling two felt layers on the opposite sides of a knitted fabric 5. Figs. 2-4 illustrate a single knitted fabric 5 as a re¬ inforcement layer. Other types of knitted fabric can also be used, as will be explained later. The use of a knitted fabric as a reinforcement for mate- rial 8 offers a major benefit because of the excellent compliancy of a knitted fabric and, thus, the composite material complies well in sharp bends and curves when used as described above. In addition, a knitted fabric has good strength characteristics. The material further includes a thin surface layer 4 which is laid on the face of a composite material and is shown with dash-dot-lines in figs. 2-4. The relative position of felt layer 6 and knitted fabric 5 should be such that the felt layer forms the outer surface of a composite material for applying said surface or coat¬ ing layer 4 thereon e.g. by injection. Thus, the coat¬ ing layer material cannot penetrate into the knitted fabric in a fashion interfering with its function. In the case of fig. 2, for example, the needling depth can be adjusted to be such that the felt layer fibres form the outer material surface also on its face towards a knitted fabric 5. Layer 4 can be a prior known material used in similar materials, such as polyurethane, which is facing towards the interior of a flow conduit to in¬ sulate the other layers therefrom. A heat-setting resin, such as epoxy resin or unsaturated polyester resin, can be absorbed in the material, e.g. just prior to its application, by impregnating felt layer 6 and knitted fabric 5 with such agent. The material of felt layer 6 comprises preferably thermo¬ plastic fibres, most preferably discontinuous fibres. In terms of their properties, the polyester fibres are particularly suitable for a felt materiallt is also possible to employ mineral fibres, such as glass fibres. Fig. 5 illustrates a knitted fabric which is particular¬ ly suitable for use in a material of the invention as a reinforcement. The knitted fabric is of a type manufac¬ tured by the application of so-called laying-in tech¬ nique, i.e. it includes reinforcement filaments 3 which are separate from a fabric-forming yarn 1 and extend substantially in a single direction inside the knitted fabric. The reinforcement filaments 3 extend in a di¬ rection perpendicular to the direction of the fabric loop slots and will extend in peripheral direction in a finished tubular lining material in order to obtain radial strength. Filaments 3 can be mono- or multi- filaments, e.g. of polyester or glass fibre. The knitted fabric shown in fig. 5 is of an interlock or double-knitting type, wherein the reinforcement fil¬ aments extend in a mutually parallel relationship through oppositely placed loops 2 perpendicularly to the direction of loop slots. An interlock type of knitted fabric is indeed a preferred type of knitting for the invention. The knitting yarn comprises un¬ threaded multifilament, preferably polyester or or glass. This type of knitting provides a particularly good compliancy. A material of the invention can be manufactured with ■ normal knitting and felt-forming machines and the join¬ ing of knitted fabric 5 and felt layer 6 can be ef- fected by the application of normal needling technique. A tubular sleeve formed by the repair material can be manufactured e.g. by seaming together the side edges of a flat, continuous blank which comprises felt 6 and knitting 5. The sleeve can also be manufactured by first forming a knitted fabric with a circular knitting machine, whereafter a sleeve formed by the knitted fabric and a felt layer or layers are driven together in a manner that the sleeve is in flat condition at the time of joining, whereafter the resulting flat material is seamed together by its side edges to form a finished sleeve. Thus, such a product comprises a layer consisting of two superimposed knittings. The invention as described above is not limited only to the embodiments explained in the specification and shown in the drawings but modifications can be made thereto within the inventive concept defined in the annexed claims. The method can be applied in connec¬ tion of repair operations of all types of pipe lines and the material employed can also comprise other materials than the above-described sleeve. This re- lates primarily to pieces or elements of varying shapes and sizes formed of a material blank having an equal thickness, generally a thickness of at least 4-5 mm, said elements being intended for patching possible leakages in pipe lines. This can be done by using all sorts of suitably cut elements or also shorter tubular elements which are inserted inside a pipe to be repair¬ ed- and, thus, it is possible to utilize the strength, elongation and compliancy of a composite material. Due to its special characteristics, however, a fluid is particularly well suitable for use as a reinforcement in a long tubular repair material as said special char¬ acteristics thereof will be put to best possible use in this context.

Claims: Claims 1. A method for repairing flow conduits, such as pipe lines, wherein the inner surface of a conduit (7) is provided with a flexible material (8) , including a curing agent as well as a reinforcement layer (5) , and the curing agent is hardened, c h a r a c t e r i z e d in that said reinforcement layer (5) comprises a knitted fabric. 2. A method as set forth in claim 1, c h a r a c t e r - i z e d in that said material (8) is inserted in a con¬ duit as a tubular element which covers the entire inner periphery of said conduit. 3. A method as set forth in claim 2, c h a r a c t e r - i z e d in that the insertion is effected in a per se known manner by forcing a tubular sleeve, which is clamp¬ ed at one end thereof, by the application of the pressure of a medium, such as a gas or a fluid, into the interior of flow conduit (7) from the end thereof. 4. A method as set forth in any of the preceding claims, c h a r a c t e r i z e d in that said reinforcement layer (5) is provided with a felt layer (6) , which con¬ sists of fibres and in which is absorbed said curing agent prior to the insertion of material (8) in conduit (7) . 5. A material for repairing flow conduits, such as pipe lines, said material comprising a flexible material which includes a reinforcement layer (5), c h a r a c ¬ t e r i z e d in that said reinforcement layer (5) comprises a knitted fabric. 6. A material as set forth in claim 5, c h a r a c ¬ t e r i z e d in that the material comprises a felt layer (6) which consists of fibres and to which one or a plurality of knitted fabrics, serving as a reinforce- ment layer (5) , are fastened. 7. A material as set forth in claim 6, c h a r a c ¬ t e r i z e d in that said one or a plurality of knitting fabrics serving as reinforcement layer (5) and said felt layer (6) are bound together by needling. 8. A material as set forth in any of preceding claims- 5 - 7, c h a r a c t e r i z e d in that said knitted fabric serving as reinforcement layer (5) comprises reinforce- ment filaments (3) which are separate from a fabric- forming yarn and extend inside the knitted fabric substantially in a single direction. 9. A material as set forth in any of preceding claims 5 - 8, c h a r a c t e r i z e d in that said material forms a tubular element. 10. A material as set forth in claims 8 and 9, c h a r a c t e r i z e d in that said reinforcement filaments (3) extend in the peripheral direction of a pipe.

Inventors: JAERVINEN SEPPO, KARTTUNEN MIKKO, MAEKELAE SEPPO, SUOKAS ESA, JAERVINEN, SEPPO, KARTTUNEN, MIKKO, MAEKELAE, SEPPO, SUOKAS, ESA
Applicants: SUOMEN PUTKISANEERAUS OY
Application year: 1991
Main classification: F16L55
IPC codes: D04B1, F16L55