METHOD FOR IN SITU RENOVATION OF A MANHOLE, PARTICULARLY A SEWER MANHOLE, AND PREFABRICATED LINER THEREFORE

Abstract: There is described a method and a liner for in situ renovation of a sewer manhole, e.g. a transition well, where inside the well there is inserted a prefabricated liner in the shape of a glass fibre reinforced stocking of thermosetting polyester or epoxy formed by winding, weaving or braiding externally of a unilaterally suspended mould with a diameter allowing the mould to be lowered through a manhole curb or cone, the rubber coating consisting of a detachable rubber bag that is fastened to a flange to be displaced externally on the mould, said polyester or epoxy liner being winded, woven or braided in such a way that the length/diameter ratio of the liner may subsequently be changed by changing the length/diameter ratio of the liner as the polyester or epoxy impregnated glass fibres are connected with said flange by the winding, weaving or braiding.

Description: Method for in situ renovation of a manhole, particularly a sewer manhole, and prefabricated liner therefore The present invention concerns a method for in situ renovation of underground tanks or wells, especially sewer manhole, where a prefabricated liner of reinforced plastic is inserted inside the well. It is commonly known to perform renovation in situ of underground pipelines, e.g. sewer conduits, by means of a thermosetting polyester impregnated tubular stocking, which is made to fit by a longitudinal seam according to a specific task, and which then is turned into location by a special turning technique by means of water pressure for subsequent setting by supplying hot water. Furthermore, to a lesser extent it is known to use such in site renovation technique for renovating vertical tubular shafts in buildings, e.g. ventilation ducts or refuse chutes. However, so far it has not been known to use a corresponding technique when the case is more voluminous vertical shafts such as transition wells which normally consist of a conical transition from 600 mm to 1000 mm, concrete rings with internal diameter of 1000 mm at a depth of about 1 to 4 m, depending on installation and a bottom section where inlet and outlet conduits and possible influx are joined. The bottom section is furthermore usually shaped with berms for obtaining an optimum sewage water flow in the well. The transition wells are located in the sewer network with a distance of about 50 m, and the transition wells are used for inspection, cleaning and the like. Furthermore, transition wells are also established where several sewer conduits are joined into a main conduit, or where there is inlet to a main conduit. A relatively large part of the many transition wells existing e.g. in Denmark need replacement within the next 10 years, corresponding to several thousand wells per year. The wells often lie in the roadway, which means that the cost of digging up and lowering into position of a new well will run up to about DKK 50,000 per well, and to this is added very great traffic inconveniences in the surroundings. It is expected that the problem has the same magnitude in other countries. On this background the object of the invention is to provide a method of the kind mentioned in the introduction for in site renovation of transition wells, and which can result in a considerable economic saving and a considerable reduction of the negative implications of the renovation. The method according to the invention is characterised in that there is used a liner in the form of a glass fibre reinforced stocking of thermosetting polyester or epoxy formed on a rubber coated mould by winding, weaving or braiding, the liner being designed in such a way that the length diameter ratio of the liner subsequently may be changed by changing the angle of inclination of the glass fibres relative to the longitudinal axis of the liner, i.e. adjusting the cross-section of the liner and simultaneous adjusting the length of the liner. By means of the method so indicated it becomes possible to perform in situ renovation of underground manholes, e.g. transition wells, with simple measures and without the said negative traffic implications. According to the invention, the renovation may furthermore be performed relatively fast and without real digging work, i.e. considerably cheaper than a prior art renovation with replacement of a defective manhole. In terms of personnel, we are also speaking of considerable savings as a team of two or three persons may be counted on to renovate several manholes per working day, thus furthermore avoiding a long-term disruption of the sewer conduit. Furthermore, we are speaking of a very optimal utilisation of the composite materials of the liner, glass fibres and thermosetting plastic (polyester or epoxy), where the sin- gle glass fibres are bonded together in such an intense way that by a wall thickness of 6 - 8 mm there is achieved a compression strength corresponding to the compression strength of a known plastic impregnated felt stocking with a wall thickness of about 20 mm. Suitably, the method according to the invention may be thus modified, so that there is used a liner in the shape of a glass fibre reinforced stocking of thermosetting polyester or epoxy formed by winding, weaving or braiding externally of a unilaterally sus- pended, rubber coated mould with a diameter allowing the mould to be lowered through a sewer manhole curb or cone, i.e. with a diameter of the magnitude 500 - 900 mm, the rubber coating consisting of a detachable rubber bag that may be expanded with a factor of about 3, and which is preferably fastened to a flange that may be dis- placed externally of the mould, said polyester or epoxy liner being winded at an angle of about 15 - 20° relative to the longitudinal direction of the mould in such a way that the length/diameter ratio of the liner may subsequently be changed by changing the angle of inclination of the glass fibres up to about 120° relative to the longitudinal direction as the polyester or epoxy impregnated glass fibres are connected with said flange by the winding, weaving or braiding. The prefabricated liner may possibly finally be covered by winding with e.g. polyethylene film for possible cool storage until mounting in the well. Preferably, the renovation of a manhole by the method according to the invention takes place in such a way that the mould with the closed end of the stocking shaped, glass fibre reinforced polyester or epoxy liner is lowered into the manhole, that pressure is supplied between rubber bag and mould, preferably by filling with water so that the liner expands and assumes the shape of the internal surface of the manhole simultaneously with the external flange being allowed to be displaced downward in such a way that the angle of inclination of the glass fibre winding is allowed to increase at the expansion of the liner, and, when the liner has accommodated to the internal surface of the manhole, hot water is supplied between mould and rubber bag so that the polyester or epoxy liner sets. Surprisingly, it has appeared that the polyester or epoxy liner expands rather easily by the water pressure and lies close to possible un- evenesses at the inner side of the well, so that by the subsequent setting of the liner a smooth new, easy-to-clean surface is formed which furthermore may resist attack from chemicals occurring in sewage water. If considered necessary, the method according to the invention may be further modi- fied by the winding with polyester or epoxy impregnated glass fibre being combined with cutter glass, length about 25 mm, and possibly unifila mat. In addition, the invention concerns a prefabricated liner for in situ renovation of wells, especially transition wells, said liner being characterised in that it consists of polyester or epoxy impregnated glass fibres, that the liner is formed with a wall thickness of 5 - 10 mm, preferably about 7 - 8 mm, by winding on a mainly horizontal, unilaterally and rotatably suspended, tubular mould with a diameter of about 500 mm, a length of about 6000 mm and a domed bottom with a centre support opposite to the rotary suspension, the tubular mould being covered by a detachable rubber bag prior to the winding, where the bag may expand with a factor of about 3 and is fastened to a flange situated close to the rotary suspension and which may be displaced externally of the tubular mould, and which is connected with the glass fibres. In order to achieve a smooth inner side wall of the liner, said rubber bag is surrounded by a polyethylene film prior to the winding with polyester or epoxy impregnated glass fibres. With the purpose of further reinforcing the liner according to the invention it may be suitable that the winding with polyester or epoxy impregnated glass fibres is combined with cutter glass, length about 25 mm, and possibly unifila mat. The invention is explained in more detail in the following with reference to the drawing, in which: Fig. 1 shows a side view of a prefabricated liner consisting of polyester or epoxy impregnated glass fibres winded upon a horizontal tubular mould with a domed bottom opposite to a displaceable flange which is disposed close to a rotary suspension for the tubular mould, Fig. 2 shows a prefabricated liner according to the invention on a tubular mould which is lowered through a well curb, a tube cone and a transition well with bottom berm, and Fig. 3 shows how the cross-section of the liner is expanded by supplying a pressure medium, e.g. water, between the outer side of the tubular mould and the rubber bag so that the liner bears against the inner side of the well as the flange which is suspended displaceable externally of the tubular mould, and flange in which the liner is suspended by means of polyester or epoxy impregnated glass fibres, are simultaneously displaced downwards. The liner 2 shown in Fig. 1 is winded, woven or braided on a tubular mould 4 arranged rotatable about a mainly horizontal axis and with a curved, closed end part 6 and a flange 8 suspended displaceable externally of the mould 4, where individual polyester or epoxy impregnated glass fibres are connected to the flange 8 as the glass fibres by the winding, weaving or braiding performed from the side in a way known per se, while the mould, as indicated with arrow 10, is rotated, are passed around radially projecting turning pins fastened in or connected with the flange 8. The mould 4 having a diameter of about 500 mm and a length of about 6000 mm is applied a rubber coating, preferably in the form of a detachable rubber bag 12 having an expansion factor of about 3. For protecting the rubber bag 12, this is then winded with cheap polyethylene film which simultaneously gives the mould surface a rela- tively smooth outer side. Then the liner 2 is formed by winding, weaving or braiding polyester or epoxy impregnated glass fibres externally of the rubber coated mould 4 until the wall thickness of the liner reaches 5 - 10 mm, preferably about 8 mm. Finally, the liner 2 thus prefabricated is covered by polyethylene film for cool storage of the liner 2 until mounting as the utilised polyester or epoxy is thermosetting. Mounting of the liner 2, e.g. in a transition well 14 (Fig. 2) to be renovated, occurs in the following way, while it is presupposed that the transition well is cleaned beforehand, and that inlets and outlets are shut off with balloons so that the well is approximately dry. By means of crane equipment and scaffolding, the mould 4 with the liner 2 is lowered through the manhole curb 16 and well cone 18 until the closed, curved end part 6 is disposed immediately over the bottom 20 of the transition well 12. Here- after pressure medium, preferably cold or tempered water, is supplied between the outer side of the mould 4 and the inner side of the rubber bag 12, whereby this and the liner 2 are expanded under simultaneous reduction of the length of the liner 2 until this is pressed against the inner side of the transition well 14. When the liner 2 has assumed the same shape as the contour of the inner side of the transition well 14 including possible bottom berms with connecting pipe stubs 22, the supplied water is substituted with hot water so that the liner 2 consisting of glass fibres impregnated with a thermosetting polyester or epoxy sets. After the setting, the mould 4 and the rubber bag 12 are lifted up from the well, whereafter inlets and outlets are cut free and the well may be put into service when possible balloon blockings are removed. In that connection it is very important that during the renovation work according to the invention itself, no people have to work in the well. As mentioned, the liner 2 is formed e.g. by winding, weaving or braiding the mould 4 with polyester or epoxy impregnated glass fibres until there is achieved a uniform wall thickness of about 8 mm as the winding, weaving or braiding is performed with angles of inclination of the magnitude 15 - 20° relative to the longitudinal direction of the mould/liner, i.e. relative to horizontal. By the subsequent expansion a change of the angles of inclination between the glass fibres occurs, up to about 120° relative to ver- tical direction (liner and mould are raised to standing position). During this angular displacement the polyester or epoxy material remains in place, i.e. one is working with a constant, known glass fibre position and constant wall thickness in prefabricated liner as well as in the finished and finally expanded liner 2. It is expected that it is possible to remove the prefabricated liner 2 from the mould 4 quite early after the winding, weaving or braiding in that presumably it does not matter that the liner collapses during storage because there is relatively good control of the position of the polyester or epoxy material. Possibly the mould 4 may also be substituted by a relatively thin-walled and cheap tube which before winding, weaving or braiding has been inserted around the mandrel shaped mould, i.e. between this and the rubber bag. Cf. a further alternative, a special rubber bag with a certain basic rigidity could be used and which may prevent total collapse of the liner, but which anyway allows necessary expansion of the rubber bag. Finally, it should be mentioned that the mentioned flange 8 to be displaced externally of the mould 4 because the individual glass fibres are connected with the flange 8 may in principle be substituted by a local, annular setting of the liner 2, e.g. immediately before the flange 8. Such a local annular setting may easily be established by means of electric heating wires that are only passed around the liner locally. Under special circumstances, for example when the case is renovation of very deep manholes, it may be suitable, out of consideration to the transport, to make the liner at the factory with extra large diameter on an extra wide mould tube or on a possibly inflated rubber bag, i.e. with diameter much greater than the access opening (well curb opening). On the site of use the liner may be lifted up by a crane to vertical position, and the diameter of the liner may be reduced by letting air out of the rubber bag and possibly exchanging the mould tube with a thinner mould tube to a size allowing the liner to be lowered through the well cover opening, after which the diameter of the liner is increased again, as described hereinabove, by filling water into the rubber bag so that the liner is pressed outward against the inner wall of the well. In the end it shall be mentioned that it will be within the scope of the invention to use the described method for internal reinforcing of quite different items. For example, the case could be making a conical stocking reinforcement with varying wall thickness for disposing and expanding inside a wind mill wing in order to impart necessary strength and optimum force transmission conditions to it.

Claims: CLAIMS 1. A method for in situ renovation of underground tanks or manholes, e.g. sewer manholes, where a prefabricated liner of reinforced plastic is placed at the inner wall of the cavity, c h a r a c t e r i s e d in that there is used a liner in the form of a glass fibre reinforced stocking of thermosetting polyester or epoxy formed on a rubber coated mould by winding, weaving or braiding, the liner being designed in such a way that the length/diameter ratio of the liner subsequently may be changed by changing the angle of inclination of the glass fibres relative to the longitudinal axis of the liner, i.e. adjusting the cross-section of the liner and simultaneous adjusting the length of the liner. 2. A method according to claim 1 and for renovation of a sewer manhole, c h a r a c t e r i s e d in that there is used a liner in the shape of a glass fibre rein- forced stocking of thermosetting polyester or epoxy formed by winding, weaving or braiding externally of a unilaterally suspended, rubber coated mould with a diameter allowing the mould to be lowered through a sewer manhole curb or cone, i.e. with a diameter of the magnitude 500 - 900 mm, the rubber coating consisting of a detachable rubber bag that may be expanded with a factor of about 3, and which is preferably fastened to a flange that may be displaced externally of the mould, said polyester or epoxy liner being winded at an angle of about 15 - 20° relative to the longitudinal direction of the mould in such a way that the length diameter ratio of the liner may subsequently be changed by changing the angle of inclination of the glass fibres up to about 120° relative to the longitudinal direction as the polyester or epoxy impregnated glass fibres are connected with said flange by the winding, weaving or braiding. 3. A method according to claim 1 and 2, c h a r a c t e r i s e d in that the mould with the closed end of the stocking shaped, glass fibre reinforced polyester or epoxy liner is lowered into the manhole, that pressure is supplied between rubber bag and mould, preferably by filling with water so that the liner expands and assumes the shape of the internal surface of the manhole simultaneously witb*&ιe external flange being allowed to be displaced downward in such a way that the angle of inclination of the glass fibre winding is allowed to increase at the expansion of the liner, and, when the liner has accommodated to the internal surface of the manhole, hot water is supplied between mould and rubber bag so that the polyester or epoxy liner sets. 4. A method according to claim 1 -3, characterised in that the winding with polyester or epoxy impregnated glass fibre is combined with cutter glass, length about 25 mm, and possibly unifila mat. 5. Prefabricated liner for in situ renovation of underground cavities or manholes, e.g. a transition well, characterised in that the liner consists of polyester or epoxy impregnated glass fibres, that the liner is formed with a wall thickness of 5 - 10 mm, preferably about 7 - 8 mm, by winding on a mainly horizontal, unilaterally and rotatably suspended, tubular mould with a diameter of about 500 mm, a length of about 6000 mm and a domed bottom with a centre support opposite to the rotary suspension, the tubular mould being covered by a detachable rubber bag prior to the winding, where the bag may expand with a factor of about 3 and is fastened to a flange situated close to the rotary suspension and which may be displaced externally of the tubular mould, and which is connected with the glass fibres. 6. Prefabricated liner according to claim 5, characterised in that prior to the winding with polyester or epoxy impregnated glass fibres, the rubber bag is surrounded by a polyethylene film. 7. Prefabricated liner according to claim 5, characterised in that the winding with polyester or epoxy impregnated glass fibres is combined with cutter glass, length about 25 mm, and possibly unifila mat.

Inventors: HOVAD KARL ERIK, HOVAD, KARL, ERIK
Applicants: HOVAD KARL ERIK, TUNETANKEN AS, HOVAD, KARL, ERIK, TUNETANKEN A/S
Application year: 2000
Main classification: F16L55
IPC codes: B29C53, B29C63, D04C1, E02D29, E03F5, F16L55