Description

METHOD FOR MAINTAINING CONDUIT LINE USING SHEET

HEATING ELEMENT

Technical Field

[1] The present invention relates to a method for maintaining a conduit line using a sheet heating element, more specifically to a method for maintaining a conduit line using the sheet heating element whereby thermohardening resin can be hardened by using a proper sheet heating element which has a good thermal efficiency and does not make a noise for hardening the thermohardening resin that is coated on an inner wall when maintaining part or all of damaged conduit line. Background Art

[2] Various methods are disclosed for maintaining conduit lines made of concrete, synthetic resin and glass fiber materials in general. Of these, a method of hardening a thermohardening resin after coating the thermohardening resin on the inner surface of the conduit line with a damaged portion is widely used as it is comparatively simple and has a good effect.

[3] Below will be described the maintenance method carried out on the conduit line with reference to Fig. 1 attached.

[4] As shown in Fig. 1, in the maintenance method of the conventional art, after coating the outer surface of a tubular resin absorbing material 13 with plastic film 11, lining material 10 that is made by impregnating liquid-phase thermohardening resin 15 in resin absorbing material 13 is prepared. Next, the lining material 10 is inversion- inserted into the conduit line P and the thermohardening resin 15 of the lining material 10 is hardened to maintain the conduit line.

[5] At this time, as a method of hardening the thermohardening resin 15, the method, in which the water W that is injected to inversion-insert the lining material 10 into the conduit line P is heated to harden the thermohardening resin 15 having thermosetting characteristics, is widely used.

[6] Meanwhile, in the case of injecting pressurized air instead of water to inversion- insert the lining material 10 into the conduit line P, the thermohardening resin 15 of the lining material 10 is hardened by a method of spraying hot water using a separate apparatus.

[7] However, according to such a conventional art, a boiler disposed separately outside the conduit line P is used to prepare hot water to be used to harden the thermohardening resin 15. But since the noise of the boiler is excessively high, there is a problem in carrying out the conduit line maintenance work for a long time in a

residential area or shopping district. Also, because the boiler should be provided, there is another problem that the whole equipment becomes complicated and unwieldy. Not only that, there is constraint of needing a long time to prepare hot water by heating a large quantity of water W of a high specific weight and hardening the thermohardening resin 15 with this hot water. So work time gets longer, causing a large burden in terms of manpower and expenses. Another drawback is that it is not possible to harden at uniform temperature because the water heating speeds are different between start and end when using the boiler to heat the water that was injected to inversion-insert the lining material into the conduit line. Disclosure of Invention Technical Problem

[8] The present invention is to solve such conventional problems with an object to provide a method for maintaining conduit lines using sheet heating element whereby thermohardening resin can be hardened quickly and uniformly on the whole by using the sheet heating element when maintaining conduit lines. Technical Solution

[9] To achieve the above objects, there is provided a maintenance method by hardening a thermohardening resin after coating it on an inner wall of a conduit line, wherein a sheet heating element which generates heat when electricity is supplied from a power supply is disposed in a condition contacted with thermohardening resin or buried in it, and said thermohardening resin is hardened by heat transmitted to the thermohardening resin by heat from said sheet heating element.

Advantageous Effects

[10] The method for maintaining conduit lines using a sheet heating element according to the present invention positively utilizes the sheet heating element to harden the thermohardening resin coated on the inner wall when maintaining part or all of the conduit line, such that it not only shortens work time by a great deal but also removes problems due to unnecessary noise.

[11] In addition, the maintenance method of the present invention does not need complicated and unwieldy high-priced equipment such as a boiler for preparing hot water, and work itself is very simple, so cost can be reduced and work quality can be improved.

[12] Moreover, the maintenance method of the present invention provides high work reliability since the sheet heating element has a property that it is capable of operating even in the partially damaged state.

[13] Furthermore, the maintenance method of the present invention follows the forced heating method by a sheet heating element, so a high hardening effect can be expected

even in an environment where it is difficult to harden thermohardening resin due to low temperature and high humidity because the structure to be maintained is buried under or is on ground.

[14] Furthermore, the maintenance method of the present invention has an excellent maintenance effect as hardening occurs uniformly on the whole because thermohardening resin is heated at a uniform temperature on the whole. Brief Description of the Drawings

[15] These and other objects, features, aspects, and advantages of preferred embodiments of the present invention will be more fully described in the following detailed description, taken in conjunction with the accompanying drawings. In the drawings:

[16] Fig. 1 is a sectional view of a conduit line for describing a conventional maintenance method;

[17] Fig. 2 and Fig. 3 are sectional views of a conduit line for describing a maintenance method according to a first embodiment of the present invention;

[18] Fig. 4 is an exploded perspective view schematically showing a sheet heating element according to the first embodiment of the present invention;

[19] Fig. 5 is a perspective view illustrating a resin absorbing material according to a second embodiment of the present invention; and

[20] Figs. 6 to 11 are a series of reference diagrams for describing the maintenance method according to the second embodiment of the present invention.

[21] (Description of numerals for main portions of the drawings)

[22] 100: sheet heating element 110: insulator

[23] 120, 150: heating element 130: electrode

[24] 131, 132: power terminal 210: lining material

[25] 211: plastic film 213, 310: resin absorbing material

[26] 215, 330 : thermohardening resin 320: maintenance member

Best Mode for Carrying Out the Invention

[27] Below will be described in detail the conduit line maintenance method according to the present invention with reference to the accompanying drawings.

[28] The conduit line maintenance method according to the present invention discloses a scheme of utilizing a sheet heating element whereby quiet work is possible since the thermal efficiency is high and almost no noise is generated in hardening a thermohardening resin which is coated on the damaged portion to form a shield layer. In general, most conduit lines are buried under or are on ground, so they are located in an environment in which it is difficult for thermohardening resin to be hardened because temperature is low and humidity is high in most cases. Accordingly, the present

invention involves a scheme of positively utilizing a sheet heating element that can display best performance in such an adverse environment.

[29] Below will be described the conduit line maintenance method using a sheet heating element according to the present invention by using the following embodiments as examples.

[30] (First Embodiment)

[31] Fig. 2 and Fig. 3 are sectional views for describing the maintenance method according to the first embodiment of the present invention, and Fig. 4 is an exploded perspective view showing a schematic configuration of a sheet heating element according to the first embodiment of the present invention.

[32] As illustrated in the drawings, in the maintenance method according to the present invention, first, a lining material assembly in which a sheet heating element 100 is assembled to the lining material 210 is made by making a film-shaped sheet heating element 100 adhere to thermohardening resin 215 that composes the lining material 210. At this time, the sheet heating element 100 may be composed by monolithically embedding it in the lining material 210, or by contacting it with the lining material after making a sheet heating element separately. Next, as a method of inserting the lining material 210 into the conduit line by using the conventional method of inverse insertion as it is, the thermohardening resin 215 can be simply hardened by the sheet heating element 100, after inserting the lining material assembly of the lining material 210 assembled with the sheet heating element 100 into the conduit line.

[33] To describe it in more detail, the maintenance method of the present invention comprises a step for preparing the lining material, a step for coating the sheet heating element to the lower surface of the thermohardening resin of the lining material, a step for inserting the lining material assembly of the lining material coated with the sheet heating element into the conduit line, and a step for hardening the thermohardening resin.

[34] In the step for preparing the lining material, the upper surface of a tubular resin absorbing material 213 is coated with plastic film 211, and then liquid-phase thermohardening resin 215 is impregnated in the tubular resin absorbing material 213 to prepare a lining material 210. At this time, the tubular resin absorbing material 213 is not particularly limited, and resins of various materials may be used as long as they are of a quality that can absorb the thermohardening resin 215 such as non woven fabric and felt, which are fiber materials. As for the thermohardening resin 215, any material that has the thermosetting characteristic of being hardened if heated, such as unsaturated polyester, epoxy or vinyl ester may be used. And as material of the plastic film 211, for example polyethylene, nylon, polyurethane, etc. are used.

[35] In the step for coating the sheet heating element, the sheet heating element 100 is

coated on the inner surface of the resin absorbing material 213 impregnated in a lining material 210. The sheet heating element 100 is not particularly limited, and any one of a thin film shape that can be coated on the inner surface of the tubular resin absorbing material 213 may be used. If the sheet heating element 100 is coated on the inner surface of the tubular resin absorbing material 213 and adheres to the thermohardening resin 215 at high density, contact is made across a wider area, so a sufficient heating area can be secured. Therefore, it is possible to heat quickly and harden the thermohardening resin 215 in a short time. Even if it is partially torn or damaged, the sheet heating element 100 has almost no risk of an electrical short circuit unlike a heating coil, which is a line heating element; and even if it is used for a long time, it does not become inoperable because of oxidation, etc. due to contact with air. Like this, the sheet heating element 100 has high operation reliability even under adverse conditions. With no particular limit, any product of a film shape made of materials such as carbon black, metal and ITO (indium-tin oxide) mixed with carbon, which are widely used at present and made into heating elements 120 and 150, may be used as material of the sheet heating element 100.

[36] In the present invention, the sheet heating element 100 is an object generating sheet- shaped heating element having a concept in contrast with a line heating element, and one of its basic forms is illustrated schematically in Fig. 4.

[37] Referring to Fig. 4, the sheet heating element 100 comprises a pair of insulators 110 having a sheet shape of a film form so as to be in close contact with a large area of the target, heating elements 120 and 150 which are placed between insulators 110 and generate heat when electricity is applied, and power terminals 131 and 132 which are connected by way of an electrode 130 to supply outside electricity to the heating elements 120 and 150. It also includes conductive adhesive 140 which makes the electrode 130 and heating elements 120 and 150 adhere to the insulators 110 to fix them stably. For material of the insulators 110, such as polyester, polyethylene, polypropylene, polyvinylchloride, etc. are mainly used as polymer insulating members, and besides these, polyamide, polyimide, polyurethane, epoxy, epoxy resin impregnated glass woven fabric, Teflon , mica plate, etc. may be used. Meanwhile, as materials of heating elements 120 and 150, there is a variety belonging to metal heating elements, nonmetallic heating elements and other heating elements. But it seems most preferable these days to use those of carbon material which are light with low coefficient of thermal expansion while heat resistance and durability are strong and heat conduction is good. Such a sheet heating element 100 is being actively researched recently in various fields, so it is expected those with better form will be developed. Therefore, the present invention does not set any particular limits, and may adopt and use any heating element 100 of better form. In the above, only a basic form

of the sheet heating element 100 is mentioned.

[38] In the step for inserting the lining material assembly into the conduit line, the lining material assembly that is formed with the sheet heating element 100 coated under the thermohardening resin of the lining material 210 are inversion-inserted into the conduit line by pressured air by way of an air tube (not shown). That is, air A that jets through an air supply nozzle 221 connected with an air compressor (not shown) disposed outside is injected through a guide tube 223 to expand an air tube. Then, the lining material 210 that has its end portion fixed by an inversion nozzle 225 due to expansion of the air tube is gradually inverted to adhere to the inner wall of the conduit line P slowly together with the sheet heating element 100.

[39] This is followed by the step for hardening the thermohardening resin. In this step, electricity is supplied to the power terminal of the sheet heating element 100 to harden the thermohardening resin 215 that adhered in a coated form to the inner wall of the conduit line P together with the sheet heating element 100. At this time, the sheet heating element 100, which adheres to the whole of the lower surface of the thermohardening resin 215 coated on the inner wall of the conduit line P, quickly transmits high-temperature heat to the thermohardening resin 215 to harden it quickly. Compared with the conventional hardening method using hot water, it is possible to carry out the work at a speed almost 3 times faster because such a step for hardening the thermohardening resin does not need time taken to heat hot water and generates heat of relatively high temperature. And, because it does not require a high-priced boiler for making hot water, the equipment becomes simple and work can go on quietly. Also, it is possible to carry out work by heating the thermohardening resin 215 at uniform temperature on the whole. Here, in case the section of the conduit line P to be maintained is long, the inside of the conduit line P is divided into a plurality of sections and the power terminals 131 and 132 for supplying power to the sheet heating element 100 are disposed in the respective sections. Thus it is possible to prevent in advance the problem that the sheet heating element 100 can not generate enough heat due to shortage of power supply.

[40] Subsequently, the sheet heating element 100 is separated from the thermohardening resin 215 that was hardened in the inner wall of the conduit line P. This way the maintenance of the conduit line P is completed, and the sheet heating element 100 that was separated can be re-used for later maintenance of the conduit line. Meanwhile, if the sheet heating element 100 is disposed while buried inside the thermohardening resin 215 without contact with the outer surface of the thermohardening resin 215, it is practically impossible to separate the sheet heating element 100 from the thermohardening resin 215 that has already hardened. However, since the price of sheet heating element 100 is relatively low, it is not a big problem. So it may be left disposed

in the thermohardening resin 215.

[41] Now, the conduit line maintenance method according the second embodiment of the present invention will be described as follows. Mode for the Invention

[42] (Second Embodiment)

[43] In the second embodiment, an example of utilizing the sheet heating element of the present invention is shown in the maintenance method of using a cylindrical maintenance member also called as a reinforcing ring, which, after being inserted into the conduit line in a condition rolled and contracted in a cylinder shape, is adhered to the inner wall of the conduit line while it is expanded by elastic energy that was stored in itself while being restored to its original state. And, in the second embodiment of the present invention, a resin absorbing material having a unique composition is used as well as the sheet heating element. After describes the composition of the resin absorbing material first, will be described in detail the conduit line maintenance method using these components.

[44] Fig. 5 is a perspective view showing a resin absorbing material according to the second embodiment of the present invention.

[45] As shown in Fig. 5, the resin absorbing material 310 according to the second embodiment of the present invention has a cylindrical shape so as to cover the outside of a conduit line maintenance member 320. Also, the resin absorbing material 310 is made of fiber material to which thermohardening resin 330 is coated and impregnated. The resin absorbing material 310 is woven by crossing materials forming the width wise latitudes 311 and stretchable circumferential longitudes 313 at right angles. Of these, the circumferentially woven longitudes 313 use any one of stretchable yarn, spandex or rubber thread. Of course, the material of the longitudes 313 is not limited by these materials, and any other kinds besides the fibers of the aforementioned kinds may be adopted as long as they have a certain degree of elasticity and are stretchable. But for the latitudes 311, rigid unstretchable fiber is used. Fig. 5 shows a resin absorbing material 310 in expanded condition, and we can see that the array intervals between latitudes 311 are flexibly increased by the extended longitudes 313 during expansion.

[46] By dint of such a composition, the resin absorbing material 310 is stretched circumferentially without trouble when the maintenance member 320 is expanded while maintaining its original width. Also, because the resin absorbing material 310 is composed of fiber material woven with latitudes 311 and longitudes 313, it is possible to coat and impregnate the thermohardening resin without difficulty.

[47] Figs. 6 to 11 are a series of reference drawings for describing the maintenance

method according the second embodiment of the present invention.

[48] In the maintenance method according to the second embodiment of the present invention, first a conduit line member 320 in a cylindrically rolled and contracted condition as shown in Fig. 6 is prepared, and its outside is enveloped in a sheet heating element 100. At this time, it is preferable to prepare the sheet heating element 100 in a sufficient size in preparation for the time when the maintenance member 320 is expanded.

[49] Subsequently, as shown in Fig. 7, a resin absorbing material 310, which has a cylinder shape and can be stretched by latitudes 311 and longitudes 313 in the circumferential direction only as described above, is covered.

[50] Subsequently, as shown in Fig. 8, the resin absorbing material 310 is coated uniformly with thermohardening resin 330. Then, the thermohardening resin 330 penetrates into the resin absorbing material 310 to be stably impregnated.

[51] Subsequently, as shown in Fig. 10, the maintenance member 320 is mounted on the outside of an expandable body 351 of the conduit line maintenance apparatus 350 and then it is inserted into the conduit line P that needs maintenance.

[52] Subsequently, as shown in Fig. 11, if the body 351 of the conduit line maintenance apparatus 350 is expanded, the resin absorbing material 310 also is extended circum- ferentially as the maintenance member 320 is expanded. Nevertheless, the resin absorbing material 310 does not extend width wise but maintains its original width to take a form as shown in Fig. 9. This way, the thermohardening resin 330 coated on and impregnated in the resin absorbing material 310 fills the gap between the inner wall of the conduit line P and the maintenance member 300 to maintain a watertight condition.

[53] Subsequently, the conduit line maintenance member 320 disposed in adherence to the inner wall of the conduit line P is left alone as it is and only the maintenance apparatus 350 is contracted to be taken out from the conduit line.

[54] Subsequently, if necessary, according to the method as described above, the maintenance member 320 that is covered with the resin absorbing material 310 and is coated with the thermohardening resin 330 is disposed on the whole inside of the conduit line or the whole of a partial sector. As such it is possible to maintain a large area inside the conduit line P.

[55] Subsequently, if electricity is supplied to the heating elements 120 and 150 included in the sheet heating element 100 through the power terminals 131 and 132 of the sheet heating element 100, high-temperature heat is generated from the heating elements 120 and 150. Then the thermohardening resin 330 that adhered to the sheet heating element 100 receives high-temperature heat generated from the sheet heating element 100 to be hardened in a short time. When the thermohardening resin is hardened like this, maintenance of the conduit line P is completed.

[56] The preferred embodiments of the present invention are described above, but the present invention can use a variety of variations, modifications and equivalents. It is evident that the present invention can be applied identically by suitably modifying the embodiments. That is, the present invention can be widely used not only in conduit lines and tunnels buried underground as mentioned in the above embodiments but also for maintaining various concrete structures like box culvert and housing. Therefore, the description is not intended to limit the scope of the present invention defined by the limitations of patent claims below. Industrial Applicability

[57] The maintenance method using a sheet heating element according to the present invention can be applied to the method for maintaining structures such as a tunnel, house wall and box culvert as well as a conduit line.