JPS59188409A - Method for covering inner surface of buried pipe - Google Patents

Abstract

PURPOSE:To make it possible to form a lining in firm contact with the inner surface of an buried pipe, by deforming at normal temperatures the cross section of a plastic pipe having approximately the same outer diameter as the inner diameter of the buried pipe, heating the deformed pipe, then cooling it thereby it can be readily inserted into the buried pipe, inserting the deformed pipe into the buried pipe, heating the deformed pipe and applying pressure into the deformed pipe. CONSTITUTION:A plastic pipe is deformed into a U-shape, and with the U-shape kept, it is heated and then spontaneously or forcibly cooled to normal temperatures. Thereafter if the plastic pipe is allowed to stand, its deformed cross section can be kept. After this plastic pipe is inserted into a buried pipe, internal pressure is applied or vacuum is applied to the gap between the plastic pipe and the buried pipe to expand the plastic pipe and at the same time the plastic pipe is heated by steam or using a heater or the like up to its melting point. Thus the plastic pipe can restore its circular shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention mainly provides a tube for restoring the function of an existing buried pipe in soil or the like.

[Background of the invention]

Cast iron pipes, steel pipes, asbestos pipes, etc. are used for water pipes and gas pipes, but as they age, rust and deposits form on the inner surface of the pipes, resulting in a decrease in flow rate and deterioration of the pipes. According to
Water leakage and gas leakage from connections and defective parts has become a major problem.

In order to repair this, digging up the buried pipe and adding protection from the outside or replacing it is not only extremely expensive, but also poses the problem of blocking traffic, making it extremely difficult to carry out. Therefore, there is a need for a method of cleaning the inner surface of the buried pipe and applying some kind of coating to it while the pipe remains buried, and several methods have already been proposed and put into practice.

They can be roughly divided into two types: short (several meters) plastic pipes that are inserted while being welded on-site, and those that are inserted by some method.
There are two types that allow paint to adhere to the inner surface of the tube. The former method requires considerable effort, and the latter method has a problem in that it is difficult to completely cover the defective portion.

Therefore, in one unit of long plastic pipe,
It would be very advantageous to have a device that can be inserted continuously and can form a coating that adheres to the inner surface of the tube. However,
It is very difficult to insert a plastic pipe with a length of, for example, 100 m into a buried pipe when the outside diameter of the plastic pipe is approximately equal to the inside diameter of the buried pipe. Due to the frictional force between the plastic pipe and the wall of the buried pipe, the tension during insertion and retraction becomes large, and even if the traction force can be increased and retraction is possible, there is a problem that the plastic pipe may be damaged. - If the diameter of the plastic pipe into which the blade has been inserted is smaller than the inner diameter of the buried pipe, it is difficult to bring the plastic pipe into close contact with the inner wall of the buried pipe, resulting in a gap.

In this case, if there is a defect in the buried pipe, rainwater or the like will infiltrate from the outside and run along the length of the pipe, which is not preferable. Therefore, a process of filling this gap by some means is required, which cannot be said to be an effective method.

The key is to have a long plastic pipe that has an outer diameter equal to or slightly smaller than the inner diameter of the buried pipe, that can be easily inserted into the buried pipe, and that can be brought into close contact with the wall of the buried pipe. If obtained, it will serve the intended purpose.

In the conventional method of inserting and connecting plastic pipes, for example, a 100m pipe has a thickness of 5 mm and a thickness of 300 mm.
For the tubes, thick-walled plastic tubes with a thickness of 9 mm are used. This is to withstand the tensile force during insertion, the injection pressure of the 7-mention milk used to fill the gap, etc. If the plastic pipe could be brought into close contact with the inner wall of the buried pipe, even if internal pressure is applied like a water pipe, the inserted plastic pipe would not be directly exposed to pressure, so there would be no problems when inserting it. If not, the thickness may be smaller. In addition, in the case of gas pipes, the internal pressure is low, so as long as the inner surface can be tightly coated, the thickness will not be a problem. Pipes made of polyolefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer have high strength at room temperature, but when the temperature rises to near their melting point, the strength decreases significantly. It has the property of being easily deformed. Moreover, even at room temperature, if the plastic tube is thin, it can be relatively easily deformed.

[Summary of the invention]

The present invention focuses on the above-mentioned fact, and after deforming the cross section of a plastic pipe having an outer diameter approximately equal to the inner diameter of the buried pipe at room temperature, heat treatment is performed to cool it so that it can be easily inserted into the buried pipe. The present invention provides a method of restoring the buried pipe to its original shape and coating the inner surface of the buried pipe.

[Detailed description of the invention]

For example, in Figure 1 (a), (1) is a plastic pipe with a leaky circular cross section, but if the thickness is small, it can be crushed to have a flat cross section as shown in Figure 1 (b). Is possible. However, as it is, the long diameter will become larger than the original pipe diameter, making it difficult to insert it into the buried pipe, but if you fold it in half again as shown in Figure 5-2 (a), the diameter will return to the original diameter. It becomes smaller by about the same as the pipe diameter. If this shape is maintained, it can be easily inserted into a buried pipe.

The holding method is to utilize the thermoplasticity of the tube in a plastic tube, heat treat the circular tube (1) shown in Figure 1 (a), mold it into the shape shown in Figure 2 (a), and then cool it or heat it. One possible method is to physically form the shape as shown in FIG. 2(A) without any processing, and then wrap and fix plastic tape on top of it. After the thermoformed plastic tube is inserted into a buried pipe, it can be restored to its circular shape by raising the temperature of the plastic tube to its melting point and applying internal pressure at the same time. In addition, in the second method, if the thickness of the plastic tape shown in Figure 2 (b) is made small, the bound plastic tube can be inserted into the buried pipe and then internal pressure can be applied to the tube. As it tries to return to its circular shape, tension is applied to the plastic tape (2).
Finally, it is cut, and the tape is no longer restrained, resulting in a pipe with a circular cross section.

However, with this method, the 6-bind plastic tape (2) breaks during insertion into the buried pipe, and the plastic pipe (1) is inserted into the buried pipe as shown in Figures 1 (a) and (b).
On the other hand, the heated plastic pipe (1) does not restore its shape unless internal pressure is applied or heat is applied, so it can be easily inserted.

A specific method for obtaining a plastic pipe having a cross-sectional shape as shown in FIG. 2(A) is to convert a plastic pipe having a cross-sectional shape as shown in FIG. The plastic pipe is heated when it is deformed into a U-shape (the heating temperature varies depending on the material of the plastic pipe, but it is preferable to heat it above the softening point to the melting point of the material or higher). Or forcefully cool to room temperature.

After inserting this plastic pipe into the buried pipe, apply internal pressure or reduce the pressure in the gap between the plastic pipe and the buried pipe to create a pressure difference, expand the plastic pipe, and at the same time adjust the temperature of the plastic pipe using steam or a heater. A plastic pipe can be restored to its circular shape by heating it to its melting point.

Next, in order to firmly adhere the plastic pipe to the inner wall of the buried pipe, it is desirable to use an adhesive. Examples of adhesives include pine resin, asphalt, polyamide resin,
Preferred are polyolefin resins with wax and tackifier added thereto, and other adhesives that melt at high temperatures, solidify again when cooled, and function as adhesives, that is, hot-melt adhesives. These adhesive coatings are applied in advance to the inner surface of the buried pipe, and when the heat-treated plastic pipe is inserted into the buried pipe, the adhesive is coated with a roll (as shown in Figure 3).
According to 4), there is a method of forming the shape as shown in FIG. 1 (b) and inserting it after applying adhesive. The former requires a coating step, but the latter is more advantageous because it allows the adhesive to be applied and inserted at the same time. Moreover, since no heat is applied during adhesive application, the adhesive returns to its original state after passing through the adhesive applicator (6) as shown in FIG. 2(a), so it can be smoothly inserted into the buried pipe.

The latter process of plastic pipe deformation, heat treatment, and cooling in the present invention will be explained in more detail with reference to the drawings. Fig. 3 shows an example of the process, in which a plastic pipe (1) deformed into a U-shaped cross section is supplied from a plastic pipe supply (3) at stage A, where the plastic pipe (1) has a U-shaped cross section (7 ) are retained. After passing through the rolls (4), the U-shaped plastic pipe cross section is expanded and introduced into the adhesive applicator (5). At stage B in the adhesive applicator, the cross section (8) of the plastic pipe has a flattened shape, so the adhesive is applied to the entire surface of the plastic pipe (1). Upon exiting the adhesive applicator (5), the plastic pipe (1) passes through a uniforming roll (4) to remove excess adhesive and homogenize the applied adhesive. Thereafter, the plastic pipe (1) is deformed into a U-shape again while the adhesive is still applied, and is inserted into the buried pipe (6).

=9- This deformation can be performed without applying any particular force because the deformation from the previous step is memorized. (9) is a cross section of the plastic pipe that was deformed again at stage C.

In addition, if the plastic pipe is made of polyolefin resin, for example, it is preferable that the pipe be cross-linked in advance, since if a cross-linked pipe is used, there is no risk of it melting when heated after being inserted into the buried pipe, and it also makes insertion easier. If the cross-sectional shape is changed by heating after crosslinking, it is easier to return to the original shape by reheating, which is more advantageous in terms of work than non-crosslinked products.

As mentioned above, the material constructed by the method of the present invention can be easily inserted into an existing buried pipe whose inner surface has been cleaned, and after it is inserted, it is heated by an appropriate means and heated inside. When pressure is applied, the cross section becomes circular and it adheres to the inner surface of the buried pipe, forming a coating, so it is possible to quickly and easily restore the functionality of the existing buried pipe, and prevent water leakage from the existing buried pipe. It has the advantage of effectively preventing gas leakage, intrusion of bad water, generation of red water, etc.

10-

[Brief explanation of the drawing]

Figure 1 (a) is a cross-sectional view of an ordinary plastic pipe, (
B) is a cross-sectional view of the pipe that has been deformed into a flattened shape, and Figure 2 (A)
1 is a cross-sectional view of a plastic pipe deformed in the present invention, (b) is a perspective view of a plastic tube that has been physically bent and a bind tape is wrapped around it, and FIG. A specific example of inserting a plastic pipe and a cross-sectional diagram of a plastic pipe in an adhesive device are shown. (1)...Plastic pipe, (2)...Plastic tape, (3)...Plastic pipe supply, (4)...Roll, 碩...Uniform roll, (5)...
...Adhesive applicator, (6)...Buried pipe, (7)...
Cross-sectional view of the plastic pipe before entering the roll (3),
(8)...Cross-sectional view of a plastic pipe with adhesive coating (medium and small), (9)...Cross-sectional view of a plastic pipe with adhesive coating layer (C) Representative Patent Attorney Tetsu Tsukasa Kamiyo 11- Chopsticks 10 ( b) 1 unit) ″A: 3 diagrams

Claims (3)

[Claims] (1) Transform the outer diameter of the plastic pipe into a shape that can be easily inserted into the buried pipe, heat-treat it above the softening point of the plastic, cool it, then insert the plastic pipe into the buried pipe, and A method for coating the inner surface of a buried pipe, characterized in that the inner surface of the buried pipe is coated by restoring it to its original shape. (2) The method for coating the inner surface of a buried pipe according to claim (1), wherein the deformation is performed by flattening the plastic pipe and then bending the pipe along its longitudinal direction. (3) A method for coating the inner surface of a buried pipe according to claim (1), wherein the plastic pipe is made of a crosslinked polyolefin resin.