JP3594484B2 - Manufacturing method of insertion pipe - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an insertion pipe made of a thermoplastic resin, which is softened in a reduced-diameter deformed state, inserted into an existing pipe, and expanded and deformed so as to cover an inner surface of the existing pipe with a pressurized and heated gas supplied inside. And a method for producing the same.
[0002]
[Prior art]
The insertion pipe is inserted into the existing pipe by softening it in a reduced-diameter deformed state so that it can be smoothly inserted even in the existing pipe that is bent.Conventionally, a pipe made of an extruded thermoplastic resin is used. After cooling, the pipe is heated to the softening point to forcibly reduce the diameter, and the reduced-diameter deformed pipe is cooled as it is to produce an insertion pipe.
[0003]
[Problems to be solved by the invention]
Since the insertion pipe manufactured by the above conventional manufacturing method cools the pipe whose diameter has been reduced and deformed as it is, internal stress is generated to return to the shape before the diameter reduction and inserted into the existing pipe. While heating to soften while heating, there is a drawback that the diameter tends to be expanded and deformed in an attempt to return to the shape before the diameter reduction deformation, and the insertion resistance into the existing pipe increases.
The present invention has been made in view of the above-described circumstances, and has as its object to manufacture an insertion pipe capable of reducing insertion resistance into an existing pipe.
[0004]
[Means for Solving the Problems]
A characteristic feature of the invention according to claim 1 is that the thermoplastic resin is softened in a reduced-diameter deformation state, inserted into an existing pipe, and expanded and deformed so as to cover the inner surface of the existing pipe with a pressurized heating gas supplied inside. A method for manufacturing a resin insertion pipe, wherein after cooling an extruded thermoplastic resin pipe, the pipe is heated to a softening point and forcibly reduced in diameter, and the reduced diameter is deformed. The point is to perform annealing by heating the pipe in a state where the expansion deformation is regulated.
[0005]
In other words, since the pipe that has been heated to the softening point and forcibly reduced in diameter is heated and annealed in a state of restricting the expansion, the internal stress is removed while maintaining the reduced diameter, and the existing pipe is removed. As the material is heated to be softened while being inserted into the tube, it is difficult to expand and deform.
[0006]
Therefore, an insertion pipe that can reduce the insertion resistance into the existing pipe can be manufactured.
[0007]
A feature of the invention according to claim 2 is that the pipe whose diameter has been reduced and deformed is wound around a drum to restrict the expansion and deformation.
[0008]
In other words, by winding the reduced-diameter deformed pipe around the drum, the expanded-diameter deformation can be restricted by abutment between pipes that are radially adjacent to each other.
[0009]
Therefore, as compared with the case where it is restricted by a restraining device such as a belt or the like, the expansion deformation can be more easily regulated, and the insertion pipe wound around the drum can be manufactured, so that it can be used during transportation or use. Handling becomes easy.
[0010]
A feature of the invention according to claim 3 is that, after cooling the pipe whose diameter has been reduced and deformed, the pipe is preheated before the start of the annealing.
[0011]
In other words, after cooling the pipe whose diameter has been reduced and deformed, even if the pipe is rapidly heated to start annealing, the entire pipe does not uniformly heat up. It tends to be deformed to return to the shape before diameter reduction deformation, especially when the diameter expansion deformation of the pipe is restricted by restricting with a belt or other restricting device, the restricted part bites into the restricting device. The pipe may be finished in such a shape, but since the pipe is preheated before the start of annealing, the entire pipe is easily heated uniformly, and the entire pipe is hard to return to the shape before the diameter reduction deformation.
[0012]
Therefore, it is possible to manufacture an insertion pipe having a substantially uniform finish, which can be easily inserted into the existing pipe.
[0013]
A feature of the invention according to claim 4 is that the pipe is preheated before the start of the annealing by adjusting the generated pressure of steam for performing the annealing.
[0014]
That is, by adjusting the generated pressure of steam, the temperature of the steam can be adjusted, and it is easy to adjust so that the pipe can be preheated to a desired temperature.
[0015]
A feature of the invention according to claim 5 is that the pipe is made of a medium density polyethylene resin, and the annealing is performed at about 120 ° C. to 125 ° C. for 2.0 hours to 2.5 hours.
[0016]
That is, in the case of a medium-density polyethylene resin pipe, annealing is performed at about 120 ° C. to 125 ° C. for 2.0 hours to 2.5 hours, so that the insertion pipe having a substantially uniform finish can be easily inserted into the existing pipe. Can be manufactured.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIGS. 1 and 2 show a method of manufacturing an insertion pipe P according to the present invention, and a cylindrical pipe (outer diameter) manufactured by extrusion molding a medium density polyethylene resin (based on JIS K 6774: an example of a thermoplastic resin). (140 mm, thickness 3 mm) After the P1 is once naturally cooled, the pipe P1 is accommodated in the heating chamber A and heated to a softening point of 120 ° C. to 130 ° C. to be softened, and the softened pipe P2 is forcibly compressed. The pipe P3, which has been radially deformed and whose diameter has been reduced, is heated and annealed in a state where the diameter expansion deformation is regulated, thereby producing an insertion pipe P.
[0018]
To the heating chamber A, a steam supply pipe B for supplying steam for heating generated by a boiler (not shown) is connected, and a lower receiving jig 1 for receiving and supporting the pipe P1 along its longitudinal direction, and a lower receiving jig thereof. A pressing blade 2 that is pressed down toward the inside of the jig 1 and a drum 3 that winds up a pipe P3 whose diameter has been reduced are provided.
[0019]
The boiler is provided with pressure adjusting means for adjusting the generated pressure of the steam (hereinafter referred to as steam pressure). The steam pressure is adjusted by operating the pressure adjusting means, and the steam temperature supplied into the heating chamber A is adjusted. So that the temperature in the heating chamber A is adjusted.
[0020]
The lower receiving jig 1 is formed in a gutter shape that can swing freely around a lower horizontal axis along a pipe longitudinal direction in a diameter reducing direction and a diameter expanding direction.
[0021]
The pressing blades 2 are provided in series along the longitudinal direction of the pipe with substantially the same length as the lower receiving jig 1, and when the air cylinder 4 expands and contracts, the pressing blade 2 is pushed down to the inside of the lower receiving jig 1. The switching operation is provided so that the jig 1 can be lifted upward.
[0022]
Then, the cylindrical pipe P1 is received and supported by the lower receiving jig 1, and reheated to the softening point by steam supplied from the steam supply pipe B (see FIG. 1A). Then, the pressing blade 2 is depressed to bend in the radial direction (see FIG. 1 (b)), and the lower receiving jig 1 is rocked in the diameter reducing direction to forcibly make the cross section substantially heart-shaped. (See FIG. 2 (c)).
[0023]
The pipe P3 whose diameter has been reduced is continuously wound around and constrained on the drum 3 so that the pipe P3 does not expand and deform in annealing described later, and the drum 3 is naturally cooled, and the cross section is maintained in a substantially heart shape. save.
The start end of the pipe P3 wound around the drum 3 is connected to a steam supply path 3a provided in the drum 3.
[0024]
Next, as shown in FIG. 2D, annealing is performed with steam supplied from the steam supply pipe B. Even if the steam pressure is rapidly increased to increase the steam temperature, the film is wound around the drum 3. The temperature of the entire pipe P3 does not rise uniformly, the temperature of the part wound around the outer periphery of the drum 3 rises quickly, and the part softens before the internal stress is sufficiently removed, and before the diameter reduction deformation. There is a strong tendency to return to the shape of.
[0025]
Therefore, in the present embodiment, before the start of annealing, the steam pressure is held at 0.08MP-G for 10 minutes by operating the pressure adjusting means, and then the steam pressure is held at 0.10MP-G for 30 minutes. The pipe P3 is preheated while gradually increasing the steam temperature.
[0026]
Thereafter, the steam pressure is maintained at 0.12 MP-G for 2.0 hours to 2.5 hours, annealing is performed at a temperature of 120 ° C. to 125 ° C., and then the steel is naturally cooled and wound around the drum 3. A substantially homogeneous insertion pipe P is manufactured.
[0027]
FIGS. 3 and 4 show a method of covering the inner surface of a gas pipe GP (an example of an existing pipe) buried underground using the insertion pipe P manufactured by the above-described manufacturing method. The pits C1 and C2 are excavated at both ends, and at the entrance of one pit (hereinafter referred to as a starting pit) C1, an insertion pipe P wound around the drum 3 and a steam is inserted inside the insertion pipe P. A work vehicle 6 carrying a boiler 5 for supplying steam through the supply path 3a is made to stand by, and a work vehicle 8 carrying a winch 7 at the entrance of the other pit (hereinafter referred to as an arrival side pit) C2 is made to stand by.
[0028]
Then, the gas pipe GP in each of the pits C1 and C2 is opened, a wire WP to be pulled is inserted from the opening, one end of the wire WP is connected to the feeding end of the insertion pipe P, and the other end is connected. It is connected to the winch 7 (see FIG. 3A). Note that the feed-out side end of the insertion pipe P is sealed in advance.
[0029]
Then, the steam generated by the boiler 5 is fed into the insertion pipe P wound on the drum 3 and heated, and when the insertion pipe P is softened, the winch 7 is driven to drive the gas pipe GP by the wire W. And is inserted into the starting pit C1 and the reaching pit C2 (see FIGS. 3B and 3C).
[0030]
Then, pressurized steam pressure ^{0.1kgf / cm 2 ~1.7kgf / cm 2} , after the insertion pipe P is enlarged deformed along the inner surface of the gas tube GP, cooled, it has been Then, the inner surface of the gas pipe GP is covered with the insertion pipe P (see FIGS. 4A and 4B).
[0031]
Incidentally, when the above-mentioned insertion pipe P was inserted into a steel gas pipe having an inner diameter of 150 mm provided with four 45-degree bends at four locations, the traction resistance was about 4.9 kN (500 kgf). This is about 1/5 of the conventional one.
[0032]
[Another embodiment]
1. In the above embodiment, the medium density polyethylene resin is shown as the thermoplastic resin. However, for example, a polyolefin resin may be used.
2. In the above-described embodiment, annealing is performed after the pipe whose diameter has been forcibly deformed is once naturally cooled, but annealing may be performed without cooling the pipe whose diameter has been forcibly deformed.
3. In the above-mentioned embodiment, the pipe whose diameter has been forcibly reduced is wound around the drum to restrict the expansion, but the belt is wound at regular intervals around the pipe whose diameter has been forcibly deformed, and its diameter is deformed. May be regulated.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a method of manufacturing an insertion pipe. FIG. 2 is a schematic perspective view showing a method of manufacturing an insertion pipe. FIG. 3 is a schematic view showing a coating method using an insertion pipe. Schematic diagram showing the pipe coating method [Explanation of reference numerals]
GP Existing pipe P1 Thermoplastic pipe P3 Reduced diameter pipe 3 Drum

Claims (5)

A method for manufacturing an insertion pipe made of a thermoplastic resin, which is softened in a reduced diameter deformed state, inserted into an existing pipe, and expanded and deformed so as to cover the inner surface of the existing pipe with a pressurized and heated gas supplied inside. So,
After cooling the extruded thermoplastic resin pipe, the pipe is heated to the softening point and forcedly deformed, and the reduced-diameter deformed pipe is heated in a state that restricts the expanding deformation. Manufacturing method of an insertion pipe that performs annealing. 2. The method according to claim 1, wherein the diameter-reduced pipe is wound around a drum to restrict the diameter-expansion deformation. 3. The method of manufacturing an insertion pipe according to claim 1, wherein, after cooling the reduced-diameter deformed pipe, the pipe is preheated before the start of the annealing. 4. The method of manufacturing an insertion pipe according to claim 3, wherein the pressure at which steam is generated for performing the annealing is adjusted, and the pipe is preheated before the start of the annealing. The method according to any one of claims 1 to 4, wherein the pipe is made of a medium density polyethylene resin, and the annealing is performed at about 120C to 125C for 2.0 hours to 2.5 hours. .

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