JPH0556255B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a pipe lining method.

Conventional technology and its problems Conventionally, as a lining for a conduit, a hard or semi-hard thermoplastic tube with a diameter smaller than that of the conduit is inserted into the conduit, and then the plastic tube is heated and pressurized from the inside to form a radius. A construction method has been proposed in which the pipe is expanded in the same direction and coated on the inner surface of the pipe as a lining.
However, metal pipes such as iron and copper that make up the pipes,
The coefficient of linear expansion of the plastic pipe that makes up the lining side is much higher, so it is suitable for pipes where high-temperature fluids repeatedly flow, such as exhaust pipes that exhaust air from the kitchen of buildings. In this case, each time the hot fluid flows through the plastic tube, the plastic tube is stretched more than the conduit. As shown in FIG. 5, both ends of the plastic tube 1' are fixed to the mouth of the conduit a by end rings b, b, so that the plastic tube 1' receives a compressive force due to its expansion and buckles 1a. ' is likely to occur, and measures to prevent it have been desired.

Means for Solving the Problems The present invention involves inserting a hard or semi-rigid thermoplastic tube of a small diameter into a conduit, and then heating and pressurizing the plastic tube from the inside to expand it in the radial direction. However, in the pipe lining method for coating the inner surface of the pipe, the plastic pipe is heated and pressurized under conditions such that the expansion rate of the plastic pipe in the radial direction alternately changes in size at an appropriate pitch. The present invention relates to a pipe lining method characterized in that the inner surface of the pipe is coated with a plastic pipe in a wavy manner.

Embodiment An embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows a situation in which a hard or semi-rigid thermoplastic pipe 1 inserted into a conduit a is lined in a corrugated manner on the inner surface of the conduit a by applying the construction method of the present invention.

The plastic tube 1 has a small diameter and is inserted into the conduit a by a conventional method, for example, using a wire passing through the conduit a (not shown). The pipe is preliminarily expanded using a pipe expanding means to have an outer diameter approximately equal to the inner diameter of the pipe a, and a heating pig 2 with a built-in electric heater 2a is installed within this enlarged diameter portion 1a.

The heating pig 2 has a conical shape, for example, and has a maximum outer diameter slightly smaller than the inner diameter of the conduit a, and is provided with a pulling rope 3 on the distal end side and a connecting cord 4 on the proximal end side. The tow rope 3 passes through the distal stopper 5 and is wound around a winch 6, and the connection cord 4 passes through the proximal stopper 7 and is connected to a power source (not shown). The proximal plug body 7 has a supply port 7a which is connected to a compressor 9 via a conduit 8. If the heating pig 2 is provided with a through hole 2b as shown in the figure, the plastic tube 1 before expansion can be preheated by using the compressed air inside the tube that passes through the through hole 2b while being heated.

In the process of the present invention, the plastic pipe 1 inserted into the conduit a is basically heated internally as the heating pig 2 moves inside the pipe, as in the conventional construction method, while the compressor 9, the conduit 8 and the supply port It is internally pressurized by compressed air supplied into the pipe through 7a, expands in the radial direction, and coats the inner surface of the pipe a.

At this time, in the construction method of the present invention, plastic pipe 1
It is characterized in that the plastic tube 1 is coated in a wavy manner on the inner surface of the conduit a by heating and pressurizing it from the inside under conditions such that the expansion rate in the radial direction changes in size at an appropriate pitch.

In the method of the present invention, in order to create a corrugated coating, for example, while the heating temperature inside the pipe is kept constant (above the softening point of the plastic pipe), the pressure inside the pipe is adjusted at an appropriate pitch between the maximum pressure and the minimum force. Alternately raised and lowered. As shown in Fig. 2, when the pressure inside the pipe is at its maximum value, the degree of expansion of the plastic pipe 1 in the radial direction reaches its maximum, and the plastic pipe 1 comes into close contact with the inner surface of the pipe a, forming a crest 1A of the corrugated part. . On the other hand, when the pressure inside the tube is at its minimum value, the degree of expansion of the plastic tube 1 in the radial direction becomes the minimum, as shown in FIG. 3, forming a trough 1B of the corrugated portion. By raising and lowering the pressure inside the tube alternately between the maximum and minimum values, a wavy lining as shown in FIG. 4 can be obtained. Note that instead of alternately changing the pressure inside the tube up and down, means such as alternately changing the temperature inside the tube or the moving speed of the pig inside the tube may be adopted.

Effects According to the construction method of the present invention, the plastic pipe 1 can be lined in a corrugated manner with respect to the pipe a, so that if both ends of the plastic pipe 1 are connected to the pipe opening of the pipe a as shown in FIG. Even when fixed with the rings 10, 10, the elasticity based on the wavy shape makes it possible to correct and absorb the difference in linear expansion that occurs between the rings and the pipe a, preventing the occurrence of buckling, and reducing the It can maintain a good lining condition for a long period of time, and is particularly useful for lining pipes through which thermal fluid flows.

[Brief explanation of the drawing]

Fig. 1 is an overall diagram schematically showing the implementation status of the construction method of the present invention, Fig. 2 is an explanatory diagram showing the formation of the peaks of the corrugated portion, and Fig. 3 is an explanatory diagram showing the formation of the valleys. , FIG. 4 is a vertical sectional view schematically showing the situation at the completion of construction, and FIG. 5 is an explanatory diagram of the conventional construction method. In the figure, 1 is a hard or semi-hard plastic tube, and 2 is a heating pig.

Claims (1)

[Claims] 1. Insert a small-diameter hard or semi-rigid thermoplastic tube into the conduit, and then heat and pressurize the plastic tube from the inside to expand it in the radial direction, thereby forming a tube that coats the inner surface of the conduit. In the lining method, the plastic pipe is heated and pressurized under conditions such that the expansion rate in the radial direction of the plastic pipe changes in size alternately at an appropriate pitch, so that the plastic pipe is sealed against the inner surface of the pipe. A conduit lining method characterized by coating the pipe in a wavy pattern.