JP2007261199A - Resin pipe welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin pipe welding method which enables the easy detection of the presence of a through hole at an application site and continuously perform a welding work. <P>SOLUTION: This method comprises the following processes: (1) a process to apply a fluorescent liquid 20 loaded with a fluorescent dye to the outer surface or the inner surface of the resin pipes 10 and 12 including a filling molten resin part, (2) a process to apply an airtight box 22 with an opening part to the surface of the resin pipes 10 and 12 on the surface side to which the fluorescent liquid is applied or the opposite side to the former surface in the way the opening edge of the airtight box 22 comes into contact with the resin pipe surface, and leak the applied fluorescent liquid to the opposite surface of the resin pipes 10 and 12 by pressurizing the interior of the airtight box 22 or making its internal pressure negative, (3) a process to detect the possible leakage of the fluorescent liquid to the resin pipe surface by shining a black light including ultraviolet light to the resin pipe surface of the opposite side to the surface to which the fluorescent liquid is applied, and (4) a process to reweld the part where the through hole is presumed to exist, in case the leakage is found in the resin pipe surface of the opposite side to the side where the fluorescent liquid is applied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a resin pipe welding method.

Recently, resin pipes are often used for water pipes that are buried in the soil. In the case of a long water channel, a plurality of these water pipes are connected and arranged.
The resin pipe is joined using a special joint if it has a relatively small diameter. However, there are also large-diameter resin pipes having a diameter exceeding 1000 mm, and it is not easy to join such a large-diameter resin pipe from the outside using a dedicated joint.

As shown in Japanese Patent Application Laid-Open No. 2005-199478, welding by a large diameter resin pipe having a diameter exceeding 1000 mm is performed by welding.
The joining method shown in the above publication uses a dedicated welding machine, and the two resin pipes are opposed to each other with a necessary gap between the end surfaces to be joined, and from the nozzle of the dedicated machine into the gap, the nozzle The resin pipe is welded by filling the molten resin while moving in the circumferential direction of the resin pipe.

JP 2005-199478

By the way, when using the above-mentioned dedicated welding machine, the nozzle is inserted into the gap between the opposing surfaces of the resin pipe to start injecting the molten resin, and the nozzle is moved along the gap while discharging the molten resin. In addition, the molten resin is filled in the gap by removing the nozzle from the gap.
However, there is a problem that fine through holes are easily formed in the vicinity where the nozzle is inserted into the gap, particularly in the vicinity where the nozzle is extracted from the gap. If there is a through hole, water leakage will occur. Therefore, it is necessary to inspect for the presence of through holes. When detecting the presence or absence of such a through-hole, it is conceivable to inspect using ultrasonic waves or X-rays, but in the former case, the presence of a bubble can be detected, but the presence of a through-hole is easily detected. I understood that it was not possible. This is because air bubbles cannot be distinguished from through holes, and even if some air bubbles are present, water leakage does not necessarily occur. In the latter case, the apparatus becomes large and inconvenient for use at the construction site.
Accordingly, the present invention has been made to solve the above-described problems, and the object of the present invention is to provide a resin pipe welding method that can easily detect the presence or absence of a through-hole at a construction site and can continuously perform a welding operation. In offer.

  The method for welding resin pipes according to the present invention is a resin pipe for welding two resin pipes by facing the end faces to be joined with a required gap therebetween and filling the gap with molten resin from a nozzle. In the welding method, a step of applying a fluorescent liquid to which a fluorescent dye is added to the outer side surface or the inner side surface of a resin tube containing a filled molten resin portion, and a surface side coated with the fluorescent liquid or a resin opposite to the surface An airtight box having an opening is applied to the surface of the tube so that the opening edge is in contact with the surface of the resin tube, and the inside of the airtight box is pressurized or negative pressure so that the applied fluorescent liquid is on the opposite side of the resin tube. Whether or not the fluorescent liquid leaks to the resin tube surface by irradiating the resin tube surface opposite to the surface coated with the fluorescent liquid with ultraviolet light containing ultraviolet light. And the process of detecting If the fluorescent liquid had leaked into the resin tube surface opposite the coated side, a through hole exists, characterized in that it comprises a step of re-welding the parts.

  By making the inside of the airtight box pressurized or negative pressure, the fluorescent liquid can pass through the through hole and leak to the opposite side, and the black light can detect the leakage and the presence of the through hole. Further, when a thin film portion exists in the welded portion, the thin film portion can be positively broken and repaired by applying pressure or negative pressure.

It is preferable to check whether or not the welded portion has a through hole, and when a through hole is present, repair the portion and sequentially join a plurality of resin pipes.
When the two resin pipes and the welding resin are the same resin material, welding can be performed with good adhesion.

  It is preferable that the fluorescent liquid is applied to the outer surface of the resin tube, and the inner surface side of the resin tube is set to a negative pressure by the airtight box. If there is a through hole, the fluorescent liquid leaks to the inner wall side of the resin tube, but since the inside of the resin tube is dark, it is easy to find a small through hole with black light.

If the airtight box is moved along the welded portion of the resin pipe and the presence / absence of the through hole is detected over the entire welded portion, the accuracy is improved.
The hermetic box is characterized in that a packing that adheres to the surface of the resin tube is attached to the edge of the opening edge.
When the airtight box is formed of a transparent material, it is preferable because leakage of the fluorescent liquid can be confirmed with black light.

  According to the present invention, by making the inside of the airtight box pressurized or negative pressure, the fluorescent liquid can pass through the through hole and leak to the opposite side, and the black light causes the leakage and the presence of the through hole. Can be detected. Further, when a thin film portion exists in the welded portion, the thin film portion can be positively broken and repaired by applying pressure or negative pressure. Further, it is preferable because repair and welding operations can be continued while easily detecting the presence or absence of through holes at the construction site.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
1-3 is explanatory sectional drawing which shows the welding method of a resin pipe. The fracture surface is the wall portion of the resin tube. FIG. 4 is an explanatory diagram of an airtight box.

As a resin pipe welding apparatus (not shown), a known apparatus disclosed in JP-A-2005-199478 and the like can be used.
First, as shown in FIG. 1, the two resin pipes 10 and 12 are opposed to each other with the required gap A between the end surfaces to be joined.
The sealing member 14 that covers the outer side of the gap A and has the concave portion B on the inner side is brought into close contact with the outer surfaces of the end portions of both the resin tubes 10 and 12 and is held.
Next, the nozzle 16 of the welding apparatus is inserted into the gap A, the molten resin 18 is filled into the gap A and the recess B by a known method, and the resin tubes 10 and 12 are welded.

The resin tubes 10 and 12 have a large diameter of about 1000 mm to 2200 mm and are made of a high density polyethylene resin. The large-diameter resin tubes 10 and 21 can be manufactured by a known method in which a hollow profile is wound in a spiral shape and welded between the contacting walls.
The resin 18 for welding the resin tubes 10 and 12 is also preferably made of high-density polyethylene made of the same material as the resin tubes 10 and 12 from the viewpoint of adhesion.

Once the nozzle 16 is rotated once and the molten resin 18 is filled in the gap A and the recess B, the nozzle 16 is slowly pulled out from the gap A while discharging the molten resin so as not to generate a through hole as much as possible.
After the molten resin 18 is cooled, the seal member 14 is removed from the outer walls of the resin tubes 10 and 12.

Next, as shown in FIG. 2, a fluorescent liquid 20 to which a fluorescent dye is added is applied to the outer surfaces of the resin tubes 10 and 12 including the filled molten resin portion 18.
The fluorescent dye can use the well-known thing marketed. When a black light containing ultraviolet rays is applied to the fluorescent liquid to which the fluorescent dye is added, the fluorescent liquid emits fluorescence and emits light.

  Next, as shown in FIG. 3, an airtight box 22 is applied to the surface of the resin tubes 10 and 12 opposite to the surface coated with the fluorescent liquid, and the airtight box 22 is connected to a suction device P to connect the airtight box. The inside of 22 is made negative pressure. When the through hole is formed in the welded portion, the fluorescent liquid leaks to the opposite side through the through hole. Further, when a thin film-like portion is generated in the welded portion, the thin film-like portion is broken by the negative pressure, and thus the fluorescent liquid can be leaked to the opposite side.

  The airtight box 22 has a surface that is open to the surface of the resin tubes 10 and 12, and the opening edge is curved so as to follow the curved surface of the resin tubes 10 and 12. A packing 24 that is in close contact with the surfaces 10 and 12 is attached. In addition, it is preferable that a part or the front part of the airtight box 22 is formed of a transparent material so that the airtight box 22 can be visually recognized from the outside or irradiated with black light.

  Next, irradiate a black light containing ultraviolet rays with a light (not shown) from the surface that has been made negative pressure by the airtight box 22 to detect whether the fluorescent liquid has leaked to the surface that has been made negative pressure. To do. When the fluorescent liquid leaks, the fluorescent liquid emits fluorescence by the black light, thereby detecting the presence of the through hole. Further, when a thin film portion exists in the welded portion, the thin film portion is positively destroyed by the negative pressure, and the fluorescent liquid leaks out by this, so that the thin film portion can also be found.

In this way, since the presence of the through hole and the thin film portion can be detected, the portion can be re-welded and repaired.
In this way, it is preferable to confirm whether or not a through hole or the like is present in the welded portion, and when a through hole or the like is present, it is preferable to sequentially join a plurality of resin pipes while repairing the portion.

  The surface on which the fluorescent liquid is applied may be either the outer side surface or the inner side surface of the resin tubes 10, 12, but it is easier to apply the coating to the outer side surface. In this case, the airtight box 22 is applied to the inner surfaces of the resin tubes 10 and 12, and the fluorescent liquid is leaked to the inner surfaces of the resin tubes 10 and 12. This is because the inside of the resin tubes 10 and 12 is dark, so that it is possible to easily detect the fluorescent liquid that has leaked when irradiated with black light, and thus it is possible to detect the presence of small through holes.

  It is preferable that the hermetic box 22 is moved along the welded portions of the resin pipes 10 and 12 to detect the presence or absence of the through-holes over all parts of the welded portions.

  In the above description, the inside of the airtight box 22 is set to a negative pressure so as to leak to the resin tube surface on the side opposite to the surface coated with the fluorescent liquid. However, the surface of the airtight box 22 on the side coated with the fluorescent liquid ( It may be applied to the inner or outer surface of the resin tube, and the inside of the airtight box 22 may be pressurized to leak (push out) the resin tube surface on the side opposite to the side where the fluorescent liquid is applied. In the case of a water distribution pipe, pressure is applied from the fluid to the inner wall, so pressurizing the weld from the inside is in line with the current situation.

It is explanatory drawing sectional drawing of the process of filling molten resin in the junction part of a resin pipe. It is explanatory sectional drawing of the state which applied the fluorescent liquid covering the welding part. It is explanatory sectional drawing which shows the process of applying an airtight box to the surface on the opposite side which apply | coated the fluorescent liquid, and making it a negative pressure. It is a perspective view of an airtight box.

Explanation of symbols

10, 12 Resin pipe 14 Sealing material 16 Nozzle 18 Molten resin 20 Fluorescent liquid 22 Airtight box 24 Packing

Claims (7)

In the resin pipe welding method of welding two resin pipes, facing the end faces to be joined with a required gap therebetween and filling the gap with molten resin from a nozzle,
Applying a fluorescent liquid with a fluorescent dye added to the outer or inner surface of the resin tube containing the filled molten resin part;
An airtight box having an opening is applied to the surface on which the fluorescent liquid is applied or on the surface of the resin tube opposite to the surface so that the opening edge is in contact with the surface of the resin tube, and the inside of the airtight box is pressurized or A process of making the applied fluorescent liquid leak to the opposite surface of the resin tube by applying a negative pressure;
Irradiating the resin tube surface opposite to the surface coated with the fluorescent liquid with a black light containing ultraviolet rays to detect whether or not the fluorescent liquid leaks to the resin tube surface;
A resin pipe joining method comprising a step of re-welding a portion where a through-hole is present when a leakage occurs on the resin pipe surface opposite to the side to which the fluorescent liquid is applied.   2. The resin according to claim 1, wherein whether or not the welded portion has a through-hole is confirmed, and when the through-hole is present, the plurality of resin pipes are sequentially joined while repairing the portion. Pipe welding method.   3. The resin pipe welding method according to claim 1, wherein the two resin pipes and the welding resin are made of the same resin material.   4. The resin pipe welding method according to claim 1, wherein the fluorescent liquid is applied to an outer surface of the resin tube, and the inner surface side of the resin tube is set to a negative pressure by the airtight box.   The resin tube according to any one of claims 1 to 4, wherein the airtight box is moved along a welded portion of the resin tube, and the presence or absence of a through hole is detected over the entire portion of the welded portion. Welding method.   The resin tube welding method according to any one of claims 1 to 5, wherein the airtight box is provided with a packing closely attached to a surface of the resin tube at an edge of the opening edge.   The said airtight box is formed with the transparent material, The welding method of the resin pipe of any one of Claims 1-6 characterized by the above-mentioned.