JPH1058191A - Back seal method used for tube welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a using quantity of a back seal material by conducting back sealing with using a water soluble material subjected to foaming or a water soluble film forming body accommodating a fluid or a solidified foamed body in the inside. SOLUTION: A tube 2 is welded while inserting a back seal material 1B above/below a groove part 20 of a tube 2. A foaming water soluble paper 1A is produced by conducting foaming to a water soluble paper having polyvinyl alcohol as an essential component. A back seal material 1B is produced by forming the foaming water soluble paper 1A to a cylindrical body slightly larger than the inner diameter of the tube 2. The back seal material 1B is inserted at a position of roughly 200-300mm in upper/lower directions of both sides of the groove part 20 of the tube 2 to be welded. Argon gas is charged in the closed space 20 sandwiched between a pair of back seal materials 1B. The outside of the groove part 20 is welded by a welding torch 4. Air in a formed body gains for volume, a weight of the back seal material 1B is decreased to 1/5 to 1/10 as compared to a conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back sealing method used for pipe welding, and more particularly to a back sealing method used for butt welding of pipes.

[0002]

2. Description of the Related Art In butt welding of evaporator tubes, reheater tubes, superheater tubes and the like, or various heat exchangers and pipes of a boiler, in order to prevent welding defects due to mixing of air or oxygen, a welded portion is formed. Enclose with argon gas. At this time,
A water-soluble paper or a back seal material of roll paper such as toilet paper is sealed in a predetermined position in the pipe sandwiching the welding position, and an operation for preventing the diffusion of argon gas is performed.

[0003]

However, the back sealing material such as the water-soluble paper or roll paper is required to be approximately 200 to 300 m upward and downward on both sides of the groove of the pipe to be welded.
m, but at that time the sealing material may fall,
Or, they are usually tightly rolled and stuffed so as not to be unable to seal. For example, 54φ × 3.5t
The amount of the sealing material to be inserted into one place of the pipe (inner diameter 47mmφ) is the paper size 430mm × 560mm × 0.03mm
In the case of t, about 21 g is used in three sheets.

Therefore, the number of welds per construction is 100
In the case of zero locations, the number of seal locations is 2,000, and the amount of paper used is as large as 42 kg. When water-soluble paper is used as the back seal material, the boiler is started up after the construction, in principle, through processes such as a water pressure test and a water blow blow. Thus, the water-soluble paper remaining in the pipe after welding is dissolved in water and discharged out of the system by blowing, so that it does not hinder the start of the boiler.

[0005] However, in some cases, water cannot be filled due to the structure and configuration of the boiler. In this case, the water-soluble paper must be started while remaining in the pipe. However, the following problems arise. Occurs. That is, during the period from the boiler ignition to the addition of the generator, steam does not flow through the reheater tubes, so that the tube group is exposed to an empty firing state. As a result, the water-soluble paper mainly composed of, for example, polyvinyl alcohol remaining in the tube is melted by heat and fused to the inner surface of the tube. After that, when the plant was added and steam was introduced into the reheater tube, the residue of the water-soluble paper that had been fused was carried on the steam flow, and the turbine inlet valve, turbine rotor, condenser, and condensate It will flow into the boiler via a pump and a water supply pump. In this series of steam and water flows, the components of the plant, especially the strainers of the pumps, may become clogged, leading to condensed water or a decrease in the amount of supplied water, and in some cases, may cause a plant trip problem.

[0006] In view of the drawbacks of the prior art, the present invention provides
The present invention is directed to a back seal method used for pipe welding which can solve the above-mentioned disadvantages by subjecting these back seal materials to foaming processing and greatly reducing the amount of the back seal material used per unit welding as compared with the current situation.

[0007]

According to the present invention, in order to solve the above-mentioned problems, a water-soluble material subjected to a foaming process or a liquid or solidified foam inside thereof is provided at a predetermined position in a pipe near the back side of the welding position. It is characterized in that the stored water-soluble coating is disposed and a back seal is performed. That is, the present invention is to reduce the absolute amount of water-soluble paper as a back seal material to be packed in the pipe at the time of pipe welding, as compared with the prior art, so that the first means for packing into water-soluble paper is used. An object of the present invention is to form a water-soluble back seal material into a shape containing air bubbles (air) by processing it into a shape containing an air phase like a cushion material, thereby reducing the absolute amount of water-soluble paper packed in a tube.

The second means is to process water-soluble paper into a bag shape corresponding to the inner diameter of the tube, and fill the bag (water-soluble coating) with a liquid or solidified foam, more preferably a water-soluble foaming solution. In this state, the bag body is housed in the pipe so that the opening side of the bag body is located on the welding position side, and sealing in the pipe is performed. Note that a granular water-soluble solidified foam may be used as the foam stored in the bag. As the water-soluble liquid foam, for example, a foamable water-soluble solution containing triethanol and glycerin as main components can be used.

In order to drastically solve the problems of the present invention, it is necessary to provide a material having no contact residue even when heated. ,
No problems such as clogged pump strainer occur. From this, if the absolute amount of the water-soluble paper packed in the tube can be significantly reduced, the above-mentioned problem can be sufficiently solved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.

(Embodiment 1) FIG. 1 shows a back sealing method according to a first embodiment of the present invention, which is a foamable water-soluble paper 1A obtained by subjecting a water-soluble paper mainly composed of polyvinyl alcohol to a foaming 1a process. Is formed into a cylindrical shape having a diameter slightly larger than the inner diameter of the pipe 2 to form a back seal material (wound portion) 1B, and then upward and downward on both sides of the groove 20 of the pipe 2 to be welded. Insert at a position of about 200 to 300 mm. On this occasion,
At this time, the diameter of the wound portion 1B of the foaming water-soluble paper is set to be slightly larger than the inner diameter of the tube 2 so that the wound portion 1B does not drop or the sealing becomes impossible. On this occasion,
In order to improve the sealing property, the periphery of the winding part 1B may be covered with a bag 10 made of water-soluble paper. And
After passing the narrow tube 3 through the groove 20 into the closed space 30 sandwiched between the pair of winding portions 1B, the closed space 30 inside the tube 2 is sealed with the argon gas from the narrow tube 3, and then the tube groove 2 is closed.
Predetermined welding is performed with the welding torch 4 located on the outer peripheral side.
According to this embodiment, the weight of the winding portion 1B of the water-soluble paper packed in the tube is reduced to 1/5 to 1/10 of that of the related art by increasing the volume with the foam air. Can be done.

(Embodiment 2) FIG. 2 shows a back sealing method according to a second embodiment of the present invention. In this embodiment, a water-soluble paper has a diameter slightly larger than the inner diameter of the tube and has an opening 11 on one side.
a) Processed into a cylindrical bag shape, this bag body (water-soluble coating)
11 is filled with the water-soluble foaming solution 111, and the upper and lower sides of the groove 2 of the pipe 2 to be welded so that the opening 11a side of the bag body 11 is located at the welding position side. The tube 2 is inserted at a position of 300 mm to seal the inside of the tube 2. Then, the narrow tube 3 is passed from the groove 20 into the closed space 30 sandwiched between the pair of bag bodies 11, and the closed space 30 in the tube is sealed with the argon gas from the narrow tube 3, and then the outer circumferential side of the groove 20. A predetermined welding is performed by the welding torch 4 located at the position shown in FIG. The water-soluble liquid foam contained in the bag 11 is foamed by bubbling a foamable water-soluble solution (trade name: Sunfoam) containing, for example, triethanol and glycerin as main components. According to such an embodiment,
Both the bag body 11 and the foamable water-soluble solution 111 are soluble in water, and the weight ratio is 1/1 compared to the above-mentioned prior art.
It can be reduced to 0 to 1/20.

[0013]

As described above, according to the present invention, the back seal material is subjected to the foaming process, so that the amount of the back seal material used per unit welding can be greatly reduced as compared with the present condition. In particular, in the first embodiment, since the water-soluble shape is simply wound from the conventional flat paper using the bubble (air) -containing paper, the same operation as in the prior art is performed without adding advanced technology. Problems can be solved. In the second embodiment,
Since the sealing is performed in a state where the liquid or solidified foam is loaded in the opening bag, the sealing can be effectively performed in accordance with the inner shape of the pipe.

[Brief description of the drawings]

FIG. 1 is an operation diagram showing a back sealing method according to a first embodiment of the present invention.

FIG. 2 is an operation diagram showing a back seal method according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1A Foamable water-soluble paper 1B Winding part 2 Tube 3 Thin tube 4 Welding torch 10 Bag 11 Bag (water-soluble coating) 11a Opening 20 Groove 111 Water-soluble foam solution

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masakazu Yabuki 2-8-19 Shinhama, Arai-cho, Takasago-shi, Hyogo Prefecture Inside Takahashi Engineering Co., Ltd.

Claims (2)

[Claims] 1. A back sealing method used for pipe welding, wherein a foamed water-soluble material or a liquid or solidified foam is stored in a predetermined position in a pipe near the back side of the welding position. And sealing the inside of the tube. 2. Processed into a bag shape substantially corresponding to the inner diameter of the pipe,
In a state where a liquid or solidified foam, more preferably a water-soluble foaming solution is filled in a bag-shaped water-soluble coating body with one side opened, the bag is disposed in the pipe such that the opening side of the bag is located on the welding position side. 2. The back sealing method according to claim 1, wherein the inside of the pipe is sealed.