JPS6127171A - Back sealing method of final joint - Google Patents

Abstract

PURPOSE:To eliminate the need for back sealing over the entire part of pipes and to economize labor, time and materials by forming a local block in the pipes with the final joint part of the pipes in a piping operation as a center and subjecting the joint to back sealing with an inert gas. CONSTITUTION:Small-diameter holes 4, 5 are provided at a suitable space from the groove of the pipes 2, 3 facing each other via an insert pipe 1 to act as the final joint. Shingle balls 6, 7 shrunk from the size of the respective holes 4, 5 are inserted into the pipes. Gaseous argon is blown into the balls 6, 7 to expand the balls and to fix the same to the inside of the pipes. The pipe 1 is inserted between the pipes 2 and 3 and is attached by the piping jigs. The groove is sealed by a heat resistant seal. Gaseous argion 8 for back sealing is injected into the pipes through a small hole 4 and air is discharged through the small hole. The pressure of the gas 8 is decreased and welding is started when the concn. of the oxygen contained in the waste gas is measured to be 0% by an oxygen concn. meter 9. The injection of the back sealing gas is stopped to shrink the balls 6, 7 and the balls are drawn out of the holes 4, 5 upon completion of welding of the 2nd layer.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to back 7-
This is related to LE.

[Prior art]

In welding that is sealed with an inert gas such as TIG welding, a backing metal is generally used to back seal the back side of the weld, but in the case of pipes, back sealing is performed using an internal clamp. When adding pipes one after another, it is possible to move the internal clamp, but when welding the final pipe joint to complete the pipeline, the internal clamp must be removed from the pipe. Therefore, bank sealing from inside the pipe is impossible. For this reason, it was unavoidable to flow inert gas through the entire pipeline, but this required a large amount of inert gas, and it took a long time to remove the oxygen in the pipe. It had the disadvantage of being time consuming.

[Purpose of the invention]

The present invention has been made in order to overcome the above-mentioned drawbacks, and aims to provide a method that can perform bank sealing of the final joint of a pipe in piping work using a small amount of inert gas and also saves time. shall be.

[Summary of the invention]

The present invention has been made to achieve the above-mentioned object.In piping work, small holes are provided at appropriate positions on both sides of the pipe, centering on the final joint, and each small hole has a single bulb that can be expanded and contracted. This method is characterized in that a local section is created in the pipe by pushing it in and expanding it in the pipe, and back-sealing it by blowing an inert gas into it.

[Embodiments of the invention]

The present invention will be explained using the drawings. FIGS. 1 to 4 are side views showing work procedures according to an embodiment in which the present invention is applied to liquid receiving pipes (60B to 6B) for LNG receiving facility construction. Fig. 1 shows the grooves of pipes 2 and 6 facing each other at a distance determined according to the length of the intubation 1, which is the final joint). A state in which shrunken single balls 6 and 7 are pushed into the small diameter holes 4 and 5, respectively, is shown.

The single bulbs 6 and 7 are then inflated by blowing argon gas into them and fixed in place within their respective tubes. This state is shown in FIG. After confirming that the single bulbs 6 and 7 were fixed to the VC in the specified positions, the intubation 1 was inserted between the pipes 2 and 5, installed using a piping jig (horse), and the grooves were aligned. Seal the posterior vaginal opening with heat-resistant tape. Then, argon gas 8 for air sealing is injected through one small hole 4, air is exhausted from the other small hole 5, and the concentration of oxygen contained in the exhaust gas is measured using an oxygen concentration meter 9. When the oxygen concentration is measured to be 0 by 9, the amount of argon gas 8 injected is reduced to reduce the pressure of the back seal gas, and then main welding is started. This state is shown in FIG. After the second layer of welding is completed, the injection of the bag seal gas is stopped.

After the actual welding is completed and the radiographic test has been passed, the single balls 6 and 7 are shrunk, returned to the state shown in FIG. 1, and pulled out through the small holes 4 and 5, respectively.

FIG. 4 shows the state in which the small holes 4 and 5 are treated after the above work has been completed. A boss 11 is attached.

As a result, the gamma plug 10 is not required if the insertion position of the intubation tube 1, which serves as the final joint, can be selected at a location where there is a small hole for attaching a branch pipe or pulp. or,
The small holes 4 and 5 need only be large enough to push a single ball in a contracted state, and the diameter of the hole is 60 mm.
・If you are below the Cabinet level, you are generally not subject to strict regulations. Also, natural rubber is generally used as the material for the single bulb, but if you use a heat-resistant material instead,
It is possible to set a single bulb close to the welding point, and the section in which the back seal gas is sealed can be further reduced.

〔Effect of the invention〕

According to the back sealing method of the present invention, there is no need to inject inert gas into the entire pipe for welding the final joint as in the conventional method, which is effective in reducing labor time and materials by one hour.

[Brief explanation of the drawing]

The first section is a diagram of a single bulb pushed in, Figure 2 is a diagram of a single bulb inflated, and Figure 6 is a diagram of an intubated state.
Figure 4 is a diagram of the completed construction. 1: Intubation, 2, 6: Pipe, 4, 5: Small hole, 6.7: Single bulb, 9: Oxygen concentration meter, 1o: Gamma plug, 11
:boss.

Claims (1)

[Claims] Small holes are made at appropriate positions on both sides of the pipe, centering on the final joint, and a single bulb that can be expanded and contracted by gas is inserted into each small hole, and the single bulb is inflated within the pipe. A method for back-sealing a final joint, comprising forming a section centered around the joint, and back-sealing the section by blowing an inert gas into the section.