JPS60141368A - Water cooled welding method - Google Patents

Abstract

PURPOSE:To obtain a joint for preventing SCC having high reliability by subjecting circumferentially the butt part of horizontal pipes of a nuclear power plant to water cooled welding while ejecting cooling water from a jet nozzle to the recess provided in the groove of the inside surface of said butt part and removing thoroughly foam. CONSTITUTION:A nozzle 32 for ejecting a jet is inserted through a gamma plug seat 30 for inspecting the weld zone 28 of the above-described horizontal pipings 26, 27 by radiations into the pipes and is brought near the peak of a weld line 29. Cooling water is ejected from the nozzle 32 to remove the foam 33 to be generated in a recess 21 in the stage of water cooled welding. The nozzle 32 is formed to a curved shape and the curvature thereof is set by the position of the seat 30 and the line 29. The feed rate of the water to the nozzle 32 is adjusted by operating a feed water pump 40 and adjusting the operation of valves 39, 41, 43 via a conduit 38 and a bypass pipe 44.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a flowing water type water-cooled welding method for butting together horizontal stainless steel piping, etc. other than SCC-resistant materials in a nuclear power plant, and is particularly directed to the development of piping. The present invention relates to a water-cooled welding method that is optimal for butt welding while completely removing air bubbles that remain in the concave portions of the mating parts.

[Background of the invention]

The treatment methods for welded parts of stainless steel pipes other than SCC-resistant materials that fall within the scope of SCC countermeasures in nuclear power plants include:
Currently, there are the following methods.

(1) Method of changing the material of piping (2) Stress relief method using induction heat treatment (IH8I) (3) Water-cooled welding method The most reliable method is to change the material of all piping in the SCC target range to SCC countermeasure materials. However, there are some aspects of live commentary that are realistically impossible. Some places are taking measures such as stress relief through high-frequency heat treatment (IH8I) and water-cooled welding of existing joint welds.

There are two cooling methods for water-cooled welding:

(1) Spray method (2) Flowing water method The spray method is a reliable method for water-cooled welding.

FIGS. 1 and 2 are a cross-sectional view and an external view of a spray nozzle for explaining a method of water-cooling a welded part using a conventional spray-type water-cooled welding jig.

In the figure, elbow 2 is newly installed on existing piping 1.
When welding, align the pipe 1 and the elbow 2, insert the spray nozzle 4 from the lower end opening 3 of the elbow 2,
The outer periphery spout 5 of the spray nozzle 4 is positioned at the abutting portion 6, and the cooling water is supplied to the inner peripheral surface of the abutting portion 6 through the cylindrical spout 5 of the cylindrical spray nozzle 4 via the conduit 8 by the pressurizing pump 7. It is a method of gushing.

In this spray type water-cooled welding method, Suff'v-/, (Le 4
An inlet is required to be inserted into the pipe. Therefore, when welding all the pipes in a nuclear power plant, the spray method cannot be used because there may be no entrance for inserting the spray nozzle 4. For example, when welding a plurality of spools in sequence and welding the final spool, there is no way to insert a cylindrical spray nozzle 4. In such a case, it is necessary to perform water-cooled welding using running water.

FIG. 3 is an explanatory diagram showing an example of the piping route of the nuclear couplant, showing the pump 9 and the reactor pressure vessel (PV) 1.
0 shows a piping route in which piping spools 11 to 17 are welded.

The piping route is welded sequentially starting from the piping spool 11 on the pump 9 side, and the piping spool 17 becomes the final spool.

In such piping routes, if the material of the piping is not an SCC countermeasure material, or if a part of the existing plant piping is
Welding is generally performed when replacing piping with non-CC material.

When performing welding with the weld, it is necessary to perform water-cooled welding to prevent SCC at the weld.

When welding the pipes 11 to 16, spray type water-cooled welding can be used, but the final pipe spool 17
When butt welding the pipe spool 16 to the pipe spool 16, spray type water-cooled welding cannot be used because there is no entrance for inserting the spray nozzle 4 into the pipe. therefore,
In this final welding process, it is necessary to use a flowing water-cooled welding method.

In addition, when assembling the final piping spool 17 between the existing piping 18 and the piping 16, as shown in FIG. Since the inner surface of the abutting portion 19 is vertical, since the piping is filled with cooling water and circulated, air bubbles escape from the inner surface in the vertical direction, so that air bubbles do not stay there.

On the other hand, in a nuclear power plant, horizontal piping 17.
Generally, a recessed portion (PC portion) 21 is provided on the inner surface of the welded portion 20 where the welded portions 20 are brought into contact with each other for radiological inspection.

This recessed part 21 is provided to inspect the welded part using gamma rays, etc., and complies with the construction guidelines regulated by law when welding piping in nuclear power plants. .

Furthermore, an r-plug seat 22 is provided near the welding portion 19, 20 for inserting a radiation irradiation nozzle. After the radiographic inspection, the γ plug 23 can be screwed into the γ plug seat 22 and water-sealed. Bubbles generated in the cooling water flowing through this pipe are removed from the depression 21 of the butt 20.
It tends to stay at the top of the mountain. A method for removing such accumulated air bubbles is to increase the flow rate of cooling water flowing through the pipes. However, since this method deals with the problem within the design conditions (for example, pump function) of the piping system in the existing plant, it may not be possible to obtain a flow rate high enough to completely remove air bubbles. For example, in the permitted construction method of water-cooled welding, the flow rate of cooling water is limited to about 50 t/■. For this cooling water flow rate, 8B piping has a flow rate of 7.4 cm.
/s flow rate, 12B piping can only obtain a flow rate of 3.6 cm/s. At this level of flow velocity, the air bubbles remaining in the recessed portion 21 of the welded portion cannot be swept away.

FIG. 5 is an enlarged view of the recessed part of the welded part to be circumferentially welded with the TIG welding torch 24. Air bubbles in the cooling water flowing in the pipe float to the top of the recessed part 21. 25
This indicates a state in which there is a stagnation.

The air bubbles 25 that remain in the recess 21 of the welding part reduce the cooling rate during welding, resulting in stress corrosion cracking (SCC).
) Not suitable for countermeasures.

As mentioned above, in the piping construction structure of a nuclear power plant, a special groove, that is, a depression 21 is carved on the inner surface of the groove for radiation inspection of the welded part, and the structure is such that air bubbles 25 tend to accumulate. There is.

Therefore, the inventors created a transparent piping model using an acrylic material, visually observed the state of the fluid inside the piping, and confirmed the phenomenon that causes bubbles.

In order to monitor the phenomenon in which bubbles 25 are generated, it has now been found that it is necessary to perform running water-cooled welding by using ultrasonic waves to inspect the generation of bubbles as the flow rate increases.

However, due to the structure of the actual plant system, it may not be possible to secure a sufficient flow rate, and it is currently difficult to ensure welding reliability.

The reality is that there is no known technique for effectively removing air bubbles from welded parts, and it is difficult to find countermeasures.

[Purpose of the invention]

The present invention provides a water-cooled welding method that completely removes air bubbles that may impair the cooling effect of welded parts in piping construction for nuclear power plants, and can obtain highly reliable SCC countermeasure joints. There is a particular thing.

[Summary of the invention]

The present invention provides a flow-through water-cooled welding method in which horizontal pipes of a nuclear power plant are abutted against each other and circumferentially welded while water is flowing inside the pipes. The feature is that air bubbles are removed by jetting cooling water through the air.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

<Example 1> FIG. 6 is an explanatory diagram showing an example of an apparatus used to carry out the water-cooled welding method according to the present invention.

In the atomic couplant piping 26 and 27, the welded part 2
8 to be inspected by radiation, approximately 30 mm from the weld line 29.
An r plug seat 3o is provided at a distance of 0+o+. When carrying out this radiation inspection, an r-ray source is introduced into the pipe from the γ plug seat 30 so that defects in the welded portion 28 can be inspected. After the welding inspection, move the γ plug 31 to the r plug seat 3.
o and is water sealed.

The present invention is a method of removing air bubbles 33 by using a gamma plug seat 30 to bring a jet fountain nozzle 32 close to the top of the weld line 29 and jetting cooling water.

The jet fountain nozzle 32 has a bay shape, and γ
The plug seat 30 is inserted into the pipe, and the curvature is set by the position of the γ plug seat 30 and the weld line 29.

The γ plug seat 30 is longer than a normal R plug seat, has a thread carved on its inner surface, and is fitted with a P1 backing type water seal R plug 31 with an O-ring 34 interposed therebetween. Further, the jet nozzle 32 can be inserted into a through hole 35 formed in the center of the γ plug 34 of the backing type water seal with an O ring 36 interposed therebetween in a water seal state.

Geno) The jet nozzle 32 connects to the pipe 3 via the union 37.
It is connected to 8. 1. The pipe 38 is connected to a water supply tank 42 through a valve 39, a jet water pressurizing pump 40, and a valve 41. Further, a bypass pipe 44 is provided which branches off from the jet water pressure pump 40 via a valve 43 midway.

The water supply system path is composed of a water supply tank 42, a water supply pump 4o1 bypass pipe 44, a water pipe 38, and a valve 39°41.43.

The amount of water supplied to the jet fountain nozzle 32 is regulated by operating the water supply pump and by regulating the valves 39, 41, 43 via the conduit 38 and the bypass pipe 44.

A running water type water-cooled welding method is performed using an apparatus having the above-mentioned configuration.

First, the pressure pump 40 blows the cooling water from the water supply tank 42 through the pipe 38 and from the jet fountain nozzle 32 into the flowing water in the pipe to remove the air bubbles 33 that have accumulated in the recess 21 of the welding part 28. Can be completely removed.

<Example 2> FIG. 7 is an explanatory diagram showing a modification of the jet fountain nozzle. In the figure, the distance between the r plug seat 30 and the welding line 29 is approximately 3
In this application example, an L-shaped deformed jet nozzle 45 is used to disturb the flowing water in the pipe, and the turbulent force causes air bubbles 33 to stay in the recessed part 21 of the welded part 28. It is characterized by the removal of

<Embodiment 3> On the other hand, FIG. 8 is an explanatory diagram showing another example of application of the present invention. For example, the air bubble suction nozzle 46 is inserted into the pipe from the gamma plug seat 30 in a water-sealed state, and the opening 47 at the tip is placed close to the recess 21 of the welding part 28 to cool the air bubbles 33 staying in the pipe. It is characterized by being inhaled together with water. The cooling water and bubbles 33 sucked into the upper tube are conveyed to the cooling water drain collection box 51 by the cooling water suction pump 48 through the bubble suction nozzle 46, the pipe 49, and the valve 50.

The shape and dimensions of the bubble suction nozzle 46 are determined by the distance between the γ plug seat 30 and the weld line 29 and the diameter of the γ plug seat 30, and the position is determined by a model test.

Even in such an application example, the recessed portion 21 of the welded portion 28
It is possible to completely remove air bubbles that accumulate in the pipe and impair the cooling effect, and highly reliable flowing water cooling welding can be performed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the
To completely remove air bubbles that accumulate in the recessed part of a welded part in a flowing water-cooled welding method for stainless steel horizontal piping other than CC piping, and at the same time to perform water-cooled welding with high reliability in terms of SCC countermeasures. This has the remarkable effect of completely reducing the probability of an abnormality occurring in a nuclear power plant due to defective water cooling welding to zero.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing an example of a conventional spray type water-cooled welding method, Figure 2 is an explanatory perspective view showing a typical example of the shape of a spray nozzle used in spray type water-cooled welding, and Figure 3 is a nuclear power plant piping An explanatory diagram showing an example of the route, Fig. 4 is an explanatory diagram showing how the new piping suguru is welded and assembled to the existing piping, Fig. 5 is an enlarged view of the recessed part for radiographic inspection at the welded part, and Fig. 6 is FIGS. 7 and 8 are explanatory diagrams showing an example of an apparatus used in the water-cooled welding method of the present invention, and FIGS. 7 and 8 are explanatory diagrams showing an embodiment of the water-cooled welding method of the present invention. 11-17... Piping spool, 22... Hollow portion, 2
6...γ plug seat, 27...jet fountain nozzle,
28...Bubbles. Agent Patent Attorney Tatsunokyo Unuma l Kokyo 3 Figure 4 Kuchikyo 5 Kokyo A Figure z Certain 7 Figure 42 Bud δ Yen a't , f0

Claims (1)

[Claims] 1. In a flowing water type water-cooled welding method in which pipes in horizontal piping used in a nuclear power plant are abutted against each other and circumferentially welded while water is flowing inside the pipes, a recess provided on the inner surface of the abutting portion. A water-cooled welding method characterized by the formation of a rapid current in the area. 2. The water-cooled welding method according to claim 1, wherein the horizontal piping of the nuclear power plant is stainless steel piping other than SCC-resistant material. 3. The water-cooled welding method according to claim 1, wherein the jet nozzle is a curved tube inserted through a gamma plug seat provided near the abutment. 4. The water-cooled welding method as set forth in claim 3, wherein the γ plug seat is provided near the welded portion for inspection of the welded portion.