KR102021245B1 - Method for repairing nozzle - Google Patents

Abstract

The present invention provides a nozzle maintenance method. The nozzle maintenance method is to maintain a nozzle welded and provided by passing through a provision hole provided in a welding base material. The nozzle comprises: an upper nozzle portion having a first through hole formed therein; an intermediate nozzle portion formed integrally with a lower portion of the upper nozzle portion and having a second through hole communicating with the first through hole; and a lower nozzle portion formed integrally with a lower portion of the intermediate nozzle portion, and having a third through hole communicating with the second through hole and tapered so that the inner diameter thereof becomes narrower toward the lower portion. The method comprises: a first step of sealing the third through hole by inserting a plug member having an outer diameter formed corresponding to the inner diameter of the third through hole in a lower end portion of the third through hole; a second step of removing the upper nozzle portion and the intermediate nozzle portion; a third step of welding, to a surface of the welding base material, a pad provided with a pad hole communicating with the provision hole; a fourth step of forming a J-shaped grooved in the pad hole provided in the pad; a fifth step of removing the plug member from the third through hole; a sixth step of assembling a new nozzle, through which a nozzle hole communicating with the third through hole passes, on an upper portion the lower nozzle portion, which is the remained portion of the nozzle, by passing through the provision hole; and a seventh step of welding a gap between an outer circumferential surface of the new nozzle and the J-shaped groove. According to the present invention, it is possible to prevent thermal stress from being transferred to a pad and a J-shaped groove.

Description

NOZZLE MAINTENANCE {METHOD FOR REPAIRING NOZZLE}

The present invention relates to a nozzle maintenance method, and more particularly to a nozzle maintenance method for minimizing damage to the welding base material.

A nuclear power plant consists of a primary system, a system directly related to radiation, and a secondary system, a system not related to radiation.

The primary system includes the Nuclear Steam Supply System (NSSS), the reactor safety-related system, the reactor auxiliary system and other radiation-related auxiliary systems, and the secondary system includes turbines and generators, their auxiliary systems and other non-radioactive systems. Include. Here, the NSSS includes a reactor, a pressurizer, a steam generator, and a coolant pump. The reactor stores fuel and provides a place for a nuclear reaction, and the pressurizer serves to regulate pressure in the primary system.

In addition, the steam generator heat-exchanges the water cooled in the secondary system with the coolant heated by the nuclear fuel to make water into steam, and the coolant pump serves to supply the cooled coolant back to the reactor after heat exchange. The reactor vessel, which consists of a lower vessel and an upper reactor head, is provided with a large number of small and medium pipes or nozzles, such as nozzles related to a removal rod drive, in addition to a large nozzle into which coolant is introduced and discharged.

In addition, a large number of small pipes and nozzles such as sampling nozzles and RTD pipes (Resistance Temperature Detectors) exist in the reactor, steam generator, pressurizer, and main pipes therebetween.

When such small pipes or nozzles are old, replacement and maintenance work must be performed. When replacing and welding a part of a defective nozzle using conventional maintenance work, a gap may occur in the welded area due to corrosion of the welding part or welding defects. It can be, and there is a problem that the pressure vessel is corroded and damaged as the primary water flows into the generated gap.

In addition, when the nozzle replacement operation by welding is carried out there is a problem that damage to the reactor pipe which is a welding base material.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a nozzle maintenance method that does not damage the reactor pipe, which is a welding base material, during maintenance of the nozzle.

Another object of the present invention is to provide a nozzle maintenance method for preventing stress corrosion cracking from occurring at a welded part by forming a gap spaced properly between a residual nozzle and a new nozzle.

In addition, an object of the present invention is to provide a nozzle maintenance method for preventing foreign matter from entering the reactor during the maintenance work of the nozzle.

In order to achieve the above object, the maintenance method of the nozzle according to the present invention, in the maintenance method of the nozzle installed by welding through the installation hole provided in the welding base material, the nozzle is, the upper nozzle portion formed with the first through hole, An intermediate nozzle part integrally formed in the lower part of the upper nozzle part and having a second through hole communicating with the first through hole, and integrally formed in the lower part of the intermediate nozzle part and in communication with the second through hole; A lower nozzle portion having a tapered third through hole, the inner diameter of which is narrowed, and a plug member having an outer diameter corresponding to the inner diameter of the third through hole is inserted into a lower end of the third through hole to seal the third through hole. And a second step of removing the upper nozzle part and the intermediate nozzle part, and welding a pad having a pad hole communicating with the installation hole to a surface of the welding base material. A third step, a fourth step of forming a J-groove in the pad hole provided in the pad, a fifth step of removing the plug member from the third through hole, and the nozzle through the installation hole. A sixth step of assembling a new nozzle through which the nozzle hole communicating with the third through hole passes through the lower nozzle portion, which is a remaining portion of the lower nozzle portion, and welding the outer circumferential surface of the new nozzle and the J-groove; Includes seven steps.

By using the nozzle maintenance method according to an embodiment of the present invention, it is possible to prevent damage to the reactor piping, which is a welding base material, during maintenance of the nozzle.

In addition, the present invention is formed by a gap (gap) properly spaced between the residual nozzle and the new nozzle, when the welding base material flowing high temperature cooling water is thermally expanded, the stress corrosion on the welding portion between the lower end of the lower nozzle portion and the welding base material inside the welding base material The occurrence of cracks can be prevented in advance. And it is possible to prevent the thermal stress is transmitted during the welding of the pad and the J-shaped groove made on the upper side of the welding base material.

In addition, the present invention can prevent the foreign substances from entering the reactor by inserting the plug member in the lower nozzle portion during the nozzle maintenance work.

1 is a view showing a state in which a nozzle that is a maintenance target according to the present invention installed on a welding base material.
2 is a view showing a state in which a part of the nozzle is replaced with a new nozzle using the maintenance method of the nozzle according to the present invention.
3 is a diagram illustrating a process of drawing out a measuring sensor guide tube from a nozzle;
4 shows a first step according to the invention;
5 is a view showing a nozzle cutting step in a second step according to the present invention.
6 is a view showing a protruding nozzle removal step in a second step according to the present invention;
7 is a view showing a processing guide installation step in the second step according to the present invention.
8 is a view showing a middle nozzle portion removing step in a second step according to the present invention.
9 is a view showing a processing guide removal step in a second step according to the present invention.
10 is a view showing a sacrificial plug installation step in a third step according to the present invention.
11 is a view showing a pad welding step in a third step according to the present invention;
12 is a view showing a sacrificial plug processing and removal step in a third step according to the present invention.
13 is a view showing a pad surface processing step in a third step according to the present invention.
14 shows a fourth step according to the invention;
15 is a view showing a hole expansion processing step according to the present invention.
16 shows a fifth step according to the invention;
17 shows a sixth step according to the invention.
18 shows a seventh step according to the invention.
19 is a view showing a step of inserting a measuring sensor guide tube according to the present invention.

Hereinafter, preferred embodiments of the present invention according to the accompanying drawings will be described in detail.

First, the embodiments described below are embodiments suitable for understanding the technical features of the nozzle maintenance method of the present invention. However, the technical features of the present invention are not limited by the embodiments described or applied to the embodiments described below, and various modifications are possible within the technical scope of the present invention.

1 is a view showing a state in which the nozzle 30, the maintenance target according to the present invention is installed on the welding base material (10). The welding base material 10 applied to the present invention may be an RCS pipe cooling the steam generator in a reactor coolant system (hereinafter referred to as RCS). The nozzle 30 may be a small diameter through tube installed through the outer surface of the RCS pipe, and may be a nozzle in which a resistance temperature detector (RTD) for the thermometer side is installed. However, the type of the welding base material 10 and the nozzle 30 is not limited thereto, and may be applied to various nozzles requiring maintenance.

Referring to FIG. 1, the nozzle 30 to which the present invention is applied includes an upper nozzle part 31, an intermediate nozzle part 33, and a lower nozzle part 35. The upper nozzle part 31 has a first through hole 32 formed therethrough. The intermediate nozzle part 33 is formed integrally with the lower part of the upper nozzle part 31 and has a second through hole 34 communicating with the first through hole 32. The lower nozzle part 35 is integrally formed under the middle nozzle part 33 and has a third through hole 36 communicating with the second through hole 34. The third through hole 36 may be tapered so that the inner diameter thereof becomes narrower toward the lower portion.

Here, the first through hole 32 may have a larger inner diameter than the second through hole 34 and the third through hole 36. In addition, the inner diameter of the third through hole 36 may be similar to that of the second through hole 34, and the inner diameter of the third through hole 36 may be inclined toward the center toward the lower portion thereof.

The nozzle 30 may be provided as an RTD nozzle which is a nozzle in which a resistance temperature detector (RTD) for the thermometer side is installed. Specifically, the measurement sensor guide tube 40 is inserted into the nozzle 30, and the measurement sensor guide tube 40 includes the first through hole 32, the second through hole 34, and the third through hole ( 36 may be installed through. The measuring sensor guide tube 40 may serve to guide the installation of the resistance temperature measuring instrument having a resistance temperature measuring instrument inserted therein. Here, the material of the nozzle 30 may be an alloy 690 material resistant to stress corrosion cracking, but is not limited thereto.

The welding base material 10 has an installation hole 11 formed therethrough, and the nozzle 30 penetrates the installation hole 11 and is coupled by welding. However, when a nozzle 30 made of Alloy 600, which is sensitive to stress corrosion cracking, is installed, a welding portion between the lower end of the lower nozzle portion 35, which is the inner side of the welding base material 10, and the welding base material 10 after a predetermined time passes. Cracks due to first order stress corrosion cracking may occur at 112. In addition, a problem may occur in which the coolant inside the welding base material 10 flows out through the gap 11 generated between the upper nozzle part 31 and the welding base material 10, which is the outer side of the welding base material 10.

As described above, in the case where a defect in the welded portion between the welding base material 10 and the nozzle 30 occurs, maintenance may be performed through maintenance work of the nozzle according to the present invention.

2 illustrates a state in which a part of the nozzle 30 is replaced with a new nozzle 130 by using a method of maintaining the nozzle 30 according to the present invention. As shown in the embodiment shown in Figure 2 the present invention by forming a new welding site while removing a portion of the existing nozzle 30 and installing a new nozzle 130, by the first stress corrosion cracking in the welding site 112 Even if a crack is generated, it is possible to prevent the cooling water inside the welding base material 10 from flowing out.

The maintenance method of the nozzle 30 according to the present invention includes the first to seventh steps.

In the first step, the third through hole 36 may be inserted into a lower end of the third through hole 36 by inserting a plug member 50 having an outer diameter corresponding to the inner diameter of the third through hole 36. Sealing step. The second step is to remove the upper nozzle portion 31 and the intermediate nozzle portion 33.

The third step is to form a pad 210 having a pad hole 213 communicating with the installation hole 11 on the surface of the welding base material 10. The fourth step is to form the J-groove 220 in the pad hole 213 provided in the pad 210. The fifth step is to remove the plug member 50 from the third through hole 36.

The new nozzle through which the nozzle 30 hole communicating with the third through hole 36 passes through the sixth step of the installation hole 11 and communicates with the third through hole 36 on the upper portion of the lower nozzle part 35 remaining in the nozzle 30. 130 is assembled, and the seventh step is a step of welding between the outer peripheral surface of the new nozzle 130 and the J-shaped groove 220.

Hereinafter, a maintenance method of the nozzle 30 according to the present invention will be described with reference to FIGS. 3 to 19.

First, referring to FIG. 3, the measurement sensor guide tube 40 may be removed from the nozzle 30 before the first step.

Referring to FIG. 4, the first step is to insert and plug the plug member 50 into the third through hole 36. The plug member 50 may serve to prevent foreign substances from flowing through the nozzle 30 during maintenance of the nozzle 30. The outer diameter of the plug member 50 may be formed to correspond to the inner diameter of the third through hole 36. In addition, the shape of the outer circumferential surface of the plug member 50 may be formed in a tapered structure corresponding to the shape of the inner circumferential surface of the third through hole 36. The plug member 50 may be inserted into the inner circumferential surface of the third through by an insertion tool (not shown) to maintain the sealed state of the nozzle 30.

In this case, a part of the upper nozzle part 31 may be cut before the first step, thereby facilitating the insertion process of the plug member 50.

Next, referring to FIGS. 5 to 9, the second step is to remove the upper nozzle part 31 and the intermediate nozzle part 33.

The second step may include cutting the nozzle 30 and removing the intermediate nozzle part 33. In addition, the second step may further include removing the surface protruding nozzle and installing the processing guide 60.

Referring to FIG. 5, the cutting step of the nozzle 30 is a step of cutting the intermediate nozzle part 33 at a position spaced upward from the outer surface of the welding base material 10. Specifically, the cutting step of the nozzle 30 is a step of cutting the nozzle 30 from the outside of the welding base material 10 by using a cutting tool, and the intermediate nozzle at a position spaced upward from the outer surface of the welding base material 10. The part 33 is cut to remove a part of the intermediate nozzle part 33. At this time, the sealing state of the nozzle 30 may be maintained through the plug member 50 inserted into the lower nozzle part 35.

Next, referring to FIG. 6, the protruding nozzle removing step may include a part of the intermediate nozzle part 33 protruding outward from the outer surface of the welding base material 10 using a processing tool after the cutting step of the nozzle 30. It is the process of removing by processing. In the protruding nozzle removing step, the intermediate nozzle part 33 is cut in the cutting step of the nozzle 30, and then the intermediate nozzle part 33 protruding from the outer surface of the welding base material 10 is removed, and the nozzle 30 is removed. The protruding middle nozzle portion 33 may be removed using a processing tool (not shown).

7 to 9, the removing of the intermediate nozzle part 33 is a step of removing the intermediate nozzle part 33 remaining inside the welding base material 10 after the cutting step of the nozzle 30.

In detail, the removing of the intermediate nozzle part 33 may include installing the processing guide 60, processing and removing the nozzle 30, and removing the processing guide 60.

Referring to FIG. 7, in the installing of the processing guide 60, the processing guide 60 is inserted into the second through hole 34 and the third through hole 36, and the lower end of the processing guide 60 is formed in the third through hole. By fitting to (36).

Here, the lower end portion of the processing guide 60 is formed in a shape corresponding to the tapered shape of the third through hole 36, and the lower end portion 61 in close contact with the inner circumferential surface of the third through hole 36 by expansion. It may be coupled to the third through hole 36 provided with. Accordingly, the machining guide 60 may be tightly fastened to the lower nozzle part 35. In this case, various methods may be applied to the expansion method of the processing guide 60.

Referring to FIG. 8, the processing and removal steps of the nozzle 30 are performed by processing the lower end of the intermediate nozzle part 33 using the nozzle 30 processing tool installed through the processing guide 60, and remaining when the processing is completed. The intermediate nozzle portion 33 can be removed from the welding base material (10). Accordingly, all of the intermediate nozzle portion 33 can be removed.

Referring to FIG. 9, in the removing of the processing guide 60, after removing the intermediate nozzle part 33, the processing guide 60 may be removed from the third through hole 36. When the machining guide 60 is removed, only the lower nozzle part 35 remains inside the installation hole 11 of the welding base material 10 as shown.

Next, referring to FIGS. 10 to 13, a third step is a step of welding the pad 210 having the pad hole 213 communicating with the installation hole 11 on the surface of the welding base material 10.

Specifically, the third step may include installing the sacrificial plug 70, welding the pad 210, and processing and removing the sacrificial plug 70.

Referring to FIG. 10, in the installing of the sacrificial plug 70, the sacrificial plug 70 is inserted into the installation hole 11 of the welding base material 10, and the insertion portion 71 of the sacrificial plug 70 is installed in the installation hole ( 11) and the upper end 72 of the sacrificial plug 70 provided on the upper end of the insertion part 71 may protrude from the outer surface of the welding base material 10.

Referring to FIG. 11, in the welding step of the pad 210, the pad 210 may be welded to the surface of the welding base material 10 about the upper end 72 of the sacrificial plug 70. According to the present invention, the pad 210 is welded to the surface of the welding base material 10 to seal a portion into which the new nozzle 130 is inserted, thereby preventing corrosion of the portion. Here, the filler metal for welding the pad 210 may be, for example, one of Alloy 690, Alloy 52M, Alloy 52, and Alloy 152 having excellent high temperature corrosion resistance, but is not limited thereto.

Here, the upper end portion 72 of the sacrificial plug 70 may be formed in a trapezoidal shape with an outer diameter smaller toward an upper side thereof. In addition, the welding step of the pad 210 may be performed such that a cross section of the pad 210 has a trapezoidal shape that is symmetrical about a central axis of the installation hole 11. That is, the sacrificial plug 70 may be formed such that the horizontal cross-sectional area decreases as the upper end portion 72 moves upward, and the cross-sectional shape of the pad 210 may be formed in a trapezoidal shape by this shape.

As such, the shape of the pad 210 is trapezoidal, thereby minimizing the difference between the width (diameter) of the top surface of the pad 210 and the width (diameter) of the bottom surface of the pad 210. In welding, it is possible to minimize the difference between the number of welding per floor of the bottom surface and the number of welding per floor of the top surface.

In addition, in the pad 210 welding step, temper bead welding may be performed on the lower surface of the pad 210 in contact with the welding base material 10. Specifically, when the pad 210 is welded to the surface of the reactor coolant system piping welding base material 10, which is a low carbon steel, with an Inconel alloy filler (Alloy 52M), the welding bead directly welded to the base material is used for rapid cooling of the welding heat input. As a result, fragile tissues such as martensite coarse formed in the heat affected zone may be formed, thereby lowering mechanical properties such as fracture toughness.

Therefore, ASME Sec. III NX-4620 requires post-weld heat treatment to obtain sound welds that do not exhibit this fragile structure. However, ASME Code Case N-638 allows the alternative application of the temper bead welding technique because it is difficult to apply post-weld heat treatment due to physical interference and heat loss in the field. Temper bead welding produces a tempering effect by repeatedly overlapping beads within the same bead layer during multilayer bead welding, which deposits multiple bead layers on the welding substrate 10, and also in the above layer during subsequent bead lamination. It is a welding technique that imparts a tempering effect by allowing the generated heat input to pass through the lower layer weld metal to the weak microstructure of the heat affected zone (HAZ). The main requirement for the temper bead welding process using Inconel alloys (Alloy 52M) is that the weld metal must be welded by automatic or mechanical welding, and the maximum interpass temperature for field construction is maintained at 180 ° C. Weld heat input should not exceed 45kJ / inch. However, the temper bead welding applied to the present invention is not limited to applying the filler metal and the temperature and calorie, and may be variously modified.

Referring to FIG. 12, in the processing and removing of the sacrificial plug 70, after the sacrificial plug 70 is processed using a processing tool (not shown), the sacrificial plug 70 may be removed from the welding base material 10. have. Specifically, after the pad 210 is formed, the sacrificial plug 70 may be removed using a processing tool for processing the sacrificial plug 70. Here, the processing tool for processing the sacrificial plug 70 may be, for example, about 27mm in diameter, but is not limited thereto.

Meanwhile, referring to FIG. 13, the third step may further include surface treatment of the pad 210. In the surface processing step of the pad 210, after the sacrificial plug 70 is removed, the surface 210 of the pad 210 is uniformly processed using the planar processing tool, and the pad 210 is formed using the side processing tool. The side surface 212 of the can be processed to be uniform. Accordingly, durability of the pad 210 may be improved.

Meanwhile, referring to FIG. 14, the fourth step is to form the J-groove 220 in the pad hole 312 provided in the pad 210.

In detail, when the surface processing of the pad 210 is completed in the third step, the J-shaped groove 220 may be formed in an upper portion of the pad hole 312 of the pad 210 using a groove processing cylinder (not shown). have. J-shaped groove 220 is formed in the direction toward the center of the pad hole 213 on the upper surface 211 of the pad 210, the curved portion 221 is curved downward in the J-shape toward the center of the pad 210 ) And a flat portion 222 formed parallel to the upper surface 211 at the lower end of the curved portion 221. As described above, the J-shaped groove 220 includes the curved portion 221 and the flat portion 222, so that the penetration of the J-shaped groove 220 at the lower surface 212 of the J-shaped groove 220 is insufficient. It is possible to prevent the occurrence of weld joints such as poor fusion.

Meanwhile, the fifth step is to remove the plug member 50 from the third through hole 36.

Referring to FIG. 15, the present invention may further include a hole expanding processing step before the fifth step. In the hole expanding processing step, the hole located in the pad hole 213 and the installation hole 11 may be expanded by processing a portion located above the lower nozzle part 35. Accordingly, the new nozzle 130 installed through the installation hole 11 and the pad hole 213 can be easily mounted.

Referring to FIG. 16, the fifth step may remove the plug member 50 from the lower nozzle part 35 after the hole expansion processing step.

Referring to FIG. 17, in a sixth step, the nozzle hole 130a communicating with the third through hole 36 on the upper portion of the lower nozzle part 35, which is a remaining portion of the nozzle 30, passes through the installation hole 11. This penetrated new nozzle 130 can be assembled.

Specifically, the new nozzle 130 may be assembled to the upper end of the lower nozzle portion 35. The new nozzle 130 is composed of an upper nozzle portion 131 and an intermediate nozzle portion 133 to replace the existing upper nozzle portion 31 and the intermediate nozzle portion 33, the remaining of the lower nozzle portion 35 It can be installed on top.

As shown in the exemplary embodiment of the present invention, a new nozzle (G, see FIGS. 17 to 19) is formed between the upper end of the lower nozzle part 35 and the lower end of the new nozzle 130 at a predetermined distance. 130) can be installed. That is, when assembling the new nozzle 130, the gap (G) is formed by separating the lower nozzle part 35, which is the residual nozzle 30, and the new nozzle 130, by a predetermined distance from the lower end of the intermediate nozzle part 133. can do.

As described above, in the present invention, when the gap G is formed between the lower nozzle part 35 and the new nozzle 130, when the welding base material 10 in which the high-temperature cooling water flows is thermally expanded, the lower part that is the inner side of the welding base material 10 is formed. It is possible to prevent the occurrence of stress corrosion cracking in the welding portion 112 between the lower end of the nozzle portion 35 and the welding base material 10.

In addition, the present invention is formed by the gap (G) between the lower nozzle portion 35 and the new nozzle 130, the pad 210 and the J-shaped groove 220 formed on the upper surface 212 of the welding base material 10 By the thermal stress transfer to the lower nozzle portion 35 is blocked during welding of the stress can be prevented from increasing in the above-described welding portion 112 that can cause stress corrosion cracking.

Referring to FIG. 18, a seventh step is a step of welding between the outer circumferential surface of the new nozzle 130 and the J-groove 220.

In detail, in the seventh step, when the assembly of the new nozzle 130 is completed in the sixth step, the groove welding part 230 may be formed by welding between the J-shaped groove 220 and the outer circumferential surface of the new nozzle 130. . Accordingly, the installation work of the new nozzle 130 may be completed.

Meanwhile, the present invention further includes inserting the measurement sensor guide tube 40 through the third through hole 36 and the nozzle hole 130a after the installation of the new nozzle 130 is completed in the seventh step. can do. Specifically, the measurement sensor guide tube 40 removed before the first step may be inserted into the new nozzle 130 and the lower nozzle part 35 which is the existing nozzle 30.

By using the nozzle maintenance method according to an embodiment of the present invention, it is possible to prevent damage to the reactor piping, which is a welding base material, during maintenance of the nozzle.

In addition, the present invention is formed by a gap (gap) properly spaced between the residual nozzle and the new nozzle, when the welding base material flowing high temperature cooling water is thermally expanded, the stress corrosion on the welding portion between the lower end of the lower nozzle portion and the welding base material inside the welding base material The occurrence of cracks can be prevented in advance. And it is possible to prevent the thermal stress is transmitted during the welding of the pad and the J-shaped groove made on the upper side of the welding base material.

In addition, the present invention can prevent the foreign substances from entering the reactor by inserting the plug member in the lower nozzle portion during the nozzle maintenance work.

Although specific embodiments of the present invention have been described above, the spirit and scope of the present invention are not limited to these specific embodiments, and are described in the claims by those skilled in the art. Various modifications and variations are possible without departing from the spirit of the invention.

10: welding base material 11: mounting hole
21: welding part 30: nozzle
31: upper nozzle portion 32: first through hole
33: intermediate nozzle portion 34: second through hole
35: lower nozzle portion 36: third through hole
40: measuring sensor guide tube 50: plug member
60: processing guide 61: lower expansion portion
70: sacrificial plug 71: insert
72: upper part 130: new nozzle
130a: nozzle hole 131: upper nozzle portion
133: intermediate nozzle portion 210: pad
211: top face 212: side face
213: pad hole 220: J groove
221: curved portion 222: flat portion
230: groove weld portion G: gap

Claims (12)

In the maintenance method of the nozzle installed by penetrating through the installation hole provided in the welding base material,
The nozzle includes an upper nozzle portion having a first through hole, an intermediate nozzle portion formed integrally with a lower portion of the upper nozzle portion, and having a second through hole communicating with the first through hole, and a lower portion of the intermediate nozzle portion. And a lower nozzle portion communicating with the second through hole and having a third through hole tapered such that an inner diameter thereof becomes narrower toward the lower portion,
A first step of sealing the third through hole by inserting a plug member having an outer diameter corresponding to the inner diameter of the third through hole at a lower end of the third through hole;
A second step of removing the upper nozzle portion and the intermediate nozzle portion;
Welding a pad having a pad hole communicating with the installation hole on a surface of the welding base material;
A fourth step of forming a J-groove in the pad hole provided in the pad;
A fifth step of removing the plug member from the third through hole;
A sixth step of assembling a new nozzle through the installation hole and through which the nozzle hole communicating with the third through hole passes on the lower nozzle part, which is a remaining part of the nozzle; And
And a seventh step of welding between the outer circumferential surface of the new nozzle and the J-shaped groove,
The third step,
Inserting a sacrificial plug into the installation hole of the welding base material, the insertion portion of the sacrificial plug is inserted into the installation hole, the upper end of the sacrificial plug provided on the insert portion is installed to protrude from the outer surface of the welding base material Sacrificial plug installation step;
A pad welding step of welding forming the pad around the upper end of the sacrificial plug on a surface of the welding base material; And
And a sacrificial plug machining and removing step of removing the sacrificial plug from the welding base material after machining the sacrificial plug using a machining tool. The method of claim 1,
The nozzle is a nozzle in which a resistance temperature detector for the thermometer side is installed, and guides the installation of the resistance temperature meter through the first through hole, the second through hole, and the third through hole. Measuring sensor guide tube is inserted,
Before the first step, withdraw the removal of the measuring sensor guide tube from the nozzle,
And after the seventh step, inserting the measurement sensor guide tube through the third through hole and the nozzle hole. The method of claim 1,
The sixth step, the nozzle maintenance method of assembling the new nozzle so that a gap (gap) spaced a predetermined distance between the upper end of the lower nozzle portion and the lower end of the new nozzle is formed. The method of claim 1,
Before the first step, cutting a portion of the upper nozzle portion. The method of claim 1,
The second step,
A nozzle cutting step of cutting the intermediate nozzle part at a position spaced upward from an outer surface of the welding base material; And
And an intermediate nozzle part removing step of removing the intermediate nozzle part remaining in the welding base material after the nozzle cutting step. The method of claim 5,
The second step,
After the nozzle cutting step, further comprising a projection nozzle removing step of processing by removing a portion of the intermediate nozzle portion protruding outward from the outer surface of the welding base material using a processing tool, the maintenance method of the nozzle. The method of claim 5,
The intermediate nozzle portion removing step,
A processing guide insertion step of inserting a processing guide into the second through hole and the third through hole, and inserting a lower end of the processing guide into the third through hole;
Processing and removing a nozzle for processing the lower end of the intermediate nozzle part using a nozzle processing tool installed through the processing guide, and removing the intermediate nozzle part from the welding base material when the machining is completed; And
And removing the processing guide after removing the intermediate nozzle part from the third through hole.
The lower end of the processing guide is formed in a shape corresponding to the tapered shape of the third through hole, and provided with a lower expansion part in close contact with the inner circumferential surface of the third through hole by expansion, and coupled to the third through hole. Of maintenance. delete The method of claim 1,
The upper end of the sacrificial plug, the outer diameter is reduced toward the upper side is formed in a trapezoidal cross section,
The pad welding step, the maintenance method of the nozzle to form a trapezoidal shape axially symmetrical with respect to the center axis of the installation hole, the cross section of the pad. The method of claim 1,
The pad welding step, the maintenance method of the nozzle to perform a temper bead (Temper Bead) welding on the lower surface of the pad in contact with the welding base material. The method of claim 1,
The third step,
After the sacrificial plug is removed, further comprising a pad surface processing step of processing the top surface of the pad to be uniform using a planar processing tool, and processing the side surface of the pad to be uniform using a side processing tool, Maintenance of the nozzle. The method of claim 1,
Before the fifth step,
And a hole expanding processing step of processing and expanding a portion of the pad hole and the mounting hole located above the lower nozzle part by using a hole processing tool.

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