JPH0362512B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to installing a sleeve inside a heat exchange tube for the purpose of repairing the heat exchange tube, and in particular, the present invention relates to installing a sleeve inside a heat exchange tube for the purpose of repairing the heat exchange tube. This invention relates to a new method of welding in exchange tubes by means of explosive action. BACKGROUND OF THE INVENTION In heat exchangers such as nuclear steam generators that use tubes arranged in bundles by tube sheets or tube support plates, the tubes are subject to corrosion damage or mechanical damage that requires repair. There must be. One method for making such repairs is to insert a sleeve into the damaged tube of sufficient length to extend over the damage. Thus, the sleeve often extends beyond the tube support portion of the tube sheet or tube support plate.
Additionally, the sleeve must be sealed to the inner surface of the tube to hold it in place and prevent fluid from leaking around the sleeve. Current methods of sealing the sleeve include inflating and crimping the sleeve to the tube wall and then brazing the sleeve to the tube wall, and welding the sleeve to the tube wall by explosive action. However, the latter explosive action welding method usually requires some external tube support means to prevent excessive deformation of the tube. Techniques for explosively welding tubes to heat exchangers for tube assembly or repair are well known. For example, U.S. Pat. No. 3,411,198 discloses a cylindrical force transmitting member made of polyethylene having a gap at one end for expanding and crimping a tube into a hole in a tubesheet, and an explosive insert loaded within the force transmitting member. A plastic insert is disclosed. U.S. Pat. No. 3,590,877 discloses a cylindrical metal plug that is installed by explosive action to close off a damaged heat exchange tube in the vicinity of its external support tube sheet. In that patent, an explosive charge of a specific shape is formed by wrapping a cylindrical central explosive block with a cylindrical styrofoam filler and wrapping a sheet of explosive around the filler. U.S. Pat. No. 3,724,062 also discloses a plug that is installed by explosive action to occlude a damaged heat exchange tube in the vicinity of its tube sheet. The plug has a cylindrical body portion and frusto-conical end portions, and the explosive charge is cylindrically shaped and loaded within the cylindrical body portion of the plug. U.S. Pat. No. 3,790,060 discloses the use of a pair of explosive members, one of which is
It serves to weld the pipe to the perforated plate through which it passes, and the other explosive member serves to crimp the pipe into enlarged holes or counterbores formed in both sides of the perforated plate. Applicant's own US Pat. No. 3,912,1489 discloses a combination welding and brazing apparatus for repairing leaks in heat exchanger tube-to-tubesheet joints. This device fills a number of grooves in one end of a metal sleeve with braze metal. The other end of the sleeve is thin-walled and is adapted to accommodate a relatively large amount of nitroguanidine. A relatively small amount of PETN (pentaerythritol,
Tetranitrate) to eject the charge. When these explosive charges are detonated, the narrow part of the sleeve (inserted through the tubesheet of the heat exchanger tube) is welded to the inner surface of the tube, and the free end of the tube (away from the hole in the tubesheet) is welded to the inner surface of the tube. The other end of the sleeve, which is within the extended portion, is then pressed against the inner surface of the tube for brazing. Actual brazing is performed as a second step by heating and melting the brazing metal with a cartridge type electric resistance heater inserted into the sleeve. The prior art column of the above-mentioned US Pat. It is pointed out that brazing is suitable for use in free sections of tubes (those not constrained by holes in the tubesheet). In the latter case, the explosive action of the explosive in the free part of the tube is used merely to expand and press the part of the sleeve to be brazed against the inner surface of the tube, the brazing itself being carried out later. U.S. Patent No. 4,028,789 is also
A combined welding and brazing method similar to that of No. 3912148 is disclosed. In this method, too, welding is carried out only in the tubesheet-penetrating portions of the heat exchanger tubes, i.e., in the portions supported by the tubesheets, and brazing only causes the free portions of the tubes to expand. U.S. Pat. No. 4,021,907 discloses an explosive action plug for sealing damaged tubes retained in the tubesheet of a heat exchanger. The ends of the plug each have a cylindrical or frusto-conical end for filling a similarly shaped explosive insert. In each of the embodiments of the patent, one end of the plug is provided with a detonator and the other end is provided with a detonator pin to detonate the inserts at both ends almost simultaneously. U.S. Pat. No. 4,513,903 discloses yet another method and apparatus for welding a sleeve directly to a damaged portion of a heat exchange tube supported by a tubesheet. Also, U.S. Pat. No. 4,567,632 discloses an explosive action method for repairing damage to a portion of a tube that is not supported by the tubesheet; requires the provision of an external support consisting of a cast-in-place low melting point alloy. U.S. Pat. No. 4,587,904 discloses a debris-free plug assembly for repairing a tube through a tube plate. In general, each of the prior patents mentioned above teaches welding a sleeve by explosive action to the portion of the tube held by the hole in the tube sheet or tube support plate. If an explosive charge is used to expand the sleeve or plug at a portion of the heat exchanger tube remote from the part held by the holes in the tube plate or tube support plate, welding by explosive action shall not be performed. do not have. None of the above-mentioned patents teaches or even suggests the possibility of welding the sleeve by explosive action inside a portion of the heat exchange tube that is not mechanically supported from the outside. Problems to be Solved by the Invention The present invention is intended to solve the problem of welding sleeves by explosive action into parts of heat exchange tubes that are not mechanically supported from the outside. Means for Solving the Problems To achieve this object, the present invention provides a method for welding a sleeve to the inner surface of a tube by explosive action, comprising an enlarged diameter extension and a wall thickness tapering towards one end. and positioning the sleeve within the tube, wherein the tapered portion of the sleeve is positioned within the tube at a location remote from an external mechanical support for the tube. loading a cup containing an explosive charge into the sleeve, and gradually decreasing the amount of the explosive charge along a tapered portion of the tapered wall thickness of the sleeve. providing the cup with a frusto-conical central portion to taper the explosive charge; and centering the sleeve within the tube to establish an annular spacing between the sleeve and the tube. detonating the explosive charge to expand the sleeve;
Welding to the pipe is provided. The present invention also provides a device for repairing a damaged portion of a pipe, which has an enlarged diameter extension and an outer surface extended at a taper angle of 1° to 5.7° to form a tapered wall thickness. a sleeve adapted to be positioned within the tube to cover the damaged portion; and a position configured to engage an inner surface of the sleeve for axial positioning within the sleeve. an explosive charge retaining assembly disposed within a tapered portion of the sleeve, the charge retaining assembly having an explosive charge retaining assembly disposed within a tapered portion of the sleeve and configured to weld the tapered portion of the sleeve to the inner surface of the tube by detonation action when detonated; a quantity of explosive charge held by said explosive charge retaining assembly within a tapered portion, said quantity (C) of said explosive charge being a predetermined length of said explosive charge; Provided is a repair device characterized in that the amount is proportional to the mass (M) of the sleeve corresponding to the amount of damage, and the ratio C/M ratio is within the range of 0.2 to 0.7. In accordance with the present invention, a method and apparatus for explosive welding a sleeve into a tube without the need for a removable external support, such as a removable die, or a fixed external support, such as a tube sheet. is provided. According to the present invention, a sleeve having a tapered portion is used as the sleeve inserted into the heat exchange tube so as to cover the damaged portion of the tube. The tapered part of the sleeve can be expanded by explosive action and can be welded to the inner surface of the tube without the need to provide a mechanical external support for the heat exchange tube. Because the tapered portion of the sleeve has a progressively thinner wall, there is less mass to be welded, so less explosive charge is required to expand or expand radially outward and weld to the inner surface of the tube. Therefore, welding performance can be improved. In the present invention, the explosive charge is contained within a plastic explosive charge holding assembly. The plastic explosive charge includes a cup for retaining the explosive charge and positioned within a tapered portion of the sleeve and an inner surface of the sleeve for positioning the explosive charge retaining assembly within the sleeve. and locating flanges adapted to engage.
The cup may also include a conical central part (core part) which shapes the explosive charge into a specific shape in order to optimize the explosive performance of the explosive charge. One end of the cup can be provided with a closed cap for covering the explosive charge, and the closed cap can carry a detonator for the explosive charge. The closed cap is shaped so that no force is transmitted to the sleeve or tube when the detonator is energized. Therefore, the sleeve also
The tube is also not deformed by the action of the detonator. The closed cap also serves to form a liquid-tight seal for the explosive charge. Embodiment When described with reference to FIGS. 1 and 2, the present invention includes:
A tube having a constant inner diameter and near at least one of the ends 6, in order to cover in a bridging manner a damaged portion 4 of a tube 1, such as a heat exchange tube, supported by a tube sheet 2 and a tube support plate 3. Outer peripheral surface 7 tapered at
A sleeve 5 having a diameter is used. This taper progressively reduces the mass of the sleeve 5 to be welded, thereby allowing the explosive charges 13, 14 to be welded as described below.
To reduce the required amount and improve welding performance. The sleeve 5 has an enlarged end portion 16 extending from the tapered end. Expanded diameter end portion 1
6 serves to center the sleeve 5 within the tube 1 and to establish a predetermined spacing between the outer surface of the sleeve 5 and the inner surface of the tube 1, as will be explained below. The explosive preferably consists of an explosive charge 13 made of nitroguanidine, an auxiliary charge made of PETN (pentaerythritol tetranitrate), and a bridgewire type detonator 12.
These explosive components are housed within an explosive charge holding assembly made of a plastic, such as acrylic resin, which serves multiple functions. The main parts of this assembly are:
It is a generally cylindrical cup 8 having a flange 9 at one end for axially positioning the explosive charge 13,14. Inside the cup 8 there is optionally a frusto-conical central part 10 whose cross-sectional area increases gradually towards the flange 9 (i.e. towards the tapered end 6 of the sleeve 5). can be provided. The central portion 10 encloses the explosive charge 13 in the sleeve 5 to achieve optimal welding performance.
serves to shape the explosive charge so as to gradually taper along the tapered portion of the explosive charge, thereby gradually reducing the amount of the explosive charge. At the other end of the cup 8, opposite to the side with the flange 9, there is fitted a closing cap 11 for sealing off the explosive charge, in which a bridge wire detonator 12 is held. This explosive charge holding assembly 8, 9, 1
0,11 are advantageously made of acrylic resin. As shown in FIG. 3, when the explosive charge holding assembly is detonated, the tapered portion of the sleeve 5 is expanded and welded by the explosive action to the inner surface of the tube 1, as indicated at 15. This is achieved without the aid of external mechanical supports, ie at a location remote from the tube sheet 2 or the tube support plate 3. Moreover, according to the present invention, the deformation or bulge of the sleeve 5 and the tube 1 at the welded portion 15 is minimized, and the increase in the outer diameter of the tube 1 is kept to approximately 17%. Surrounding the tube with an aqueous environment, such as by simply applying water to the outer periphery of the tube 1, can even further reduce tube bulge by about 30%. Besides water, other aqueous environments such as ice or aqueous solutions can also be used for this purpose. Setting up such an aqueous environment is easy, especially in the case of a heat exchanger. That is, in the case of a heat exchanger, water may be allowed to flow on the surface of the tube plate or tube support plate of the heat exchanger during the explosive welding process, and such water will not have any harmful effect on the welded part of the sleeve. can be easily removed. By adhering to certain parameters, the tapered section of the sleeve can be removed without rupturing the tube, even when welding is carried out at locations remote from external mechanical supports, such as the tube sheet or tube support plate. can be welded to the inner surface of the tube by explosive action. As used herein, "separation" refers to the distance that the sleeve must travel after detonation of the explosive before it contacts the inner surface of the tube. In the case of tubes such as heat exchangers, this spacing is 1/6 of the wall thickness of the sleeve.
A range of .about.2 times is advantageous. This spacing establishes an annular space between the sleeve and the tube. The separation must be a sufficient distance to displace the sleeve with sufficient velocity to create an impact pressure large enough for the sleeve to achieve welding with the tube. It has also been recognized that the mass of the sleeve must be less than the mass of the tube.
This is determined in relation to the wall thickness of the sleeve, assuming that the wall thickness and shape of the tube are constant. According to the present invention, the sleeve wall thickness must taper to about 60% to 75% of the tube wall thickness to achieve an acceptable weld. As previously mentioned, tapering the portion of the sleeve to be welded to the inner surface of the tube is also an important element of the invention. Tests have shown that satisfactory results can be obtained with a taper of 1° to 5.7° on the sleeve, but the best results have been obtained with a taper angle of 3° to 4.5°. Tapering the sleeve provides several advantages. First, the taper reduces the mass of the sleeve to be welded. This reduces the amount of explosive needed to weld the sleeve and thus reduces the amount of tube deformation. Second, the taper increases the angle of impact between the flyer and the substrate. This angle of impact is important in creating an explosive jet that removes surface oxides and is important in creating a corrugated weld interface due to the plastic flow of the tube and sleeve material upon impact. be. Third
Additionally, by tapering the sleeve, a continuously increasing separation distance is established, thereby providing better welding conditions. It is also important to select the appropriate amount of explosive charge. The amount of explosive charge required is directly proportional to the amount of flyer that must be discharged to accomplish the weld. Therefore, the amount (total weight) of the explosive charge (C) is the mass of the sleeve (M) for a given length of the explosive charge.
It is expressed by the ratio C/M. This ratio is obtained by dividing the total weight of the explosive charge (C) by the mass of the sleeve of length (M) corresponding to the given length of the explosive charge. When nitroguanidine is used as an explosive,
The density of the explosive charge that gives the best results is 0.45
It was ~0.65g/ ^cm3 . The total weight of the explosive charge includes:
Also includes an auxiliary charge consisting of PETN. The amount and location of the auxiliary charge is important both in starting the welding process and in obtaining a good quality weld. The best results were obtained with a ratio of total weight of explosive per unit weight of sleeve, ie, a C/M ratio of 0.25 to 0.43.
Proper C/M ratios were maintained by shaping the explosive charge into a specific shape using the tapered conical center portion of the plastic explosive charge holding assembly described above. However, this C/M ratio was not constant over the entire length of the explosive charge. According to the invention, 0.2 to 0.7 to obtain an acceptable weld.
A range of C/M ratios can be used. It has also been found that sleeves made of Inconel (registered trademark of International Nickel Company) alloy 600 or 690 can be welded to tubes made of Inconel alloy 600. In that case, the wall thickness of the sleeve is
0.762~1.4224mm (0.030~0.056in), the inner diameter of the tube is 19.685mm (0.775in), and the outer diameter is 22.225mm
(0.875in). The explosive action of the explosive caused the tube to bulge to an outer diameter of 25.4 mm (1 in).
When water is added to the outer circumference of the tube, the tube bulges out by approximately 30%.
reduced, its bulged final outer diameter is approximately 24.384mm
(0.960in). Inconel alloy in two different sizes below
The parameters of the sleeve for repairing the 600 heat exchange tube were selected as follows. Parameters for other sizes of tubes and tubes and sleeves made of other materials may be readily selected as an extension of the data below.

Table: Final Outer Diameter Effects As can be seen from the above description, the explosive action welding process of the present invention provides an advantageous alternative to the time-consuming brazing methods used heretofore. Brazing methods are generally time consuming, complex, and require a lot of equipment. Unlike brazing, explosive welding uses explosives that can be detonated remotely, allowing the operator to carry out the welding process at a distance from where the sleeve is to be welded (remote location). Allows most to be implemented. This is particularly advantageous when working in areas of high radioactivity, such as in heat exchangers of nuclear steam generators. This is because workers can perform welding operations at remote locations, thereby reducing the amount of radiation they are exposed to.

[Brief explanation of drawings]

FIG. 1 is an elevational view, partially in section, showing a plurality of tubes supported between a tube sheet and a tube support plate, with a sleeve inserted into one of the tubes to repair a damaged section therebetween; FIG. Show the place. FIG. 2 is an enlarged partial cross-sectional view showing one end of a sleeve in a pipe to be repaired, and an explosive is charged in the sleeve for welding the sleeve. Figure 3 shows
FIG. 3 is a cross-sectional view showing the end of the sleeve welded to the inner surface of the tube by explosive action; Figure 4 is a graph showing the relationship between the wetness of the sleeve and the layer weight of the explosive insert required to inflate the sleeve, as well as the conditions required to weld the sleeve to the inner surface of the tube. be. DESCRIPTION OF SYMBOLS 1... Pipe, 5... Sleeve, 7... Tapered outer peripheral surface (tapered part), 8... Cup, 9... Positioning flange, 10... Tapered truncated conical center part, 11
... closed cap, 12 ... detonator, 13 ... main explosive, 14 ... auxiliary charge.

Claims (1)

Claims: 1. A method for welding a sleeve to the inner surface of a tube by explosive action, comprising: providing a sleeve including an enlarged diameter extension and a tapered portion having a wall thickness tapering toward one end; positioning the sleeve within the tube;
positioning the tapered portion of the sleeve within the tube at a location remote from an external mechanical support for the tube; and loading a cup containing an explosive charge into the sleeve. providing the cup with a frusto-conical center portion for tapering the explosive charge so that the amount of the explosive charge is gradually reduced along a tapered portion of the tapered wall thickness of the sleeve; , aligning the sleeve within the tube to establish an annular spacing between the sleeve and the tube; and detonating the explosive charge to expand and weld the sleeve to the tube. A welding method consisting of a process. 2. The step of aligning the sleeve sleeve within the pipe includes:
The sleeve is positioned radially apart from the inner surface of the tube so that a separation distance of 1/6 to 2 times the wall thickness of the sleeve is established between the sleeve and the tube in a region adjacent to the tapered portion. A welding method according to claim 1, characterized in that the welding method comprises: 3. The welding method according to claim 1, wherein the tapered portion of the sleeve has an extended outer surface with a taper angle of 1° to 5.7°. 4. The welding method according to claim 3, wherein the taper angle is 3° to 4.5°. 5 The sleeve has a thickness of about 60% to about 60% of the wall thickness of the tube.
The welding method according to claim 1, characterized in that the welding method has a wall thickness of 100%. 6. Welding according to claim 1, characterized in that it includes the step of surrounding the tube in an aqueous environment to reduce the amount of bulge in the tube when the sleeve is welded to the tube by explosive action. Method. 7. The welding method according to claim 6, wherein the aqueous environment is water. 8. The welding method according to claim 6, wherein the aqueous environment is ice. 9. The welding method according to claim 6, wherein the aqueous environment is an aqueous solution. 10 A device for repairing a damaged part of a pipe, which has an expanded diameter extension and an outer surface extended at a taper angle of 1° to 5.7° to form a tapered wall thickness,
a sleeve adapted to be positioned within the tube over the damaged portion; and a locating flange adapted to engage an inner surface of the sleeve for axial positioning within the sleeve. an explosive charge retaining assembly disposed within a tapered portion of the sleeve; and an explosive charge retaining assembly disposed within the tapered portion so as to weld the tapered portion of the sleeve to the inner surface of the tube by explosive action when detonated. and a quantity of explosive charge held by said explosive charge holding assembly, said quantity (C) of said explosive charge corresponding to a predetermined length of said explosive charge. A repair device characterized in that the amount is proportional to the mass (M) of the sleeve to be removed, and the ratio C/M is within the range of 0.2 to 0.7. 11 the explosive charge retaining assembly includes a cup for receiving and positioning the explosive charge within the tapered portion of the sleeve; having a conical central portion shaping the explosive charge to gradually taper along the section, thereby progressively reducing the amount of the explosive charge; 11. The repair device according to claim 10, wherein the repair device is fixed. 12. Claim characterized in that a closed cap for covering the explosive charge is provided in the cup, and a detonator for the explosive charge is held in the cap. range 1
The repair device according to item 1. 13. The repair device according to claim 12, characterized in that an auxiliary charge is provided between the detonator and the explosive charge. 14. The repair device according to claim 10, wherein the taper angle is 3° to 4.5°. 15 The enlarged diameter extension of the sleeve has a wall thickness of 1/1 of the wall thickness of the sleeve between the sleeve and the inner surface of the tube.
Claim 12, characterized in that it is dimensioned to set a separation distance of 6 to 2 times.
Repair equipment as described in section. 16 The sleeve has a diameter of 0.762 to 1.4224 mm (0.03 to
13. The repair device according to claim 12, wherein the repair device has a wall thickness of 0.056 inches. 17. The repair device according to claim 16, wherein the tube is made of Inconel alloy 600, and the sleeve is made of Inconel alloy 600 or Inconel alloy 690.