JPH0454878B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a repaired heat exchange tube in which a corrosion-resistant inner tube is closely attached to the corroded inner surface of the heat exchange tube via a filler, and a repair method. [Prior Art] Copper alloys with good thermal conductivity are widely used as materials for heat exchange tubes. However, when copper alloy pipes are used with corrosive fluids such as seawater as working fluids, the inner surface of the pipes that comes into contact with it corrodes.
As it progresses, the wall thickness decreases, and when this thinning exceeds a certain limit, it becomes necessary to replace the tube. In this case, it may be possible to use a corrosion-resistant metal tube, such as a titanium tube, but this is much more expensive than a copper alloy tube, so when using it, it is necessary to make the wall thicker than the tube. I have no choice but to make it thinner. In such a case, the spacing between the tube support plates that supported the original tube will remain the same, so the new tube will not be compatible with the new tube, and there is a risk of damage due to vibration. It cannot be exchanged. Therefore, the pipe is usually replaced with a new copper alloy pipe made of the same material as the original pipe. [Problems to be solved by the invention] However, such conventional maintenance does not change the situation in which the pipes are subject to corrosion, so it is necessary to replace the pipes with new ones after a certain period of use. Become. Therefore, in order to save labor on maintenance work that requires such manual labor, we developed a system that can withstand the corrosive environment even when using corrosive working fluids such as seawater, enables semi-permanent use, and has good heat transfer performance. hold,
It was also desired that it could be repaired at low cost. This invention solves these technical problems. Means for Solving the Problems] As schematically shown in FIG. This is a double tube for heat exchange in which the inner tube 2 is brought into close contact with the inner tube 2. The heat exchange tube 1 is made of a material conventionally used for heat exchange such as a copper alloy, and its inner surface is corroded during use. The easily fusible filler 3 fills the recesses formed by corrosion on the inner surface of the outer tube, improves the contact between the outer tube and the inner tube, and has the effect of increasing heat transfer. Examples of such easily meltable fillers include easily meltable metal fillers and oil-based fillers. As the easily meltable alloy filler, low melting point alloys such as Wood, Lipovitz, Newton, and Dulce can be used. Examples of the oil-based filler include lubricating grease, thermally conductive grease containing a thermally conductive material such as carbon or fine metal powder to improve contact thermal conductivity, and butter. The corrosion-resistant inner tube 2 is selected from suitable known corrosion-resistant metals depending on the conditions of use, but is preferably made of titanium, and may be either a welded tube or a drawn tube, but a welded titanium tube is particularly preferred. Next, we will discuss the repair method which is the second invention.
Figure 5 will be explained. FIG. 2 shows an embodiment in which heat exchange tubes are repaired directly within a heat exchange device according to the present invention. (1) Clean the inner surface of the heat exchange tube 1 in service using carborundum ball cleaning, sandblasting, jet water cleaning, chemical cleaning, etc., or a combination thereof, to remove as much corrosion products as possible from the inner surface. . After cleaning, remove moisture inside the pipe by air purge, felt hammering, etc. (2) As shown in FIGS. 3 and 4, the easily fusible filler 3 is attached to the recess 5 provided along the welded portion 4 in the axial direction of the outer surface of the corrosion-resistant inner tube 2. Since this easily fusible filler 3 fills the corroded recesses on the inner surface of the outer tube, the amount used varies depending on the corrosion state of the heat exchange tube 1, which is the outer tube, but it is distributed on the average around the circumferential outer surface of the inner tube. It is preferable to set it to 0.3 mmt or less. The corrosion-resistant inner tube 2 with the filler thus prepared is inserted into the cleaned heat exchange tube 1. At this time, the outer diameter of the corrosion-resistant inner tube 2 is originally slightly smaller than the inner diameter of the heat exchange tube 1, which is the outer tube, for example.
Although it is made smaller by about 1.0 to 1.5 mm, as mentioned above, the recess is formed in the axial direction of the inner tube, so
The effective outer diameter becomes smaller and the insertion process becomes easier. (3) The heat medium is circulated through the corrosion-resistant inner tube 2 through the pump 6 to melt the easily meltable filler 3. (4) Close the valve 7 and pressurize the inner surface of the corrosion-resistant inner tube 2 with the plunger 8 to bring it into close contact with the inner surface of the heat exchange tube 1. (This hydraulic pressure pipe expansion method is described, for example, in Japanese Patent Publication No. 47616/1983.) The pressurization curve in this case is as shown in FIG. In FIG. 5, the corrosion-resistant inner tube 2 expands between A and B, and at point B, the corrosion-resistant inner tube 2 expands to the filler 3.
It comes in contact with the heat exchange tube 1, which becomes the outer tube, through the tube. Pressurization is stopped slightly beyond point B, and after maintaining this pressure, the pressure is released. In addition to the hydraulic pipe expansion method described above, the inner and outer pipes are brought into close contact with each other.
By using a heating medium, the adhesion can be increased due to the slight difference in expansion between the inner and outer tubes. [Example] Example 1 Aluminum brass tube (Albrac tube manufactured by Sumitomo Light Metal Industries) 25, 4φ x 1.25t x 2200mm removed from a heat exchange device that uses moderately contaminated seawater as cooling water
The inner surface was cleaned by sandblasting. On the other hand, a 0.3 mmt titanium welded pipe was made with a recessed part along the welded part, and an amount of wood alloy filler with an average thickness of 0.15 mmt was attached thereto and inserted into the aluminum brass pipe (Albrak pipe manufactured by Sumitomo Light Metal Industries). . The inner surface of this aluminum brass tube (Albrac tube manufactured by Sumitomo Light Metal Industries) was microscopically affected by intergranular corrosion, but macroscopically it was affected by pock-like contaminated seawater corrosion. Warm water at 90°C was passed through the inner tube and pressurized. The heat transfer performance of the various double-walled pipes manufactured in this way was measured using a test device that condenses low-pressure steam, and compared with new aluminum brass pipes (Albrak new pipes manufactured by Sumitomo Light Metal Industries) as a standard. The results are shown in Table 1.

[Table] Example 2 Aluminum brass tube 25, 4φ x 1.25t extracted from a heat exchange device that uses moderately contaminated seawater as cooling water
The inner surface of ×2200 mm was cleaned by sandblasting. On the other hand, a 0.3 mmt titanium welded tube was provided with a recessed portion along the welded portion, and lubricating grease containing fine copper powder in an average amount of 0.15 mmt was placed in the recessed portion and inserted into the aluminum brass tube. The inner surface of this aluminum brass tube was microscopically affected by intergranular corrosion, but macroscopically it was affected by pock-like contaminated seawater corrosion. Warm water at 90°C was passed through the inner tube and pressurized. The heat transfer performance of the various double-walled pipes manufactured in this way was measured using a test device that condenses low-pressure steam, and compared with new aluminum-brass pipes as a standard. The results are shown in Table 1.

[Table] [Effects of the invention] By using a corrosion-resistant metal pipe for the inner pipe of the repaired double heat exchange pipe of this invention, the usable period is simply extended and maintenance work can be saved. As is clear from Tables 1 and 2, the easily soluble filler on the outer surface of the corrosion-resistant inner tube fills the space between the inner tube and the outer tube with a corroded inner surface, improving the contact between the two and improving heat transfer. will also be improved. Further, by using a heating medium in the repair method, remarkable effects such as being able to increase the adhesion between the inner tube and the outer tube due to the difference in thermal expansion between the two can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a repaired heat exchange tube of the present invention, FIG. 2 is a diagram showing an example of a method for repairing a heat exchange tube of the present invention, and FIG. 3 is a diagram showing an example of a method for repairing a heat exchange tube of the present invention. FIG. 4 is a front view showing how to install the same A-A.
The cross-sectional view, FIG. 5, is a diagram showing a pressurization curve. DESCRIPTION OF SYMBOLS 1... Heat exchange tube, 1a... Corroded inner surface, 2... Corrosion-resistant inner tube, 3... Easily fusible filler, 4... Welded part, 5... Recessed part, 6... Pump, 7... Valve, 8... Plunger.

Claims (1)

[Scope of Claims] 1. A repaired heat exchanger tube characterized in that an inner tube made of a corrosion-resistant metal is brought into close contact with the corroded inner surface of a heat exchange tube via a fusible filler provided on the outer peripheral surface of the inner tube. exchange tube. 2. Inserting an inner tube made of a corrosion-resistant metal and having an easily meltable filler into a recess provided on the outer surface of the heat exchange tube having a corroded inner surface, heating the inner tube with a heating medium to melt the filler, A method for repairing a heat exchange tube, comprising: then pressurizing the heating medium to bring the corrosion-resistant inner tube into close contact with the heat exchange tube.