JPH0835789A - Heat-exchanger and method for sealing its tube plate and heat-transfer pipe - Google Patents

Abstract

PURPOSE:To provide a heat-exchanger which is structured to prevent the occurrence of gap corrosion between the pipe hole wall of a tube plate and the outer surface of a heat-transfer pipe. CONSTITUTION:A main part 10 of a heat-exchanger comprises a tube plate 12, a heat-transfer pipe 16 inserted in a tube hole 14 of the tube plate 12, a fixed part 18 fixing the heat-transfer pipe 16 to the tube plate 12, and a sealing part 20 for the tube plate 12 and the heat-transfer pipe 16. A fixed part for the heat-transfer pipe and the tube plate consist of a means similar to a conventional heat-exchanger. The seal part is positioned at the opening edge part on the drum side of the pipe hole. Formation of the seal part is such that after the heat-transfer pipe is securely inserted in the pipe hole, laser beams are positioned above the seal part in such a state to approach the interior of the heat-transfer pipe from the channel side of the tube plate and the constituting metal of the heat-transfer pipe is molten in the constitution metal of the tube plate and mutually fused through laser welding throughout the whole periphery of the inner periphery of the heat-transfer-pipe. This constitution seals together the tube plate and the heattransfer pipe at the opening edge part on the drum side of the pipe hole throughout the whole of the outer periphery of the heat-transfer pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger having a sealing structure between a tube sheet and a heat transfer tube on the barrel side of the tube sheet, and a sealing method for forming the sealing structure. is there.

[0002]

2. Description of the Related Art Tube heat exchangers, especially multitubular heat exchangers,
In order to effectively use the thermal energy in the discharged fluid, it is widely used in various plants such as a chemical plant, an oil refinery plant or a petrochemical plant. The multi-tube heat exchanger is shown in Fig. 2.
As shown in (a), a fixed tube plate type heat exchanger having a structure in which a heat transfer tube bundle in which a large number of heat transfer tubes 16 are fixed by fixed tube plates 12 at both ends is housed in a case S, FIG. As shown in FIG. 2B), one tube plate 12A floats, and the other tube plate 12B is a fixed tube plate, or a floating head heat exchanger, or, as shown in FIG. There is a type of U-tube heat exchanger that is formed of tubes and the tubesheet is the fixed tubesheet 12 only.

The end portion of the heat transfer tube 16 is inserted into a tube hole 14 provided in the tube plate 12, and the tip portion thereof is as shown in FIG. 3 which is an enlarged area "d" in FIG. It is fixed to the tube sheet by means. The fixing means is a method of welding the tip portion of the heat transfer tube 16 to the tube sheet 12 as shown in FIG. 3A, or a method of welding the tip portion of the heat transfer tube 16 to the tube sheet 12 as shown in FIG. 3B. 3 (c), in order to suppress the distortion of the heat transfer tube due to the difference in heat capacity between the tube plate and the heat transfer tube, an annular groove 13 is formed around the tube hole of the tube plate. 4 (a) and 4 (b), after inserting the heat transfer tube 16 into the tube hole 14 provided with one or two annular grooves 15 as shown, and then expanding and fixing the tube. Also, as shown in (c), there is a method in which the tip portion is seal-welded to prevent leakage.

[0004]

However, in the conventional fixing method of the tube sheet and the heat transfer tube, when the corrosive fluid is flowing on the shell side of the heat exchanger, that is, outside the heat transfer tube, the heat exchanger is not used. During use, the corrosive fluid causes a slight gap between the heat transfer tube and the body side opening edge of the tube hole provided with the tube sheet as shown by A in FIGS. 3 (a), (b) and (c). Often penetrated between the wall of the tube hole and the outer surface of the heat transfer tube, causing crevice corrosion. Therefore, as shown in FIG. 5A, a method is provided in which an annular protruding portion B is provided at the body side opening edge portion of the tube hole 14 of the tube sheet 12, and the protruding portion B and the tip end portion of the heat transfer tube 16 are butt welded together. Alternatively, FIG.
As shown in (b), an annular groove C is provided around the body-side opening edge of the tube hole 14, and a method of butt welding the annular edge D inside the annular groove and the tip of the heat transfer tube 16 is adopted. However, this increases the cost of machining the tube sheet,
For economic reasons, it has been difficult to put it into practical use in general industrial applications apart from special applications.

Therefore, an object of the present invention is to provide a heat exchanger provided with a structure which prevents crevice corrosion between the tube hole wall of the tube sheet and the outer surface of the heat transfer tube by an economical means. .

[0006]

In order to achieve the above object, the heat exchanger according to the present invention has a heat transfer tube inserted at least halfway through a tube hole penetrating the tube sheet. In a heat exchanger in which the end of the heat tube is welded to the tube plate or the end of the heat transfer tube is expanded and fixed to the tube plate, the body side opening edge of the tube hole and the tube wall of the heat transfer tube are It is characterized in that a sealing structure formed by welding from the inside of the heat transfer tube so as to be fused is provided between the tube sheet and the heat transfer tube.

Further, according to the method of sealing a tube plate and a heat transfer tube of a heat exchanger according to the present invention, the heat transfer tube is inserted at least halfway through a tube hole provided in the tube plate, and an end portion of the inserted heat transfer tube. In a heat exchanger that is fixed to the tube sheet by welding or expanding the tube sheet to the tube sheet, the body side opening edge of the tube hole of the tube sheet and the tube wall of the heat transfer tube are fused together. It is characterized in that the tube plate and the heat transfer tube are sealed by laser welding from the inside of the heat transfer tube.

Conventional methods such as the TIG welding method are difficult to apply when the heat capacities of the members to be joined are remarkably different, because the heat generated by the reaction is transferred by heat conduction to melt and fuse the members. For example, in the conventional method such as the TIG welding method, when the heat capacity of the heat transfer tube is significantly smaller than the heat capacity of the tube sheet, such as fusion between the heat transfer tube and the tube sheet, the heat transfer tube metal is melted. , It is difficult to uniformly melt the molten heat transfer tube metal into the tube sheet metal, and fusion failure or the like is likely to occur during welding. By the way, laser welding is welding using high-density energy, and even if there is a difference in heat capacity between the members to be joined, it is possible to melt necessary parts of the members with the energy of the laser beam. Therefore, it is suitable for forming the sealing structure of the tube plate and the heat transfer tube of the heat exchanger according to the present invention. Also, laser welding is YAG
It is characterized by being applied by a laser. that is,
This is because YAG laser welding is suitable for welding thin plates such as welding of heat transfer tubes. INDUSTRIAL APPLICABILITY The present invention can be applied to a heat exchanger in which a heat transfer tube is fixed to a tube plate without limitation on the number of heat transfer tubes.

[0009]

In the present invention, since the gap between the opening side of the tube hole on the cylinder side and the outer surface of the heat transfer tube is sealed, the corrosive fluid flowing inside the cylinder on the outer side of the heat transfer tube is protected from the tube hole wall and the outer surface of the heat transfer tube. Can't break in between. Therefore, crevice corrosion due to the corrosive fluid is prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view of a heat transfer tube showing a configuration of a main part of a heat exchanger according to the present invention. FIG. 1 (a) shows a front end of the heat transfer tube flush with a channel side surface of a tube sheet. Combined, fixed heat transfer tube, and Fig. 1
(B) shows the case where the tip of the heat transfer tube is inserted partway into the tube hole of the tube plate and fixed there. The main part 10 of the heat exchanger according to the present invention includes a tube sheet 12, a heat transfer tube 16 inserted into a tube hole 14 of the tube sheet 12, a fixing portion 18 that fixes the heat transfer tube 16 to the tube sheet 12, and a tube. It is composed of a plate 12 and a sealing portion 20 for the heat transfer tube 16. The fixed portion 18 between the heat transfer tube 16 and the tube plate 12 is configured by the same means as the conventional heat exchanger shown in FIGS. 3 and 4.

The sealing portion 20 is located at the body side opening edge of the tube hole 14 of the tube sheet 12. The sealing section 20 inserts and fixes the heat transfer tube 16 into the tube hole 14, and then approaches the inside of the heat transfer tube 16 from the channel side of the tube sheet 12 to position the laser beam on the sealing section 20. It is formed by melting the constituent metals of the heat transfer tube 16 into the constituent metals of the tube sheet 12 by laser welding over the entire inner circumference of the tube 16 and fusing them together. Thereby, the tube sheet 12 and the heat transfer tube 16 are
It is possible to seal the entire circumference of the heat transfer tube 16 at the trunk side opening edge of the tube hole 14.

In carrying out laser welding, it is desirable to use a YAG laser suitable for requiring a thin member. The YAG laser is a kind of solid-state laser, and is laser oscillated using YAG (Y ₃ Al ₅ O ₁₂ , yttrium aluminum garnet) as a laser crystal.
The laser beam is guided from the YAG laser oscillating device to a desired place by the optical fiber, is condensed by the condenser lens provided at the tip of the optical fiber, and is radiated to the welding portion. When laser welding a carbon steel heat transfer tube with an outer diameter of 25.4 mm and a wall thickness of 1.2 mm to a carbon steel tube plate with a thickness of 50 mm, output 8
If a YAG laser of 00w is used, welding can be performed at a welding speed of 200 mm / min.

Depending on the operating conditions of the heat exchanger, the heat transfer tube may be more likely to thermally expand and contract than the tube plate. In a heat exchanger that needs to be operated under such conditions, when adopting a means for fixing the heat transfer tube to the tube sheet by welding,
As shown in FIG. 1 (b), the insertion of the heat transfer tube is stopped in the middle of the tube hole, and the tip of the heat transfer tube is welded there to shorten the distance between the welding line of the sealing part and the welding line of the fixed part. Therefore, it is desirable to prevent the occurrence of cracks due to the generation of thermal stress. Alternatively, a method of welding in a spiral shape between welding lines may be adopted.

[0014]

According to the structure of the present invention, even when a corrosive fluid is flowing on the barrel side of the heat exchanger, the heat transfer tube and the tube plate are sealed at the barrel side opening edge of the tube hole. Therefore, it is possible to prevent the corrosive fluid from penetrating between the heat transfer tube and the wall of the tube hole through the gap between the heat transfer tube and the tube hole of the tube plate to cause crevice corrosion. Further, by laser-welding the tube plate and the heat transfer tube from the inside of the heat transfer tube so as to fuse the body side opening edge of the tube hole of the tube plate and the tube wall of the heat transfer tube, it is easy to In addition, the tube sheet and the heat transfer tube can be economically sealed.

[Brief description of drawings]

FIG. 1 (a) and FIG. 1 (b) are cross-sectional views in the longitudinal direction of a heat transfer tube showing a main part of a heat exchanger according to the present invention.

2 (a), 2 (b) and 2 (c) are longitudinal sectional views of various heat exchangers.

3 (a), (b), (c) and (d) are cross-sectional views showing a method of fixing a heat transfer tube to a tube plate.

4 (a), (b) and (c) are cross-sectional views showing seal welding when a heat transfer tube is fixed to a tube sheet by expansion.

5A and 5B are cross-sectional views showing a conventional sealing method between a heat transfer tube and a tube sheet.

[Explanation of symbols]

 10 Main parts of heat exchanger according to the present invention 12 Tube plate 13 Tube plate annular groove 14 Tube hole 15 Tube hole annular groove 16 Heat transfer tube 18 Fixing section 20 Sealing section

Claims (3)

[Claims] 1. A heat transfer tube is inserted at least halfway through a tube hole penetrating the tube plate, the end of the inserted heat transfer tube is welded to the tube plate, or the end of the heat transfer tube is expanded. In the heat exchanger that is fixed to the tube plate with a tube plate, the sealing structure is formed by welding from the inside of the heat transfer tube so that the body side opening edge of the tube hole and the tube wall of the heat transfer tube are fused. A heat exchanger provided between the heat transfer tube and the heat transfer tube. 2. A heat transfer tube is inserted at least halfway through a tube hole penetrating the tube plate, the end of the inserted heat transfer tube is welded to the tube plate, or the end of the heat transfer tube is expanded. In the heat exchanger fixed to the tube plate, the tube plate and the heat transfer tube are laser-welded from the inside of the heat transfer tube so that the body side opening edge of the tube hole and the tube wall of the heat transfer tube are fused. And a gap between the tube plate and the heat transfer tube of a heat exchanger. 3. The method of sealing a tube plate and a heat transfer tube of a heat exchanger according to claim 2, wherein the laser welding is performed by a YAG laser.