JP2014040929A - Method of manufacturing heat exchanger, and heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily prevent crevice corrosion by closing a clearance gap between a tube plate and a heat transfer tube without causing poor welding.SOLUTION: In a method of manufacturing a heat exchanger in which a tip portion of a heat transfer tube 4 is welded and fixed to a tube plate 2, a resin coating material 6 is applied to an outer surface excluding a melting portion 5 by welding, of the heat transfer tube 4, the heat transfer tube 4 coated with the resin coating material 6 is inserted into a tube hole 3 to weld its tip portion, a clearance gap 7 between an anti-shell side opening edge portion 3A of the tube hole 3 and the heat transfer tube 4 is sealed by the welding, and a clearance gap 7 between a shell-side opening edge portion 3B of the tube hole 3 and the heat transfer tube 4 is sealed by the coated resin coating material 6.

Description

  The present invention relates to a heat exchanger manufacturing method and a heat exchanger.

  In the shell-and-tube heat exchanger, there is a gap between the tube sheet and the heat transfer tube, and crevice corrosion occurs when concentration occurs in the gap. For the purpose of preventing this crevice corrosion, a method of welding after expanding the heat transfer tube to close the gap between the tube sheet and the heat transfer tube is known (see Patent Document 1).

JP-A-8-35789

  According to the method of welding after expanding the heat transfer tube, the gas held inside during tube expansion is released as bubbles during welding, resulting in poor welding.

  The main problem to be solved by the present invention is to close the gap between the tube sheet and the heat transfer tube without causing poor welding and to easily prevent crevice corrosion. Moreover, a sub subject is to shorten the manufacturing time of a heat exchanger.

  This invention was made in order to solve the said subject, and the invention of Claim 1 inserts a heat exchanger tube into the tube hole provided by penetrating the tube plate, and the front-end | tip of the said heat exchanger tube inserted In a method of manufacturing a heat exchanger in which a part is welded and fixed to the tube plate, a resin paint is applied to an outer surface excluding a melted part by welding of the heat transfer tube, and the heat transfer tube to which the resin paint is applied is connected to the tube hole. And the end of the tube hole is welded to seal the gap between the tube-hole-side opening edge of the tube hole and the heat transfer tube, and the tube-side opening edge of the tube hole is coated with the applied resin paint. A gap with the heat transfer tube is sealed.

  According to the first aspect of the present invention, since the gap between the tube-side opening edge of the tube hole and the heat transfer tube, which is difficult to weld, is sealed with the resin paint, crevice corrosion can be easily prevented. In addition, the gap is sealed without performing pipe expansion, and the resin paint is applied to the outer surface excluding the melted part due to welding of the heat transfer pipe, so that it is possible to prevent welding failure due to resin paint mixing. .

  The invention according to claim 2 is characterized in that, in claim 1, the resin paint is dried by heating accompanying the welding.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, since the resin coating is dried by heating accompanying welding, the time required for drying the resin coating can be shortened, and the heat exchanger There is an effect that it is possible to shorten the time required for the manufacture.

Furthermore, the invention according to claim 3 is a heat exchanger in which a heat transfer tube is inserted into a tube hole penetrating through the tube plate, and a distal end portion of the inserted heat transfer tube is welded and fixed to the tube plate. The heat transfer tube having a resin coating applied to the outer surface thereof excluding the melted portion due to welding of the heat transfer tube is inserted into the tube hole, and the tube-hole-side opening edge portion of the tube hole is welded to the heat transfer tube by welding And the heat transfer tube are sealed, and the resin coating paints the gap between the tube-side opening edge of the tube hole and the heat transfer tube.

  According to invention of Claim 3, since the clearance gap between the trunk side opening edge part of a pipe hole and the heat exchanger tube which are difficult to weld is sealed with the apply | coated resin coating material, crevice corrosion can be prevented easily. it can. Also, the present invention provides a heat exchanger that seals the gap without expanding the pipe and applies a resin paint to the outer surface excluding the melted part due to welding of the heat transfer pipe, thereby preventing poor welding due to resin paint mixing. There is an effect that can be.

  According to the present invention, the gap between the tube sheet and the heat transfer tube can be closed without causing poor welding, and crevice corrosion can be easily prevented.

It is a schematic diagram of the principal part longitudinal cross-section of the heat exchanger manufactured by the Example of the manufacturing method of the heat exchanger of this invention. It is a schematic diagram of the principal part longitudinal cross-section of the heat exchanger explaining one manufacturing process of the Example. It is a schematic diagram of the principal part longitudinal cross-section of the heat exchanger explaining the other manufacturing process of the Example.

  An embodiment of a method for manufacturing a heat exchanger according to the present invention will be described with reference to FIGS. First, the heat exchanger 1 to which the manufacturing method of the embodiment is applied will be described. As shown in FIG. 1, the heat exchanger 1 is configured by arranging a pair of tube plates 2 and 2 (only one tube plate is shown) with a space in a heat exchanger cylinder (not shown). ing.

  Then, a large number of heat transfer tubes 4, 4,... Are inserted up to substantially the upper ends of a large number of tube holes 3, 3,. It is manufactured by welding the upper end portion of each heat transfer tube 4 to the tube plate 2. The material of each tube plate 2 and each heat transfer tube 4 is the same material (for example, SUS), but is not limited thereto, and can be a different material or a material that can be welded.

  The heat exchanger 1 is typically a shell and tube heat exchanger, but is not limited thereto, and can be a steam boiler can. In the shell-and-tube heat exchanger, a first fluid Y made of a corrosive liquid (for example, water) circulates outside each heat transfer tube 4, and the inside of each heat transfer tube 4 is made of a gas or liquid such as steam. It is assumed that the two fluid Z circulates.

  The manufacturing method of the embodiment of the present invention is characterized by the following. That is, as shown in FIG. 2, first, as a resin paint, a predetermined range H of the trunk side opening edge 3 </ b> B of the tube hole 3 of the outer surface 4 </ b> A excluding the fusion part 5 (see FIG. 1) by welding of each heat transfer tube 4 The fluororesin paint 6 is applied. The melting portion 5 refers to a portion where the heat transfer tube 4 is melted by welding described later, and the depth of penetration in the tube axis direction is, for example, about 1 to 2 mm. Therefore, the fluororesin paint 6 is not applied to the outer surface 4A excluding the melted portion 5 in a range of 1 to 2 mm from the tip of the heat transfer tube 4. Welding is TIG welding in this embodiment, but is not limited to this, and can fill the gap 7 between the tube-hole-side opening edge 3A of the tube hole 3 and the heat transfer tube 4 such as laser welding. Anything is fine.

  Next, as shown in FIG. 2, the heat transfer tube 4 coated with the fluororesin paint 6 thicker than the gap 7 is inserted into the tube hole 3 in the direction indicated by the arrow X before the fluororesin paint 6 is dried. Then, as shown in FIG. 3, the thicker portion 6 </ b> A having a larger thickness is formed by scraping a portion thicker than the gap 7 of the fluororesin paint 6 by the trunk side opening edge 3 </ b> B of the tube hole 3. The thick portion 6A is formed by inserting the heat transfer tube 4 into the tube hole 3 before the fluororesin paint 6 is dried, so that the gap 7 between the trunk side opening edge 3B of the tube hole 3 and the heat transfer tube 4 is formed. Formed to effectively fill. The heat transfer tube 4 is inserted until the tip thereof is substantially flush with the anti-trunk side surface 2A of the tube plate 2.

  Then, as shown in FIG. 3, the welding torch 8 is turned R and the tip of the heat transfer tube 4 is welded to form the annular molten portion 5 shown in FIG. 1 by the arc from the welding torch 8. The melted portion 5 seals the gap 7 between the opposite barrel side opening edge 3 </ b> A of the tube hole 3 and the heat transfer tube 4. The reason why the melted portion 5 swells from the barrel side surface 2B of the tube sheet 2 is that welding is performed with a filler (not shown) during welding by the welding torch 8.

  In this welding, if a component of the fluororesin paint 6 is mixed into the melted part 5, a welding defect occurs. In the method according to this embodiment, since the portion that becomes the melted portion 5 is excluded from the range where the fluororesin paint 6 on the outer surface 4A is applied, it is possible to prevent the fluororesin paint 6 from being mixed into the melted portion 5 and Generation of weld defects can be prevented. The application range H of the fluororesin paint 6 is limited in the tube axis direction (a predetermined range in the tube axis direction sandwiching the body side surface 2B of the tube plate 2 at the body side opening edge 3B of the tube hole 3). Therefore, it is possible to prevent the fluororesin paint 6 from becoming a thermal resistance and maintain the desired heat transfer performance as compared with the case where the fluororesin paint 6 is applied to the heat transfer tube 4 by dipping. Can do.

  On the other hand, the gap 7 between the trunk-side opening edge 3B of the tube hole 3 and the heat transfer tube 4 is sealed with the applied fluororesin paint 6 as described above. Since the gap 7 between the cylinder side opening edge 3B of the tube hole 3 and the heat transfer tube 4 is sealed by the fluororesin paint 6, the crevice corrosion generated by the concentration of the corrosive liquid entering from the gap 7 is prevented. Can be prevented.

  In the sealing with the fluororesin paint 6, in this embodiment, heating accompanying the welding of the tip portion (depending on the welding method, for example, it is heated to about 300 to 1000 ° C. at a distance of 1 mm from the welding portion. ), The applied fluororesin paint 6 is dried. The natural drying of the fluororesin paint takes about 8 to 12 hours, but according to the method of the embodiment, the fluororesin paint is sintered and dried at 300 to 400 ° C. You can save time. As a result, the time required for manufacturing the heat exchanger 1 can be shortened.

  The present invention is not limited to the above embodiments. For example, in the above embodiment, a fluororesin paint is used as the resin paint, but the resin paint has a function of sealing the gap 7, a function of applying to the surface of the heat transfer tube 4, and natural drying or heating. Any material having a function of curing may be used. In addition to the fluororesin paint, for example, an epoxy resin paint, a polyurethane resin paint, and an acrylic silicon resin paint that are volatile polymerized and dried similarly to the fluororesin paint can be used.

DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Tube sheet 3 Tube hole 3A Anti-trunk side opening edge 3B Trunk side opening edge 4 Heat transfer tube 5 Melting part 6 Fluoro resin paint (resin paint)
7 Clearance

Claims (3)

In a method of manufacturing a heat exchanger, a heat transfer tube is inserted into a tube hole provided through the tube plate, and the tip of the inserted heat transfer tube is welded and fixed to the tube plate.
Applying a resin paint on the outer surface excluding the melted part by welding the heat transfer tube,
Inserting the heat transfer tube coated with the resin paint into the tube hole and welding its tip,
Sealing the gap between the tube-side opening edge of the tube hole and the heat transfer tube by welding, and sealing the gap between the tube-side opening edge of the tube hole and the heat transfer tube with the applied resin paint The manufacturing method of the heat exchanger characterized by these.   The method for manufacturing a heat exchanger according to claim 1, wherein the resin paint is dried by heating accompanying the welding. In a heat exchanger that inserts a heat transfer tube into a tube hole provided through the tube plate, and welds and fixes the tip of the inserted heat transfer tube to the tube plate,
The heat transfer tube coated with a resin paint on the outer surface excluding the melted portion by welding of the heat transfer tube is inserted into the tube hole,
Sealing the gap between the tube-hole-side opening edge of the tube hole and the heat transfer tube by welding the tip of the heat transfer tube,
A heat exchanger characterized in that a gap between the tube-side opening edge of the tube hole and the heat transfer tube is sealed with the resin paint.

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