A heat exchange tube and tube plate structure and connecting method of a titanium alloy double tube plate heat exchanger

Abstract

The application relates to the technical field of heat exchanger manufacturing, in particular to a heat exchange tube and tube plate connecting method of a titanium alloy double tube plate heat exchanger. The heat exchange tube and tube plate connecting method of the titanium alloy double tube plate heat exchanger comprises the following steps: S100, machining inner tube plate tube holes on an inner tube plate, machining two grooves in each inner tube plate tube hole, machining outer tube plate tube holes and sealing welding side grooves on an outer tube plate; S200, inserting a heat exchange tube into the inner tube plate and the outer tube plate, and performing mechanical strength expansion on the heat exchange tube and the inner tube plate; S300, performing one-time paste expansion on the heat exchange tube and the outer tube plate, and then performing one-time local mechanical strength expansion; and performing flat hole machining and strength sealing welding on the part of the heat exchange tube protruding to the side of the outer tube plate far away from the inner tube plate. The heat exchange tube and tube plate connecting method of the titanium alloy double tube plate heat exchangers has the advantages that the connection reliability is high, the heat exchange tube and the double tube plate connection position are not prone to leakage, and the safety is very high.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger manufacturing technology, and in particular to a structure and connection method of heat exchange tubes and tube sheet for a titanium alloy double tube sheet heat exchanger. Background Technology

[0002] Titanium alloy heat exchangers are increasingly widely used in many manufacturing fields due to the outstanding advantages of titanium alloys, such as low density, high specific strength, non-magnetic properties, resistance to corrosion from various media, and good weldability. There are many types of heat exchangers, one of which uses a double tube sheet structure, called a double tube sheet heat exchanger. Each end of the heat exchange tubes is connected to two tube sheets; the one closer to the shell side is called the inner tube sheet, and the one closer to the tube side is called the outer tube sheet. The heat exchange tubes are typically connected to the two tube sheets using expansion joints, welding, or a combination of both. A certain space is left between the inner and outer tube sheets in a double tube sheet heat exchanger, and a connecting pipe or vent is provided. When a leak occurs at the connection between the heat exchange tube and one side of the tube sheet, the leaked fluid is collected in this space and led out through the connecting pipe or vent, thus ensuring that the shell-side fluid and the tube-side fluid do not cross-leak or contaminate each other. Compared with single tube sheet heat exchangers, double tube sheet heat exchangers have higher requirements for tube sheet processing, higher requirements for heat exchange tube manufacturing processes and quality, more complex heat exchange tube-to-tube sheet connection processes, and higher reliability requirements. For the entire heat exchanger, the most problematic area, and also the one with the strictest quality requirements and the greatest manufacturing difficulty, is the connection between the heat exchange tubes and the tube sheet. Double tube sheet heat exchangers are difficult to manufacture overall, and their use is generally avoided in engineering projects. However, for applications involving highly corrosive or toxic media requiring recovery, or where mixing of the tube-side and shell-side media is strictly prohibited, double tube sheet heat exchangers are a necessary choice and have a wide range of applications.

[0003] For shell-and-tube heat exchangers, the reliability of the connection between the heat exchanger tubes and the tube sheet directly determines the manufacturing quality and normal operation of the heat exchanger. The connection process between the heat exchanger tubes and the tube sheet is the key and core technology in heat exchanger manufacturing. For double tube sheet heat exchangers, the connection between the heat exchanger tubes and the tube sheet is complex. For example, Chinese utility model patent CN203464830U discloses a connection structure between heat exchanger tubes and the tube sheet, including heat exchanger tubes and a tube sheet. The tube sheet has tube holes, and a connecting tube is inserted into the tube. Both ends of the connecting tube are exposed on the sides of the tube sheet. A first weld overlay and a second weld overlay are welded to the connecting tube on both sides of the tube sheet, respectively. The first and second weld overlays are strength welded to the two sides of the tube sheet, and the first and second weld overlays are sealing welded to the connecting tube. The connecting tube is connected to the tube hole by an expansion joint. One end of the heat exchanger tube is connected to the connecting tube by an inner deep hole weld. The connection method of this patent is technically challenging and requires high reliability. Especially for dual tube sheet heat exchangers that are subjected to harsh operating conditions, such as those subjected to strong corrosive media, high temperature, high pressure, impact, and vibration, if the connection process is not reliable, leakage can easily occur at the connection between the heat exchange tubes and the tube sheet, causing the heat exchanger to malfunction or even resulting in catastrophic consequences. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method for connecting heat exchange tubes and tube sheets in a titanium alloy double tube sheet heat exchanger. The method adopts an expansion joint connection between the heat exchange tubes and the inner tube sheet. The inner tube sheet has two expansion joint grooves in the tube holes. The heat exchange tubes and the outer tube sheet are connected by two expansion joints and then sealed on the outer surface by welding. This method solves the problems of high process difficulty, high reliability requirements, and easy leakage at the connection between the heat exchange tubes and the tube sheet, which can lead to the heat exchanger not working properly or even causing catastrophic consequences.

[0005] To address the above problems, this invention provides a heat exchange tube and tube sheet structure for a titanium alloy double tube sheet heat exchanger, comprising:

[0006] Tube sheet assembly includes an inner tube sheet and an outer tube sheet disposed opposite to each other. The inner tube sheet has a plurality of inner tube sheet holes, and the outer tube sheet has a plurality of outer tube sheet holes. The inner tube sheet holes and the outer tube sheet holes are disposed opposite to each other. At least two annular grooves are provided on the inner peripheral wall of each inner tube sheet hole.

[0007] A heat exchange tube is inserted between each of the corresponding inner tube sheet hole and outer tube sheet hole, and the heat exchange tube is connected to the inner tube sheet hole and outer tube sheet hole by means of expansion and welding.

[0008] A method for connecting heat exchanger tubes to a tube sheet in a titanium alloy double tube sheet heat exchanger, as described above, includes:

[0009] S100, machining inner and outer tube sheets

[0010] S110. To adapt to the size and quantity of the heat exchange tubes, multiple inner tube sheet holes are machined on the inner tube sheet, grooves are machined in the inner tube sheet holes along the circumferential direction, and chamfers are machined at both ends of the tube holes.

[0011] S120. Based on the size and quantity of the heat exchange tubes and the tube holes of each inner tube sheet, adaptably process the outer tube sheet tube holes; process a semi-V-shaped sealing weld bevel at the first end of each outer tube sheet tube hole, the first end being the end of the outer tube sheet tube hole away from the inner tube sheet, and process a chamfer at the other end.

[0012] S200, connecting heat exchange tubes and inner tube sheet

[0013] S210. Insert a heat exchange tube into each corresponding inner tube sheet and outer tube sheet hole, and mechanically expand the portion of the heat exchange tube located in the inner tube sheet hole to ensure an expansion tightness of 6-10%.

[0014] S220. The sealing degree of the expansion joint shall be inspected in accordance with the shell-side pressure test procedure. The outer tube sheet may be expanded only after it passes the test.

[0015] S300, connecting heat exchange tubes and outer tube sheet

[0016] S310. Perform the first expansion joint operation on the part of each heat exchange tube inserted into the tube hole of the outer tube sheet. The expansion joint method is to apply the tube to the tube to eliminate the gap between the heat exchange tube and the tube hole of the outer tube sheet. The tightness shall not exceed 3%.

[0017] S320. Perform a second expansion operation on a localized part of the part that was expanded during the first expansion operation. The expansion method is mechanical strength expansion, and the expansion tightness is 2-5%.

[0018] S330. The portion of the heat exchange tube protruding from the outer tube sheet away from the inner tube sheet is machined to form a sealing zone. The sealing zone is then cleaned and dried.

[0019] S340. Perform a sealing weld operation on the side of the heat exchange tube and outer tube sheet away from the inner tube sheet.

[0020] Furthermore, in step S110, the surface roughness of the inner tube sheet bore is ≤6.3;

[0021] The groove dimensions are: width W = 3–8 mm, depth S = 0.3–0.5 mm;

[0022] There are two grooves, and the distance between the two grooves is T = 6-12 mm;

[0023] The chamfers at both ends of the pipe hole are R1 to R2.

[0024] Furthermore, in step S120,

[0025] The surface roughness of the tube holes in the outer tube sheet is ≤6.3;

[0026] The depth d of the semi-V-shaped sealing groove at the tube hole sealing point of the outer tube sheet is 0.5 to 1.0 mm, the groove angle β is 50° to 65°, and the chamfer at the other end is R1 to R2.

[0027] Furthermore, the length of the portion of the first end of the heat exchange tube extending out of the outer tube sheet is 0 to 0.5 mm.

[0028] Furthermore, in step S210, the distance between the expanded portion of the heat exchange tube located inside the tube hole of the inner tube sheet and the two surfaces of the inner tube sheet is 3 to 5 mm.

[0029] Furthermore, in step S310, the distance between the first expansion joint portion and the surface of the outer tube sheet away from the inner tube sheet is 12-17 mm, and the distance between the first expansion joint portion and the surface of the outer tube sheet relative to the inner tube sheet is 1-3 mm.

[0030] When the length of the first expansion joint is less than or equal to 50mm, mechanical expansion is used.

[0031] When the length of the first expansion joint is greater than 50mm, hydraulic expansion is used.

[0032] Furthermore, in step S320,

[0033] The distance between the second expansion joint and the surface of the outer tube sheet relative to the inner tube sheet is 10-20 mm;

[0034] The length difference between the second expansion joint and the length of the expansion joint inside the inner tube sheet of the heat exchange tube is ±1mm.

[0035] Furthermore, in step S340, the sealing method includes:

[0036] The sealing welding adopts pulsed tungsten inert gas welding. First, a root pass is welded to ensure root fusion, and then two more passes are filled with wire.

[0037] Furthermore, the shielding gas for the welding torch shall be Ar with a purity of not less than 99.999%, and the shielding gas for the back of the weld shall be Ar with a purity of not less than 99.99%.

[0038] Compared with the prior art, the method for connecting heat exchange tubes and tube sheet in a titanium alloy double tube sheet heat exchanger described in this invention has the following advantages:

[0039] The advantage of this technical solution is that it reduces the difficulty of the process and the requirements for reliability. It makes it less likely for leaks to occur at the connection between the heat exchange tubes and the tube sheet, ensuring that the heat exchanger can work normally and avoiding catastrophic consequences. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the heat exchange tube and tube sheet structure according to an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1-Inner tube sheet, 2-Outer tube sheet, 3-Heat exchange tube, 4-Groove. Detailed Implementation

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0044] In this invention, the terms "first," "second," "upper," and "lower," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," "upper," or "lower" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. Where the technical solutions of the embodiments can be combined, they are all within the scope of protection claimed by this invention.

[0045] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] like Figure 1 As shown, a heat exchange tube and tube sheet structure for a titanium alloy double tube sheet heat exchanger includes:

[0047] The tube sheet assembly includes an inner tube sheet 1 and an outer tube sheet 2 arranged opposite to each other. The inner tube sheet 1 is provided with a plurality of inner tube sheet holes, and the outer tube sheet 2 is provided with a plurality of outer tube sheet holes. The inner tube sheet holes and the outer tube sheet holes are arranged opposite to each other. At least two annular grooves 4 are provided on the inner peripheral wall of each inner tube sheet hole.

[0048] A heat exchange tube 3 is inserted between each of the corresponding inner tube sheet holes and outer tube sheet holes, and the heat exchange tube 3 is connected to the inner tube sheet holes and outer tube sheet holes by means of expansion and welding.

[0049] The heat exchange tube 3 is connected to the tube sheet by expansion and welding, which reduces the process difficulty and reliability requirements. The connection between the heat exchange tube 3 and the tube sheet is less prone to leakage, ensuring that the heat exchanger can work normally and avoiding catastrophic consequences.

[0050] A method for connecting heat exchanger tubes to a tube sheet in a titanium alloy double tube sheet heat exchanger, as described above, includes:

[0051] S100, machining inner and outer tube sheets

[0052] S110. To adapt to the size and quantity of the heat exchange tubes, multiple inner tube sheet holes are machined on the inner tube sheet, grooves are machined in the inner tube sheet holes along the circumferential direction, and chamfers are machined at both ends of the tube holes.

[0053] The surface roughness of the tube holes in the inner tube sheet is ≤6.3;

[0054] The groove dimensions are: width W = 3–8 mm, depth S = 0.3–0.5 mm;

[0055] There are two grooves, and the distance between the two grooves is T = 6-12 mm;

[0056] The chamfers at both ends of the pipe hole are R1 to R2.

[0057] S120. Based on the size and quantity of the heat exchange tubes and the tube holes of each inner tube sheet, adaptably process the outer tube sheet tube holes; process a semi-V-shaped sealing weld bevel at the first end of each outer tube sheet tube hole, the first end being the end of the outer tube sheet tube hole away from the inner tube sheet, and process a chamfer at the other end.

[0058] The surface roughness of the tube holes in the outer tube sheet is ≤6.3;

[0059] The depth d of the semi-V-shaped sealing groove at the tube hole sealing point of the outer tube sheet is 0.5 to 1.0 mm, the groove angle β is 50° to 65°, and the chamfer at the other end is R1 to R2.

[0060] The length of the portion of the first end of the heat exchange tube extending out of the outer tube sheet is 0 to 0.5 mm.

[0061] S200, connecting heat exchange tubes and inner tube sheet

[0062] S210. Insert a heat exchange tube into each corresponding inner tube sheet and outer tube sheet hole, and mechanically expand the portion of the heat exchange tube located in the inner tube sheet hole to ensure an expansion tightness of 6-10%.

[0063] The distance between the expanded portion of the heat exchange tube located inside the tube hole of the inner tube sheet and the two surfaces of the inner tube sheet is 3-5 mm.

[0064] S220. The sealing degree of the expansion joint shall be inspected in accordance with the shell-side pressure test procedure. The outer tube sheet may be expanded only after it passes the test.

[0065] S300, connecting heat exchange tubes and outer tube sheet

[0066] S310. Perform the first expansion joint operation on the part of each heat exchange tube inserted into the tube hole of the outer tube sheet. The expansion joint method is to apply the tube to the tube to eliminate the gap between the heat exchange tube and the tube hole of the outer tube sheet. The tightness shall not exceed 3%.

[0067] The distance between the first expansion joint and the surface of the outer tube sheet away from the inner tube sheet is 12-17 mm, and the distance between the first expansion joint and the surface of the outer tube sheet relative to the inner tube sheet is 1-3 mm.

[0068] When the length of the first expansion joint is less than or equal to 50mm, mechanical expansion is used.

[0069] When the length of the first expansion joint is greater than 50mm, hydraulic expansion is used.

[0070] S320. Perform a second expansion operation on a localized part of the part that was expanded during the first expansion operation. The expansion method is mechanical strength expansion, and the expansion tightness is 2-5%.

[0071] The distance between the second expansion joint and the surface of the outer tube sheet relative to the inner tube sheet is 10-20 mm;

[0072] The length difference between the second expansion joint and the length of the expansion joint inside the inner tube sheet of the heat exchange tube is ±1mm.

[0073] S330. The portion of the heat exchange tube protruding from the outer tube sheet away from the inner tube sheet is machined to form a sealing zone. The sealing zone is then cleaned and dried.

[0074] S340. Perform a sealing weld operation on the side of the heat exchange tube and outer tube sheet away from the inner tube sheet.

[0075] Sealing methods include:

[0076] The sealing weld uses pulsed tungsten inert gas (TIG) welding. First, a root pass is welded to ensure root fusion, followed by two filler passes with wire. The weld throat dimension must be no less than the pipe wall thickness. The shielding gas used in the welding torch must be Ar with a purity of no less than 99.999%, and the shielding gas on the back of the weld must also be Ar with a purity of no less than 99.99%, ensuring the post-weld sealing weld is silvery-white or pale yellow. Specific welding process parameters are shown in Table 1.

[0077] Table 1

[0078]

[0079] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for connecting heat exchange tubes and tube sheet in a titanium alloy double tube sheet heat exchanger, characterized in that, The heat exchange tube and tube sheet structure includes: Tube sheet assembly includes an inner tube sheet and an outer tube sheet disposed opposite to each other. The inner tube sheet has a plurality of inner tube sheet holes, and the outer tube sheet has a plurality of outer tube sheet holes. The inner tube sheet holes and the outer tube sheet holes are disposed opposite to each other. At least two annular grooves are provided on the inner peripheral wall of each inner tube sheet hole. A heat exchange tube is inserted into each of the corresponding inner tube sheet holes and outer tube sheet holes, and the heat exchange tube is connected to the inner tube sheet holes and outer tube sheet holes by means of expansion and welding. The method for connecting the heat exchange tubes to the tube sheet includes: S100, machining inner and outer tube sheets S110. To adapt to the size and quantity of the heat exchange tubes, multiple inner tube sheet holes are machined on the inner tube sheet, grooves are machined in the inner tube sheet holes along the circumferential direction, and chamfers are machined at both ends of the tube holes. The surface roughness of the tube holes in the inner tube sheet is ≤6.3; The groove dimensions are: width W = 3~8mm, depth S = 0.3~0.5mm; There are two grooves, and the distance between the two grooves is T = 6~12mm; The chamfers at both ends of the pipe hole are R1~R2; S120. Based on the size and quantity of the heat exchange tubes and the tube holes of each inner tube sheet, adaptably process the outer tube sheet tube holes; process a half-V-shaped sealing weld bevel at the first end of each outer tube sheet tube hole, the first end being the end of the outer tube sheet tube hole away from the inner tube sheet, and process a chamfer at the other end. The surface roughness of the tube holes in the outer tube sheet is ≤6.3; The depth d of the semi-V-shaped sealing groove at the sealing weld of the tube hole on the outer tube sheet is 0.5~1.0mm, the groove angle β is 50°~65°, and the chamfer at the other end is R1~R2; S200, connecting heat exchange tubes and inner tube sheet S210. Insert a heat exchange tube into each corresponding inner tube sheet and outer tube sheet hole, and mechanically expand the portion of the heat exchange tube located in the inner tube sheet hole to ensure an expansion tightness of 6-10%. S220. The sealing degree of the expansion joint shall be inspected in accordance with the shell-side pressure test procedure. The outer tube sheet may be expanded only after the test is qualified. S300, connecting heat exchange tubes and outer tube sheet S310. Perform the first expansion joint operation on the portion of each heat exchange tube inserted into the tube hole of the outer tube sheet. The expansion joint method is patch expansion to eliminate the gap between the heat exchange tube and the tube hole of the outer tube sheet. The expansion tightness shall not exceed 3%. The distance between the first expansion joint and the surface of the outer tube sheet away from the inner tube sheet is 12~17mm, and the distance between the first expansion joint and the surface of the outer tube sheet relative to the inner tube sheet is 1~3mm. When the length of the first expansion joint is less than or equal to 50mm, mechanical expansion is used. When the length of the first expansion joint is greater than 50mm, hydraulic expansion is used. S320. Perform a second expansion operation on a localized portion of the part that underwent the first expansion operation. The expansion method is mechanical strength expansion, and the expansion tightness is 2-5%. The distance between the second expansion joint and the surface of the outer tube sheet relative to the inner tube sheet is 10~20mm; The length difference between the second expansion joint and the length of the heat exchange tube expansion joint inside the inner tube sheet is ±1mm. S330. The portion of the heat exchange tube protruding from the outer tube sheet away from the inner tube sheet is machined to form a sealing zone. The sealing zone is then cleaned and dried. S340. Perform a sealing weld operation on the side of the heat exchange tube and outer tube sheet away from the inner tube sheet. The sealing welding adopts pulsed tungsten inert gas welding. First, a root pass is welded to ensure root fusion, and then two more passes are filled with wire.

2. The method for connecting the heat exchange tubes and tube sheet of the titanium alloy double tube sheet heat exchanger according to claim 1, characterized in that, The length of the portion of the first end of the heat exchange tube extending out of the outer tube sheet is 0~0.5mm.

3. The method for connecting the heat exchange tubes and tube sheet of the titanium alloy double tube sheet heat exchanger according to claim 1, characterized in that, In step S210, the distance between the expanded portion of the heat exchange tube located inside the tube hole of the inner tube sheet and the two surfaces of the inner tube sheet is 3~5mm.

4. The method for connecting the heat exchange tubes and tube sheet of the titanium alloy double tube sheet heat exchanger according to claim 1, characterized in that, The shielding gas for the welding torch shall be Ar with a purity of not less than 99.999%, and the shielding gas for the back of the weld shall be Ar with a purity of not less than 99.99%.

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