Method for determining the wall thickness reduction% WR of a tube fixed in a tube plate hole, system therefor and use of the method

Abstract

The invention relates to a method (100) for determining the wall thickness reduction,% WR (20), of a tube (2) fixed by expansion in a tube sheet hole (4) of a tube sheet (6). The method comprises: an operation of receiving an initial inner diameter (10) of the tube prior to expansion, an outer diameter (12) of the tube prior to expansion, an inner diameter (14) of the tube sheet orifice, and a final inner diameter (16) of the tube after expansion; and an operation of determining a wall thickness reduction rate (% WR) of the pipe based on the received diameter. The invention also relates to an imaging system (1) for carrying out the method and to the use of the method.

Description

Technical Field

[0001] The present invention relates to a method for determining the wall thickness reduction ratio %WR of a tube fixed in a tube sheet hole of a tube sheet by expansion.

[0002] The method includes: receiving an initial inner diameter of the tube before expansion, an outer diameter of the tube before expansion, an inner diameter of a tube sheet hole, and a final inner diameter of the tube after expansion; and determining a wall reduction rate %WR of the tube based on the received diameters.

[0003] The invention also relates to an imaging system for carrying out the method and to the use of the method. Background Art

[0004] It is known to install and fix the tubes in the tube sheet by expansion of the tubes after positioning them in the holes of the tube sheet. This technique is used in the production of various devices to obtain adequate tightness between the tubes penetrating the plate, in particular in applications where it is desirable to have, for example, a liquid on one side of the plate and air or another liquid / medium on the other side of the plate. Leakage at the connection between the tube and the plate is undesirable.

[0005] The technique of assembling these parts by expansion of tubes is used in particular in heat exchangers and steam generators used in the petroleum industry, chemical industry, natural gas production, energy, metallurgical industry and shipbuilding, including marine atomic energy installations, nuclear power plants and related industries.

[0006] The expansion process commonly used involves a mandrel (i.e., a tool with rollers) acting on the tube from the inside, and controlling the expansion of the tube by predetermined parameters of motor torque delivered to the mandrel. The parts involved in the process include various variables such as tube wall thickness, tube diameter and hole diameter in the tube sheet, as well as individual characteristics of each mandrel assembly (including overall mandrel wear).

[0007] JPS55161532A discloses an automatic pipe expansion device having a pipe expansion unit, a thrust moving device for moving the unit, and a control device for controlling the operation of the unit and the thrust moving device, wherein a wall thickness reduction rate during pipe expansion is based on a pipe expansion torque.

[0008] The assembly is usually leak tested after each tube assembly is tested individually.

[0009] However, this leak test does not test the quality of the tube after expansion. In order to obtain good quality of the device with tubes fixed in the tube sheet, the tube must undergo plastic deformation during the expansion process, while the plate sheet should only undergo elastic deformation, so as to restore the original pore size after the expansion process, while the tube should remain deformed after the expansion process. Furthermore, the plastic deformation of the tube must remain below the critical point of rupture.

[0010] Furthermore, testing and repairing such connections is cumbersome and impractical.

[0011] Therefore, a method of verifying the assembly of a tube in a tube bore is disclosed to verify the quality of the assembly.

[0012] Purpose of the Invention

[0013] It is therefore an object of the present invention to provide a method for determining the wall thickness reduction ratio %WR of a tube fixed in a tube sheet hole (4) of a tube sheet by expansion.

[0014] One object is to achieve a method which is easy to use, easy to apply and can be applied in a very fast and safe manner for the quality control of assembled tubes penetrating a tube sheet.

[0015] Another object is to provide a system for implementing the method. Summary of the invention

[0016] The present invention achieves these objects by providing a method for determining the wall reduction ratio %WR of a tube fixed in a tube sheet hole of a tube sheet by expansion.

[0017] The method includes an operation for receiving the following diameters:

[0018] - the initial inner diameter of the tube before expansion, d_i,

[0019] - the outer diameter of the tube before expansion, d_o,

[0020] - the inner diameter of the tube sheet hole, D_i, and

[0021] - Final inner diameter of the tube after expansion, d_ia.

[0022] The method also includes an operation of determining a wall reduction ratio %WR of the tube based on the received diameters d_i, d_o, D_i, and d_ia.

[0023] Particularly, for heat exchangers or large cooling facilities, in order to provide enough heat exchange area in the heat exchanger, a large number of tubes need to be fixed as through-tubes in the end plate. In these structures, the tubes are usually very close to each other, so there is not much space for operation.

[0024] Leak tests usually performed after assembly only indicate whether the seal is tight. However, these tests cannot indicate the quality of the assembled seal and tube.

[0025] The quality of an installation with tubes fixed in a tube sheet can be controlled by determining the wall reduction % WR of the tube after assembly. In this type of installation, sealing is achieved by subjecting the tube to plastic deformation during expansion, while the sheet should only be subjected to elastic deformation, thereby recovering the original pore size after the expansion process, while the tube remains deformed after the expansion process. In addition, the plastic deformation of the tube must be kept below the critical point of rupture in order to maintain the durability of the tube according to the intended application (i.e. exposure to pressure).

[0026] Due to the reduction in wall thickness caused by tube expansion, the tube material will stretch along the longitudinal axis of the tube.

[0027] Using only the final inner diameter d_ia of the tube as the only parameter of the assembled part after expansion of the tube, a reliable method for determining the wall thickness reduction rate is achieved. The tube is expanded to such an extent that plastic deformation of the tube is achieved while only elastic deformation of the sheet plate is achieved, resulting in yield extension of the tube material beyond the plate hole, i.e., after expansion, the tube material may bulge over the edge of the tube sheet hole, thereby covering the edge of the plate hole, thereby preventing the determination or measurement of the inner diameter of the tube sheet hole and the outer diameter of the expanded tube.

[0028] In another embodiment of the method, the wall thickness reduction rate %WR of the expanded tube is determined by the following formula:

[0029]

[0030] This can also be expressed as, where:

[0031] ΔR is the change in the inner diameter of the tube before and after expansion,

[0032] c is the gap between the tube and the tube sheet before expansion, and

[0033] t is the tube thickness before expansion.

[0034] In another embodiment of the method, the received diameters d_i, d_o, Di_i and d_ia are estimated based on the detection of multiple points related to the initial inner diameter d_i of the tube before expansion and / or the outer diameter d_o of the tube before expansion, the inner diameter Di of the tube sheet hole and the final inner diameter d_ia of the expanded tube, respectively.

[0035] The diameter may be estimated by an appropriate form of triangulation, curve fitting or other mathematical modeling based on identifiable features associated with one or more tube diameters and tubesheet hole diameters.

[0036] This estimation can be accomplished by applying computer modeling, machine learning, or other computer-implemented calculations or estimations.

[0037] Machine learning can be implemented by using SVM, KNN, rCNN or similar methods.

[0038] However, extreme care must be taken to obtain a reliable estimate of the diameter.

[0039] In another embodiment, the method includes using an imaging device disposed external to the tube sheet with an optical axis aligned substantially parallel to a longitudinal axis of the tube sheet hole, wherein the method includes the operations of capturing a first image of the tube sheet with the tube inserted in the tube sheet hole and prior to expansion, and determining from the first image:

[0040] - the initial inner diameter of the tube before expansion, d_i,

[0041] - the outer diameter of the tube before expansion, d_o, and

[0042] -Inner diameter of the tube sheet hole, D_i,

[0043] And the method comprises a further operation of capturing a second image of the tube sheet with the tube inserted in the tube sheet hole and after expansion, and determining from the second image a final inner diameter d_ia of the expanded tube.

[0044] One effect of using an imaging device located on the plate and therefore on the outside of the tubes may be to facilitate an efficient method in which only a single image is required to determine the wall reduction % WR for a number of tubes. This may allow for rapid inspection of assembled parts.

[0045] Furthermore, the captured images can be stored and saved for later quality inspection.

[0046] In another embodiment of the method, image analysis may be used to determine the diameters d_i, d_o, D_i and d_ia.

[0047] In another aspect of the method comprising using an imaging device, the imaging device is an optical imaging device and the captured image is an optical image.

[0048] The objects of the present invention are achieved by a system for determining the wall thickness reduction ratio %WR of a tube fixed in a tube sheet hole by expansion.

[0049] The system may include an imaging device configured to be disposed externally of the tube sheet, the imaging device having an optical axis aligned substantially parallel to a longitudinal axis of the tube and configured to capture an image.

[0050] The system may also include: a processor configured to receive the captured image and perform image analysis on the captured image to determine the diameter of the object contained in the captured image; and a means (means) suitable for performing operations according to any one or more embodiments of the disclosed method to determine the wall thickness reduction rate %WR.

[0051] The effects and benefits achieved with such a system are consistent with those already described in connection with the various embodiments of the method.Thus, the present system supports the implementation and performance of the method of determining the wall reduction %WR.

[0052] The object of the present invention can also be achieved by a computer program comprising instructions, which, when executed by a computer, causes the computer to perform one or more method operations (method acts, method steps) of the method for determining the wall thickness reduction rate %WR.

[0053] Therefore, the present embodiment can have the effects and advantages consistent with the effects and advantages described above in conjunction with the method for determining the wall thickness reduction rate %WR and the system thereof.

[0054] The object of the present invention can be achieved by a computer-readable medium including instructions, which, when executed by a computer, cause the computer to perform one or more method operations of the method for determining the wall thickness reduction rate %WR.

[0055] The instructions to be executed may be contained in or output from an algorithm in a computer program product including one or more method operations of a method for determining wall reduction % WR.

[0056] This embodiment also supports the effects and advantages of the method and system described above.

[0057] The object of the present invention can be achieved by using a method according to any one or more embodiments for determining the wall thickness reduction ratio %WR for diagnosing a tube fixed in a tube sheet hole by expansion, wherein the wall thickness reduction ratio is in the range of 2% to 15%, preferably in the range of 4% to 10%, and even more preferably in the range of 4% to 6%.

[0058] The optimum wall thickness reduction rate depends on the specific material of the tube. Typical materials may be stainless steel or copper. However, the tube may be made of other materials selected taking into account the specific application of the device including the fixed tube sheet.

[0059] In another aspect, the method is applied of the type where expansion of a tube fixed in a tube sheet hole is achieved by causing a tool having rollers to act on the tube and controlling the expansion process according to parameters of the expansion force transmitted to the tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 An embodiment of the method is shown.

[0061] Figure 2 Another embodiment of the method is shown.

[0062] Figure 3 One embodiment of the system is shown.

[0063] Figure 4 One embodiment of a tube sheet and tubes is shown.

[0064] Figure 5 Shown are tests performed on tubes arranged in tube sheet holes that were expanded by rolling. DETAILED DESCRIPTION

[0065] Serial number: Project

[0066] 1: System

[0067] 2: Tube

[0068] 4: Tube sheet hole

[0069] 6: Tube sheet

[0070] 8: Longitudinal axis, tube

[0071] 10: Initial inner diameter of the tube before expansion, d_i

[0072] 12: The outer diameter of the tube before expansion, d_o

[0073] 14: Inner diameter of the tube sheet hole, D_i

[0074] 16: Final inner diameter of the expanded tube, d_ia

[0075] 18: o'clock

[0076] 20: Wall thickness reduction rate, %WR

[0077] 30: Imaging device

[0078] 32: Optical axis

[0079] 40: First Image

[0080] 42: Second Image

[0081] 100: Methods

[0082] 102: Receive

[0083] 104: OK

[0084] 106: Capture

[0085] 108: OK

[0086] Figure 1 One embodiment of a method 100 for determining the wall reduction % WR of a tube secured in a tube sheet hole by expansion is shown.

[0087] The illustrated embodiment of the method includes the operation of receiving 102 an initial inner diameter d_i(10) of the tube before expansion, an outer diameter d_o 12 of the tube before expansion, an inner diameter D_i 14 of the tube sheet hole, and a final inner diameter d_ia 16 of the expanded tube. The method also includes the operation of determining 104 a wall reduction rate %WR of the tube based on the received diameters 10, 12, 14, 16.

[0088] Figure 2 Shown as Figure 1 Another embodiment of a method 100 for determining wall reduction %WR is shown. In this embodiment, the method includes capturing 106 a first image 40 and a second image 42 of a tube sheet before and after expansion of the tube, respectively, wherein the tube is inserted into a tube sheet hole.

[0089] From the first image 40 , the diameters d_i( 10 ), d_o( 12 ) and D_i( 14 ) are determined 108 . From the second image 42 , the diameter d_ia( 16 ) is determined 108 .

[0090] Figure 3 An embodiment of a system 1 is shown, the system comprising an imaging device 30 arranged outside the tube sheet 6 , the optical axis 32 of the imaging device 30 being substantially parallel to the longitudinal axis 8 of the tube sheet hole 4 .

[0091] In this embodiment, the tube 2 is shown inserted into one of the tube sheet holes 4 .

[0092] Figure 4 A and Figure 4 B shows an embodiment of a tube sheet 6 having tube sheet holes 4 and a tube 2 adapted to be inserted into one of the tube sheet holes 4. Figure 4 In A, an embodiment of the tube 2 before it is inserted into the hole 4 is shown. Figure 4 B shows an embodiment in which the tube 2 is inserted into the hole 4 and the diameters d_i (10), d_o (12) and Di (14) are indicated.

[0093] Figure 5A shows the measured wall thickness reduction (%) versus the measured maximum torque of the expansion tool used to expand the tube. The maximum torque was measured before terminating the expansion process. The wall thickness reduction was measured by rolling the tube at rolling depths of 15 mm and 21 mm.

[0094] Figure 5 B shows the torque [Nm] versus the number of revolutions of the expansion process by rolling. The portion of the curve above ~85 shows the process of plastic deformation of the tube and elastic deformation of the tube sheet, as well as the operating area for fixing the tube in the tube sheet hole.

[0095] from Figure 5 A can be inferred as the point at which the tubesheet also undergoes plastic deformation. As the deformation changes from elastic to plastic, the torque required to further expand the tubesheet hole decreases, and for the test specimens performed, this decrease occurs somewhere between 7% and 10% WR. The test specimen tubes consist of Made of CuNi10.

Claims

1. A method (100) for determining the wall thickness reduction ratio % WR of a tube (2) fixed in a tube sheet hole (4) in a tube sheet (6) by expansion, the method comprising the following operations: -Receive (102): - the initial inner diameter of the tube before expansion, d_i(10), - the outer diameter of the tube before expansion, d_o(12), - the inner diameter of the tube sheet hole, D_i (14), and - the final inner diameter of the expanded tube, d_ia(16), and - determining (104) the wall thickness reduction ratio % WR (20) of the tube (2) based on the received diameter (10, 12, 14, 16), - capturing the first image (40) and the second image (42) using an imaging device (30) arranged outside the tube sheet (6), the optical axis (32) of the imaging device (30) being aligned substantially parallel to the longitudinal axis (8) of the tube sheet hole (4), - capturing (106) a first image (40) of the tube sheet (6) wherein the tube (2) is inserted into the tube sheet hole (4) and prior to expansion, and based on the first image (40) -Confirm (108): - the initial inner diameter of the tube before expansion, d_i(10), - the outer diameter of the tube before expansion, d_o(12), and -Inner diameter of the tube sheet hole, D_i (14); - capturing (106) a second image (42) of the tube sheet (6) with the tube (2) inserted into the sheet hole (4) and after expansion, and based on the second image (42) - Determine (108) the final inner diameter of the expanded tube, d_ia (16).

2. The method (100) according to claim 1, wherein the wall thickness reduction ratio %WR(20) of the tube (2) after expansion is determined by the following formula:

3. A method (100) according to any one of the preceding claims, wherein the received diameter (10, 12, 14, 16) is estimated based on the detection of a plurality of points (18) respectively related to an initial inner diameter (10) of the tube before expansion and / or an outer diameter (12) of the tube before expansion, an inner diameter (14) of the tube sheet hole and a final inner diameter (16) of the expanded tube.

4. The method (100) according to any one or more of the preceding claims, wherein the diameter (10, 12, 14, 16) is determined using image analysis.

5. The method (100) according to any one of claims 1 to 5, wherein the imaging device (30) is an optical imaging device (50) and the captured image is an optical image (52).

6. A system (1) for determining the wall thickness reduction ratio % WR of a tube (2) fixed in a tube sheet hole (4) by expansion, the system (1) comprising: - an imaging device (30) configured to be arranged outside the tube sheet (6), the optical axis (32) of the imaging device (30) being aligned substantially parallel to the longitudinal axis (8) of the tube (2) and configured to capture an image, - a processor (50) configured to receive the captured image and perform image analysis on the captured image to determine a diameter of an object contained in the captured image, - means (52) adapted to perform the operations of the method (100) of any one or more of claims 1-5 to determine said wall reduction % WR (20).

7. A computer program (60) comprising instructions which, when the program (60) is executed by a computer, cause the computer to perform one or more method operations of the method (100) of any one or more of claims 1-5.

8. A computer-readable medium (62) comprising instructions which, when executed by a computer, cause the computer to perform one or more method operations of the method (100) of any one or more of claims 1-5.

9. Use of the method (100) according to any one or more of claims 1-4 for diagnosing tubes (2) fixed in tube sheet holes (4) by expansion, wherein the wall thickness reduction % WR (20) is in the range of 2% to 15%, preferably in the range of 4% to 10%, even more preferably in the range of 4% to 6%.

10. Use according to claim 9, wherein the expansion of the tube (2) fixed in the tube sheet hole (4) is of the type achieved by causing a tool with rollers to act on the tube and controlling the expansion process according to the parameters of the expansion force transmitted to the tool.

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