Heat transfer tube drawing method adopting machining process

Abstract

The invention relates to a heat transfer tube drawing method adopting a machining process, which comprises the following steps of: disassembling a seal head, removing a seal welding seam of an outer tube of a heat exchanger, removing a heat transfer tube in a tube expansion area and a tube expansion groove of an inner tube plate and an outer tube plate of the heat exchanger, taking out excess materials of the heat transfer tube, and pushing out the heat transfer tube. One end of the milling cutter machining head is connected with a transmission shaft of the rotating motor, and the other end of the milling cutter machining head extends into the heat transfer tube body and accurately mills a tube expansion area in the tube body; according to the method, the defective heat transfer tube can be effectively pulled out under the condition that an original heat exchanger is damaged, and the limitation of a traditional method in the complex structure is solved.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical processing, and in particular to a heat transfer tube drawing method using a mechanical processing technology. Background Art

[0002] Shell and tube heat exchangers usually adopt various types of structural designs, such as fixed type, expansion joint type, floating head type, U-tube type, corrugated type and segmented type, etc., to adapt to different working conditions; the core components of shell and tube heat exchangers are heat transfer tubes and the connection structure between them and the tube sheet. Heat transfer tubes are usually made of seamless steel pipes, and different materials are selected according to the working medium, such as carbon steel, stainless steel or copper. The material requirements of heat transfer tubes are very high and must undergo strict inspection before they can be put into use. The connection method between the tube and the tube sheet determines the sealing and reliability of the heat exchanger. Common connection methods include welding only, expansion only, and welding plus expansion.

[0003] During the manufacturing process, the heat transfer tube may be damaged due to bumps, scratches, etc., which will affect the heat transfer efficiency. In order to ensure the quality of the heat exchanger, eddy current testing is usually performed after manufacturing is completed. If the heat transfer tube is found to have defects exceeding the standard, it needs to be processed. There are two common treatment methods: plugging the tube and replacing the tube. Although plugging the tube is simple, if the number of defects exceeding the standard is too large, it will affect the performance of the heat exchanger. At this time, the only option is to replace the tube; the traditional hydraulic tube pulling method is to process the internal thread at the tube mouth and use a hydraulic tube pulling machine to pull out the heat transfer tube. However, this method has many limitations when facing designs with double-layer or multi-layer tube sheets and expansion grooves: 1. Excessive pulling force: Hydraulic tube pulling needs to overcome the expansion force of the multi-layer tube sheet, which may cause the heat transfer tube to break or fall into the shell, thus causing the heat exchanger to be scrapped; 2. Sealing surface risk: Huge tensile force may damage the sealing surface between the tube sheets, resulting in leakage; 3. Difficulty in fixing: A great fixing force is required to offset the reaction force during tube extraction, which may lead to the failure of the fixing device. Therefore, it is urgent to develop a new tube extraction method that can effectively remove defective heat transfer tubes without damaging the tube sheet and the overall structure of the heat exchanger. Summary of the invention

[0004] In view of the technical problems existing in the background technology, the present invention provides a heat transfer tube extraction method using a machining process, which can smoothly remove the damaged heat exchange tube when the original heat exchanger is damaged.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve: A heat transfer tube drawing method using a machining process, the test method comprising the following steps: S1. Preparation; S1.1. Shut down the nuclear reactor heat exchanger, ensure that the system has been safely isolated, and depressurize and cool it in accordance with safety regulations; S1.2. Prepare necessary tools and equipment, including special disassembly and assembly tools, measuring tools, cleaning tools and protective equipment; S2, dismantle the head; S2.1. According to the design drawings, identify the position of the 1 / 2 side head; S2.2. Use an appropriate wrench or hydraulic tool to loosen and remove the connecting bolts between the head and the tube sheet, safely remove the head, and place it in the designated location to prevent damage; S3, remove the sealing weld of outer tube No. 1; S3.1. Use a milling machine with an appropriate tool to locate the No. 1 outer tube sealing weld. S3.2, start milling, gradually remove the sealing weld, pay attention to control the feed speed to avoid damaging the tube sheet, after completion, check whether there is residual welding material, and perform secondary cleaning if necessary; S4, remove the heat transfer tubes in the expansion area of ​​the No. 1 outer tube sheet; S4.1. Also use the milling machine to locate the expansion area of ​​outer tube sheet No. 1; S4.2. Slowly and accurately remove the heat transfer tubes in the expanded area, ensuring that the tube sheet or other untreated heat transfer tubes are not damaged; S5. Remove the heat transfer tube in the expansion groove of the No. 1 outer tube sheet; S5.1. Position inside the expansion groove of the No. 1 outer tube sheet and continue to use the milling machine to remove the remaining heat transfer tubes; S5.2. Cut inside and outside the tube sheet until all heat transfer tubes are completely cut off, and check and confirm that all heat transfer tubes have been successfully cut off; S6. Take out the remaining heat transfer tube in the No. 1 outer tube sheet; S6.1. Use special tools to remove the remaining heat transfer tube material in the No. 1 outer tube sheet; S6.2. Clean the inner wall of the pipe hole, remove all residues, and ensure that the hole is clean; S7, remove the heat transfer tubes in the expansion area of ​​the No. 1 inner tube sheet; S7.1. Repeat step S4, but this time perform the operation on inner tube sheet No. 1 S8, remove the heat transfer tube in the expansion groove of the No. 1 inner tube sheet; S8.1. Install a special tool on one side of the No. 1 outer tube sheet to prevent the heat transfer tube from falling during subsequent operations; S8.1. Repeat steps S5 and S6, but this time perform the operation on inner tube plate No. 1 S9, switch the machine tool position and remove the sealing weld at the end of the No. 2 inner tube sheet; S9.1. Adjust the machine tool position to the position of the No. 2 inner tube sheet, and use the milling machine to remove the sealing weld of the No. 2 inner tube sheet; S10, removing the heat transfer tubes in the No. 2 outer tube sheet and the inner tube sheet; S10.1, repeat the operations of steps S4-S8 to remove the heat transfer tubes of the outer tube sheet and inner tube sheet section No. 2; S11.1. Use sandpaper or special tools to remove burrs from all processed areas; S11.2. Thoroughly clean the processing area to ensure there is no residue; S11, push out the heat transfer tube; S11.1. Use special tools (such as hydraulic tube pushers) to push out the remaining heat transfer tubes; take measures (such as laying soft cushions underneath) to prevent the heat transfer tubes from falling and causing damage; S12, cleaning the tube holes of the tube sheet; S12.1. Use a special brush or high-pressure air gun to clean the tube holes on each tube sheet; S12.2 Measure the diameter of each tube hole, record the data, and compare it with the original specifications to ensure that it meets the requirements for assembling new heat transfer tubes.

[0006] In the preferred embodiment, in steps S4, S5, S7 and S9, a milling cutter head is used to process the expansion area of ​​the heat transfer tube body. One end of the milling cutter head is connected to the transmission shaft of the rotating motor, and the other end of the milling cutter head extends into the heat transfer tube body and mills the expansion area in the tube body.

[0007] In the preferred scheme, the milling cutter processing head includes an upper sleeve and a lower movable plate, the side of the lower movable plate is vertically provided with a side plate, the lower end surface of the upper sleeve is correspondingly provided with a slide groove and is clamped with the upper end surface of the side plate, the axis of the lower movable plate is vertically connected with the central axis, and a telescopic plate is arranged between the upper sleeve and the lower movable plate, and the telescopic plate is annularly symmetrically arranged around the central axis and slides inward and outward along the axial direction of the central axis.

[0008] In a preferred solution, the upper sleeve is coaxially arranged with the central axis, and the central axis drives the lower movable plate to rotate around its own axis.

[0009] In a preferred solution, a connector is provided at the end of the upper sleeve, and an adjusting knob is provided at the end of the central shaft.

[0010] In the preferred solution, a vortex plate is disposed on the upper end surface of the lower movable plate, an arc-shaped clamping plate is correspondingly disposed on the lower end surface of the telescopic plate and meshedly connected with the vortex plate, and a milling cutter head is disposed on the side of the telescopic plate.

[0011] In the preferred solution, during the processing, the gap between the tube sheets will be contacted. In order to prevent the cutting fluid from entering the gap between the tube sheets and contaminating the equipment, dry cutting is adopted without using cutting fluid.

[0012] A heat transfer tube drawing method using a machining process, the beneficial effects of the method include but are not limited to the following points: 1. The existing hydraulic tube pulling process is mainly applicable to single-layer or double-layer tube sheet structures. For the tube pulling operation of the four-layer tube sheet structure, the traditional method is difficult to achieve because it needs to overcome a greater pulling force. The method of the present invention is specially designed for processing the heat exchanger with a four-layer tube sheet structure, which can effectively pull out the defective heat transfer tubes and solve the limitations of the traditional method in such complex structures; 2. The existing hydraulic tube pulling process relies on the high strength of the tube sheet material, because a strong pulling force needs to be applied during the tube pulling process. However, for some tube sheets with lower material strength, this strong pulling force may cause the tube sheet to break. The method of the present invention replaces the traditional strong pulling force tube pulling through machining technology, avoiding the application of strong pulling force on the tube sheet, thereby greatly reducing the requirements for the strength of the tube sheet material and reducing the risk of tube sheet breakage; 3. The traditional hydraulic tube pulling process requires setting a force point on the end face of the tube sheet and fixing the heat exchanger very firmly, which may cause the surface of the tube sheet to be crushed. The method of the present invention only needs to fix the heat exchanger firmly according to the conventional machining process, without applying additional pressure to the tube sheet, thereby effectively avoiding the risk of crushing the surface of the tube sheet; 4. When using the hydraulic tube pulling process, it is necessary to apply pressure on the end face of the tube sheet, which may cause the tube sheet to loosen or the shell seal to fail, and eventually cause the entire heat exchanger to be scrapped. The method of the present invention only needs to find the correct inner hole of the heat transfer tube to perform the operation to achieve the tube pulling operation, without applying additional pressure on the end face of the tube sheet, thereby avoiding the risk of loose tube sheet and shell seal failure, and improving the overall safety and reliability of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a cross-sectional view of the internal structure of the outer tube sheet and the inner tube sheet in the present invention; Figure 2 It is a schematic diagram of the connection method of the milling cutter processing head in the present invention; Figure 3 A cross-sectional view of the internal structure of the milling cutter processing head of the present invention; Figure 4 A bottom view of the structure of the bottom portion of the telescopic plate of the present invention; Figure 5 This is a picture of the tube extraction test piece and the heat transfer tube debris removed from the present invention; Figure 6 This is a real picture of the heat transfer tube after the debris is taken out of the present invention.

[0014] In the figure: heat transfer tube body 1, upper sleeve 2, lower movable plate 3, vortex plate 4, telescopic plate 5, side plate 6, connector 7, center shaft 8, adjustment knob 9, arc clamping plate 10, milling cutter head 11, outer tube plate 12, inner tube plate 13, expansion groove 14, sealing weld 15. DETAILED DESCRIPTION

[0015] Step 1. Turn off the nuclear reactor heat exchanger, ensure that the system has been safely isolated, and depressurize and cool it according to safety regulations; prepare necessary tools and equipment, including special disassembly and assembly tools, measuring tools, cleaning tools and protective equipment; the equipment: gantry boring and milling machine, model GNU32×50, worktable 2500×5000mm, stroke 5.5×3.2×1.25m; tool: Φ20×135 solid alloy end mill Step 2: Identify the position of the No. 1 / 2 side head according to the design drawing; use an appropriate wrench or hydraulic tool to loosen and remove the connecting bolts between the head and the tube sheet, safely remove the head, and place it in the designated location to prevent damage; Step 3: Use a milling machine with an appropriate tool to locate the sealing weld 15 of the No. 1 outer tube, and gradually remove the sealing weld 15. Pay attention to controlling the feed speed to avoid damaging the tube sheet. After completion, check whether there is any residual welding material, and perform secondary cleaning if necessary; Step 4: Also use the milling machine to locate the expansion area of ​​outer tube sheet No. 12; slowly and accurately remove the heat transfer tubes in the expansion area, ensuring that the tube sheet or other untreated heat transfer tubes are not damaged; Step 5: Locate inside the expansion groove 14 of the No. 1 outer tube sheet 12, and continue to use the milling machine to remove the remaining heat transfer tubes; cut inside and outside the tube sheet until all the heat transfer tubes are completely cut off, and check and confirm that all the heat transfer tubes have been successfully cut off; Step 6: Use special tools such as a long-rod magnet to remove the remaining heat transfer tube material in the No. 1 outer tube sheet 12; clean the inner wall of the tube hole to remove all residues and ensure that the hole is clean (such as Figure 4 shown); Step 7, removing the heat transfer tubes in the expansion area of ​​the No. 1 inner tube sheet 13; repeating step S4, but this time performing the operation on the No. 1 inner tube sheet 13; Step 8: Install a special tool on one side of the No. 1 outer tube sheet 12 to prevent the heat transfer tube from falling during subsequent operations; repeat steps 5 and 6, but this time perform the operation on the No. 1 inner tube sheet 13; Step 9, adjust the machine tool position to the position of the No. 2 inner tube sheet 13, and use a milling machine to remove the sealing weld 15 of the No. 2 inner tube sheet 13; Step 10. Repeat steps 4 to 8 to remove the heat transfer tubes of the No. 2 outer tube sheet 12 and the inner tube sheet 13; use sandpaper or special tools to remove burrs from all processing areas; and thoroughly clean the processing area to ensure that there is no residue (such as Figure 5 shown); Step 11: Use special tools to push out the remaining heat transfer tubes and take measures to prevent the heat transfer tubes from falling and causing damage; Step 12: Use a special brush or high-pressure air gun to clean the tube holes on each tube sheet; measure the diameter of each tube hole, record the data, and compare it with the original specifications to ensure that it meets the requirements for assembling new heat transfer tubes.

[0016] The preferred solution is Figures 1 to 4 As shown, in steps 4 and 5, and steps 7 and 9, a milling cutter processing head is used when processing the expansion area of ​​the heat transfer tube body 1. The steps of using the milling cutter processing head are as follows: S1, inserting the upper sleeve 2 and the lower movable plate 3 into the heat transfer tube body 1 until they are moved to the position to be milled; S2. Turn the adjusting knob 9 to drive the lower movable plate 3 and the vortex plate 4 to rotate. The arc-shaped clamping plate 10 at the lower end of the telescopic plate 5 is meshed and connected with the vortex plate 4. Therefore, it will slide outward driven by the lower movable plate 3 until the milling cutter head 11 abuts against the heat transfer tube body 1. S3, installing the connector 7 by means of a high-speed rotating motor, driving the milling cutter processing head to rotate, so that the milling cutter head 11 mills the inner wall of the heat transfer tube body 1; S4. During the milling process, the adjusting knob 9 is continuously adjusted, and the feed amount is adjusted by adjusting the scale on the adjusting knob 9, so as to achieve the purpose of precise cutting.

[0017] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from all points of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention; any reference numerals in the claims should not be regarded as limiting the claims involved.

Claims

1. A heat transfer tube drawing method using machining technology, characterized in that: The test method includes the following steps: S1. Preparation; S1.

1. Shut down the nuclear reactor heat exchanger, ensure that the system has been safely isolated, and depressurize and cool it in accordance with safety regulations; S1.

2. Prepare necessary tools and equipment, including special disassembly and assembly tools, measuring tools, cleaning tools and protective equipment; S2, dismantle the head; S2.

1. According to the design drawings, identify the position of the 1 / 2 side head; S2.

2. Use an appropriate wrench or hydraulic tool to loosen and remove the connecting bolts between the head and the tube sheet, safely remove the head, and place it in the designated location to prevent damage; S3, removing the sealing weld (15) of the No. 1 outer tube; S3.

1. Use a milling machine with an appropriate tool to locate the No. 1 outer tube sealing weld (15). S3.2, start milling, gradually remove the sealing weld (15), pay attention to control the feed speed to avoid damaging the tube sheet, after completion, check whether there is residual welding material, and perform secondary cleaning if necessary; S4, removing the heat transfer tubes in the expansion area of ​​the No. 1 outer tube sheet (12); S4.

1. Also use the milling machine to locate the expansion area of ​​the No. 1 outer tube sheet (12); S4.

2. Slowly and accurately remove the heat transfer tubes in the expanded area, ensuring that the tube sheet or other untreated heat transfer tubes are not damaged; S5, removing the heat transfer tube in the expansion groove (14) of the No. 1 outer tube sheet (12); S5.

1. Position the tube expansion groove (14) inside the No. 1 outer tube sheet (12), and continue to use the milling machine to remove the remaining heat transfer tubes; S5.

2. Cut inside and outside the tube sheet until all heat transfer tubes are completely cut off, and check and confirm that all heat transfer tubes have been successfully cut off; S6, taking out the remaining heat transfer tubes in the No. 1 outer tube sheet (12); S6.

1. Use a special tool (such as a long-rod magnet) to remove the remaining heat transfer tube material in the No. 1 outer tube sheet (12); S6.

2. Clean the inner wall of the pipe hole, remove all residues, and ensure that the hole is clean; S7, removing the heat transfer tubes in the expansion area of ​​the No. 1 inner tube sheet (13); S7.

1. Repeat step S4, but this time perform the operation on inner tube sheet No. 1 (13). S8, removing the heat transfer tube in the expansion groove (14) of the No. 1 inner tube sheet (13); S8.

1. Install a special tool on one side of the No. 1 outer tube sheet (12) to prevent the heat transfer tube from falling during subsequent operations; S8.

1. Repeat steps S5 and S6, but this time perform the operation on inner tube sheet No. 1 (13). S9, switching the machine tool position to remove the sealing weld (15) at the end of the No. 2 inner tube plate (13); S9.

1. Adjust the machine tool to the position of the No. 2 inner tube sheet (13), and use a milling machine to remove the sealing weld (15) of the No. 2 inner tube sheet (13); S10, removing the heat transfer tubes in the No. 2 outer tube sheet (12) and the inner tube sheet (13); S10.1, repeat the operations of steps S4-S8 to remove the heat transfer tubes of the No. 2 outer tube sheet (12) and the inner tube sheet (13); S11.

1. Use sandpaper or special tools to remove burrs from all processed areas; S11.

2. Thoroughly clean the processing area to ensure there is no residue; S11, push out the heat transfer tube; S11.

1. Use special tools to push out the remaining heat transfer tubes and take measures to prevent the heat transfer tubes from falling and causing damage; S12, cleaning the tube holes of the tube sheet; S12.

1. Use a special brush or high-pressure air gun to clean the tube holes on each tube sheet; S12.2 Measure the diameter of each tube hole, record the data, and compare it with the original specifications to ensure that it meets the requirements for assembling new heat transfer tubes.

2. The heat transfer tube drawing method using machining technology according to claim 1, characterized in that: In steps S4, S5, S7 and S9, a milling cutter head is used when processing the expansion area of ​​the heat transfer tube body (1). One end of the milling cutter head is connected to the transmission shaft of the rotating motor, and the other end of the milling cutter head extends into the heat transfer tube body (1) and mills the expansion area in the tube body.

3. The heat transfer tube drawing method using machining technology according to claim 2, characterized in that: The milling cutter processing head comprises an upper sleeve (2) and a lower movable plate (3), a side plate (6) is vertically arranged on the side of the lower movable plate (3), a sliding groove is correspondingly opened on the lower end surface of the upper sleeve (2) and is clamped with the upper end surface of the side plate (6), a central axis (8) is vertically connected to the axis center of the lower movable plate (3), and a telescopic plate (5) is arranged between the upper sleeve (2) and the lower movable plate (3), and the telescopic plate (5) is annularly symmetrically arranged around the central axis (8) and slides inward and outward along the axial direction of the central axis (8).

4. The heat transfer tube drawing method using machining technology according to claim 3, characterized in that: The upper sleeve (2) and the central axis (8) are coaxially arranged, and the central axis (8) drives the lower movable plate (3) to rotate around its own axis.

5. The heat transfer tube drawing method using machining technology according to claim 3, characterized in that: A connector (7) is provided at the end of the upper sleeve (2), and an adjustment knob (9) is provided at the end of the central shaft (8).

6. The heat transfer tube drawing method using machining technology according to claim 2, characterized in that: The upper end surface of the lower movable plate (3) is provided with a vortex plate (4), the lower end surface of the telescopic plate (5) is correspondingly provided with an arc-shaped clamping plate (10) which is meshedly connected with the vortex plate (4), and the side of the telescopic plate (5) is provided with a milling cutter head (11).

7. The heat transfer tube drawing method using machining technology according to claim 2, characterized in that: During the processing, the gap between the tube sheets will be contacted. In order to prevent the cutting fluid from entering the gap between the tube sheets and contaminating the equipment, dry cutting is adopted and cutting fluid is not used.

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