Method of assembling and welding a galvanized sleeve

Abstract

This invention belongs to the field of marine pipeline welding technology and discloses a method for welding galvanized sleeves. This method involves prefabricating and welding a first pipe body and a first sleeve, as well as a second pipe body and a second sleeve, and then galvanizing the entire assembly. The galvanized layer is not damaged by the high-temperature welding. The double-sided prefabrication and welding of the stainless steel sleeve and carbon steel pipe before galvanizing ensures that the inner ends of the first and second pipe bodies are sealed with welds after closure. This prevents the flowing medium from easily entering the surrounding gaps. The sealed inner ends and the galvanized layer significantly improve resistance to corrosion, extending service life and reducing corrosion rate. While achieving high welding efficiency, this indirectly extends the service life of related equipment. Furthermore, during pre-assembly in the ship section stages, the connecting sleeve and the second sleeve are appropriately recessed into their respective sections to prevent contact and collision during the closure and hoisting of the ship sections, thus improving the construction efficiency of the ship section closure and hoisting.

Description

Technical Field

[0001] This invention relates to the field of marine pipeline welding technology, and in particular to a welding method for galvanized sleeves. Background Technology

[0002] During the welding and assembly of ship piping, a significant number of galvanized pipes are connected using sleeves. The steel pipes and sleeves undergo internal and external cleaning and galvanizing during the prefabrication stage, becoming components: galvanized pipe body 1', galvanized pipe body 2', and galvanized sleeve 3'. Then, during the ship section construction stage, galvanized pipe body 1' and galvanized pipe body 2' are installed and fixed onto two adjacent ship sections. During installation, such as... Figure 1 As shown, firstly, the galvanized sleeve 3' is temporarily welded and fixed onto the galvanized pipe body 1'. After the ship sections are joined, the temporary fixing weld is removed, and the galvanized sleeve 3' is slidably fitted onto the galvanized pipe body 2', thus achieving the sleeve connection between the galvanized sleeve 3' and the adjacent galvanized pipe body 1' and galvanized pipe body 2', and welding to form a galvanized sleeve fillet weld 4', as shown. Figure 2 As shown.

[0003] The existing welding methods for galvanized sleeves have the following main disadvantages:

[0004] 1) During the welding process of fillet weld 4', the high temperature generated will damage the galvanized layer of the pipe structure. The high temperature will enter the interior of the pipe structure through heat transfer, causing severe burning of the galvanized layer at the inner end of the galvanized sleeve 3', as well as the galvanized layers on the corresponding inner walls of galvanized pipe body 1' and galvanized pipe body 2'. The galvanized layer will be severely oxidized or violently burned due to the high temperature, resulting in serious damage to the galvanized layer in this area and greatly reducing the protective effect of the galvanized layer on the pipe body.

[0005] 2) After welding is completed, the galvanized layer at the inner end of the galvanized sleeve 3' is severely damaged. This area is located on the inner wall of the galvanized sleeve and has a small space, making welding impossible. The medium flowing inside the galvanized steel pipe will have a direct corrosive effect on this area, accelerating the corrosion at the inner end of the galvanized sleeve 3'.

[0006] 3) After welding is completed, because the ends of galvanized pipe body 1' and galvanized pipe body 2' inserted into galvanized sleeve 3' cannot be welded to the inner wall of galvanized sleeve 3' again (the welding space is small and internal welding is not possible), the medium flowing in galvanized pipe body 1' and galvanized pipe body 2' will enter the back of galvanized sleeve fillet weld 4' through the circumferential gap between galvanized pipe body and galvanized sleeve 3', thereby accelerating the corrosion rate on the back of galvanized sleeve fillet weld 4'.

[0007] 4) Since the galvanized pipe body 1', galvanized pipe body 2' and galvanized sleeve 3' have all been galvanized during the component prefabrication process, the workload of removing the galvanized layer in the area to be welded during the welding and closing stage of the galvanized sleeve 3' is large. After removal, the galvanized layer is also prone to remain. The remaining galvanized layer will participate in the metallurgical reaction during the welding process, causing welding defects in the weld and reducing the welding quality.

[0008] 5) Due to the damage to the galvanized layers of galvanized pipe body 1', galvanized pipe body 2', and galvanized sleeve 3', their corrosion resistance is poor, their effective service life is short, and this will accelerate the corrosion rate of other related equipment or facilities. The reason is that when the flowing medium passes through the pipe body, it comes into contact with locally exposed surfaces and undergoes an electrochemical reaction. While the pipe is corroded, the flowing medium carries a large number of metal ions and free electrons. When the flowing medium passes through other related equipment or facilities, these metal ions and free electrons will cause a certain degree of corrosion, thus accelerating the corrosion rate.

[0009] In summary, there is an urgent need for a welding method for galvanized sleeves to solve the above problems. Summary of the Invention

[0010] The purpose of this invention is to provide a welding method for galvanized sleeves to solve the problem that the galvanized layer is easily damaged during sleeve welding, leading to easy corrosion at the weld and affecting the service life.

[0011] To achieve this objective, the present invention adopts the following technical solution:

[0012] A method for welding galvanized sleeves, comprising:

[0013] Step S1: Pre-weld the first sleeve and the second sleeve onto the first pipe body and the second pipe body respectively. After the flaw detection is qualified, clean and galvanize them.

[0014] Step S2: Draw a center mark line through the midpoint of the connecting sleeve along its length, and clean the connecting sleeve.

[0015] Step S3: Pre-install the connecting sleeve inside the first sleeve. The end of the connecting sleeve extending out of the first sleeve is a distance L from the ship section closing joint. The end of the second sleeve facing away from the second pipe body is a distance L from the ship section closing joint.

[0016] Step S4: After the welding of the ship section closure joint is completed, remove the connecting sleeve so that both ends of the connecting sleeve are inserted into the first sleeve and the second sleeve, and the center mark line on the connecting sleeve is equidistant from the first sleeve and the second sleeve.

[0017] Step S5: Grind the galvanized layer at the end where the first sleeve connects to the connecting sleeve and at the end where the second sleeve connects to the connecting sleeve.

[0018] Step S6: Weld the first sleeve, the second sleeve and the connecting sleeve together and perform post-weld flaw detection.

[0019] Optionally, in step S1, the length of the first sleeve is greater than the length of the second sleeve, and the pre-welding is performed using CO2 gas shielded welding with stainless steel flux-cored welding wire. 24 hours after the pre-welding is completed, the pre-welded area is subjected to dye penetrant testing.

[0020] Optionally, in step S1, during the pre-welding process, the CO2 gas purity is ≥99.5%, the welding current is 180A~220A, and the welding voltage is 26V~30V.

[0021] Optionally, in step S1, the first tube end and the inner wall of the first sleeve, the first sleeve end and the outer wall of the first sleeve, the second tube and the inner wall of the second sleeve, and the second sleeve end and the outer wall of the second sleeve are all circumferentially welded and fixed.

[0022] Optionally, step S2 may also include striking several ocean-shaped points along the center marker line.

[0023] Optionally, in step S3, the connecting sleeve is installed inside the first sleeve by temporary locating weld, and the weld of the temporary locating weld is ground away before proceeding to step S4.

[0024] Optionally, in step S3, the weld length of the temporary tack weld is ≥30mm, and after the temporary tack weld is completed, a slag removal inspection is performed on the weld.

[0025] Optionally, in step S3, the distance L ranges from 40mm to 60mm.

[0026] Optionally, step S5 further includes a pre-welding inspection of the position of the connecting sleeve after grinding is completed, and the process proceeds to step S6 after the pre-welding inspection is passed.

[0027] Optionally, in step S5, the length of the connecting sleeve is L1, the distance from the center mark line on the connecting sleeve to the first sleeve and the second sleeve is L2, L1-L2≥30mm, and the pre-welding inspection is qualified.

[0028] The beneficial effects of this invention are:

[0029] The galvanized sleeve welding method of this invention involves prefabricating and welding the first pipe body and the first sleeve, as well as the second pipe body and the second sleeve, and then galvanizing the whole assembly. This prevents the galvanized layer from being damaged by high-temperature welding. The double-sided prefabrication and welding of the stainless steel sleeve and the carbon steel pipe before galvanizing ensures that the inner ends of the first and second pipe bodies are sealed with welds after closure. This prevents the flowing medium from easily entering the surrounding gaps. The sealed inner ends and the galvanized layer protection significantly improve the resistance to corrosion from the flowing medium, extending service life and reducing the corrosion rate. The high welding efficiency indirectly extends the service life of related equipment. Furthermore, during pre-assembly in the ship section stage, the connecting sleeve and the second sleeve are appropriately recessed into their respective sections to prevent them from contacting and colliding during the closure and hoisting of the ship sections, thus improving the construction efficiency of the ship section closure and hoisting. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the operation before the existing galvanized sleeve is assembled and welded;

[0031] Figure 2 This is a schematic diagram of the operation after the existing galvanized sleeve is assembled and welded.

[0032] Figure 3 This is a schematic diagram of the welding method for galvanized sleeves described in the embodiments of the present invention. Figure 1 ;

[0033] Figure 4 This is a schematic diagram of the connecting sleeve structure according to an embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of the welding method for galvanized sleeves described in the embodiments of the present invention. Figure 2 ;

[0035] Figure 6 This is a schematic diagram of the welding method for galvanized sleeves described in the embodiments of the present invention. Figure 3 ;

[0036] Figure 7 This is a schematic diagram of the welding method for galvanized sleeves described in the embodiments of the present invention. Figure 4 .

[0037] In the picture:

[0038] 1' Galvanized pipe body one; 2' Galvanized pipe body two; 3' Galvanized sleeve; 4' Galvanized sleeve fillet weld;

[0039] 1. First sleeve; 11. First sleeve outer fillet weld; 12. First sleeve inner fillet weld; 2. Second sleeve; 21. Second sleeve outer fillet weld; 22. Second sleeve inner fillet weld; 3. Connecting sleeve; 31. Center mark line; 32. Surface punch point;

[0040] 100, First tube body; 200, Second tube body; 300, Ship section joining joint. Detailed Implementation

[0041] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0042] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0044] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0045] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0046] This invention provides a method for assembling and welding galvanized sleeves, the assembly and welding process of which is as follows: Figures 3-6 As shown, it includes the following steps:

[0047] Step S1: Pre-weld the first sleeve 1 and the second sleeve 2 onto the first pipe body 100 and the second pipe body 200 respectively. After the flaw detection is qualified, clean and galvanize them.

[0048] Specifically, in step S1 above, as Figure 3 As shown, the first sleeve 1 and the second sleeve 2 are both 316L stainless steel sleeves, which are prefabricated and welded to the first pipe body 100 and the second pipe body 200 respectively. The first pipe body 100 and the second pipe body 200 are both carbon steel pipes. The corrosion resistance of the 316L stainless steel sleeve joint is much higher than that of the original carbon steel joint, which is beneficial to improving the corrosion resistance of the joint.

[0049] More specifically, the first pipe body 100 is circumferentially welded and fixed between its end and the inner wall of the first sleeve 1, between its end and the outer wall of the first sleeve 1, between its second pipe body 200 and the inner wall of the second sleeve 2, and between its end and the outer wall of the second sleeve 2, so that the first pipe body 100 is welded to the first sleeve 1 internally and externally to form the outer fillet weld 11 and the inner fillet weld 12 of the first sleeve, respectively; the second pipe body 200 is welded to the second sleeve 2 internally and externally to form the outer fillet weld 21 and the inner fillet weld 22 of the second sleeve, respectively.

[0050] Preferably, in step S1 above, the length of the first sleeve 1 is greater than the length of the second sleeve 2. Pre-welding is performed using CO2 gas shielded welding with 309L stainless steel flux-cored welding wire (1.2mm diameter). During pre-welding, the CO2 gas purity is ≥99.5%, the welding current is 180A~220A, and the welding voltage is 26V~30V. 24 hours after pre-welding, the pre-welded area undergoes 100% dye penetrant testing (PT testing) to ensure the quality of the fillet weld. After passing the testing, the entire assembly is cleaned (pickled) and galvanized. The first sleeve 1 and the second sleeve 2 become galvanized stainless steel sleeves, and the first pipe body 100 and the second pipe body 200 become galvanized carbon steel pipes. They are then protected and stored for later use.

[0051] Step S2: Draw a center mark line 31 through the midpoint of the length direction of the connecting sleeve 3, and clean the connecting sleeve 3.

[0052] Specifically, in step S2 above, as Figure 4 As shown, the connecting sleeve 3 is a stainless steel tube with a fixed length of L1. A center mark line 31 perpendicular to the length direction is made through the midpoint of the length of the connecting sleeve 3. Optionally, several punch marks 32 can be made along the center mark line 31 to facilitate the identification of the position of the center mark line 31. After completion, the connecting sleeve 3 is thoroughly cleaned and protected and stored for later use.

[0053] Step S3: Pre-install the connecting sleeve 3 inside the first sleeve 1. The end of the connecting sleeve 3 extending out of the first sleeve 1 is a distance L close to the ship section closing joint 300. The end of the second sleeve 2 away from the second pipe body 200 is a distance L from the ship section closing joint 300.

[0054] Specifically, in step S3 above, such as Figure 5 As shown, in the later stages of ship section construction, the prefabricated first pipe assembly (including the prefabricated and welded first pipe 100 and first sleeve 1, and the connecting sleeve 3 inserted into the first sleeve 1) and the second pipe assembly (including the prefabricated and welded first pipe 200 and first sleeve 2) are installed on the ship sections according to the drawings. In particular, it is ensured that the end of the second sleeve 2 is recessed into the ship section by a distance L from the position of the ship section closure joint 300. After the connecting sleeve 3 is pre-installed on the first sleeve 1, the end of the connecting sleeve 3 extending out of the first sleeve 1 is also recessed by a distance L from the ship section closure joint 300. The distance L ranges from 40mm to 60mm, and in this embodiment, it is preferably 50mm. This is to prevent the second sleeve 2 from contacting and bumping against the connecting sleeve 3 during the hoisting of the ship section closure, and to avoid the gap being too small after closure, which would be detrimental to the assembly and welding of the connecting sleeve 3.

[0055] Furthermore, to prevent the connecting sleeve 3 from slipping out of the first sleeve 1 and being lost, in this embodiment, the connecting sleeve 3 is inserted into the first sleeve 1 (inserted to the bottom), the center mark line 31 of the connecting sleeve 3 is rotated to an open side that is easy to observe, and the connecting sleeve 3 and the first sleeve 1 are temporarily positioned and fixed by CO2 gas shielded welding. Before proceeding to step S5, the weld of the temporary positioning weld is ground and removed, and the temporary welded connection between the connecting sleeve 3 and the first sleeve 1 is released. The length of the temporary positioning weld is ≥30mm. After the temporary positioning weld is completed, the weld slag is cleaned and inspected.

[0056] Step S4: After the welding of the ship section closure joint 300 is completed, remove the connecting sleeve 3 so that both ends of the connecting sleeve 3 are inserted into the first sleeve 1 and the second sleeve 2 respectively, and the center mark line 31 on the connecting sleeve 3 is equidistant from the first sleeve 1 and the second sleeve 2.

[0057] Specifically, in step S4 above, such as Figure 6 As shown, after the ship sections are hoisted and joined, and the 300 joint of the ship sections is welded, a grinding wheel is used to grind away the temporary positioning weld of the connecting sleeve 3 and the first sleeve 1. Then, the connecting sleeve 3 is slowly pulled out from the first sleeve 1 and inserted into the first sleeve 2, ensuring that the first sleeve 1 and the first sleeve 2 are in an overlapping state. The center mark line 31 on the connecting sleeve 3 is rotated to an open side that is easy to observe, and the center mark line 31 is located at the center of the open position between the first sleeve 1 and the first sleeve 2, so that the overlapping lengths at both ends of the connecting sleeve 3 are equal to meet the overlapping length requirements.

[0058] Step S5: Grind the galvanized layer at the end where the first sleeve 1 connects to the connecting sleeve 3 and at the end where the second sleeve 2 connects to the connecting sleeve 3.

[0059] Specifically, in step S5 above, after the connecting sleeve 3 is moved and assembled, a grinding wheel must be used to thoroughly grind away the outer galvanized layer of all areas to be welded, including but not limited to the end of the first sleeve 1 connected to the connecting sleeve 3, and the end of the second sleeve 2 connected to the connecting sleeve 3. After grinding, the position of the connecting sleeve 3 must be submitted to the quality inspection department or the shipowner's inspection department (if there are relevant requirements). The pre-welding inspection includes confirming whether the center mark line 31 is in the center of the empty position between the first sleeve 1 and the first sleeve 2, the length of the connecting sleeve 3 is L1, and the distance from the center mark line 31 to the first sleeve 1 and the second sleeve 2 is L2. If L1-L2≥30mm, it means that the overlap length of the two ends of the connecting sleeve 3 is ≥15mm, which is considered as passing the pre-welding inspection. Only after the pre-welding inspection is passed can the next step be carried out.

[0060] Step S6, as follows Figure 7 As shown, the first sleeve 1, the second sleeve 2, and the connecting sleeve 3 are welded and fixed. All lap fillet welds of the first sleeve 1, the second sleeve 2, and the connecting sleeve 3 are then welded and inspected post-weld. CO2 gas shielded welding is performed using 316L stainless steel flux-cored welding wire (1.2mm diameter). During pre-welding, the CO2 gas purity is ≥99.5%, the welding current is 180A~220A, and the welding voltage is 26V~30V. All lap fillet welds should be cleaned and inspected to ensure there are no welding defects. The welding of the galvanized sleeves is then complete.

[0061] The galvanized sleeve welding method of the present invention involves prefabricating and welding the first pipe body 100 and the first sleeve 1, the second pipe body 200 and the second sleeve 2, and then galvanizing the whole. The galvanized layer will not be damaged by high-temperature welding. The double-sided prefabrication and welding of the stainless steel sleeve and the carbon steel pipe before galvanizing ensures that the inner ends of the first pipe body 100 and the second pipe body 200 are sealed by weld after welding. This prevents the flowing medium from entering the surrounding gaps. The inner end is sealed by weld and protected by galvanization, which greatly improves the resistance to corrosion of the flowing medium, extends the service life, reduces the corrosion rate, and improves the welding efficiency, thereby indirectly extending the service life of related equipment. Furthermore, during the pre-assembly of ship sections, the connecting sleeve 3 and the second sleeve 2 are appropriately recessed into their respective sections to prevent them from contacting and bumping each other during the hoisting of ship sections, thus improving the construction efficiency of ship section hoisting. Moreover, after the connecting sleeve 3 is assembled or even welded during the hoisting stage, the overlap length of the sleeve can be accurately detected and calculated, which facilitates inspection and clarification of questions from relevant parties.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method of welding a galvanized sleeve, characterized by, include: Step S1: Pre-weld the first sleeve (1) and the second sleeve (2) onto the first pipe body (100) and the second pipe body (200) respectively. After the flaw detection is qualified, clean and galvanize. Step S2: Draw a center mark line (31) through the midpoint of the length direction of the connecting sleeve (3), and clean the connecting sleeve (3); Step S3: Pre-install the connecting sleeve (3) inside the first sleeve (1). The end of the connecting sleeve (3) extending out of the first sleeve (1) is a distance L close to the ship section closing joint (300). The end of the second sleeve (2) facing away from the second pipe body (200) is a distance L from the ship section closing joint (300). Step S4: After the welding of the ship section closing seam (300) is completed, remove the connecting sleeve (3) so that the two ends of the connecting sleeve (3) are inserted into the first sleeve (1) and the second sleeve (2) respectively. The center mark line (31) on the connecting sleeve (3) is equidistant from the first sleeve (1) and the second sleeve (2). Step S5: Grind the galvanized layer at the end of the first sleeve (1) connected to the connecting sleeve (3) and at the end of the second sleeve (2) connected to the connecting sleeve (3). Step S6: Weld and fix the first sleeve (1), the second sleeve (2) and the connecting sleeve (3), and perform post-weld flaw detection inspection; In step S3, the distance L ranges from 40mm to 60mm.

2. The method of assembling and welding a galvanized sleeve as defined in claim 1, wherein, In step S1, the length of the first sleeve (1) is greater than the length of the second sleeve (2), and the pre-welding uses stainless steel flux-cored welding wire. Gas shielded welding is performed. 24 hours after the pre-welding is completed, the pre-welded area is subjected to dye penetrant testing.

3. The method of assembling and welding a galvanized sleeve as defined in claim 2, wherein, In the step S1, in the pre-welding process, Gas purity ≥ 99.5%, welding current is 180A-220A; welding voltage is 26V-30V.

4. The method of assembling and welding a galvanized sleeve as defined in claim 1, wherein, In step S1, the end of the first tube (100) is circumferentially welded and fixed between the end of the first tube (1) and the inner wall of the first sleeve (1), the end of the first sleeve (1) and the outer wall of the first sleeve (1), the second tube (200) and the inner wall of the second sleeve (2), and the end of the second sleeve (2) and the outer wall of the second sleeve (2).

5. The method of assembling and welding a galvanized sleeve as defined in claim 1, wherein, In step S2, several ocean-piercing points (32) are also made along the center marker line (31).

6. The method of assembling and welding a galvanized sleeve as defined in claim 1, wherein, In step S3, the connecting sleeve (3) is installed inside the first sleeve (1) by temporary positioning welding. Before entering step S4, the weld of the temporary positioning welding is ground and removed.

7. The method of assembling and welding a galvanized sleeve as defined in claim 6, wherein, In step S3, the length of the temporary tack weld is ≥30mm. After the temporary tack weld is completed, the weld is cleaned and inspected.

8. The welding method for galvanized sleeves according to claim 1, characterized in that, In step S5, the position of the connecting sleeve (3) is inspected before welding after grinding is completed. After the pre-welding inspection is qualified, the process proceeds to step S6.

9. The method of assembling and welding a galvanized sleeve as defined in claim 8, wherein, In step S5, the length of the connecting sleeve (3) is L1, the distance between the center mark line (31) on the connecting sleeve (3) and the first sleeve (1) and the second sleeve (2) is L2, L1-L2≥30mm, and the pre-welding inspection is qualified.

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