A method for welding pipeline jumper cables with minimal loss

Abstract

The present invention provides a method for micro-loss welding of pipeline jumper cables, which relates to the field of cathode anti-corrosion technology. The method comprises the following steps: grinding the conductive sheet; inserting the prefabricated heat insulation board into the pipe gap, spreading the copper core flat, close to the conductive sheet, and fixing it with a fixing clamp; heating the copper welding rod, inserting the heated copper welding rod into the borax bottle, and wrapping a layer of borax on the surface of the copper welding rod; preheating the conductive sheet; dipping the end of the copper welding rod with borax to the place where the copper core of the cable and the conductive sheet are close, heating, and the copper welding rod melts and flows to the contact surface of the copper cable and the conductive sheet, and the cable and the conductive sheet are welded together; after the cable cools down, pull the cable upward to confirm whether the welding head is firmly welded to the pipeline; measure the welding resistance; and repair the welding joint. The damage to the pipeline anti-corrosion and copper core is minimized to the greatest extent, the welding performance is strong, the damaged anti-corrosion area is secondary reinforced and repaired, the external corrosion is isolated, the conductive performance is excellent, and it is suitable for large-diameter PCCP pipeline joint processing operations.

Description

Technical Field

[0001] The invention relates to the technical field of cathode anti-corrosion, and in particular to a pipeline jumper cable micro-loss welding method. Background Art

[0002] Metal corrosion is a phenomenon in which metals are damaged by chemical or electrochemical reactions with the surrounding medium to form metal compounds. Corrosion is a key factor in the reliability and service life of pipeline systems. Corrosion not only causes oil, gas, and water leakage losses due to perforation, as well as waste of materials and manpower due to maintenance, and losses caused by shutdowns, but may also cause fires due to corrosion. Because the corrosive environment is almost everywhere, the forms of corrosion are also varied. A single anti-corrosion measure often cannot effectively control metal corrosion, especially electrochemical corrosion. Once a corrosion cell is formed in a metal structure, its anode area is much smaller than the cathode area, and the corrosion rate is also very fast. In order to protect these pipelines from severe corrosion damage and ensure their long-term safe operation, effective cathodic protection must be implemented on steel pipelines.

[0003] Cathodic protection is to use the principle of corrosion cell, take the metal structure to be protected as cathode, and continuously provide electrons to cathode through anode, first polarize the structure, then enrich the electrons on the surface of the structure, making it difficult to generate ions, thus greatly slowing down the corrosion rate of the structure. There are two types of cathodic protection: sacrificial anode protection and impressed current protection.

[0004] Cathodic protection of pipelines must be carried out by connecting the pipelines to the cathodic protection device through cables welded on the underground pipelines. Pipelines are connected by jumper cables to form a whole. Excellent jumper cable welding technology is the key to achieving the purpose of cathodic protection.

[0005] For example, Chinese patent CN 103014719 B discloses a method for welding deep underground pipelines and connecting cables, which includes the following steps: first, drill a hole to the upper surface of the pipeline at the cable welding point, and install a welding well pipe in the drilled hole; use a bolt as a welding head, and drill a blind hole larger than the diameter of the welding rod in the center of the screw end of the bolt; weld the connecting cable that needs to be welded to the underground pipeline on the outer side of the welding head, and connect it to the ground wire of the welding machine; connect the screw of the welding head to the screw hole at the lower end of an insulating sealing tube; connect the upper end of the insulating sealing tube to the lower end of a sealed steel pipe; clamp the welding rod on the welding rod clamp, and the upper end of the clamp is connected to the positive electrode of the welding machine through an aluminum tube; insert one end of the welding rod together with the clamp and the aluminum tube into the sealing tube for welding, and weld the welding head to the pipeline; remove the insulating sealing tube and the sealed steel pipe after welding. After adopting this method, you only need to drill a hole on the ground to the surface of the pipeline, and then you can safely and efficiently complete the welding of the underground pipeline and the cable.

[0006] In general welding processes, the copper welding heating method is torch copper welding, the fuel is acetylene-oxygen, the solder is brass welding rod, and the flux is borax. The operation method is as follows: (1) Heat the copper welding rod with a welding gun and insert the heated welding rod into a borax bottle; (2) Heat the conductive sheet with a welding gun until it turns red, twist the copper core of the cable to be welded into strands, and put it close to the steel sheet, then dip the end of the copper welding rod with borax to the close position of the copper core of the cable and the steel sheet, and heat it with a welding gun. After the copper welding rod melts, it flows to the contact surface between the copper cable and the conductive sheet, and the cable and the conductive sheet are welded together. The problems with this welding process are as follows: (1) The torch flame burns the pipe wall during welding, causing damage to the pipeline's corrosion protection; (2) The corrosion protection of the conductive piece is destroyed during heating, and the conductive piece is not repaired for corrosion; (3) The welding thickness is increased after twisting into strands. In order to ensure the effect, over-welding occurs, burning the copper core; (4) The anti-corrosion layer at the conductive piece welding point is not peeled off, which has a certain impact on the conductive performance after welding; (5) The copper core and welding point are not repaired for corrosion after welding, which is easy to be corroded in the soil environment and generates copper acid, affecting the conductivity.

[0007] Based on the above problems, how to ensure the welding effect and give full play to the anti-corrosion performance of cathodic protection has become the focus and difficulty of developing pipeline jumper cable welding technology. The researchers of this invention have developed a new process for micro-loss welding of jumper cables suitable for large-diameter prestressed concrete cylinder pipes (PCCP pipes for short), which isolates external corrosion to the maximum extent and has excellent electrical conductivity, making it very suitable for large-diameter PCCP pipeline joint processing operations. Summary of the invention

[0008] In view of the above problems, the present invention provides a method for micro-loss welding of pipeline jumper cables. By optimizing the process, the damage to the pipeline anti-corrosion and copper core is minimized, the welding performance is firm, and the damaged anti-corrosion area is reinforced and repaired for the second time, and both the anti-corrosion performance and the conductive performance are excellent.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] A pipeline jumper cable micro-loss welding method comprises the following steps:

[0011] S1: Grind the prefabricated conductive plates at both ends of the pipeline until the original metal color is exposed. The grinding area of ​​each place should be larger than the welding point area;

[0012] S2: Insert the prefabricated insulation board into the gap of the pipe, spread the copper core flat, close to the conductive sheet, and fix it with a fixing clamp;

[0013] S3: Heat the copper welding rod, insert the heated copper welding rod into the borax bottle, and coat the surface of the copper welding rod with a layer of borax;

[0014] S4: Preheat the conductive sheet;

[0015] S5: Dip one end of the copper welding rod with borax to the place where the copper core of the cable and the conductive sheet are close to each other, heat it, and the copper welding rod will flow to the contact surface of the copper cable and the conductive sheet after it melts, and weld the cable and the conductive sheet together. The copper welding liquid will wrap the end face of the cable.

[0016] S6: After the cable has cooled, pull the cable upward to confirm whether the welding head is firmly welded to the pipe; measure the welding resistance;

[0017] S7: Repair the welding joints and use epoxy coal tar paint and polyethylene cold wrap tape to carry out anti-corrosion treatment on the exposed parts of the cables and conductive plates.

[0018] Preferably, the ratio of the grinding area to the welding spot area in S1 can be 5-15:3-4; further preferably, the ratio of the grinding area to the welding spot area in S1 can be 5-10:3-4; most preferably, the ratio of the grinding area to the welding spot area in S1 can be 5:2.

[0019] Preferably, the polishing area described in S1 is 9.5-15.5 cm 2 ; Further preferably, the polishing area described in S1 is 11-15.5cm 2 More preferably, the polishing area described in S1 is 15cm 2 .

[0020] Preferably, the soldering point area described in S1 is 3.5-6.5 cm 2 ; Further preferably, the solder joint area described in S1 is 5.5-6.5cm 2 More preferably, the solder joint area described in S1 is 6cm 2 .

[0021] Preferably, the heat insulation board described in S2 is composed of iron sheet and asbestos board, with one side being iron sheet and the other side being asbestos board; the iron sheet is welded and the asbestos board is in contact with the pipe wall.

[0022] Preferably, the iron sheet maintains a distance of 5mm-10mm from the tube wall, and further preferably, the iron sheet maintains a distance of 5mm-8mm from the tube wall.

[0023] Preferably, the insertion depth of the insulation board described in S2 can be 3-5.5 cm; further preferably, the insertion depth of the insulation board described in S2 can be 4-5.5 cm; most preferably, the insertion depth of the insulation board described in S2 can be 5 cm.

[0024] Preferably, the heating temperature in S3 may be 2500-3300°C, and the time may be 8-20s; further preferably, the heating temperature in S3 may be 2600-3000°C, and the time may be 9-15s; most preferably, the heating temperature in S3 may be 2800°C, and the time may be 10s.

[0025] Preferably, the preheating temperature in S4 may be 2500-3300°C, and the time may be 8-20s; further preferably, the preheating temperature in S4 may be 2600-3000°C, and the time may be 9-15s; most preferably, the preheating temperature in S4 may be 2800°C, and the time may be 10s.

[0026] Preferably, the measured resistance described in S6 is less than 0.03Ω.

[0027] Preferably, the specific operation of measuring the resistance described in S6 is: using a DC low resistance tester to detect the welding resistance of the cable and the pipeline, and making data records.

[0028] Preferably, the specific operation of S7 is: evenly cover the welding parts, exposed cable cores, and parts where the anti-corrosion layer is damaged during welding with epoxy coal tar, and avoid applying less or no epoxy; after it dries, wrap the parts coated with epoxy coal tar with polyethylene cold wrap tape.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. Before welding, grind the conductive sheet and optimize the ratio of the massage area to the solder joint area, peel off the anti-corrosion layer at the solder joint of the conductive sheet, minimize the impact on the conductive performance after welding, improve the conductivity, and thus improve the anti-corrosion performance.

[0031] 2. Preheat the conductive sheet before welding, and lay the cable copper core flat and fix it on the conductive sheet to reduce the welding thickness, improve the welding effect, and prevent over-welding from damaging the copper core, thereby affecting conductivity.

[0032] 3. Use prefabricated insulation boards for insulation, control their insertion depth and position to prevent burning of the pipe wall, damage to pipeline corrosion, and improve anti-corrosion performance.

[0033] 4. After welding is completed, use epoxy coal tar paint and polyethylene cold wrap tape to treat the exposed parts of the cable and the conductive piece for corrosion protection, reduce the impact of welding on the anti-corrosion performance of the pipeline, and ensure the anti-corrosion performance; at the same time, prevent the copper core and welding points from corroding in the soil environment, generate copper acid, and reduce conductivity; significantly improve the anti-corrosion performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1Schematic diagram of the welding method of the present invention; a is grinding the conductive sheet; b is placing the heat insulation board, laying the copper core flat, and fixing it with a fixing clamp; c is welding the jumper cable; d is confirming the welding effect; e is painting epoxy coal tar paint; f is wrapping the polyethylene type cold wrap tape;

[0035] Figure 2 This is a schematic diagram of the electrical connection of adjacent pipelines;

[0036] Figure 3 It is the PCCP tube conduction piece;

[0037] Figure 4 This is the effect diagram of traditional welding process. DETAILED DESCRIPTION

[0038] In order to make the technical means, creative features, purpose and effect of the present invention easy to understand, the present invention is further explained below in conjunction with specific embodiments, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without making creative work all belong to the protection scope of the present invention. It is worth noting that the raw materials used in the present invention are all common commercial products, and their sources are not specifically limited. The technology and scientific terms used in the embodiments have the meanings commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0039] Embodiment 1:

[0040] 1. Grind the prefabricated conductive plates at both ends of the PCCP pipe to be welded with a grinding wheel until the original color of the metal is exposed. The grinding area of ​​each place should be larger than the welding point area, and clean the residue on the surface of the conductive plate;

[0041] 2. Insert the prefabricated insulation board (iron sheet + asbestos, the iron sheet side is for welding, and the asbestos board side is in contact with the pipe wall) into the pipe gap to stabilize it in the pipe wall and prevent it from falling. Spread the copper core to be welded flat, close to the conductive sheet, and fix it with a fixing clamp to prevent it from closing together during welding and affecting the welding effect.

[0042] 3. Heat the copper welding rod with a welding gun, insert the heated welding rod into the borax bottle, and coat the surface of the welding rod with a layer of borax;

[0043] 4. Heat the conductive sheet with a welding gun until it turns red, then dip one end of the copper welding rod with borax to the place where the copper core of the cable and the steel sheet are close together, and heat it with a welding gun. After the copper welding rod melts, it flows to the contact surface between the copper cable and the steel sheet, and welds the cable and the steel sheet together. As the welding proceeds, the copper welding liquid wraps the end face of the cable.

[0044] 5. After the cable has cooled, pull the cable by hand. If the cable connection is firm, it means the welding is reliable.

[0045] Use a DC low resistance tester to test the welding resistance between the zinc anode cable and the PCCP pipeline. The welding resistance should be less than 0.03Ω, and record the data;

[0046] 6. To repair the welding joints, evenly cover the welding parts, exposed cable cores, and parts where the anti-corrosion layer is damaged during welding with epoxy coal tar. Do not apply too little or no epoxy. After it dries, wrap the parts coated with epoxy coal tar with polyethylene cold wrap tape.

[0047] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A pipeline jumper cable micro-loss welding method, characterized in that: The following steps are involved: S1: Grind the prefabricated conductive plates at both ends of the pipeline until the original color of the metal is exposed. The grinding area of ​​each place should be larger than the welding point area; S2: Insert the prefabricated insulation board into the gap of the pipe, spread the copper core flat, close to the conductive sheet, and fix it with fixing clamps; S3: Heat the copper welding rod, insert the heated copper welding rod into the borax bottle, and coat the surface of the copper welding rod with a layer of borax; S4: Preheat the conductive sheet; S5: Dip one end of the copper welding rod with borax to the place where the copper core of the cable and the conductive sheet are close to each other, heat it, and the copper welding rod will flow to the contact surface of the copper cable and the conductive sheet after it melts, and weld the cable and the conductive sheet together. The copper welding liquid will wrap the end face of the cable. S6: After the cable has cooled, pull the cable upward to confirm whether the welding head is firmly welded to the pipe; measure the welding resistance; S7: Repair the welding joints and use epoxy coal tar paint and polyethylene cold wrap tape to carry out anti-corrosion treatment on the exposed parts of the cables and conductive plates.

2. The welding method according to claim 1, characterized in that: The ratio of the grinding area to the solder joint area described in S1 is 5-15:3-4.

3. The welding method according to claim 2, characterized in that: The grinding area described in S1 is 9.5-15.5cm 2 ; The soldering point area described in S1 is 3.5-6.5cm 2 .

4. The welding method according to claim 1, characterized in that: The heat insulation board described in S2 is composed of iron sheet and asbestos board, one side is iron sheet and the other side is asbestos board; the iron sheet is welded and the asbestos board is in contact with the pipe wall.

5. The welding method according to claim 4, characterized in that: The iron sheet maintains a distance of 5mm-10mm from the pipe wall.

6. The welding method according to claim 1, characterized in that: The heat insulation board described in S2 is inserted to a depth of 3-5.5 cm.

7. The welding method according to claim 1, characterized in that: The heating temperature in S3 is 2500-3300° C. and the heating time is 8-20 seconds.

8. The welding method according to claim 1, characterized in that: The resistance described in S6 is less than 0.03Ω.

9. The welding method according to claim 1, characterized in that: The specific operation of the resistance described in S6 is: use a DC low resistance tester to detect the welding resistance of the cable and the pipeline, and make good data records.

10. The welding method according to claim 1, characterized in that: The specific operation of S7 is: evenly cover the welding parts, exposed cable cores, and parts where the anti-corrosion layer is damaged during welding with epoxy coal tar, and avoid applying less or no epoxy; after it dries, wrap the parts coated with epoxy coal tar with polyethylene cold wrap tape.

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