A continuous preparation process of high-qualification mineral insulated fireproof cable

Abstract

This invention relates to the field of fire-resistant insulated cable manufacturing technology, and discloses a continuous manufacturing process for high-yield mineral-insulated fire-resistant cables, comprising: pretreatment, drawing pure copper rods into wires and then stranding and pressing them to obtain stranded copper conductors; insulation wrapping, wrapping mica tape around the outer wall of the stranded copper conductors to obtain an insulating core; filling and forming, longitudinally wrapping copper tape around the outer wall of the insulating core, and filling the space between the copper tape and the insulating core with magnesium oxide powder to form an insulating layer; sheath welding, welding the gaps between the copper tapes after longitudinal wrapping to obtain a copper protective sheath; corrugating and shaping, rounding the copper protective sheath, and then rolling the copper protective sheath into a corrugated tube shape to obtain a cable; softening and straightening, performing a first annealing treatment and a second annealing treatment on the cable in sequence, and performing a first water cooling treatment on the cable after the first annealing treatment; protection and cooling, placing the cable after step six into a nitrogen pipeline for cooling, and then performing a second water cooling treatment on the cable.

Description

Technical Field

[0001] This invention relates to the field of fire-resistant insulated cable manufacturing technology, specifically to a continuous manufacturing process for high-yield mineral-insulated fire-resistant cables. Background Technology

[0002] Mineral-insulated fire-resistant cables, with their excellent fire resistance, high temperature resistance, and insulation properties, have become the core cables for critical fire-resistant power supply systems in industrial and civil buildings, such as fire elevators, fire pumps, fire alarms, smoke exhaust systems, and emergency lighting. Their performance directly determines the stability and safety of the power supply during a fire.

[0003] An existing patent discloses a mineral-insulated fireproof cable and its preparation method (publication number: CN117558499A), which includes multiple conductors, a temperature detection unit, an inner liner, and an outer sheath. The conductors include a conductor, a fire-resistant layer, and a double-layer co-extruded insulation layer. The fire-resistant layer covers the outer periphery of the conductor, and the double-layer co-extruded insulation layer covers the outer periphery of the fire-resistant layer. The double-layer co-extruded insulation layer includes an irradiated cross-linked polyethylene insulation layer and an irradiated ceramic insulation layer arranged from the inside out. The temperature detection unit can monitor the temperature of the conductors. Its length is consistent with the length of the conductors and it is twisted together with multiple conductors to form a cable core. The inner liner covers the outer periphery of the cable core. The inner liner is formed by spirally winding a non-hygroscopic material. The outer sheath covers the outer periphery of the inner liner.

[0004] Existing technologies use non-hygroscopic winding inner lining and polymer outer sheath for protection, but their structure contains gaps that allow moisture and corrosive media to easily penetrate, resulting in poor moisture resistance, seepage prevention, and corrosion resistance. To address these issues, we propose a continuous manufacturing process for high-yield mineral-insulated fire-resistant cables. Summary of the Invention

[0005] The present invention aims to provide a continuous manufacturing process for high-yield mineral-insulated fireproof cables to solve the problem that water vapor and corrosive media can easily penetrate into the cable core, resulting in poor moisture resistance, seepage prevention, and corrosion resistance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a continuous manufacturing process for high-yield mineral-insulated fire-resistant cables, comprising the following steps: Step 1: Pre-treatment. The pure copper rod is drawn into wires. After the wires are drawn, they are twisted and pressed to obtain a stranded copper conductor. Step 2: Insulation wrapping. Mica tape is wrapped around the outer wall of the stranded copper conductor to obtain the insulating core. After wrapping, the core is dried. Step 3: Filling and molding. Copper strips are longitudinally wrapped around the outer wall of the insulating core. After the longitudinal wrapping is completed, magnesium oxide powder is filled between the copper strips and the insulating core to form an insulating layer. Step 4: Welding the protective sleeve. After welding the longitudinal wrapping, the gaps between the copper strips are filled to obtain the copper protective sleeve. The weld is then hammered. Step 5: Rolling and shaping. The copper protective sheath is rounded and then rolled into a corrugated tube to obtain the cable. Step 6: Softening and straightening. Perform the first annealing treatment and the second annealing treatment on the cable in sequence. After the first annealing treatment, perform the first water cooling on the cable. Step 7: Protection and Cooling. After completing Step 6, place the cable into a nitrogen pipeline for cooling, and then perform a second water cooling on the cable.

[0007] Preferably, as an improvement, it also includes step eight, inkjet printing and winding, which involves printing the specifications, target, and rated voltage parameters on the cable surface, and then winding the cable into a reel; Step 9: Inspection and warehousing. The cable reels are inspected for quality, and after passing the inspection, they are packaged and put into storage.

[0008] Preferably, as an improvement, step nine also includes: sequentially extruding a waterproof layer and an outer sheath onto the outer wall of the cable.

[0009] Preferably, as an improvement, the waterproof layer is made of polyethylene, and the outer protective layer is made of polyvinyl chloride or polyolefin.

[0010] Preferably, as an improvement, in step three, the magnesium oxide powder is heated until it is dry to the point of being free of moisture before being filled.

[0011] Preferably, as an improvement, in step four, argon arc welding is used to weld the gap after the copper strip is longitudinally wrapped, and an argon-helium mixed gas is used as the protective gas.

[0012] Preferably, as an improvement, in step six, the temperature of the first annealing treatment is set to 350°C, and the temperature of the second annealing treatment is set to 370-420°C.

[0013] Preferably, as an improvement, in steps six and seven, the temperatures of the first and second water cooling are set to 25°C.

[0014] The beneficial effects of this scheme are: (1) pure copper rods are drawn, stranded and pressed into stranded copper conductors. This process can process copper rods into conductors with standard dimensions and dense structure, eliminate gaps between copper wires, and improve conductivity uniformity and current carrying capacity; (2) Mica tape has the characteristics of high temperature resistance, non-flammability and high insulation, forming the first fire-resistant insulation barrier of the cable. After the mica tape is wrapped, it is dried to remove the moisture adsorbed by the mica tape and avoid the insulation core from getting damp and its performance deteriorating. (3) The insulating core is wrapped with copper tape to form a sheath blank, and then dried magnesium oxide powder is evenly filled in the gap. The magnesium oxide powder and mica tape are combined to form a composite insulation layer, which improves the insulation resistance and fire resistance of the cable. The magnesium oxide powder is dried to prevent it from getting damp and clumping, thus ensuring the uniformity and stability of the insulation layer. (4) Argon-helium mixed gas is used as the protective gas, and the gap after the copper strip is longitudinally wrapped is welded by argon arc welding to avoid defects such as porosity and cracks in the weld, improve the sealing performance of the copper protective sleeve, and at the same time, the weld can be hammered to compact the magnesium oxide powder inside the copper strip, eliminate the filling void, and release the residual stress generated by welding, avoid defects such as cracking and leakage in the later stage of the weld, and further improve the strength and sealing performance of the copper protective sleeve. (5) By rounding and straightening the copper protective sleeve, the tube deformation caused by welding is corrected to ensure the uniformity of the cable outer diameter. Then, the copper protective sleeve is rolled into a corrugated tube shape to improve the bending performance of the cable and adapt to various complex wiring scenarios. In addition, the radial extrusion during the corrugation rolling can compact the magnesium oxide powder again, making the composite insulation layer denser. (6) The copper protective sleeve is gradually softened by two annealing processes, eliminating the processing stress caused by welding and rolling, improving the toughness and service life of the copper protective sleeve, forming a slightly positive pressure oxygen-free environment in the nitrogen pipeline, avoiding oxidation and blackening of the high-temperature copper protective sleeve, protecting the grounding conductivity of the copper protective sleeve, and at the same time, the nitrogen pipeline can also prevent water vapor in the external environment from seeping into the gaps of the copper protective sleeve. (7) A polyethylene waterproof layer and a polyvinyl chloride or polyolefin outer sheath are extruded sequentially on the outside of the copper protective sheath, so that the outer wall of the insulating core is formed in sequence a composite protective structure of magnesium oxide powder insulation layer, copper tape protective layer, waterproof inner layer and protective outer layer. The outer sheath of the corresponding cable can be produced according to the different needs of users. The polyethylene molecular structure is dense and has low water absorption rate, which can closely fit the corrugated copper protective sheath outer wall. The polyvinyl chloride material is wear-resistant, compression-resistant and scratch-resistant, and can resist common damage such as construction dragging and external impact. It also has good flame retardancy, which can improve the overall fire resistance of the cable. Polyolefin is resistant to high and low temperatures and UV aging, and can be adapted to outdoor conditions such as outdoor installation and outdoor pipe gallery, thus improving the overall service life of the cable. Attached Figure Description

[0015] Figure 1 This is a flowchart of the continuous preparation process in Example 1 of the present invention. Detailed Implementation

[0016] The following detailed description illustrates the specific implementation method: Example 1 Example 1 is basically as shown in the appendix. Figure 1 As shown, Figure 1The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable, shown below, is carried out using a BTTZ mineral-insulated cable production line (FHL-35 type), and includes the following steps: Step 1: Pre-treatment. 99.99% high-purity copper rod is selected as the conductor raw material. A high-speed wire drawing machine (model: JCJX-LSD450-19) is used to draw the pure copper rod into wires. After drawing, the copper wires are stranded and compressed using a stranding and pressing machine (model: JLK630) to obtain 1 120mm 2 The stranded copper conductors are cleaned every 30 minutes using an industrial vacuum cleaner (model: XGB610-22BS5) to remove residual copper powder impurities from the wire drawing equipment and stranding press.

[0017] Step 2: Insulation wrapping. A fully automatic wrapping machine (model: WRBJ-BJ-2B) is used to tightly wrap mica tape around the stranded copper conductor to form a core insulation layer. The overlap rate of the mica tape wrapping is ≥20%, thus obtaining the insulating core. After wrapping, the insulating core is sent into a drying oven (model: SX-HX-01) and dried at 80℃ for 2 hours. After drying, a combined manual and machine (power frequency spark machine, model: GP-15) inspection is carried out to confirm that the insulation layer is free from damage, wrinkles, and loosening.

[0018] Step 3: Filling and molding. Place magnesium oxide powder in a heater and dry it at a constant temperature of 100℃ for 30 minutes until it is dry to the point of being free of moisture. Insert the qualified insulating core into the matching conductor core tube. Then, select a copper strip with a thickness of 1.4mm and a width of 97.53mm and complete the longitudinal wrapping of the copper strip on a fully automatic copper strip forming machine. Use a quantitative filling device to evenly fill the gap between the core tube and the insulating core with magnesium oxide powder to form an insulating layer. Then, use a high-pressure air gun to blow away the rollers of the copper strip forming machine and the gaps after the longitudinal wrapping of the copper strip, and wipe the outer wall of the longitudinally wrapped copper strip with an alcohol cloth to further clean the copper powder and magnesium oxide powder in the gaps.

[0019] Step 4: Sheath Welding. A continuous argon arc welding machine (model: EWM-AG-351-2) is used, employing an argon-helium mixed gas as the welding shielding gas. The gaps in the longitudinally wrapped copper strip are welded, and the weld seam is hammered after welding to form a sealed copper protective sleeve. During this process, the argon pressure is set to 1.5 MPa, and the helium pressure is set to 5 MPa to obtain the copper protective sleeve. Before welding, the integrity of the tungsten needle on the welding torch is checked, and the hammer hammering frequency is set to 60 times per minute. During welding, the weld quality is monitored in real time using a weld seam monitoring camera. If any abnormalities such as arc interruption or deviation occur, staff are immediately notified for assistance. If the downtime exceeds 10 minutes, the magnesium oxide powder inside the longitudinally wrapped copper strip is manually loosened to prevent agglomeration. Specifically, staff use a drilling device to drill holes on the underside of the completed longitudinally wrapped copper strip to discharge the compacted magnesium oxide powder through the holes.

[0020] Step 5: Corrugation and Shaping. The welded copper protective sleeve is fed into a horizontal rolling mill (model: LS-W35), and the running speed of the horizontal rolling mill is set to 15m / min. The oil supply pipeline is opened to inject rolling oil into the rolls to straighten and round the copper protective sleeve. Then, the copper protective sleeve is fed into a corrugating mill (model: CX-YW40) to roll the copper protective sleeve into a corrugated tube with a peak height of 5mm and a pitch of 10mm, thus obtaining the cable. After corrugation is completed, the surface smoothness of the cable is inspected by a surface inspection instrument (model: WT-182) to ensure that there are no defects such as damage, scratches, or pits on the outer wall of the cable.

[0021] Step Six: Softening and Straightening. The cable is sent into the first annealing furnace (model: CKL-AN35) for the first annealing treatment. The temperature of the first annealing treatment is set to 350℃. After the first annealing treatment, the cable is sent into the first water tank for the first water cooling. The cooling water temperature is set to 25℃. Observe whether bubbles appear on the surface of the cable. If bubbles appear, it is directly treated as a defective product. After the first water cooling, the cable is sent into the fully automatic straightening machine (model: CKL-JZ35) for straightening. After straightening, the cable is sent into the second annealing furnace for the second annealing treatment. The temperature of the second annealing treatment is set to 390℃. During this process, the cable is controlled by the traction machine (model: TQDY-2400) to move forward and backward. In this embodiment, the speed of the traction machine is set to 15m / min.

[0022] Step 7: Protection and Cooling. After the second annealing treatment, the cable is sent into a nitrogen protection pipeline (model: TP3042-BA). Nitrogen is injected into the nitrogen protection pipeline through the nitrogen pressure reducing valve. The pressure inside the nitrogen protection pipeline is set to 0.5MPa. The color and brightness of the cable are observed in real time to ensure that the cable is free of oxidation. After the cable comes out of the nitrogen pipeline, it enters the second water tank for a second water cooling. The cooling water temperature is set to 25℃. Observe whether bubbles appear on the surface of the cable. If bubbles appear, it is directly treated as a defective product.

[0023] Step 8: Inkjet coding and cable winding. Use an online inkjet printer (model: 625N-55-D) to print the specifications, target, and rated voltage parameters on the cable surface. Then, use a fully automatic winding device (model: 2000 gantry winding rack) to wind the cable into a standard cable reel.

[0024] Step 9: Inspection and warehousing. The cable reels are inspected for quality, and after passing the inspection, they are packaged and put into storage.

[0025] Example 2 Example 2 and Example 1 are largely similar in principle, with the difference being: Step 1, pretreatment, uses 99.99% high-purity copper rod as the conductor raw material, and employs a high-speed wire drawing device to draw the pure copper rod into wires. After the wire drawing process, the copper wires are twisted and compressed according to the 4-core requirement, thereby obtaining 4 cores. 70mm 2 Stranded copper conductor.

[0026] Step 2: Insulation wrapping. A fully automatic wrapping machine is used to tightly wrap mica tape around the stranded copper conductor to form a core insulation layer. The overlap rate of the mica tape wrapping is ≥20%, thus obtaining the insulating core. After wrapping, the insulating core is sent into a drying oven and dried at 80℃ for 2 hours. After drying, a combination of manual and machine inspection is carried out to confirm that the insulation layer is free from damage, wrinkles, and loosening.

[0027] Step 3: Filling and molding. Place magnesium oxide powder in a heater and dry it at a constant temperature of 100℃ for 30 minutes until it is dry to the point of being free of moisture. Insert the qualified insulating core into the matching conductor core tube. Then, select a copper strip with a thickness of 1.4mm and a width of 97.53mm and complete the longitudinal wrapping of the copper strip on a fully automatic copper strip forming machine. Use a quantitative filling device to evenly fill the gap between the copper strip and the insulating core with magnesium oxide powder to form an insulating layer. Then, use a high-pressure air gun to blow away the rollers of the copper strip forming machine and the gaps after the longitudinal wrapping of the copper strip, and wipe the outer wall of the longitudinally wrapped copper strip with an alcohol cloth to further clean the copper powder and magnesium oxide powder in the gaps.

[0028] Step 4: Sheath welding. A continuous argon arc welding machine is used, employing an argon-helium mixed gas as the welding shielding gas. The gaps in the longitudinally wrapped copper strip are welded, and the weld seam is hammered after welding to form a sealed copper protective sleeve. During this process, the argon pressure is set to 1.5 MPa and the helium pressure to 5 MPa to obtain the copper protective sleeve. Before welding, the integrity of the tungsten needle in the welding torch is checked, and the hammer hammering frequency is set to 60 times per minute. During welding, the weld quality is monitored in real time using a weld seam monitoring camera. If any abnormalities such as arc interruption or deviation occur, staff are immediately notified for assistance. If the downtime exceeds 10 minutes, the magnesium oxide powder inside the longitudinally wrapped copper strip is manually loosened to prevent clumping.

[0029] Step 5: Corrugation and Shaping. The welded copper protective sleeve is fed into a horizontal rolling mill, and the running speed of the horizontal rolling mill is set to 12m / min. The oil supply pipeline is turned on to inject rolling oil into the rolls to straighten and round the copper protective sleeve. Then, the copper protective sleeve is fed into a corrugating mill to roll it into a corrugated tube with a crest height of 5mm and a pitch of 10mm, thus obtaining the cable. After corrugation is completed, the surface smoothness of the cable is inspected by a surface inspection instrument to ensure that there are no defects such as damage, scratches, or pits on the outer wall of the cable.

[0030] Step Six: Softening and Straightening. The cable is sent into the first annealing furnace for the first annealing treatment, with the temperature set at 350°C. After the first annealing treatment, the cable is sent into the first water tank for the first water cooling, with the cooling water temperature set at 25°C. Observe whether bubbles appear on the surface of the cable. If bubbles appear, it is directly treated as a defective product. After the first water cooling, the cable is sent into the fully automatic straightening machine for straightening. After straightening, the cable is sent into the second annealing furnace for the second annealing treatment, with the temperature set at 400°C. During this process, the cable is moved forward and backward by the traction machine. In this embodiment, the speed of the traction machine is set to 12 m / min.

[0031] Step 7: Protection and Cooling. After the second annealing treatment, the cable is sent into the nitrogen protection pipeline. Nitrogen is injected into the nitrogen protection pipeline through the nitrogen pressure reducing valve. The pressure in the nitrogen protection pipeline is set to 0.5MPa. The color and brightness of the cable are observed in real time to ensure that the cable is free of oxidation. After the cable comes out of the nitrogen pipeline, it enters the second water tank for a second water cooling. The cooling water temperature is set to 25℃. Observe whether bubbles appear on the surface of the cable. If bubbles appear, it is directly treated as a defective product.

[0032] Step 8: Inkjet printing and cable winding. The specifications, model, target, and rated voltage parameters are printed on the surface of the cable using an online inkjet printer. Then, a fully automatic winding device is used to wind the cable into a standard cable reel.

[0033] Step 9: Inspection and Warehousing. The cable reel is inspected for quality. After passing the quality inspection, a polyethylene waterproof layer is extruded onto the outer wall of the cable using an extruder (model: SJ-90-25). Then, a polyvinyl chloride outer sheath is extruded onto the outer wall of the polyethylene waterproof layer. During this process, the extrusion temperature of the extruder is set to 180℃. After the extrusion is completed, the surface quality of the cable is inspected using a surface inspection instrument. After passing the inspection, the cable is packaged and put into storage.

[0034] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A continuous manufacturing process for high-yield mineral-insulated fire-resistant cables, characterized in that, Includes the following steps: Step 1: Pre-treatment. The pure copper rod is drawn into wires. After the wires are drawn, they are twisted and pressed to obtain a stranded copper conductor. Step 2: Insulation wrapping. Mica tape is wrapped around the outer wall of the stranded copper conductor to obtain the insulating core. After wrapping, the core is dried. Step 3: Filling and molding. Copper strips are longitudinally wrapped around the outer wall of the insulating core. After the longitudinal wrapping is completed, magnesium oxide powder is filled between the copper strips and the insulating core to form an insulating layer. Step 4: Welding the protective sleeve. After welding the longitudinal wrapping, the gaps between the copper strips are filled to obtain the copper protective sleeve. The weld is then hammered. Step 5: Rolling and shaping. The copper protective sheath is rounded and then rolled into a corrugated tube to obtain the cable. Step 6: Softening and straightening. Perform the first annealing treatment and the second annealing treatment on the cable in sequence. After the first annealing treatment, perform the first water cooling on the cable. Step 7: Protection and Cooling. After completing Step 6, place the cable into a nitrogen pipeline for cooling, and then perform a second water cooling on the cable.

2. The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable according to claim 1, characterized in that: It also includes step eight, inkjet printing and winding, which involves printing the specifications, target, and rated voltage parameters on the cable surface before winding the cable into a reel; Step 9: Inspection and warehousing. The cable reels are inspected for quality, and after passing the inspection, they are packaged and put into storage.

3. The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable according to claim 2, characterized in that: Step nine also includes: sequentially extruding a waterproof layer and an outer sheath onto the outer wall of the cable.

4. The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable according to claim 3, characterized in that: The waterproof layer is made of polyethylene, and the outer protective layer is made of polyvinyl chloride or polyolefin.

5. The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable according to claim 4, characterized in that: In step three, the magnesium oxide powder is heated until it is dry to the point of being free of moisture before being filled.

6. The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable according to claim 5, characterized in that: In step four, argon arc welding is used to weld the gap after the copper strip is longitudinally wrapped, and an argon-helium mixture is used as the protective gas.

7. The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable according to claim 6, characterized in that: In step six, the temperature for the first annealing treatment is set to 350℃, and the temperature for the second annealing treatment is set to 370-420℃.

8. The continuous manufacturing process for a high-yield mineral-insulated fire-resistant cable according to claim 7, characterized in that: In steps six and seven, the temperatures for the first and second water cooling are set to 25°C.

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