An external water bag type cable with self-extinguishing function and a preparation method thereof

Abstract

The present application relates to the technical field of power cable, especially to an external water bag type cable with self-extinguishing function and a preparation method thereof, comprising at least one hollow fire extinguishing pipe arranged outside the outer sheath of the cable body, the fire extinguishing pipe is made of flexible polymer material and is provided with structural weak points on the pipe wall, and the fire extinguishing pipe is filled with liquid fire extinguishing medium added with gelatinizing agent. The present application realizes active rescue and continuous protection in the early stage of fire by releasing the fire extinguishing medium and forming a gelatinizing protective film through the external fire extinguishing pipe and the gelatinizing fire extinguishing medium under high temperature of fire.

Description

Technical Background

[0001] This invention relates to the field of power cable technology, and in particular to an external water-filled cable with self-extinguishing function and its manufacturing method.

[0002] With the widespread application of power systems and communication networks, cable fires have become a major safety hazard. In tunnels, pipe corridors, shafts, and other locations where cables are densely laid, once a fire occurs, flames can easily spread along the cable surface, causing large-scale power outages, communication disruptions, and economic losses. Traditional flame-retardant cables mainly rely on adding flame-retardant materials to slow the spread of flames, but this method is passive protection and cannot actively extinguish the fire. Existing technology has developed fire-resistant cables with built-in fire-extinguishing chambers. These chambers, filled with fire-extinguishing media, are located within the sheath layer. In the event of a fire, the chamber ruptures, releasing the fire-extinguishing media. However, this type of built-in structure has inherent drawbacks: the fire extinguishing chamber is embedded inside the cable sheath, encroaching on the cable's structural space; the chamber structure has a potential impact on the cable's electrical and insulation performance; and since the chamber is integrally formed with the cable sheath, it cannot be repaired or replenished with fire extinguishing media once it ruptures, rendering its fire extinguishing capability one-time use. Furthermore, the gaseous fire extinguishing media used diffuses rapidly in open spaces, making it difficult to form continuous protection on the cable surface, which is particularly disadvantageous for vertically or inclined cables. In addition, the built-in chamber is a continuous, through-type structure in long-distance cables; a rupture in one area will lead to the complete leakage of the fire extinguishing media along the entire line, making it impossible to achieve precise zoned protection. Therefore, how to provide an active fire extinguishing cable with a fire extinguishing structure independent of the cable's electrical unit, rapid response, capable of achieving precise zoned and continuous protection, and easy maintenance is a technical problem urgently needing to be solved in this field. Summary of the Invention

[0003] The technical problem to be solved by this invention is that existing flame-retardant cable fire protection methods are passive, the built-in fire extinguishing chamber has a complex structure, affects the electrical performance of the cable, and the fire extinguishing capability is only one-time, and the gaseous fire extinguishing medium is difficult to form continuous protection in open spaces. There is a lack of an active fire extinguishing cable with an independent external fire extinguishing structure that can achieve precise and continuous protection in zones and is easy to maintain.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows: an external water-filled cable with self-extinguishing function, comprising a cable body having a conductor, an insulation layer, a core wrapping tape, and an outer sheath arranged sequentially from the inside out. At least one hollow fire extinguishing conduit is attached to the outer side of the outer sheath of the cable body. The fire extinguishing conduit is made of a flexible polymer material, and its wall has structural weak points. The melting point or softening point of the structural weak points is lower than the melting point of the outer sheath material. The fire extinguishing conduit is filled with a liquid fire extinguishing medium, which is water or an aqueous solution containing flame retardants and antifreeze. A gelling agent is added to the liquid fire extinguishing medium. The gelling agent is selected from one or a combination of sodium polyacrylate, sodium carboxymethyl cellulose, polyethylene glycol, or polyvinyl alcohol, and the mass concentration of the gelling agent in the liquid fire extinguishing medium is 0.5% to 5%. The fire extinguishing conduit is divided into multiple independent sealed fire extinguishing unit segments along its length by an isolation and sealing section. Each fire extinguishing unit segment has structural weak points on its wall.

[0005] Furthermore, the main material of the fire extinguishing conduit is selected from one or a combination of polyethylene, polyvinyl chloride, polypropylene or thermoplastic elastomer, and the fire extinguishing conduit is spirally wound or longitudinally arranged on the outside of the outer sheath.

[0006] Furthermore, structural weak points can be addressed using one or more structural forms, such as localized thinning zones, V-shaped or U-shaped notches, or composite material interfaces.

[0007] Furthermore, the local thinning zone is formed by extruding a die during the fire extinguishing conduit molding process, creating a strip on the pipe wall with a thickness lower than other areas; V-shaped or U-shaped grooves are formed on the pipe wall after the fire extinguishing conduit is formed by mechanical indentation or laser etching; and the composite material interface is formed by embedding a polymer strip with a melting point lower than that of the outer sheath material to create a heterogeneous interface weak zone.

[0008] Furthermore, the polymer strips in the composite material interface are selected from one or a combination of ethylene-vinyl acetate copolymer, polyisobutylene, or paraffin-based blends, with melting or softening points between 50°C and 90°C.

[0009] Furthermore, the gelling agent is sodium polyacrylate or sodium carboxymethyl cellulose, and the mass concentration of the gelling agent in the liquid extinguishing medium is 1% to 3%.

[0010] Furthermore, the isolation sealing section is a heat-pressed sealing structure or an injection-molded sealing structure, and the length of the fire extinguishing unit section between adjacent isolation sealing sections is 2m to 20m.

[0011] Furthermore, when the fire extinguishing conduit is installed longitudinally, it is fixedly connected to the outer sheath of the cable body by spaced reinforcing ribs or straps. The reinforcing ribs are integrally formed or welded to the fire extinguishing conduit, and the other end of the reinforcing ribs is fixed to the outer sheath by hot melt adhesive, adhesive or mechanical means.

[0012] Furthermore, the fire extinguishing conduit is equipped with sealing heads at both ends, one of which is equipped with a repeatedly openable and closed filling valve, and the end of the fire extinguishing conduit is equipped with a pressure monitoring interface for connection to an external monitoring system.

[0013] Furthermore, the above-mentioned method for preparing an external water-filled cable with self-extinguishing function includes the following steps: using cable manufacturing equipment to complete conductor drawing, insulation extrusion, core wrapping, and outer sheath extrusion of the cable body; simultaneously forming an isolation and sealing section during the fire extinguishing conduit molding process, dividing the fire extinguishing conduit along its length into multiple independent and sealed fire extinguishing unit sections; after extruding the outer sheath and before the cable is completely cooled, simultaneously attaching and fixing the prefabricated fire extinguishing conduit with reinforcing ribs to the surface of the outer sheath using hot pressing or ultrasonic welding processes, or fixing the fire extinguishing conduit with adhesive or mechanical binding tape after the cable has cooled; injecting liquid fire extinguishing medium containing gel into each fire extinguishing unit section through a filling valve and performing a sealing test; connecting the pressure monitoring interface, calibrating the system pressure, and then packaging and storing the cable in rolls.

[0014] The beneficial effects of this invention are as follows: By adding a gelling agent to the liquid extinguishing medium, after the extinguishing medium is sprayed, the water evaporates or seeps out, and the gelling agent forms a continuous viscoelastic gel film on the cable surface. This gel film can firmly adhere to the surface of vertical and inclined cables, providing continuous oxygen barrier and heat insulation protection. This effectively overcomes the defects of the gaseous extinguishing medium's instantaneous diffusion and the rapid loss of pure liquid extinguishing medium, achieving a continuous protective effect obtained from a single release. This is an unexpected technical effect that gaseous extinguishing media cannot achieve. By setting an isolation and sealing section in the extinguishing conduit to form multiple independently sealed extinguishing unit sections, it achieves... This system enables precise zoned protection along the cable route. A fire in one area only triggers the release of fire extinguishing units in that specific section, while the rest of the area remains intact. This solves the technical challenge of complete failure of protection in long-distance cables where a single rupture causes all damage. Furthermore, it allows for rapid location of the fire zone by monitoring the pressure status of each unit. The external fire extinguishing conduit is independent of the cable's electrical units and does not affect the cable's core conductivity and insulation performance. Combined with the filling valve and pressure monitoring interface, it enables the replenishment and maintenance of the medium and real-time monitoring of the system status. This upgrades the cable from a passive fireproofing material to an intelligent fire protection system with active monitoring and precise zoned protection capabilities. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 This is a schematic diagram of the fire extinguishing conduit in this invention with a longitudinal structure.

[0017] Figure 2 This is a schematic diagram of the fire extinguishing conduit in this invention, which has a spiral winding structure.

[0018] Figure 3 This is a cross-sectional view of the structural weak point in this invention as a locally thinned area.

[0019] Figure 4 This is a cross-sectional view of the structural weak point in this invention as a V-shaped or U-shaped notch.

[0020] Figure 5 This is a cross-sectional view of the composite material interface state where the structural weak point in this invention is located.

[0021] Figure 6 This is a flowchart of the present invention.

[0022] Explanation of reference numerals in the attached drawings: 100. Cable body; 110. Conductor; 120. Insulation layer; 130. Cable core wrapping; 140. Outer sheath; 200. Fire extinguishing conduit; 210. Structural weak point; 211. Local thinning area; 212. V-shaped or U-shaped notch; 213. Composite material interface; 220. Isolation and sealing section; 230. Fire extinguishing unit section; 300. Reinforcing rib; 310. Root of reinforcing rib; 400. Sealing head; 410. Filling valve; 420. Pressure monitoring interface; 500. Liquid fire extinguishing medium; 510. Gel agent; 520. Gel protective film. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. (Refer to...) Figures 1 to 6 This embodiment provides an external water-filled cable with self-extinguishing function, comprising a cable body 100 consisting of a conductor 110, an insulation layer 120, a core wrapping tape 130, and an outer sheath 140 arranged sequentially from the inside out. The cable body 100 adopts a conventional power cable structure. The conductor 110 is a conductive core wire. The insulation layer 120 covers the outside of the conductor 110 to achieve electrical insulation. The core wrapping tape 130 wraps around the outside of the insulation layer 120 for binding and protection. The outer sheath 140 is extruded on the outermost layer to provide mechanical and environmental protection for the entire cable.

[0024] The outer sheath 140 of the cable body 100 is spirally wound or longitudinally attached with at least one hollow fire extinguishing conduit 200. The fire extinguishing conduit 200 is made of a flexible polymer material and is used to store the extinguishing medium and automatically release it in the event of a fire. The main material of the fire extinguishing conduit 200 can be selected from one or a combination of polyethylene, polyvinyl chloride, polypropylene, or thermoplastic elastomers, preferably low-density polyethylene or soft polyvinyl chloride, due to their lower melting point and good flexibility, facilitating spiral winding and bending installation. The wall of the fire extinguishing conduit 200 is provided with structural weak points 210, the melting point or softening point of which is significantly lower than the melting point of the outer sheath 140 material, ensuring that the structural weak points 210 melt and rupture preferentially before the outer sheath 140 under high fire temperatures. The structural weak points 210 adopt one or more structural forms, such as local thinning zones, V-shaped or U-shaped notches, or composite material interfaces. The local thinning zones are formed by extrusion molding during the forming process of the fire extinguishing conduit 200, creating one or more strips on the wall with a thickness significantly lower than other areas. After the fire extinguishing conduit 200 is formed, V-shaped or U-shaped grooves are created on the outer or inner surface of the conduit wall through mechanical indentation or laser etching. The composite material interface is formed by embedding a polymer strip with an extremely low melting point into the fire extinguishing conduit 200 to create a weak region at the heterogeneous interface. This polymer strip is selected from one or a combination of ethylene-vinyl acetate copolymer, polyisobutylene, or paraffin-based blends, with a melting point or softening point between 50°C and 90°C.

[0025] The fire extinguishing conduit 200 is divided into multiple independently sealed fire extinguishing unit sections 230 along its length by an isolation and sealing section 220. Each fire extinguishing unit section 230 has a structural weak point 210 on its wall. The isolation and sealing section 220 is a heat-sealed or injection-molded sealing structure, which completely blocks the medium channel between adjacent fire extinguishing unit sections 230, preventing the fire extinguishing medium in each fire extinguishing unit section 230 from communicating with each other. The length of the fire extinguishing unit section 230 between adjacent isolation and sealing sections 220 is preferably 2m to 20m, and can be flexibly set according to the fire risk level of the cable laying location. For example, in densely cabled sections, the length can be increased to 2m to 5m, and in general sections, it can be set to 10m to 20m. When a fire occurs in a part of the cable, the high temperature only acts on the corresponding fire extinguishing unit section 230. The structural weak point 210 of that section will melt and release the fire extinguishing medium first, while the remaining fire extinguishing unit sections 230 remain sealed and continue to provide protection for other parts of the cable. Meanwhile, by monitoring the pressure changes in each fire-fighting unit section 230, the location of the fire can be quickly determined.

[0026] The fire extinguishing conduit 200 is filled with a liquid fire extinguishing medium 500, which is water or an aqueous solution containing flame retardants and antifreeze. The antifreeze prevents the fire extinguishing medium from freezing and expanding, damaging the conduit in low-temperature environments, while the flame retardant further enhances the fire extinguishing effect after the fire extinguishing medium is sprayed out. A gelling agent 510 is added to the liquid fire extinguishing medium 500. The gelling agent 510 is selected from one or a combination of sodium polyacrylate, sodium carboxymethyl cellulose, polyethylene glycol, or polyvinyl alcohol, preferably sodium polyacrylate or sodium carboxymethyl cellulose. The mass concentration of the gelling agent 510 in the liquid fire extinguishing medium 500 is 0.5% to 5%, preferably 1% to 3%. The gelling agent 510 exists stably in a dissolved state in the liquid fire extinguishing medium 500. When the fire extinguishing conduit 200 ruptures, the liquid fire extinguishing medium 500 is sprayed out, and the gelling agent 510 forms a three-dimensional network structure with water molecules, ultimately forming a continuous viscoelastic gel protective film 520 on the cable surface. The gel protective film 520 exhibits excellent adhesion, firmly adhering to the surfaces of both vertical and inclined cables without slippage. It also boasts a long drying time, providing continuous oxygen barrier and thermal insulation protection after spraying. Under flame conditions, the gel protective film 520 further carbonizes to form a dense carbonized layer, effectively blocking external oxygen from contacting the internal materials of the cable and inhibiting further combustion of the cable sheath.

[0027] The fire extinguishing conduit 200 is fixedly connected to the outer sheath 140 of the cable body 100 via spaced reinforcing ribs 300 or straps. The reinforcing ribs 300 are integrally formed or welded to the fire extinguishing conduit 200, and the other end of the reinforcing rib 300 is fixed to the outer sheath 140 by hot melt adhesive, bonding agent, or mechanical means. The connection point between the root 310 of the reinforcing rib 300 and the fire extinguishing conduit 200 features a rounded transition design to prevent stress concentration that could lead to conduit breakage. This spaced connection structure ensures a close and secure fit between the fire extinguishing conduit 200 and the cable, while facilitating cable bending and laying. It effectively solves the problems of thermal expansion and contraction and bending stress during long-distance laying, making the external fire extinguishing conduit 200 and the cable body 100 a flexible, collaborative whole.

[0028] The fire extinguishing conduit 200 is equipped with sealing heads 400 at both ends to seal the ends and prevent leakage of the extinguishing medium. One sealing head 400 is equipped with a reusable filling valve 410, used to inject liquid extinguishing medium 500 into each fire extinguishing unit section 230 during installation and to replenish the medium during subsequent maintenance. The fire extinguishing conduit 200 also has a pressure monitoring interface 420 at its end for connection to an external monitoring system to monitor the internal pressure of each fire extinguishing unit section 230 in real time. When a structural weak point 210 in a fire extinguishing unit section 230 ruptures and releases the extinguishing medium, the pressure in that section drops significantly. The monitoring system can then detect the anomaly and issue an alarm signal, indicating the specific location of the fire. For fire extinguishing unit sections 230 treated with gel agent 510, even after the structural weak point 210 has been triggered and released, the continued action of the gel protective film 520 can still provide protection for the cable for a period of time, buying time for subsequent maintenance and replacement of the fire extinguishing conduit 200.

[0029] When a section of the cable is exposed to fire, the high-temperature flames or heat first act on the fire extinguishing conduit 200 located outside the cable body 100. The structural weak point 210 in the corresponding section rapidly melts or softens and ruptures under high temperature. After the nozzle forms, the liquid extinguishing medium 500 stored in this extinguishing unit section 230 is instantly ejected under the action of gravity and internal pressure, covering the cable surface and surrounding fire sources, achieving rapid cooling and suffocation of the flames. The gelling agent 510 in the extinguishing medium cross-links with water molecules after being sprayed to form a gel protective film 520, which is adsorbed on the cable surface for continuous oxygen barrier and heat insulation. Simultaneously, because the remaining extinguishing unit sections 230 remain sealed, the protection of other parts of the cable is unaffected. The monitoring system detects the pressure drop at abnormal locations through the pressure monitoring interface 420, locating the fire section.

[0030] The manufacturing process of this cable is as follows: using conventional cable manufacturing equipment, the following processes are completed sequentially: conductor 110 drawing, insulation layer 120 extrusion, core wrapping tape 130 wrapping, and outer sheath 140 extrusion. During the extrusion molding of the fire extinguishing conduit 200, an isolation sealing section 220 is simultaneously formed through hot-press sealing or injection molding, dividing the fire extinguishing conduit 200 into multiple independent sealed fire extinguishing unit sections 230 along its length. After extruding the outer sheath 140 and before the cable has completely cooled, the prefabricated fire extinguishing conduit 200 with reinforcing ribs 300 is simultaneously attached and fixed to the still-warm outer sheath 140 surface through hot-pressing or ultrasonic welding; alternatively, after the cable has completely cooled, the fire extinguishing conduit 200 can be fixed to the outer sheath 140 surface using adhesive or mechanical binding tape. After fixing, liquid extinguishing medium 500 containing gel agent 510 is injected into each extinguishing unit section 230 through the filling valve 410, and a sealing test is performed to ensure there is no leakage before sealing the sealing head 400. After connecting the pressure monitoring interface 420 and calibrating the system pressure, it is packaged in rolls and stored.

Claims

1. An external water-filled cable with self-extinguishing function, comprising a cable body (100) having a conductor (110), an insulation layer (120), a core wrapping tape (130), and an outer sheath (140) arranged sequentially from the inside out, characterized in that: At least one hollow fire extinguishing conduit (200) is attached to the outer side of the outer sheath (140) of the cable body (100). The fire extinguishing conduit (200) is made of flexible polymer material. The wall of the fire extinguishing conduit (200) is provided with structural weak points (210). The melting point or softening point of the structural weak points (210) is lower than the melting point of the outer sheath (140) material. The fire extinguishing conduit (200) is filled with liquid fire extinguishing medium (500). The liquid fire extinguishing medium (500) is water or an aqueous solution with added flame retardant and antifreeze. A gelling agent (510) is added to the liquid extinguishing medium (500). The gelling agent (510) is selected from one or a combination of sodium polyacrylate, sodium carboxymethyl cellulose, polyethylene glycol or polyvinyl alcohol. The mass concentration of the gelling agent (510) in the liquid extinguishing medium (500) is 0.5% to 5%. The extinguishing conduit (200) is divided into multiple independent sealed extinguishing unit sections (230) along its length by an isolation sealing section (220). Each extinguishing unit section (230) has the aforementioned structural weak point (210) on its pipe wall.

2. The external water-filled cable with self-extinguishing function according to claim 1, characterized in that: The main material of the fire extinguishing conduit (200) is selected from one or a combination of polyethylene, polyvinyl chloride, polypropylene or thermoplastic elastomer, and the fire extinguishing conduit (200) is spirally wound or longitudinally arranged on the outside of the outer sheath (140).

3. The external water-filled cable with self-extinguishing function according to claim 1, characterized in that: The structural weak point (210) adopts one or more of the following structural forms: local thinning area (211), V-shaped or U-shaped notch (212), or composite material interface (213).

4. An external water-filled cable with self-extinguishing function according to claim 3, characterized in that: The local thinning zone (211) is formed by extruding a die during the forming process of the fire extinguishing conduit (200) to create a strip with a thickness lower than other areas on the pipe wall; the V-shaped or U-shaped groove (212) is formed on the pipe wall by mechanical indentation or laser etching after the fire extinguishing conduit (200) is formed; the composite material interface (213) is formed by embedding a polymer strip with a melting point lower than that of the outer sheath (140) material to create a heterogeneous interface weak zone.

5. An external water-filled cable with self-extinguishing function according to claim 4, characterized in that: The polymer strips in the composite material interface (213) are selected from one or a combination of ethylene-vinyl acetate copolymer, polyisobutylene or paraffin-based blends, with a melting point or softening point between 50°C and 90°C.

6. An external water-filled cable with self-extinguishing function according to claim 1, characterized in that: The gelling agent (510) is sodium polyacrylate or sodium carboxymethyl cellulose, and the mass concentration of the gelling agent (510) in the liquid extinguishing medium (500) is 1% to 3%.

7. An external water-filled cable with self-extinguishing function according to claim 1, characterized in that: The isolation sealing section (220) is a hot-press sealing structure or an injection-molded sealing structure, and the length of the fire extinguishing unit section (230) between adjacent isolation sealing sections (220) is 2m to 20m.

8. An external water-filled cable with self-extinguishing function according to claim 2, characterized in that: When the fire extinguishing conduit (200) is installed longitudinally, it is fixedly connected to the outer sheath (140) of the cable body (100) by spaced reinforcing ribs (300) or straps. The reinforcing ribs (300) are integrally formed or welded to the fire extinguishing conduit (200). The other end of the reinforcing ribs (300) is fixed to the outer sheath (140) by hot melt glue, adhesive or mechanical means.

9. An external water-filled cable with self-extinguishing function according to claim 1, characterized in that: The fire extinguishing conduit (200) is provided with sealing heads (400) at both ends, one of which is equipped with a repeatedly openable and closed filling valve (410), and the end of the fire extinguishing conduit (200) is provided with a pressure monitoring interface (420) connected to an external monitoring system.

10. A method for preparing an external water-filled cable with self-extinguishing function according to any one of claims 1 to 9, characterized in that: The process includes the following steps: Step 1, using cable manufacturing equipment to complete the drawing of the conductor (110), extrusion of the insulation layer (120), wrapping of the core tape (130), and extrusion of the outer sheath (140) of the cable body (100); Step 2, during the forming process of the fire extinguishing conduit (200), an isolation and sealing section (220) is simultaneously formed, dividing the fire extinguishing conduit (200) into multiple independent and sealed fire extinguishing unit sections (230) along its length; Step 3, after extruding the outer sheath (140) and before the cable is completely cooled, the cable is subjected to hot pressing or... The ultrasonic welding process simultaneously attaches and fixes the prefabricated fire extinguishing conduit (200) with reinforcing ribs (300) to the surface of the outer sheath (140), or after the cable cools down, the fire extinguishing conduit (200) is fixed with adhesive or mechanical strapping; Step four, each fire extinguishing unit section (230) is injected with liquid fire extinguishing medium (500) with added gel agent (510) through the filling valve (410) and a sealing test is performed; Step five, the pressure monitoring interface (420) is connected, the system pressure is calibrated, and then the conduit is rolled up, packaged, and stored.

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