A mineral-insulated fireproof cable and manufacturing process

Abstract

The application relates to the field of cables and manufacturing processes, in particular to a mineral insulation fireproof cable and a manufacturing process, the fireproof cable comprising a conductive part, an insulation part and a protection part, the conductive part comprising a plurality of twisted conductors and a conductor shielding layer covering the plurality of twisted conductors; the insulation part comprising a mineral protection layer, the mineral protection layer covering the conductor shielding layer, and the mineral protection layer comprising a binder matrix and fire-resistant aggregates dispersed in the binder matrix, the binder matrix being an elastic structure in a continuous phase; the protection part comprising an isolation protection layer covering the mineral protection layer, an armor layer covering the isolation protection layer and a flame-retardant outer sheath covering the armor layer, and the application improves the structural integrity of the mineral protection layer.

Description

Technical Field

[0001] This application relates to the field of cables and manufacturing processes, specifically to a mineral-insulated fire-resistant cable and its manufacturing process. Background Technology

[0002] Flexible mineral-insulated fire-resistant cables are widely used in high-rise buildings, rail transportation, petrochemical plants, and other locations with extremely high fire resistance requirements. These cables typically consist of multi-strand stranded conductors, a semi-conductive shielding layer covering the conductors, and an outer layer of mineral insulation material. Currently, flexible mineral-insulated fire-resistant cables are usually composed of a copper sheath encasing magnesium oxide powder.

[0003] However, in actual installation, the traditional loose powder filling structure of existing flexible mineral-insulated cables cannot fix the powder position while maintaining flexibility. Under repeated bending or axial tension caused by installation height differences, circumferential shear forces are easily generated inside the insulation. This shear force causes the internal powder to slip and accumulate, resulting in uneven insulation thickness and even delamination between the insulation and conductor shielding layer. In addition, when exposed to high-temperature environments such as fires, the binder decomposes, and the existing insulation material often loses its structural support after high-temperature carbonization, causing the powder to scatter. The loose mineral powder will fall off due to the impact of hot airflow, leading to insulation failure. Therefore, there is an urgent need for a cable structure that can maintain high flexibility at room temperature to adapt to installation and maintain a dense and non-loose structure throughout the entire fire process. Summary of the Invention

[0004] In order to solve the technical problems in the prior art, this application provides a mineral-insulated fireproof cable.

[0005] The mineral-insulated fire-resistant cable provided in this application adopts the following technical solution:

[0006] A mineral-insulated fire-resistant cable, comprising:

[0007] The conductive part includes a multi-strand stranded conductor and a conductor shielding layer covering the multi-strand stranded conductor;

[0008] An insulating portion includes a mineral protective layer covering the conductor shielding layer, and the mineral protective layer includes a binder matrix and refractory aggregate dispersed in the binder matrix, wherein the binder matrix has a continuous phase elastic structure.

[0009] The protective layer includes an isolation protective layer covering the mineral protective layer, an armor layer covering the isolation protective layer, and a flame-retardant outer sheath covering the armor layer.

[0010] By adopting the above technical solution, the film-forming properties of the binder matrix are used to wrap the refractory aggregate, which is originally dispersed and combined into a whole, thereby forming an elastic conductor shielding layer. This makes the mineral protective layer less prone to brittle fracture and eliminates the air gaps inside the insulation part, preventing slippage and misalignment between the refractory aggregates during cable bending and ensuring the stability of the cable structure.

[0011] Preferably, the space between the conductor shielding layer and the isolation protection layer is a receiving space for accommodating the mineral protection layer. The mineral protection layer further includes a restraining mesh, which divides the receiving space into a first receiving portion and a second receiving portion. The binder matrix and the refractory aggregate are respectively accommodated in the first receiving portion and the second receiving portion.

[0012] By adopting the above technical solution, the mineral protective layer is divided into inner and outer layers in the thickness direction using a constraint mesh. With the help of the through-pores distributed in the constraint mesh itself, the adhesive matrix in the first and second accommodating parts can penetrate and thermally fuse through the pores, thereby forming a mechanical interlocking structure on both sides of the constraint mesh, which enhances the interfacial bonding strength and prevents delamination inside the insulation part. At the same time, the constraint mesh acts as a physical barrier between the layers, blocking the radial propagation path of cracks from the second accommodating part to the first accommodating part, ensuring the integrity of the cable structure. In addition, the constraint mesh can absorb heat, thereby improving the heat dissipation performance of the cable.

[0013] Preferably, the first receiving portion is located between the conductor shielding layer and the constraint mesh, and the second receiving portion is located between the constraint mesh and the isolation protection layer. The distribution density of the refractory aggregate in the first receiving portion is greater than the distribution density of the refractory aggregate in the second receiving portion.

[0014] By adopting the above technical solution, the high-density aggregate stacking of the first receiving part forms a dense insulation area with high thermal conductivity and high pressure resistance, which can quickly transfer the heat generated by the conductor to the restraint mesh and withstand the electrical breakdown pressure under high field strength. The low-density aggregate distribution of the second receiving part leaves more resin-rich flexible space, making its elastic modulus lower than that of the first receiving part, thereby absorbing the deformation stress generated when the cable is bent.

[0015] Preferably, the conductor shielding layer further includes a plurality of limiting members distributed along the length direction of the cable. The limiting members include a limiting rod and a heat dissipation connecting ring formed at one end of the limiting rod. The heat dissipation connecting ring is sleeved on the conductor shielding layer, and the limiting rod passes through the mesh of the constraint net.

[0016] By adopting the above technical solution, the limiting rod passes through the mesh, thereby limiting the restraint mesh and preventing the restraint mesh from shifting relative to the conductor shielding layer. In addition, when the cable is in a bent state for a long time, the refractory aggregate powder inside the insulation part is prone to move to one side, resulting in uneven distribution of refractory aggregate in the insulation part. The limiting rod limits the distance between the isolation protection layer and the conductor shielding layer, further preventing the insulation part from becoming locally thinner due to powder displacement when the cable is bent.

[0017] Preferably, the end of the limiting rod away from the heat dissipation connecting ring is connected to an umbrella-shaped buffer cap, the bottom surface of the umbrella-shaped buffer cap abuts against the outer surface of the constraint net, and the top surface of the umbrella-shaped buffer cap abuts against the inner wall of the isolation and protective layer.

[0018] By adopting the above technical solution, the elastic umbrella-shaped buffer cap utilizes its own elastic deformation characteristics to achieve the insertion and fixation of the restraint net. In addition, the elastic umbrella-shaped buffer cap, as an elastic medium between the rigid limiting rod and the outer flexible protective layer, can absorb the radial dimensional changes generated during the cable's thermal cycling. When the cable heats up and expands internally, the umbrella-shaped buffer cap undergoes elastic contraction deformation under pressure. When the cable cools and contracts, the umbrella-shaped buffer cap rebounds using its elastic potential energy, maintaining effective contact with the isolation protective layer and preventing the internal structure from loosening.

[0019] Preferably, the heat dissipation connecting ring has a plurality of through holes along its circumferential surface, and the outer peripheral surface of the conductor shielding layer is formed with limiting flanges for abutting against the side walls of the heat dissipation connecting ring.

[0020] By adopting the above technical solution, the heat dissipation connecting ring acts as a heat conduction medium, quickly transferring the heat generated by the conductor to the limiting rod; the through hole allows the adhesive matrix in the first receiving part to pass through or penetrate in a fluid state, and after curing, it forms a mechanical interlocking structure to prevent the metal heat dissipation connecting ring from delaminating with the inner insulating material during repeated thermal expansion and contraction; the limiting flange cooperates with the side wall of the heat dissipation connecting ring to ensure the precise positioning of the limiting component in the conductor axial direction and prevent slippage during installation.

[0021] Preferably, the refractory aggregate is magnesium oxide powder modified with a silane coupling agent, and the binder matrix includes silicone rubber and glass powder dispersed in the silicone rubber.

[0022] By adopting the above technical solution, when the mineral protective layer encounters high temperature in a fire, the glass powder melts and adheres to the refractory aggregate, so that the mineral protective layer changes from a flexible state to a hard solid layer, thereby preventing the refractory aggregate from falling off and scattering.

[0023] A manufacturing process for a mineral-insulated fire-resistant cable, the process comprising the following steps:

[0024] S1. Install multiple limiting members on the surface of the conductive part, so that the heat dissipation connecting ring is located between the limiting flanges, thereby constructing the inner layer skeleton of the insulating part;

[0025] S2. Fill the space between each limiting member with adhesive matrix and refractory aggregate to fill the space of the first receiving part, wrap the restraint net around the outside of the first receiving part, and fill the outside of the restraint net with adhesive matrix and refractory aggregate to fill the second receiving part, thus constructing a mineral protective layer.

[0026] S3. The mineral protective layer is heated and cured until the adhesive matrix is ​​transformed into a continuous phase elastic structure;

[0027] S4. After the mineral protective layer has been cured, an isolation protective layer and an armor layer are sequentially wrapped around the outside of the mineral protective layer.

[0028] By adopting the above technical solution, the process involves coating the mixture of binder matrix and refractory aggregate in batches, with the intermediate constraining mesh, thus completing the orderly arrangement of the internal structure of the insulation part during the manufacturing process; the curing rather than sintering in step S3 ensures that the binder matrix is ​​in a "continuous phase elastic structure" in the factory state, retaining the flexibility of the organic polymer material, enabling the cable to be bent and laid, and avoiding the rigid brittle fracture problem caused by the pre-sintering of ceramics in traditional mineral cables.

[0029] Preferably, the construction of the mineral protective layer in step S2 specifically includes the following steps:

[0030] S21. After mixing the binder matrix with the high-density refractory aggregate, fill the conductive part surface, and control the filling thickness to be less than the height of the limiting rod.

[0031] S22. The umbrella-shaped buffer cap is made to pass through the mesh of the constraint net by its elastic deformation, and then abuts against the outer surface of the constraint net after it recovers its deformation.

[0032] S23. The binder matrix is ​​mixed with low-density refractory aggregate and then filled onto the surface of the restraint mesh to cover the limiting components and the restraint mesh.

[0033] By adopting the above technical solution, steps S21 and S23 ensure that the inner layer has high thermal conductivity and pressure resistance and the outer layer is flexible by controlling the proportion of refractory aggregate; S22 uses limiting members to pass through the mesh to achieve mechanical anchoring of the constraint mesh during the manufacturing process, preventing the mesh from slipping during the subsequent filling process, and at the same time uses the mesh to force the inner and outer layer adhesive matrix to contact, thereby enhancing the interlayer bonding force.

[0034] Preferably, step S5, which involves covering the isolation and protective layer and the armor layer, specifically includes the following steps:

[0035] S41. Wrap the protective layer around the mineral protective layer and apply radial tension to make the protective layer press against the limiting element;

[0036] S42. Cover the armor layer and make a non-adhesive sliding contact between the armor layer and the isolation and protection layer.

[0037] By adopting the above technical solution, step S41 uses the limiting component as the sizing reference to forcibly correct the concentricity of the mineral protective layer under the action of external tension, preventing uneven insulation thickness. At the same time, the limiting component bears the main radial pressure, avoiding excessive deformation of the internal adhesive matrix that has not yet fully hardened. The reserved gap in S42, in conjunction with the internal flexible matrix, reduces the interlayer frictional resistance when the cable is bent.

[0038] In summary, this application includes at least one of the following beneficial technical effects:

[0039] 1. By utilizing the film-forming properties of the binder matrix to encapsulate the refractory aggregate, the originally dispersed refractory aggregate is combined into a whole, thereby forming an elastic insulating part. This makes the mineral protective layer less prone to brittle fracture and eliminates the air gaps inside the insulating part, preventing slippage and misalignment between the refractory aggregate during cable bending and ensuring the stability of the cable structure.

[0040] 2. A constraint mesh is used to divide the mineral protective layer into inner and outer layers in the thickness direction. The interconnected pores within the constraint mesh allow the adhesive matrix in the first and second accommodating parts to permeate and thermally fuse through these pores, forming a mechanically interlocking structure on both sides of the constraint mesh. This enhances the interfacial bonding strength and prevents insulation delamination. Simultaneously, the constraint mesh acts as a physical barrier between the layers, blocking the radial propagation path of cracks from the second accommodating part to the first accommodating part, ensuring the integrity of the cable structure. Furthermore, the constraint mesh absorbs heat, improving the cable's heat dissipation performance. The high-density aggregate accumulation in the first accommodating part forms a dense insulation zone with high thermal conductivity and high pressure resistance, rapidly transferring heat generated by the conductor to the constraint mesh and withstanding electrical breakdown pressure under high field strength. The low-density aggregate distribution in the second accommodating part leaves more flexible, resin-rich space, resulting in a lower elastic modulus than the first accommodating part, thus absorbing the deformation stress generated during cable bending.

[0041] 3. The limiting rod passes through the mesh, thus limiting the restraint mesh and preventing displacement of the restraint mesh relative to the conductor shielding layer. In addition, when the cable is in a bent state for a long time, the refractory aggregate powder inside the insulation part is prone to move to one side, resulting in uneven distribution of refractory aggregate in the insulation part. The limiting rod limits the distance between the isolation protection layer and the conductor shielding layer, further preventing local thinning of the insulation part caused by powder displacement when the cable is bent. The through hole opened in the heat dissipation connecting ring allows the adhesive matrix in the second receiving part to penetrate in a fluid state. The mechanical interlock formed after curing prevents the metal heat sink and the insulation part from delaminating and falling off due to the difference in thermal expansion coefficients.

[0042] 4. When the mineral protective layer encounters high temperatures during a fire, the glass powder melts and binds the refractory aggregate, transforming the mineral protective layer from a flexible state into a hard, solid layer. This prevents the refractory aggregate from falling off and scattering. Furthermore, the refractory aggregate used in this application is magnesium oxide powder modified with a silane coupling agent. Ordinary magnesium oxide powder is prone to moisture absorption; after absorbing water, its insulation resistance drops sharply, and the vaporization of water molecules at high temperatures may cause cracking of the insulation. Through silane coupling agent modification, a hydrophobic molecular layer is formed on the surface of the magnesium oxide, preventing the magnesium oxide powder from absorbing water. The modification also improves the interfacial compatibility between the inorganic powder and the organic binder, thus improving the flowability of the mixture. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a mineral-insulated fireproof cable provided in Embodiment 1 of this application;

[0044] Figure 2 yes Figure 1 Enlarged view of region A in the middle;

[0045] Figure 3 This is a partial cross-sectional view of the installation structure of the limiting component;

[0046] Figure 4 This is a schematic diagram of the cross-sectional structure of the mineral-insulated fire-resistant cable in the multi-core cabling application scenario of this application;

[0047] Explanation of reference numerals in the attached drawings: 1. Conductive part; 11. Stranded conductor; 12. Conductor shielding layer; 2. Insulating part; 21. Mineral protective layer; 211. Adhesive matrix; 212. Refractory aggregate; 213. Restraining mesh; 214. Limiting element; 2141. Limiting rod; 2142. Heat dissipation connecting ring; 2143. Through hole; 2144. Umbrella-shaped buffer cap; 2145. Limiting flange; 22. Accommodating space; 221. First accommodating part; 222. Second accommodating part; 3. Protective part; 31. Isolation and protective layer; 32. Armoring layer; 33. Flame-retardant outer sheath; 4. Insulating color separation layer; 5. Filling layer; 6. Fireproof layer; 7. Wrapping tape layer; 8. Overall sheath. Detailed Implementation

[0048] The following is in conjunction with the appendix Figures 1-4 This application will be described in further detail.

[0049] Example 1

[0050] This application discloses a mineral-insulated fire-resistant cable. (Refer to...) Figure 1 A mineral-insulated fireproof cable includes a conductive part 1, an insulating part 2, and a protective part 3. The conductive part 1 is located at the center of the cable, the insulating part 2 covers the outside of the conductive part 1, and the protective part 3 covers the outside of the insulating part 2. This structure enables the cable to have good conductivity, insulation, and protection performance, ensuring the stable operation of the cable in different environments.

[0051] The conductive part 1 includes a multi-strand stranded conductor 11 and a conductor shielding layer 12 covering the multi-strand stranded conductor 11. The multi-strand stranded conductor 11 is formed by stranding multiple fine wires, which increases the flexibility and conductivity of the conductor. The fine wires can be made of metals such as copper and aluminum; in this embodiment, it is preferably made of soft copper wire through bundling and re-twisting, with a single wire diameter of 0.15-0.3 mm, a bundling pitch ratio of 10-12, and a re-twisting pitch ratio of 14-18; and the soft copper wire is annealed at 380-420℃ for 2.5-3.5 h, so that the DC resistance of the conductor at 20℃ is not greater than 0.017241 Ω·mm² / m, thereby improving bending performance while ensuring excellent conductivity. The conductor shielding layer 12 can be made of a semi-conductive material, such as semi-conductive rubber, preferably a semi-conductive mineral-filled rubber material, with a thickness controlled at 0.5-0.8 mm and a volume resistivity of 1×10³-1×10 5 Ω·m; it tightly wraps around the outside of the multi-strand stranded conductor 11 to uniformly distribute the electric field on the conductor surface, eliminate the tip effect on the conductor surface, and reduce electric field distortion.

[0052] The insulation portion 2 includes a mineral protective layer 21 covering the conductor shielding layer 12. The mineral protective layer 21 covers the conductor shielding layer 12 and includes an adhesive matrix 211 and refractory aggregate 212 dispersed within the adhesive matrix 211. The adhesive matrix 211 has a continuous phase elastic structure. The adhesive matrix 211 can be an organic polymer material such as silicone rubber, and the refractory aggregate 212 can be magnesium oxide powder modified with a silane coupling agent. Utilizing the film-forming properties of the adhesive matrix 211, the dispersed refractory aggregate 212 is completely encapsulated and bonded together, forming a gap-free, dense elastomer. When the cable is subjected to external bending force, the continuous phase elastic structure dissipates stress through its own deformation, preventing brittle fracture of the insulation portion 2. Simultaneously, the gap-free structural design prevents relative slippage or misalignment of the refractory aggregate 212 particles during bending, maintaining the uniformity and stability of the cable insulation structure.

[0053] The space between the conductor shielding layer 12 and the isolation protective layer 31 is a receiving space 22 for accommodating the mineral protective layer 21. The mineral protective layer 21 also includes a restraining mesh 213, which divides the receiving space 22 into a first receiving portion 221 and a second receiving portion 222. The adhesive matrix 211 and the refractory aggregate 212 are respectively accommodated in the first receiving portion 221 and the second receiving portion 222. The restraining mesh 213 can be made of metal mesh or fiber mesh and has mesh openings. During the manufacturing process, the adhesive matrix 211 in the first receiving portion 221 and the second receiving portion 222 interpenetrates and heat-melts through the openings of the restraining mesh 213, forming a mechanical interlocking structure on both sides of the restraining mesh 213 after curing. This interlocking structure enhances the interfacial bonding strength and physically prevents delamination of the insulating portion 2. Furthermore, the constraint mesh 213 acts as a physical barrier in the middle of the insulation layer 2. When external stress causes microcracks to appear in the second receiving portion 222, the constraint mesh 213 blocks the radial propagation path of the cracks towards the inner first receiving portion 221, thus protecting the integrity of the inner insulation layer. At the same time, the material of the constraint mesh 213 helps to absorb and conduct internal heat, improving the overall heat dissipation efficiency of the cable.

[0054] The first receiving portion 221 is located between the conductor shielding layer 12 and the restraint mesh 213, and the second receiving portion 222 is located between the restraint mesh 213 and the isolation and protection layer 31. The distribution density of the refractory aggregate 212 in the first receiving portion 221 is greater than that in the second receiving portion 222. The high-density aggregate stacking in the first receiving portion 221 constructs a dense insulating region with high thermal conductivity and high pressure resistance, rapidly transferring the Joule heat generated by the conductor to the restraint mesh 213 and withstanding the electrical breakdown pressure under high voltage field strength. The low-density aggregate distribution in the second receiving portion 222 reserves a resin-rich flexible space, making its elastic modulus lower than that of the first receiving portion 221. When the cable is laid and bent, the outer second receiving portion 222 undergoes a large elastic deformation to absorb deformation stress and protect the inner first receiving portion 221 from damage.

[0055] Please refer to the following: Figures 2-3The conductor shielding layer 12 also includes multiple limiting members 214, which are spaced apart along the length of the cable. At each cross-sectional position, the limiting members 214 are evenly distributed circumferentially along the conductor shielding layer. Each limiting member 214 includes a metal limiting rod 2141, a heat dissipation connecting ring 2142 formed at the bottom of the limiting rod 2141, and an elastic umbrella-shaped buffer cap 2144 prefabricated and attached to the top of the limiting rod 2141. The heat dissipation connecting ring 2142 is clamp-shaped and connected to the conductor shielding layer 12, while the elastic umbrella-shaped buffer cap 2144 abuts against the isolation protection layer 31. The rod of the limiting rod 2141 passes through the mesh of the constraint net 213. In this application, the limiting member 214 not only prevents the insulation part 2 from sliding during use, but also allows for processing based on the length of the limiting member 214 during manufacturing, ensuring the concentricity of the cable.

[0056] The heat dissipation connecting ring 2142 is a metal ring or arc-shaped structure, which is attached to the outer surface of the conductor shielding layer 12. The heat dissipation connecting ring 2142 has several through holes 2143 along its ring surface. The through holes 2143 are located within the first receiving portion 221. The adhesive matrix 211 within the first receiving portion 221 fills the through holes 2143 in a fluid state and forms a solid structure penetrating the through holes 2143 after curing. This structure utilizes a mechanical interlocking principle to prevent the heat dissipation connecting ring 2142 from separating from the surrounding insulating material due to insufficient interfacial bonding. Pairs of limiting flanges 2145 are distributed circumferentially on the outer wall of the conductor shielding layer 12. The heat dissipation connecting ring 2142 is engaged between the limiting flanges 2145 to limit its axial displacement.

[0057] The end of the limiting rod 2141 furthest from the heat dissipation connecting ring 2142 has an integrally formed elastic umbrella-shaped buffer cap 2144. The bottom surface of the elastic umbrella-shaped buffer cap 2144 abuts against the outer surface of the restraint net 213, and the top surface of the elastic umbrella-shaped buffer cap 2144 abuts against the inner wall of the isolation and protective layer 31. The limiting rod 2141 can be a metal integrally formed with the heat dissipation connecting ring 2142, and can be made of copper alloy or aluminum alloy to ensure that it can support the thickness of the insulation part 2 and quickly dissipate the heat of the conductor. The elastic umbrella-shaped buffer cap 2144 is made of a high-temperature resistant, high-resilience insulating elastic material, preferably high-temperature resistant silicone rubber, fluororubber, or ceramicized silicone rubber.

[0058] To ensure the limiting component can smoothly pass through the non-precision aligned constraint net 213, the top outer surface of the elastic umbrella-shaped buffer cap 2144 is designed as a smoothly transitioned arc-shaped or conical guide surface. This guide surface is used to convert the positive pressure applied by the mesh wires into a tangential component force during the wrapping process of the constraint net 213, guiding the metal mesh wires to slide and misalign, thereby preventing the mesh wires from directly jamming at the top of the cap. The limiting rod 2141 and the elastic umbrella-shaped buffer cap 2144 are configured as a prefabricated integrated component. The top of the limiting rod 2141 is provided with a rough surface or groove structure, and the elastic umbrella-shaped buffer cap 2144 is directly overmolded onto the top of the limiting rod 2141 through an insert injection molding process. Before cable manufacturing, the limiting rod 2141 and the elastic umbrella-shaped buffer cap 2144 are already combined as a single component.

[0059] The maximum outer diameter of the elastic umbrella-shaped buffer cap 2144 is larger than the mesh size of the constraint net 213. During assembly and threading of the net, the elastic contraction of its edges passes through the mesh, and then the rebound achieves axial locking of the constraint net 213. Because the metal limiting rod 2141 undergoes a significant radial linear expansion at high temperatures, direct contact with the external structure would generate enormous local pressure. In this embodiment, the elastic umbrella-shaped buffer cap 2144 is located between the rigid rod and the external isolation and protective layer. When the cable is fully loaded with a large current and heats up, the limiting rod 2141 pushes outward, at which point the elastic umbrella-shaped buffer cap 2144 is compressed. This displacement is accommodated by the compression deformation of the rubber material and the bending deformation of the umbrella-shaped edge. When the temperature decreases and the cable cools down, the elastic umbrella-shaped buffer cap 2144 releases its elastic potential energy and resets.

[0060] In practical use, the limiting rod 2141 passes through the mesh, providing radial and axial positioning for the constraint mesh 213 and preventing displacement of the constraint mesh 213 relative to the conductor shielding layer 12. Simultaneously, the limiting member 214 acts as a distance-fixing support, strictly limiting the distance between the isolation protection layer 31 and the conductor shielding layer 12. When the cable is in a bent state for a long time, even if the refractory aggregate 212 powder inside the insulation part 2 tends to flow, the supporting effect of the limiting member 214 maintains the consistency of the insulation part 2 thickness, preventing local thinning or compression of the insulation part 2 due to powder displacement, thus ensuring the electrical safety distance of the cable.

[0061] The protective layer 3 includes an isolation protective layer 31 covering the mineral protective layer 21, an armor layer 32 covering the isolation protective layer 31, and a flame-retardant outer sheath 33 covering the armor layer 32. The isolation protective layer 31 is made of overlapping high-silica glass fiber reinforced plastic (GFRP) tape with an overlap rate of 20%-30% and a thickness of 0.3-0.5 mm. The armor layer 32 is made of tin-plated soft copper wire with a weaving density of not less than 90% and a copper wire diameter of 0.2-0.3 mm. The flame-retardant outer sheath 33 can be made of flame-retardant polyvinyl chloride (PVC) or similar materials; in this application, the flame-retardant outer sheath 33 is preferably made of B1-grade high flame-retardant, low-smoke, halogen-free polyolefin material. The layers fit together tightly. The isolation protective layer 31 provides electrical isolation while also serving as the outer mold for the fire-resistant layer; the armor layer 32 provides radial support and impact resistance; and the flame-retardant outer sheath 33 isolates the outer layer from external flames and corrosive environments.

[0062] It should be further explained that the above Figures 1 to 3 The structure shown is a single-core cable form of a mineral-insulated fire-resistant cable according to this application. In practical engineering applications, multiple such single-core cables can be used as base cores to form multi-core cables.

[0063] Please see Figure 4 The figure shows a schematic cross-sectional structure of the mineral-insulated fire-resistant cable of this application in a multi-core cabling application scenario. This multi-core structure combines multiple... Figure 1 The single-core mineral-insulated fire-resistant cable shown is twisted together. To easily distinguish the different cores, a color-coded insulation layer 4 of a different color can be added to the outside of each single-core cable. During twisting, a filler layer 5 is used to fill the gaps between the cores. Figure 4 The diagram clearly indicates this. Afterwards, the entire cable is sequentially wrapped with the fire-resistant layer 6, the wrapping layer 7, and the outermost sheath 8. These layers are also clearly marked in the diagram, thus ultimately forming a complete multi-core fire-resistant cable.

[0064] The working principle of this embodiment is as follows: When the cable is energized, the conductor generates heat, which is transferred to the conductor shielding layer 12. The first receiving portion 221 is filled with high-density refractory aggregate 212, which has a higher thermal conductivity than the external low-density area, and conducts the heat to the restraining mesh 213. When the cable bends, the insulation portion 2 is subjected to tensile or compressive stress. The refractory aggregate 212 in the second receiving portion 222 has a lower density, a higher proportion of binder matrix 211, and a lower elastic modulus, absorbing bending stress through its own elastic deformation. The first receiving portion 221 has a higher density, supporting the conductor shielding layer 12. The limiting flange 2145 restricts the position of the heat dissipation connecting ring 2142 to prevent it from tilting. The limiting rod 2141 passes through the mesh of the restraining mesh 213, restricting the restraining mesh 213 from moving axially or radially, preventing relative displacement inside the insulation portion 2.

[0065] If the outer insulation layer cracks due to impact, the restraint mesh 213 acts as a physical barrier to prevent the crack from propagating inward. The binder matrix 211 within the pores of the restraint mesh 213 has solidified to form an interlocking structure, increasing interfacial bonding and preventing delamination of the insulation layer 2. Furthermore, because the refractory aggregate 212 has undergone hydrophobic modification, even if the outer layer is damaged, moisture cannot easily penetrate the interior and cause insulation failure. When exposed to high temperatures during a fire, the binder matrix 211 decomposes, the glass powder melts and binds the refractory aggregate 212, undergoing a ceramization reaction, transforming the flexible mineral protective layer 21 into a hard ceramic solid layer in situ. This solid layer is supported by the restraint mesh 213, maintaining the integrity of the insulation structure.

[0066] Example 2

[0067] This embodiment provides a manufacturing process for a mineral-insulated fire-resistant cable, used to manufacture the mineral-insulated fire-resistant cable described above. The process includes the following steps:

[0068] S1. Select soft copper wire with a single wire diameter of 0.15-0.3mm, anneal it at 380-420℃ for 2.5-3.5h, and then make it into a flexible conductor through stranding and re-stranding processes.

[0069] The prefabricated integral limiting components 214 are axially spaced and assembled onto the conductor shielding layer 12. The limiting component 214 includes a metal heat-dissipating connecting ring 2142, a limiting rod 2141, and an elastic umbrella-shaped buffer cap 2144 pre-attached to the top of the limiting rod. During assembly, the heat-dissipating connecting ring 2142 tightly fits against or is inserted into the outer wall of the conductor shielding layer 12, establishing the thickness reference of the insulation portion 2. At this time, the limiting rod 2141 with the elastic umbrella-shaped buffer cap 2144 stands radially on the surface of the conductor, constructing the skeleton of the insulation portion 2.

[0070] S2. Fill the space between each limiting member 214 with adhesive matrix 211 and refractory aggregate 212 to fill the space of the first receiving part 221. Wrap the restraint net 213 around the outside of the first receiving part 221 and fill the outside of the restraint net 213 with adhesive matrix 211 and refractory aggregate 212 to fill the space of the second receiving part 222, thus constructing the mineral protective layer 21.

[0071] In this application, the refractory aggregate 212 is magnesium oxide powder modified with a silane coupling agent (such as KH-550). During modification, the magnesium oxide powder and the silane coupling agent are mixed at a mass ratio of 100:1-100:2, stirred and reacted at 80-100℃ for 1-2 hours, and then dried and ground for later use. The binder matrix 211 includes silicone rubber and glass powder dispersed in the silicone rubber. Under normal operating conditions, this material system remains flexible. When the mineral protective layer 21 is exposed to high temperatures in a fire, the dispersed glass powder absorbs heat and melts, wetting and bonding the refractory aggregate 212, promoting a ceramization reaction, and rapidly transforming the mineral protective layer 21 from a flexible state into a hard and dense ceramized solid layer. This solid layer can resist flame impact and mechanical vibration, preventing the refractory aggregate 212 from falling off and scattering, and ensuring the electrical integrity of the circuit during a fire.

[0072] S21. After mixing the binder matrix 211 with the high-density refractory aggregate 212, the filler is extruded onto the surface of the conductor shielding layer 12, filling the first receiving portion 221, and then immediately cooled and shaped in a water bath. The filling thickness is controlled so that it covers the heat dissipation connecting ring 2142 and reaches about 2 / 3 of the height of the limit rod 2141, ensuring that the elastic umbrella-shaped buffer cap 2144 is completely exposed outside the filler.

[0073] S22. A wrapping machine is used to wrap or weave a constraint net 213 on the outside of the first receiving part 221. When the wrapped constraint net 213 contacts the umbrella-shaped buffer cap 2144, the mesh wires act on the arc-shaped surface of the cap. Under the wrapping tension, the metal mesh wires generate a component force that slides tangentially along the cap body, forcing the mesh wires to slide along the smooth curved surface to both sides of the cap body and bypass the axis of the limiting rod; at the same time, the reaction force of the mesh wires forces the rubber umbrella-shaped buffer cap 2144 to be compressed and contracted radially. When the mesh wires slide past the maximum outer diameter of the umbrella-shaped buffer cap 2144, the cap body loses its lateral restraint and instantly rebounds and opens using elastic potential energy. At this time, the mesh wires retract and reset, locking the umbrella-shaped buffer cap 2144 to the outside of the constraint net 213. When weaving the constraint net 213, the weaving density is small at the location of the limiting member 214 and large at the other parts. In actual implementation, multiple layers of constraint net 213 can be woven in positions other than the limiting member 214.

[0074] S23. After mixing the binder matrix 211 with the low-density refractory aggregate 212, the filler is filled onto the surface of the constraint net 213 again through an extruder, covering the limiting member 214 and the constraint net 213. Then the whole thing is cooled and shaped in a water bath. By precisely controlling the mixing ratio of the refractory aggregate 212 in steps S21 and S23, the internal hard and external soft structure of the insulation part 2 is completed during the manufacturing process, without the need for subsequent complex processing.

[0075] S3. The mineral protective layer 21 is heated and cured until the adhesive matrix 211 transforms into a continuous phase elastic structure. Heating and curing can be carried out in a furnace. This step controls the temperature to cause only cross-linking and curing of the adhesive matrix 211, rather than high-temperature sintering. The cured mineral protective layer 21 retains the flexibility of the organic polymer material, enabling the finished cable to be laid in a flexible manner, thus avoiding rigid brittle fracture caused by pre-sintering into ceramic.

[0076] S4. After the mineral protective layer 21 has been cured, an isolation protective layer 31 and an armor layer 32 are sequentially wrapped around the outside of the mineral protective layer 21.

[0077] S41. Wrap the protective layer 31 and apply radial tension to press the protective layer 31 tightly against the mineral protective layer 21 and abut against the limiting member 214. The protective layer 31 is made of high-silica glass fiber tape, with an overlap rate controlled at 20%-30%. During the wrapping process, the limiting member 214 serves as an internal rigid sizing reference, and the external tension forces the protective layer 31 to adhere tightly to the elastic umbrella-shaped buffer cap 2144 at the top of the limiting member 214, thereby forcibly correcting the concentricity of the mineral protective layer 21 and preventing uneven thickness of the insulation part 2. At the same time, the elastic umbrella-shaped buffer cap 2144 at the top of the limiting member 214 bears the main radial compressive force, protecting the internal adhesive matrix 211, which has not yet fully reached its final strength, from excessive deformation.

[0078] S42. The armor layer 32 is covered and a non-adhesive sliding contact is formed between the armor layer 32 and the isolation and protection layer 31. The armor layer 32 is made of tin-plated soft copper wire braid with a braiding density of not less than 90%. The reserved gap fits the internal flexible matrix, which reduces the frictional resistance between layers when the cable is bent and improves the flexibility of the cable. Then, the low-smoke halogen-free polyolefin material that meets the B1 grade high flame retardant requirements is extruded at 140-160℃ and covered on the armor layer 32. After cooling, the thickness of the outer sheath is controlled to be 1.5-2.5mm.

[0079] The working principle of this embodiment is as follows: The inner layer of the insulating limiting member installed in step S1 forms a rigid skeleton for the insulating part 2. When wrapping the isolation protective layer 31 in step S41, the fully assembled limiting member 214 acts as an inner mold to bear radial tension, limiting the outer diameter of the mineral protective layer 21. The concentricity and thickness uniformity of the insulating part 2 can be guaranteed without the need for a precise outer mold.

[0080] Utilizing the fluid properties of the adhesive matrix 211 in step S2, the matrix of the second receiving portion 222 is squeezed and filled to make it contact the first receiving portion 221 through the mesh of the constraint net 213. Subsequently, in step S3, heating is used to cause a chemical cross-linking reaction of the matrix molecular chains inside and outside the mesh, integrating the two layers of material that were originally filled in steps into a physically interlocked whole after curing.

[0081] Through the batch filling process in steps S21 and S23, using the constraint mesh 213 as an intermediate separating medium, two types of refractory aggregates 212 with different densities are precisely arranged within the same insulation part 2. This process solidifies the material distribution state of the inner high-density layer and the outer low-density layer, forming a heterogeneous insulation structure. The curing process in step S3 controls the heating temperature, initiating only the cross-linking reaction of the organic matrix without triggering the sintering reaction of the inorganic aggregate, ensuring the flexibility of the cable in its factory and laying conditions.

[0082] To achieve extremely high fire resistance while retaining the aforementioned flexibility, this application incorporates a specific phase transition design for the material system. The binder matrix 211 utilizes silicone rubber with low-melting-point glass powder dispersed within it (preferably PbO-B2O3-SiO2-based glass powder with a softening point of 450℃-500℃). This material combination allows the insulating portion 2 to undergo a controlled ceramic-forming reaction under the following critical conditions when exposed to high fire temperatures:

[0083] 1. First stage (350℃-500℃): When the temperature rises above 350℃, the silicone rubber matrix begins to thermally oxidize and decompose, and the insulating part 2 is temporarily in a porous and fragile state.

[0084] 2. Second stage (450℃-600℃, critical transition zone): At this time, the selected glass powder just enters the range of endothermic softening and melting. The molten glass phase rapidly wets the refractory aggregate 212 and the decomposition products of silicone rubber by capillary force.

[0085] 3. Third stage (above 600℃): As the temperature continues to rise, the molten glass powder acts as a high-temperature binder, promoting liquid-phase sintering between refractory aggregate particles and filling the pores left by the decomposition of organic matter.

[0086] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of this application.

Claims

1. A mineral-insulated fire-resistant cable, characterized in that, include: The conductive part (1) includes a multi-strand stranded conductor (11) and a conductor shielding layer (12) covering the multi-strand stranded conductor (11); The insulating part (2) includes a mineral protective layer (21), which covers the conductor shielding layer (12), and the mineral protective layer (21) includes an adhesive matrix (211) and refractory aggregate (212) dispersed in the adhesive matrix (211), wherein the adhesive matrix (211) is an elastic structure in the form of a continuous phase; The protective part (3) includes an isolation protective layer (31) covering the mineral protective layer (21), an armor layer (32) covering the isolation protective layer (31), and a flame-retardant outer sheath (33) covering the armor layer (32); The space between the conductor shielding layer (12) and the isolation protection layer (31) is a receiving space (22) for accommodating the mineral protection layer (21). The mineral protection layer (21) also includes a restraint net (213), which divides the receiving space (22) into a first receiving portion (221) and a second receiving portion (222). The binder matrix (211) and the refractory aggregate (212) are respectively accommodated in the first receiving portion (221) and the second receiving portion (222).

2. The mineral-insulated fire-resistant cable according to claim 1, characterized in that, The first receiving portion (221) is located between the conductor shielding layer (12) and the restraint net (213), and the second receiving portion (222) is located between the restraint net (213) and the isolation and protection layer (31). The distribution density of the refractory aggregate (212) in the first receiving portion (221) is greater than the distribution density of the refractory aggregate (212) in the second receiving portion (222).

3. The mineral-insulated fire-resistant cable according to claim 2, characterized in that, The conductor shielding layer (12) also includes a plurality of limiting members (214) distributed along the length of the cable. The limiting member (214) includes a limiting rod (2141) and a heat dissipation connecting ring (2142) formed at one end of the limiting rod (2141). The heat dissipation connecting ring (2142) is sleeved on the conductor shielding layer (12), and the limiting rod (2141) passes through the mesh of the constraint net (213).

4. A mineral-insulated fire-resistant cable according to claim 3, characterized in that, The end of the limiting rod (2141) away from the heat dissipation connecting ring (2142) is connected to an umbrella-shaped buffer cap (2144). The bottom surface of the umbrella-shaped buffer cap (2144) abuts against the outer surface of the constraint net (213), and the top surface of the umbrella-shaped buffer cap (2144) abuts against the inner wall of the isolation and protection layer (31).

5. A mineral-insulated fire-resistant cable according to claim 4, characterized in that, The heat dissipation connecting ring (2142) has a plurality of through holes (2143) along its circumferential surface, and the outer peripheral surface of the conductor shielding layer is formed with limiting flanges (2145) for abutting against the two side walls of the heat dissipation connecting ring (2142).

6. A mineral-insulated fire-resistant cable according to claim 1, characterized in that, The refractory aggregate (212) is magnesium oxide powder modified with a silane coupling agent, and the binder matrix (211) includes silicone rubber and glass powder dispersed in the silicone rubber.

7. A manufacturing process for a mineral-insulated fire-resistant cable, used to manufacture the mineral-insulated fire-resistant cable as described in claim 5, characterized in that, The process includes the following steps: S1. Install a plurality of the limiting members (214) on the surface of the conductive part (1) so that the heat dissipation connecting ring (2142) is locked between the limiting flanges (2145) to construct the inner skeleton of the insulating part (2); S2. Fill the space between each limiting member (214) with adhesive matrix (211) and refractory aggregate (212) to fill the space of the first receiving part (221), wrap the restraint net (213) around the outside of the first receiving part (221), and fill the outside of the restraint net (213) with adhesive matrix (211) and refractory aggregate (212) to fill the second receiving part (222) and construct the mineral protective layer (21); S3. The mineral protective layer (21) is heated and cured until the adhesive matrix (211) is transformed into a continuous phase elastic structure; S4. An isolation protective layer (31) and an armor layer (32) are sequentially wrapped around the outside of the cured mineral protective layer (21).

8. The manufacturing process of a mineral-insulated fire-resistant cable according to claim 7, characterized in that, The construction of the mineral protective layer (21) in step S2 includes the following steps: S21. The binder matrix (211) is mixed with the high-density refractory aggregate (212) and then filled onto the surface of the conductive part (1), and the filling thickness is controlled to be less than the height of the limiting rod (2141). S22. Wrap the constraint net (213) and use the elastic deformation of the umbrella-shaped buffer cap (2144) to make it pass through the mesh of the constraint net (213), and use it to restore its deformation and abut against the outer surface of the constraint net (213); S23. The binder matrix (211) is mixed with the low-density refractory aggregate (212) and then filled onto the surface of the restraint net (213) to cover the limiting member (214) and the restraint net (213).

9. The manufacturing process of a mineral-insulated fire-resistant cable according to claim 7, characterized in that, Step S4, which involves covering the isolation and protective layer (31) and the armor layer (32), specifically includes the following steps: S41. Wrap the protective layer (31) around the mineral protective layer (21) and apply radial tension so that the protective layer (31) presses against the mineral protective layer (21) and abuts against the limiting member (214); S42. Cover the armor layer (32) and make a non-adhesive sliding contact between the armor layer (32) and the isolation and protection layer (31).

Images