High-flame-retardant medium-voltage aluminum alloy power cable for chemical equipment and preparation method thereof

Abstract

The invention relates to the technical field of wires and cables, in particular to a high-flame-retardant medium-voltage aluminum alloy power cable for chemical equipment and a preparation method of the high-flame-retardant medium-voltage aluminum alloy power cable, and the high-flame-retardant medium-voltage aluminum alloy power cable comprises a cable core which is formed by wrapping and fixing a plurality of wire cores which are tangent in pairs and a filling layer filled among the wire cores by a flame-retardant wrapping layer into a circular cross section; the outer wall of the cable core is coated with the armor layer; the outer wall of the armor layer is coated with the flame-retardant layer; and the outer wall of the flame-retardant layer is coated with the reinforcing layer. According to the invention, a gradient insulation structure with soft inside and rigid outside is arranged, through continuous transition of material performance, concentrated shear stress generated by thermal expansion mismatch is effectively dispersed and absorbed, interface stripping and fatigue cracking of an insulation layer are inhibited, and electrical integrity and thermal mechanical stability of the cable under frequent temperature circulation are ensured.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, and more specifically to a high flame-retardant medium-voltage aluminum alloy power cable for chemical equipment and its preparation method. Background Technology

[0002] In industries such as chemical engineering, oil refining, and metallurgy, the power supply systems of core production facilities often operate under extremely complex conditions. These environments not only contain high concentrations of corrosive chemicals such as acids, alkalis, and solvents, but also, due to the continuous nature of production processes and the high load characteristics, cables must withstand severe temperature cycling caused by frequent start-ups, shutdowns, and equipment switching. These harsh conditions pose unprecedented challenges to the long-term operational reliability of cables, especially medium-voltage cables with aluminum alloy conductors, which are increasingly being used due to their lightweight and low-cost advantages.

[0003] Currently, these cables, which are composite structures made up of metallic materials (such as conductors and shielding layers) and polymer materials (such as insulation layers) through layering, exhibit significant differences in their coefficients of thermal expansion. When the cable undergoes drastic cyclical temperature changes, this thermal expansion mismatch between the materials generates alternating thermal stress at their interfaces. This stress, acting repeatedly over a long period, can easily lead to fatigue damage in the polymer insulation material, specifically manifested as interface peeling, microcrack initiation and propagation. This severely compromises the cable's insulation integrity, ultimately causing fatal faults such as insulation breakdown, threatening the safety of the entire power supply system.

[0004] Therefore, existing cable structures are ill-suited to meet the stringent requirements for long-term thermomechanical stability in extreme industrial environments such as chemical plants. Summary of the Invention

[0005] To address the technical problems existing in the power cables used in chemical equipment in the prior art, the first aspect of this invention proposes a technical solution: a high flame-retardant medium-voltage aluminum alloy power cable for chemical equipment, comprising: Multiple tangent wire cores and the filler layer between the wire cores are wrapped together by a flame-retardant wrapping layer to form a cable core with a circular cross-section. An armor layer, covering the outer wall of the cable core; A flame-retardant layer is wrapped around the outer wall of the armor layer; A reinforcing layer is formed by covering the outer wall of the flame-retardant layer. The outer sheath is extruded onto the outer wall of the reinforcing layer; The wire core includes an aluminum alloy stranded conductor, a double-co-extruded semi-conductive conductor shielding layer outside the aluminum alloy stranded conductor, an inner insulation layer, a double-co-extruded intermediate insulation layer outside the inner insulation layer, and an outer insulation layer. The intermediate insulation layer is a cross-linked polyethylene insulation layer. The elastic modulus of the inner insulation layer is lower than that of the intermediate insulation layer, which is used to buffer the strain of the aluminum alloy stranded conductor under temperature change environment. The tear resistance of the outer insulation layer is higher than that of the insulation layer. The outer insulation layer is used to inhibit the initiation and propagation of cracks. The armor layer includes a repeatedly wrapped galvanized aluminum alloy armor layer; The flame-retardant layer includes a double-layer non-woven fabric wrapping layer and an inorganic flame-retardant layer disposed between the double-layer non-woven fabric wrapping layer. The reinforcing layer includes an aramid fiber braided layer, and the outer sheath includes a halogen-free flame-retardant polyurethane sheath layer.

[0006] Preferably, the inner insulation layer is composed of an elastomer-modified cross-linked polyethylene composition, the tensile modulus of elasticity of the inner insulation layer at 23°C is not higher than 300 MPa, and the elongation at break is greater than 500%. The outer insulation layer is composed of a cross-linked polyethylene composition reinforced with nanofillers, and the tear strength of the outer insulation layer is not less than 30 kN / m.

[0007] Preferably, the filling layer includes a first filling structure and a second filling structure. The first filling structure includes a silicone rubber tube with a water-blocking paste layer inside. The second filling structure includes a flame-retardant filling rope and a water-blocking yarn, which are filled in the gap between the core, the silicone rubber tube and the flame-retardant wrapping layer in a mixed weaving manner.

[0008] Preferably, the flame-retardant wrapping layer comprises a double-layer glass ribbon wrapping layer, wherein the wrapping overlap rate of the inner glass ribbon wrapping layer is less than that of the outer glass ribbon wrapping layer.

[0009] Preferably, the armor layer includes a first aluminized alloy strip wrapping layer and a second galvanized aluminum alloy strip wrapping layer, wherein the wrapping direction of the first galvanized aluminum alloy strip wrapping layer is to the left and the wrapping direction of the second galvanized aluminum alloy strip wrapping layer is to the right.

[0010] Preferably, the flame-retardant layer includes an inner non-woven fabric wrapping layer and an outer non-woven fabric wrapping layer. The inner non-woven fabric wrapping layer includes a first non-woven fabric wrapping tape wrapped around the outer wall of the armor layer. The outer non-woven fabric wrapping layer includes a second non-woven fabric wrapping tape wrapped around the outer wall of the first non-woven fabric wrapping tape. The outer layer of the first non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, and the inner layer of the second non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, forming an inorganic flame-retardant layer between the inner and outer non-woven fabric wrapping layers.

[0011] Preferably, the inorganic flame-retardant particle coating includes a water-blocking adhesive that can penetrate nonwoven fabric and inorganic flame-retardant particles dispersed in the water-blocking adhesive.

[0012] Preferably, the aluminum alloy stranded conductor includes an inner conductor and an outer conductor, wherein the inner conductor is a trapezoidal aluminum alloy core stranded structure and the outer conductor is a Z-shaped aluminum alloy core stranded structure.

[0013] Preferably, the braiding angle of the aramid filament braided layer is 55~60°, and the braiding coverage of the aramid filament braided layer is greater than 50%.

[0014] The second aspect of this invention provides a technical solution: a method for preparing a high flame-retardant medium-voltage aluminum alloy power cable for chemical equipment, comprising the following steps: Step S1, Conductor stranding: Using a wire stranding device, trapezoidal aluminum alloy wire cores are first stranded to form an inner conductor, and then Z-shaped aluminum alloy wire cores are stranded to the outer layer to form a tightly stranded aluminum alloy wire conductor. Step S2, First Double-Layer Co-Extrusion: The semi-conductive conductor shielding material and the modified flexible cross-linked polyethylene insulation material are simultaneously extruded on the outside of the conductor through a double-head co-extrusion device to form a semi-conductive conductor shielding layer and an inner insulation layer. Step S3, Second Double-Layer Co-Extrusion: Before the first co-extruded layer enters the cross-linking pipeline, the standard cross-linked polyethylene insulation material and the nano-modified high-toughness cross-linked polyethylene insulation material are extruded simultaneously through the second double-head co-extrusion equipment to form the intermediate insulation layer and the outer insulation layer; then, the wire core enters the cross-linking pipeline for uniform vulcanization and cross-linking, so that the four layers of materials form a gradient insulation whole; Step S4, cabling and wrapping: Twist multiple core wires with the first filling structure and the second filling structure to form a circular cable core; then, first wrap the inner glass ribbon with a smaller overlap rate, and then wrap the outer glass ribbon with a larger overlap rate to form a flame-retardant wrapping layer. Step S5, Armor layer wrapping: First, wrap the first galvanized aluminum alloy strip to the left outside the cable core, and then wrap the second galvanized aluminum alloy strip to the right to form the armor layer; Step S6, Flame Retardant Layer Preparation and Coating: First, coat one side of the nonwoven fabric strip with a slurry made of water-based adhesive and inorganic flame retardant particles and dry it; when wrapping, first wrap the first nonwoven fabric strip with the coated side facing outward to form the inner nonwoven fabric wrapping layer, and then wrap the second nonwoven fabric strip with the coated side facing inward to form the outer nonwoven fabric wrapping layer, so that the two coated sides are facing each other and sandwiched in the middle to form an inorganic flame retardant layer; Step S7, Reinforcing Layer Weaving and Outer Sheath Extrusion: Aramid filaments are woven at a weaving angle of 55~60° outside the flame-retardant layer to form a reinforcing layer; finally, halogen-free flame-retardant polyurethane material is extruded onto the outer layer of the reinforcing layer to form an outer sheath.

[0015] Compared with the prior art, the advantages of the present invention are as follows: This invention features a gradient insulation structure that is flexible on the inside and rigid on the outside. Through the continuous transition of material properties, it effectively disperses and absorbs the concentrated shear stress caused by thermal expansion mismatch, suppresses interfacial peeling and fatigue cracking of the insulation layer, and ensures the electrical integrity and thermomechanical stability of the cable under frequent temperature cycles. This invention designs a structure with a double-layer non-woven fabric sandwiched with an inorganic flame-retardant layer, which can be transformed into a continuous and rigid ceramicized heat insulation shell at high temperatures. Together with the external aramid reinforcement layer and halogen-free flame-retardant polyurethane sheath, it forms a seamless and durable fire barrier to prevent the spread of flames and achieve a high level of fire safety with low smoke and halogen-free properties, meeting the reliability and service life requirements of power supply in chemical environments. Attached Figure Description

[0016] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of the high flame-retardant medium-voltage aluminum alloy power cable for chemical equipment as shown in this invention. Figure 2 This is a schematic diagram of the cross-sectional structure of the high flame-retardant medium-voltage aluminum alloy power cable for chemical equipment as shown in this invention. Figure 3 This is a schematic diagram of the wire core structure shown in this invention; Figure 4 This is a schematic diagram of the structure of the flame-retardant layer shown in this invention. Detailed Implementation

[0017] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0018] {Example 1} Combination Figure 1 and Figure 2 As shown, the first aspect of the present invention proposes a technical solution: a high flame-retardant medium-voltage aluminum alloy power cable for chemical equipment, comprising a cable core, an armor layer 4, a flame-retardant layer 5, a reinforcing layer 6, and an outer sheath 7. The armor layer 4 covers the outer wall of the cable core, the flame-retardant layer 5 covers the outer wall of the armor layer 4, the reinforcing layer 6 covers the outer wall of the flame-retardant layer 5, and the outer sheath 7 is extruded onto the outer wall of the reinforcing layer 6.

[0019] In an optional embodiment, the cable core is formed by multiple tangent cores 1 and a filler layer 2 between the cores 1 being wrapped and secured by a flame-retardant wrapping layer 3 to form a circular cross-section.

[0020] Combination Figure 3As shown, the core 1 includes an aluminum alloy stranded conductor 11, a semi-conductive conductor shielding layer 12 co-extruded outside the aluminum alloy stranded conductor 11, an inner insulation layer 13, an intermediate insulation layer 14 co-extruded outside the inner insulation layer 13, and an outer insulation layer 15.

[0021] The aluminum alloy stranded conductor 11 includes an inner conductor 111 and an outer conductor 112. The inner conductor is a trapezoidal aluminum alloy core stranded structure, and the outer conductor 112 is a Z-shaped aluminum alloy core stranded structure.

[0022] Thus, the aluminum alloy stranded conductor 11 provides an extremely smooth, round, and stable cylindrical surface for subsequent insulation extrusion, greatly improving the electric field distribution, reducing internal micro-gap and electric stress concentration points from the source, and the stranded structure is more compact, with high mechanical strength of the conductor itself, which can better resist deformation caused by temperature changes and reduce mechanical stress on the insulation layer.

[0023] Furthermore, the wire core 1 is formed by two double-layer co-extrusion methods and is located on the outer layer of the aluminum alloy stranded conductor 11.

[0024] Specifically, the semiconducting conductor shielding layer 12 and the inner insulation layer 13 are co-extruded for the first time to ensure perfect fusion of the interface between the two without air gaps, which is conducive to the uniformity of the electric field and prevents partial discharge. Subsequently, the intermediate insulation layer 14 and the outer insulation layer 15 are co-extruded for the second time before the first co-extruded layer is cured. Through precise temperature control and cross-linking process, the four layers of materials diffuse and entangle with each other at the molecular level to form a quasi-integrated insulation system with gradually changing physical properties but blurred interfaces.

[0025] In this way, stress concentration and delamination risks caused by clear interfaces in traditional layered designs can be effectively avoided, and it is particularly suitable for frequent thermal cycling in chemical environments.

[0026] Optionally, the intermediate insulation layer 14 is a cross-linked polyethylene insulation layer, the elastic modulus of the inner insulation layer 13 is lower than that of the intermediate insulation layer 14, and the tear resistance of the outer insulation layer 15 is higher than that of the insulation layer 14.

[0027] Specifically, the inner insulation layer 13 is composed of an elastomer-modified cross-linked polyethylene composition, the tensile modulus of the inner insulation layer 13 at 23°C is not higher than 300 MPa, and the elongation at break is greater than 500%. The outer insulation layer 15 is composed of a cross-linked polyethylene composition reinforced with nanofillers, and the tear resistance of the outer insulation layer 15 is not lower than 30 kN / m.

[0028] In a specific embodiment, the inner insulation layer 13 is modified by elastomers such as POE and EVA to reduce the elastic modulus of cross-linked polyethylene and give it extremely high elongation at break, making the material extremely soft and elastic.

[0029] Thus, in the case of sudden temperature changes caused by frequent start-ups and shutdowns of chemical equipment, the thermal expansion / contraction of the aluminum alloy conductor is much greater than that of the outer intermediate insulation layer 14. At this time, the inner insulation layer 13 actively absorbs and accommodates most of the displacement and shear stress caused by the difference in thermal expansion coefficients between the conductor 11 and the intermediate insulation layer 14 through its own large deformation, thus preventing stress from concentrating on the more fragile interface.

[0030] In a specific embodiment, the intermediate insulation layer 14 is made of standard cross-linked polyethylene (XLPE) to maintain high purity and uniformity, thereby ensuring its extremely high volume resistivity and breakdown field strength.

[0031] In a specific embodiment, the outer insulation layer 15 is reinforced with nano-inorganic fillers (such as nano-silica and organic montmorillonite). The nanoparticles form a strong interfacial effect in the polymer matrix, which can effectively terminate the propagation of microcracks and hinder the slippage of molecular chains, thereby greatly improving the tear resistance and scratch resistance of the material to resist external mechanical stress, trace corrosion in chemical environment and environmental stress cracking during laying and operation.

[0032] As described above, the three-layer gradient design of the insulating layer of the present invention achieves a smooth transition from low modulus to high modulus. When thermal stress is transmitted from conductor 11 outward, it is first absorbed and buffered by a large amount by the soft inner insulating layer 13. The remaining stress is then transmitted to the tough outer insulating layer 15 through the middle insulating layer 14. In this process, the stress is dispersed in a wide, performance-gradient area, avoiding the formation of fatal stress peaks at any single interface, thereby reducing delamination stress.

[0033] Furthermore, the filling layer 2 includes a first filling structure 21 and a second filling structure 22. The first filling structure 21 includes a silicone rubber tube, and the inside of the silicone rubber tube is provided with a water-blocking paste layer 211. The second filling structure 22 includes a flame-retardant filling rope and a water-blocking yarn. The flame-retardant filling rope and the water-blocking yarn are filled in the gap between the core 1, the silicone rubber tube and the flame-retardant wrapping layer 3 in a mixed weaving manner.

[0034] Specifically, the surface of the silicone rubber tube has micropores. Water-blocking paste is filled into the filling layer by filling the entire silicone rubber tube, and the remaining space is filled by a mixture of flame-retardant filling rope and water-blocking yarn.

[0035] In this way, it can play a water-blocking role under normal conditions. In particular, after the water-blocking yarn absorbs water and expands, it can squeeze the silicone rubber tube, causing the water-blocking paste to be squeezed out from the silicone rubber tube and fill the excess gaps, thus achieving better radial and axial water-blocking capabilities. In a fire environment, the flame-retardant filling rope can play a heat insulation role. The evaporation of water absorbed in the water-blocking yarn can reduce heat, so as to work with the flame-retardant filling rope to prevent the flame from moving closer to the core 1.

[0036] As mentioned above, the design of the filling layer achieves dual protection under normal conditions and fire conditions. Under normal conditions, the water-blocking yarn expands rapidly when it comes into contact with water, first blocking the longitudinal channel; its expansion force will squeeze the silicone rubber tube, forcing the water-blocking paste inside to seep out through the micropores of the tube wall, further filling the micro gaps, and achieving active radial and longitudinal sealing.

[0037] Furthermore, the flame-retardant wrapping layer 3 includes a double-layer glass ribbon wrapping layer, wherein the wrapping overlap rate of the inner glass ribbon wrapping layer is less than that of the outer glass ribbon wrapping layer.

[0038] In this way, by wrapping with double-layer glass ribbon, the core 1 and the filling structure are secured into a circular cross-section. The outer layer of glass ribbon wrapping has a larger wrapping overlap, making the wrapping tighter. At the same time, the glass ribbon melts in a fire and forms a glassy state, filling the gap between the armor layer 4 and the flame-retardant filling rope, forming a dense isolation layer around the cable core to prevent flames and high temperatures from spreading to the core.

[0039] Furthermore, the armor layer 4 includes a repeatedly wrapped galvanized aluminum alloy armor layer.

[0040] Specifically, in combination Figure 4 As shown, the armor layer 4 includes a first aluminum-plated alloy strip wrapping layer 41 and a second zinc-plated aluminum alloy strip wrapping layer 42. The wrapping direction of the first zinc-plated aluminum alloy strip wrapping layer 41 is to the left, and the wrapping direction of the second zinc-plated aluminum alloy strip wrapping layer 42 is to the right.

[0041] In this way, the gaps in the first layer are covered by the solid part of the second layer of tape, which greatly reduces the gaps in electromagnetic leakage, provides a more continuous and complete shielding effect, and more effectively prevents flames, smoke or moisture from longitudinally penetrating into the cable through the lap joint.

[0042] Furthermore, the flame retardant layer 5 includes a double-layer non-woven fabric wrapping layer and an inorganic flame retardant layer 52 disposed between the double-layer non-woven fabric wrapping layers.

[0043] Specifically, in combination Figure 4 As shown, the flame-retardant layer 5 includes an inner non-woven fabric wrapping layer 51 and an outer non-woven fabric wrapping layer 53. The inner non-woven fabric wrapping layer 51 includes a first non-woven fabric wrapping tape wrapped around the outer wall of the armor layer 4. The outer non-woven fabric wrapping layer 53 includes a second non-woven fabric wrapping tape wrapped around the outer wall of the first non-woven fabric wrapping tape. The outer layer of the first non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, and the inner layer of the second non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating. An inorganic flame-retardant layer 52 is formed between the inner non-woven fabric wrapping layer 51 and the outer non-woven fabric wrapping layer 53.

[0044] Specifically, flame-retardant particle coatings are respectively applied to the outer layer of the first non-woven fabric tape and the inner layer of the second non-woven fabric tape. This ensures that when the two layers of tape are wrapped and bonded together, the flame retardant is precisely positioned at the interface between the two non-woven fabric layers. This ensures that when a fire occurs, the ceramic reaction process takes place at the interface between the two skeleton layers, forming a uniform and efficient ceramic insulation layer.

[0045] In a preferred embodiment, the inorganic flame-retardant particle coating includes a water-blocking adhesive that can penetrate nonwoven fabric and inorganic flame-retardant particles dispersed in the water-blocking adhesive.

[0046] Optionally, the water-blocking adhesive can be a water-based silicone rubber-based or EVA-based adhesive that can penetrate the non-woven fabric, block the micropores between the fibers, and together with the double-layer non-woven fabric, form a solid longitudinal moisture barrier to prevent chemical products from migrating longitudinally along the cable and corroding the internal metal components.

[0047] Furthermore, the adhesive properties of the water-blocking adhesive firmly bond the inorganic flame-retardant particles to the non-woven fabric skeleton, preventing the particles from falling off and migrating when the cable is bent or vibrated, thus ensuring the long-term uniformity and reliability of the flame retardant distribution.

[0048] Optionally, the inorganic flame-retardant particles can preferably be aluminum hydroxide, magnesium hydroxide, or a compound system thereof, which decompose and absorb heat at high temperatures and generate high-temperature resistant metal oxides.

[0049] In this way, when the polymer matrix in the water-blocking adhesive is heated, it will carbonize or react with the decomposition products of inorganic flame-retardant particles, participating in the formation process of the ceramic body, strengthening the mechanical strength and density of the final ceramic body, and improving the heat insulation barrier.

[0050] Furthermore, the reinforcing layer 6 includes an aramid filament braided layer with a braiding angle of 55~60° and a braiding coverage of more than 50%.

[0051] In this way, the aramid fiber braided layer forms a high tensile strength and cut-resistant protective layer on the outside of the cable, which can work together with the armor layer 4 to bear external mechanical forces.

[0052] Furthermore, the outer sheath 7 includes a halogen-free flame-retardant polyurethane sheath layer. Halogen-free flame-retardant polyurethane combines excellent abrasion resistance, chemical corrosion resistance, high elasticity, and flame retardancy, meeting the usage requirements of chemical production environments.

[0053] {Example 2} The second aspect of this invention provides a technical solution: a method for preparing a high flame-retardant medium-voltage aluminum alloy power cable for chemical equipment, comprising the following steps: Step S1, Conductor stranding: Using a wire stranding device, trapezoidal aluminum alloy wire cores are first stranded to form the inner conductor 111, and then Z-shaped aluminum alloy wire cores are stranded to the outer layer to form a tightly stranded aluminum alloy wire conductor 11. Step S2, First double-layer co-extrusion: The semi-conductive conductor shielding material and the modified flexible cross-linked polyethylene insulation material are simultaneously extruded on the outside of the conductor 11 through a double-head co-extrusion equipment to form a semi-conductive conductor shielding layer 12 and an inner insulation layer 13. Step S3, Second Double-Layer Co-Extrusion: Before the first co-extruded layer enters the cross-linking pipeline, the standard cross-linked polyethylene insulation material and the nano-modified high-toughness cross-linked polyethylene insulation material are extruded simultaneously through the second double-head co-extrusion equipment to form the intermediate insulation layer 14 and the outer insulation layer 15; then, the wire core enters the cross-linking pipeline for unified vulcanization and cross-linking, so that the four layers of materials form a gradient insulation whole. Step S4, cabling and wrapping: multiple cores 1 are twisted together with the first filling structure 21 and the second filling structure 22 to form a circular cable core; then, the inner glass ribbon is wrapped with a smaller overlap rate first, and the outer glass ribbon is wrapped with a larger overlap rate to form a flame-retardant wrapping layer 3. Step S5, Armor layer wrapping: First, wrap the first galvanized aluminum alloy strip 41 to the left outside the cable core, and then wrap the second galvanized aluminum alloy strip 42 to the right to form the armor layer 4. Step S6, Flame retardant layer preparation and coating: A slurry made of water-based adhesive and inorganic flame retardant particles is pre-coated on one side of the non-woven fabric tape and dried; during wrapping, the first non-woven fabric tape with the coated side facing outward is first wrapped to form the inner non-woven fabric wrapping layer 51, and then the second non-woven fabric tape with the coated side facing inward is wrapped to the outer layer to form the outer non-woven fabric wrapping layer 53, so that the two coated sides are facing each other and sandwiched in the middle to form the inorganic flame retardant layer 52; Step S7, Reinforcing Layer Weaving and Outer Sheath Extrusion: Aramid filaments are woven at a weaving angle of 55~60° outside the flame-retardant layer 5 to form the reinforcing layer 6; finally, halogen-free flame-retardant polyurethane material is extruded on the outer layer of the reinforcing layer 6 to form the outer sheath 7.

[0054] In steps S2 and S3, the co-extrusion of the conductor shielding layer 12 and the inner insulation layer 13 ensures that the interface between the two is originally gapless. Then, before the first co-extrusion layer has cooled and cross-linked, a second co-extrusion is performed. At this time, the molecular chains of the inner insulation layer 13 and the intermediate insulation layer 14 diffuse and entangle with each other under high temperature and high pressure, and form covalent bonds in the subsequent vulcanization cross-linking.

[0055] Ultimately, the resulting four-layer structure forms a gradient structure with blurred interfaces and interconnected layers. This chemical and physical fusion achieved through manufacturing processes results in an interface bonding strength far exceeding that of traditional adhesive-based laminated interfaces, enabling it to meet the long-term thermomechanical stability requirements of extreme industrial environments such as chemical processing.

[0056] In step S6, flame-retardant particle coatings are respectively applied to the outer layer of the first nonwoven fabric tape and the inner layer of the second nonwoven fabric tape. This ensures that when the two layers of tape are wrapped and bonded together, the flame retardant is precisely positioned at the interface between the two nonwoven fabric layers. This ensures that when a fire occurs, the ceramic reaction process occurs at the interface between the two skeleton layers, forming a uniform and efficient ceramic insulation layer.

[0057] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A high flame retardant medium voltage aluminium alloy power cable for chemical plants, characterized in that, The cable comprises: a plurality of wire cores (1) and a filling layer (2) filled between the wire cores (1) are wrapped by a flame-retardant wrapping layer (3) to form a cable core with a circular cross section; an armor layer (4) wrapped on the outer wall of the cable core; a flame-retardant layer (5) wrapped on the outer wall of the armor layer (4); a reinforcing layer (6) wrapped on the outer wall of the flame-retardant layer (5); an outer sheath (7) extruded on the outer wall of the reinforcing layer (6); wherein the wire core (1) comprises an aluminum alloy type wire stranded conductor (11), a semi-conductive conductor shielding layer (12) and an inner insulation layer (13) which are double-layer co-extruded on the outer wall of the aluminum alloy type wire stranded conductor (11), a middle insulation layer (14) and an outer insulation layer (15) which are double-layer co-extruded on the outer wall of the inner insulation layer (13); the middle insulation layer (14) is a cross-linked polyethylene insulation layer, the elastic modulus of the inner insulation layer (13) is lower than that of the middle insulation layer (14), which is used to buffer the strain of the aluminum alloy type wire stranded conductor (11) in a temperature changing environment, and the tear resistance of the outer insulation layer (15) is higher than that of the insulation layer (14), which is used to inhibit the initiation and expansion of cracks; the armor layer (4) comprises a repeatedly wrapped galvanized aluminum alloy armor layer; the flame-retardant layer (5) comprises a double-layer non-woven fabric wrapping layer and an inorganic flame-retardant layer (52) arranged between the double-layer non-woven fabric wrapping layer; the reinforcing layer (6) comprises an aramid yarn woven layer, and the outer sheath (7) comprises a halogen-free flame-retardant polyurethane sheath layer.

2. A high flame retardant medium voltage aluminium alloy power cable for chemical industry equipment, according to claim 1, characterized in that, The inner insulation layer (13) is composed of an elastomer modified cross-linked polyethylene composition, the tensile elastic modulus of the inner insulation layer (13) at 23 DEG C is not higher than 300 MPa, and the elongation at break is greater than 500%, the outer insulation layer (15) is composed of a nano filler reinforced cross-linked polyethylene composition, and the tear resistance of the outer insulation layer (15) is not less than 30 kN / m.

3. A high flame retardant medium voltage aluminium alloy power cable for chemical industry equipment according to claim 1, characterized in that, The filling layer (2) comprises a first filling structure (21) and a second filling structure (22), the first filling structure (21) comprises a silicone rubber tube, the inside of the silicone rubber tube is provided with a waterproof paste layer (211), the second filling structure (22) comprises a flame-retardant filling rope and a waterproof yarn, and the flame-retardant filling rope and the waterproof yarn are filled in the gap between the wire core (1), the silicone rubber tube and the flame-retardant wrapping layer (3) in a mixed weaving manner.

4. A high flame retardant medium voltage aluminium alloy power cable for chemical industry equipment according to claim 1, characterized in that, The flame-retardant wrapping layer (3) comprises a double-layer glass filament tape wrapping layer, wherein the wrapping lap rate of the inner layer of the glass filament tape wrapping layer is less than that of the outer layer of the glass filament tape wrapping layer.

5. A high flame retardant medium voltage aluminium alloy power cable for chemical industry equipment as claimed in claim 1, wherein, The armor layer (4) comprises a first aluminum alloy plated tape wrapping layer (41) and a second zinc-aluminum alloy plated tape wrapping layer (42), the wrapping direction of the first zinc-aluminum alloy plated tape wrapping layer (41) is left, and the wrapping direction of the second zinc-aluminum alloy plated tape wrapping layer (42) is right.

6. A high flame retardant medium voltage aluminium alloy power cable for chemical industry equipment according to claim 1, characterized in that, The flame-retardant layer (5) comprises an inner layer non-woven fabric wrapping layer (51) and an outer layer non-woven fabric wrapping layer (53), the inner layer non-woven fabric wrapping layer (51) comprises a first non-woven fabric wrapping tape wrapped outside the armored layer (4), the outer layer non-woven fabric wrapping layer (53) comprises a second non-woven fabric wrapping tape wrapped outside the first non-woven fabric wrapping tape, the outer layer of the first non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, the inner layer of the second non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, and an inorganic flame-retardant layer (52) is formed between the inner layer non-woven fabric wrapping layer (51) and the outer layer non-woven fabric wrapping layer (53).

7. A high flame retardant medium voltage power cable for chemical plant applications in accordance with claim 6, characterized in that, The inorganic flame-retardant particle coating comprises water-blocking glue permeable to non-woven fabric and inorganic flame-retardant particles dispersed in the water-blocking glue.

8. A high flame retardant medium voltage aluminium alloy power cable for chemical industry equipment, according to claim 1, characterized in that, The aluminum alloy type wire stranded conductor (11) comprises an inner layer conductor (111) and an outer layer conductor (112), the inner layer conductor is a trapezoidal aluminum alloy core stranded structure, and the outer layer conductor (112) is a Z-shaped aluminum alloy core stranded structure.

9. A high flame retardant medium voltage aluminium alloy power cable for chemical industry equipment, according to claim 1, characterized in that, The weaving angle of the aramid yarn weaving layer is 55-60°, and the weaving coverage rate of the aramid yarn weaving layer is greater than 50%.

10. A process for the preparation of high flame retardant medium voltage aluminium alloy power cables for chemical plants as claimed in claim 1, wherein, The method comprises the following steps: Step S1, conductor stranding: through a type wire stranding device, first, trapezoidal aluminum alloy wire cores are stranded to form an inner layer conductor (111), and then Z-shaped aluminum alloy wire cores are stranded to form a compact aluminum alloy type wire stranded conductor (11); Step S2, first double-layer co-extrusion: through a double-head co-extrusion device, a semi-conductive conductor shielding material and a modified flexible cross-linked polyethylene insulating material are synchronously extruded to form a semi-conductive conductor shielding layer (12) and an inner insulating layer (13) outside the conductor (11); Step S3, second double-layer co-extrusion: before the first co-extruded layer enters a cross-linking pipeline, through a second double-head co-extrusion device, a standard cross-linked polyethylene insulating material and a nano-modified high-toughness cross-linked polyethylene insulating material are synchronously extruded to form an intermediate insulating layer (14) and an outer insulating layer (15); then, the wire core enters the cross-linking pipeline for unified vulcanization cross-linking, so that the four layers of materials form a gradient insulating whole; Step S4, cabling and wrapping: a plurality of the wire cores (1) and the first filling structure (21) and the second filling structure (22) are stranded into a circular cable core; Then, an inner layer glass yarn tape is wrapped at a smaller lap rate, and an outer layer glass yarn tape is wrapped at a larger lap rate, to form a flame-retardant wrapping layer (3); Step S5, armored layer wrapping: a first galvanized aluminum alloy tape (41) is wrapped leftward outside the cable core, and a second galvanized aluminum alloy tape (42) is wrapped rightward, to form an armored layer (4); Step S6, flame-retardant layer preparation and coating: a slurry made of a water-based adhesive and inorganic flame-retardant particles is coated on one side of a non-woven fabric tape in advance and dried; during wrapping, a first non-woven fabric tape with the coated side facing outward is wrapped to form an inner layer non-woven fabric wrapping layer (51), and a second non-woven fabric tape with the coated side facing inward is wrapped outside to form an outer layer non-woven fabric wrapping layer (53), so that the two coated sides face each other and the inorganic flame-retardant layer (52) is formed in between. Step S7, reinforcing layer weaving and outer sheath extrusion: aramid fiber is woven outside the flame-retardant layer (5) at a weaving angle of 55-60° to form a reinforcing layer (6); finally, a halogen-free flame-retardant polyurethane material is extruded outside the reinforcing layer (6) to form an outer sheath (7).

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