A fireproof cable for safe return to port and a manufacturing method thereof

Abstract

The present invention discloses a fireproof cable for safe return to port and a manufacturing method thereof, which relates to the field of cable manufacturing, including a conductor core and a calcined fire-resistant mica tape wrapped outside the conductor core, wherein the mica tape is wrapped with at least three layers, and the mica tape twisting pitch ratio is 20-30 times the outer diameter of the conductor core twisting; the conductor is wrapped with a single layer of mica tape in the left direction, with an overlap rate of 100%, and after the single layer is wrapped, the single layer of mica tape is wrapped in an overlapping manner in the right direction, with an overlap rate of 100%, and after the double layer of mica tape is wrapped, the single layer of mica tape is wrapped again in the left direction, with an overlap rate of 100%. The present invention provides a method of improving the structure, material and production process of the fire-resistant mica layer of the cable, which has a reasonable structure, advanced process and is easy to produce and manufacture. It has low-smoke, halogen-free, bundled, flame-retardant, fire-proof and spray-proof properties, so as to realize the requirements of carrying out fire supply and splashing tests under specific conditions required by the standard and continuously ensuring the normal working state of the equipment, so as to meet the safe return to port requirements of luxury cruise ships and passenger and vehicle ferries.

Description

Technical Field

[0001] The invention relates to the field of cable manufacturing, in particular to a safe return-to-port fireproof cable and a manufacturing method thereof. Background Art

[0002] The fire resistance and water spray resistance of the cable is a key indicator for safe return to port. The current marine fire-resistant cables can only meet the requirement of short-circuit prevention for a short time in the event of a fire, but they do not have the system that must remain available during safe evacuation when water enters a local area to achieve the maximum safe evacuation time of 180 minutes. They need to rely on cable sheaths for protection, which increases the overall hull weight and cost, and affects the navigation speed. Summary of the invention

[0003] The object of the present invention is to provide a safe return to port fireproof cable and a manufacturing method thereof to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for manufacturing a safe return fireproof cable, comprising a conductor core and a calcined fire-resistant mica tape wrapped around the conductor core, the mica tape being wrapped with at least three layers, and the mica tape twisting pitch ratio being 20-30 times the twisting outer diameter of the conductor core;

[0005] The conductor is wrapped with a single layer of mica tape in the left direction with an overlap rate of 100%. After wrapping the single layer, it is wrapped with a single layer of mica tape in an overlapping manner in the right direction with an overlap rate of 100%. After wrapping the double layer of mica tape, it is wrapped with a single layer of mica tape again in the left direction with an overlap rate of 100%.

[0006] Preferably, after the mica tape is wrapped, the cross-linked polyethylene insulation is extruded, and the average insulation thickness should not be less than the nominal value, and the thickness at the thinnest point should not be less than 90% of the nominal value.

[0007] Preferably, when the nominal thickness of the cross-linked polyethylene insulation layer is greater than 0.6 mm, the maximum thickness of any section should not be greater than 1.25 times the minimum thickness; when the nominal thickness of the cross-linked polyethylene insulation is less than or equal to 0.6 mm, its maximum thickness should not be greater than 1.4 times the minimum thickness.

[0008] Preferably, the insulation is extruded and then twisted into a cable, and after the cable is formed, a layer of halogen-free flame retardant tape is wrapped around it.

[0009] Preferably, the halogen-free flame retardant tape is wrapped and then extruded into a polyolefin inner sheath. The thickness of the inner sheath depends on the outer diameter of the inner sheath before extrusion. The average thickness of the sheath is not less than the nominal value, the thickness at the thinnest point is not less than 80% of the nominal value, and the maximum thickness of the sheath is not greater than 1.66 times the minimum thickness.

[0010] Preferably, the inner sheath is extruded and then braided with tinned copper wire armor, with a braiding coverage of not less than 88%; and the polyolefin outer sheath is extruded after the armor.

[0011] Preferably, the method further includes an anti-oxidation treatment process for the conductor core: the conductor uses bare copper wire. Conductor wire drawing process: after wire drawing with an oxygen-free copper rod, an antioxidant is applied to the bare copper wire to form a dense monomolecular protective layer on the copper surface.

[0012] A fireproof cable for safe return to port is manufactured by adopting the method.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention provides a method of improving the structure, material and production process of the fire-resistant mica layer of the cable, which has a reasonable structure, advanced process and is easy to manufacture. It has low-smoke, halogen-free, bundled flame retardant, fire-proof and spray-proof properties, so as to achieve the requirements of carrying out fire supply and splashing tests under specific conditions required by the standard and continuously ensuring the normal working state of the equipment, so as to meet the requirements of safe return to port for luxury cruise ships and ro-ro passenger ships. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the cable of the present invention;

[0016] Figure 2 is a parameter table of the cross-linking step of the present invention;

[0017] Figure 3 Table 1 is the extrusion process parameter table of the present invention;

[0018] Figure 4 Table 2 is the extrusion process parameters of the present invention;

[0019] Figure 5 Table 3 is the extrusion process parameters of the present invention;

[0020] Figure 6 Table 4 is the extrusion process parameter table of the present invention;

[0021] Figure 7 Table 5 is the extrusion process parameters of the present invention;

[0022] Figure 8 Table 1 is the extrusion line speed parameter table of the present invention;

[0023] Fig. 9 Table 2 is the extrusion line speed parameter table of the present invention;

[0024] Fig.10 The following is a comparison table of the products of the present invention and traditional technology.

[0025] In the figure, 1. conductor core; 2. calcined refractory mica tape; 3. cross-linked polyethylene insulation layer; 4. sheath layer. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1 The present embodiment provides a safe return to port fireproof cable, comprising a conductor core 1, a calcined fire-resistant mica tape 2 wrapped around the outer edge of the conductor core 1, a cross-linked polyethylene insulation layer 3 is arranged on the outer edge of the mica tape 2, and a sheath layer 4 is arranged outside the cross-linked polyethylene insulation layer 3, which includes a halogen-free flame retardant tape wrapping layer, a halogen-free polyolefin inner sheath, a tinned copper wire armor braided layer and a halogen-free polyolefin outer sheath from the inside to the outside.

[0028] It is worth mentioning that the key points of this embodiment are: the design of the mica tape 2 firstly adopts a three-layer mica tape structure, and the mica tape twisting pitch ratio is 20-30 times the twisting outer diameter of the conductor core 1;

[0029] During the wrapping process, control the traction line speed and take-up tension; wrap the conductor core 1 with a single layer of mica tape in the left direction, with an overlap rate of 100%, wrap the single layer of mica tape in the right direction after wrapping the single layer, with an overlap rate of 100%, wrap the double layer of mica tape in the left direction again after wrapping the single layer of mica tape, with an overlap rate of 100%. This operation is applicable to the LRBJ-2A mica tape wrapping machine produced by Shanghai Nanyang Electric.

[0030] When wrapping the mica tape, first determine the width and pitch of the mica tape by the outer diameter of the conductor core 1. For example, if the outer diameter of the conductor core 1 is 1.3mm, then the pitch of the mica tape is between 26mm and 39mm, and 30mm is the best. When determining the actual pitch, it can be selected according to product requirements. The width of the mica tape is 4 times π multiplied by the outer diameter of the conductor core 1.

[0031] In addition, in order to improve the antioxidant ability of the conductor core 1, in the wire drawing process of the conductor core 1, an antioxidant is applied to the bare copper wire after the oxygen-free copper rod is drawn, and a dense monomolecular protective film is formed on the copper surface, which can effectively isolate the contact between the air and the copper surface, prevent the conductor from corrosion and discoloration, maintain the original luster of the copper, avoid oxidation of the bare copper wire conductor, and fully ensure the electrical performance of the conductor.

[0032] Specifically: while the copper wire is being drawn and annealed, 0.5 parts per thousand of an antioxidant solution (such as benzotriazole alcohol solution) is added. The amount added is just enough to wet the copper wire, so that a dense monomolecular protective film can be formed on the surface.

[0033] This embodiment is implemented by Fig.10The performance indicators of the experiment are compared:

[0034] Conventional fire-resistant cable: The number of mica tape wrapping layers is one to two at most, it is wrapped longitudinally, the overlap rate is 25%, the mica tape twisting pitch ratio is 14-20 times the twisted outer diameter of the conductor core, and the core is wrapped with polyester tape after cabling.

[0035] It is worth mentioning that in some other embodiments, simply increasing the number of mica tape wrapping layers or the overlap rate cannot achieve the effects in the above table. Only when the above three-layer mica tape structure is met, the mica tape twisting pitch ratio is 20-30 times the twisted outer diameter of the conductor core 1, and the overlap rate is 100%, can the best technical effect be maintained, that is, satisfying Fig.10 Table contents.

[0036] The following is a specific manufacturing method and the mechanical properties of the final product. It is worth mentioning that the dimensional parameters designed in the following steps are only understood as a single embodiment and do not limit the specific implementation:

[0037] Including stranded copper conductor, power cable conductor cross-sectional area range: 1mm 2 -300mm 2 ,Communication cable conductor cross-sectional area range 0.50mm 2 -2.5mm 2 ; The conductor is longitudinally wrapped with three layers of calcined mica tape, and the mica tape has a temperature resistance of 1000℃; the mica tape overlap rate is 100%, and the thickness of a single layer of mica tape is 0.15mm; after the mica tape is wrapped, it is extruded with cross-linked polyethylene insulation, and the average insulation thickness should not be less than the nominal value, and the thickness at the thinnest point should not be less than 90% of the nominal value. When the nominal thickness is greater than 0.6mm, the maximum thickness of any cross section should not be greater than 1.25 times the minimum thickness. When the nominal thickness is less than or equal to 0.6mm, the maximum thickness should not be greater than 1.4 times the minimum thickness; cross-linking is performed after extruding the insulation;

[0038] It is further explained here that the thickness of the sheath and insulation is controlled by the concentricity of the core and sleeve diameter in the extrusion die during production. The thickness of the final extruded sheath and insulation is controlled by replacing the core and sleeve of different specifications. This operation is applicable to commonly used extruders on the market such as SJ30, SJ45, SJ50, SJ65, SJ90, and SJ120.

[0039] Cross-linking method: Seal the ends of the insulated wire cores to be cross-linked with waterproof tape, and apply ultraviolet light chemical cross-linking while squeezing the package. The wavelength of ultraviolet light is 365nm;

[0040] Crosslinking requirements according to Figure 2 As shown in the table.

[0041] After extruding the insulation, twist them into cables. After the cables are formed, wrap a layer of halogen-free flame retardant tape. The thickness of the halogen-free flame retardant tape is 0.05mm. After wrapping the halogen-free flame retardant tape, extrude the polyolefin inner sheath. The thickness of the inner sheath depends on the outer diameter of the inner sheath before extrusion. The average thickness of the sheath is not less than the nominal value, the thickness at the thinnest point is not less than 80% of the nominal value, and the maximum thickness of the sheath is not more than 1.66 times the minimum thickness. After the sheath is extruded, tinned copper wire armor is woven, and the braiding coverage is not less than 88%; after the armor is extruded, the polyolefin outer sheath is extruded. The cable surface is smooth and round, without obvious defects such as unevenness.

[0042] To achieve the braiding coverage rate, when using a braiding machine for braiding, set the single wire diameter, number of wires and angle parameters, and adjust them adaptively according to the process requirements and equipment models. When the number of wires and the angle are determined, the larger the single wire diameter, the greater the coverage rate; when the single wire diameter and the number of wires are determined, the smaller the angle, the greater the coverage rate; when the single wire diameter and the angle are determined, the more wires, the greater the coverage rate. It can be applied to braiding machines such as GSB-1Z, GSB-2Z, and WGSB-3 produced by Shanghai Nanyang Electric. In specific implementation, the diameter of the braiding wire is determined according to the outer diameter of the conductor core 1 before braiding. For example, if the outer diameter before braiding is ≤10mm, then the single wire diameter of the braiding wire is selected as 0.2mm. If 10mm<the outer diameter before braiding is ≤30mm, then the single wire diameter of the braiding wire is selected as 0.3mm. If the wire diameter before braiding is >30, then the single wire diameter of the braiding wire is selected as 0.4mm. Selecting the wire diameter of the braiding wire according to the above logic can improve the structural stability of the product and help improve the physical properties of the product. When weaving, the number of braiding wires is selected to be 5-9, and the modulation angle is set to 45°, so as to achieve a weaving coverage rate of 88%.

[0043] As for the requirements for the cable surface, normal equipment will have a defective rate. For example, improper operation may cause the braided wire to jump, resulting in an uneven cable surface. Such defective products should be destroyed, and only products with smooth, round surfaces and no bumps or defects should be retained.

[0044] Insulation and sheath extrusion process conditions:

[0045] Heat each extrusion zone according to the process requirements, and the temperature control is displayed by instruments. The heating temperature of each zone should be based on Figure 3-Figure 7 The requirements are met, and the instrument temperature is calibrated with a mercury thermometer. Figure 3-Figure 7 In the remarks column below, during the production process, the load of each device should be balanced according to the production task situation.

[0046] SJ-30 extrusion zone temperature setting reference Figure 3 As shown in the table (Note: insulation extrusion specifications are 4mm² and below);

[0047] SJ-45 extrusion zone temperature setting reference Figure 4 As shown in the table (Note: insulation extrusion specifications are 10mm² and below);

[0048] SJ-65 extrusion zone temperature setting reference Figure 5 As shown in the table (Note: insulation extrusion specifications are 185mm² and below, and the outer diameter of the sheath after extrusion is 27mm and below);

[0049] SJ-90 Extrusion Zone Temperature Setting Reference Figure 6 As shown in the table (note: insulation extrusion specification is 400mm² and below, and the outer diameter of the sheath after extrusion is 45mm and below);

[0050] SJ-120 extrusion zone temperature setting reference Figure 7 As shown in the table (Note: the outer diameter of the sheath before extrusion is above 13mm).

[0051] Sheath and insulation extrusion speed Figure 8 and Fig. 9 As shown in the table.

[0052] When the equipment is running, the noise sound pressure level is below 75dB(A), and the air quality meets the requirements of the National Ambient Air Quality Standard (GB3095-2012). The processing and production speed is fast, and it can save about 50% of electricity, which meets the requirements of energy conservation and environmental protection.

[0053] The purpose of controlling the extrusion temperature and the outlet speed is to achieve the plasticizing effect of the insulating material and the sheath material, so as to finally achieve the following mechanical properties, electrical properties and aging properties. The relationship between the extrusion temperature and the outlet speed is often ignored in conventional processes. This embodiment adjusts the outlet speed and the extrusion temperature for different extrusion materials and product specifications, which can ensure that the extruded insulation and sheath are free of bubbles and have a good plasticizing effect. It is worth mentioning that before extrusion, the conductor core 1 is wrapped with the mica tape mentioned above. Based on the special mica tape wrapping structure mentioned above, the extrusion temperature in the subsequent process can be designed to be lower than the conventional extrusion temperature, and the outlet speed can be faster. In addition, it can also maintain excellent physical properties and achieve energy-saving effects. That is, the previous and subsequent processes produce a synergistic effect, and while promoting each other, a more superior product performance is achieved.

[0054] The performance of the final product is as follows: (1) For safety return cables with voltage levels of 0.6 / 1kV and below, the cable diameter does not exceed 20mm. According to IEC60331-2 and CEI EN50200 standards, a water splash test is carried out and the cables burn continuously for 180 minutes at a flame temperature of 830℃. All safety return cables are guaranteed to be in normal working condition; (2) For safety return cables with voltage levels of 0.6 / 1kV and below, the cable diameter exceeds 20mm. According to IEC60331-1 and BS8491 standards, a water splash test is carried out and the cables burn continuously for 180 minutes at a flame temperature of 830℃. All safety return cables are guaranteed to be in normal working condition; (3) Bare copper conductors do not undergo overoxidation reaction.

[0055] Test data:

[0056] 1. Insulation mechanical and physical properties

[0057] 1.1 Insulation mechanical properties before and after aging

[0058] Tensile strength before aging: 19.8N / mm2 Requirement: ≥12.5 N / mm 2

[0059] Elongation at break before aging: 470% Requirement: ≥200%

[0060] After air oven aging (135℃×168h)

[0061] Change rate of tensile strength after aging: +17% Requirement: ≤±25%

[0062] Change rate of elongation at break after aging: -2% Requirement: ≤±25%

[0063] 1.2 Thermal extension: temperature 200°C, load time: 15min, mechanical stress: 20 N / cm 2

[0064] Elongation under load: 38% Requirement: ≤175%

[0065] Permanent elongation after cooling: 0 Requirement: ≤15%

[0066] 1.3 Mechanical properties of inner sheath before and after aging

[0067] Tensile strength before aging: 12.4N / mm2 Requirement: ≥9.0 N / mm 2

[0068] Elongation at break before aging: 160% Requirement: ≥120%

[0069] After air oven aging (100℃×168h)

[0070] Tensile strength after aging: 13.9N / mm2 Requirement: ≥7.0 N / mm 2

[0071] Change rate of tensile strength after aging: +12% Requirement: ≤±30%

[0072] Elongation at break before aging: 150% Requirement: ≥110%

[0073] Change rate of elongation at break after aging: -6% Requirement: ≤±30%

[0074] 1.4. Inner sheath high temperature pressure test

[0075] Test temperature: 80℃

[0076] Duration: 6h

[0077] Indentation depth: 9% Requirement: ≤50%

[0078] 1.5. Inner sheath thermal shock test

[0079] Test temperature: 150℃

[0080] Duration: 1h

[0081] Test result: No cracking Requirement: No cracking

[0082] 2. Mechanical and physical properties test of outer sheath

[0083] 2.1 Mechanical properties of outer sheath before and after aging

[0084] Tensile strength before aging: 13.9N / mm 2 Requirement: ≥9.0 N / mm 2

[0085] Elongation at break before aging: 210% Requirement: ≥120%

[0086] After air oven aging (100℃×168h)

[0087] Tensile strength after aging: 15.8N / mm 2 Requirement: ≥7.0 N / mm 2

[0088] Change rate of tensile strength after aging: +14% Requirement: ≤±30%

[0089] Elongation at break before aging: 210% Requirement: ≥110%

[0090] Change rate of elongation at break after aging: 0 Requirement: ≤±30%

[0091] 2.2 High temperature performance - high temperature pressure test of outer sheath

[0092] Test temperature: 80℃

[0093] Duration: 6h

[0094] Indentation depth: 9% Requirement: ≤50%

[0095] 2.3. Thermal shock test of outer sheath

[0096] Test temperature: 150℃

[0097] Duration: 1h

[0098] Test result: No cracking Requirement: No cracking

[0099] 2.4. Low temperature performance - low temperature tensile test of outer sheath

[0100] Test temperature: -15℃

[0101] Duration: 4h

[0102] Elongation: 80% Requirement: ≥30%

[0103] 2.5 Low temperature performance - low temperature tensile test of finished cable

[0104] Test temperature: -15℃

[0105] Duration: 16h

[0106] Elongation: No cracking Requirement: No cracking

[0107] 3. Additional compatibility aging test

[0108] Aging temperature: 100℃

[0109] Aging time: 168h

[0110] XLPE Insulation:

[0111] Change rate of tensile strength after aging: +8% Requirement: ≤±25%

[0112] Change rate of elongation at break after aging: -15% Requirement: ≤±25%

[0113] SHF1 inner sheath:

[0114] Change rate of tensile strength after aging: +24% Requirement: ≤±30%

[0115] Change rate of elongation at break after aging: 0 Requirement: ≤±25%

[0116] SHF1 outer sheath:

[0117] Change rate of tensile strength after aging: +20% Requirement: ≤±30%

[0118] Change rate of elongation at break after aging: -5% Requirement: ≤±30%.

[0119] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a fireproof cable for safe return to port, comprising a conductor core and a calcined fire-resistant mica tape wrapped around the conductor core, characterized in that: The mica tape is wrapped with at least three layers, and the mica tape twisting pitch ratio is 20-30 times the outer diameter of the conductor core twisting; the conductor is wrapped with a single layer of mica tape in the left direction, with an overlap rate of 100%, and after wrapping a single layer of mica tape, it is wrapped with a single layer of mica tape in the right direction, with an overlap rate of 100%, and after wrapping a double layer of mica tape, it is wrapped with a single layer of mica tape in the left direction again, with an overlap rate of 100%; after wrapping the mica tape, the cross-linked polyethylene insulation is extruded, and the average insulation thickness should not be less than the nominal value, and the thinnest thickness should not be less than 90% of the nominal value; when the nominal thickness of the cross-linked polyethylene insulation layer is greater than 0 .6mm, the maximum thickness of any section shall not be greater than 1.25 times the minimum thickness; when the nominal thickness of the cross-linked polyethylene insulation is less than or equal to 0.6mm, its maximum thickness shall not be greater than 1.4 times the minimum thickness; after extruding the insulation, it shall be twisted into a cable, and after the cable is formed, it shall be wrapped with a layer of halogen-free flame retardant tape; after the halogen-free flame retardant tape is wrapped, a polyolefin inner sheath shall be extruded. The thickness of the inner sheath depends on the outer diameter of the inner sheath before extrusion. The average thickness of the sheath shall not be less than the nominal value, the thickness at the thinnest point shall not be less than 80% of the nominal value, and the maximum thickness of the sheath shall not be greater than 1.66 times the minimum thickness.

2. The method for manufacturing a safe return fireproof cable according to claim 1, characterized in that: The inner sheath is extruded and then braided with tinned copper wire armor, with a braiding coverage of not less than 88%; the armored outer sheath is extruded with a polyolefin outer sheath.

3. The method for manufacturing a safe return fireproof cable according to claim 2, characterized in that: It also includes an anti-oxidation treatment process for the conductor core: the conductor is made of bare copper wire, and the conductor drawing process: after the oxygen-free copper rod is drawn, the bare copper wire is treated with an antioxidant to form a dense monomolecular protective film on the copper surface.

4. A safe return fireproof cable, characterized in that: The cable is manufactured by the method for manufacturing a safe return to port fireproof cable as described in any one of claims 1 to 3.

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