A heating cable based on skin effect and its processing technology

Abstract

The present invention belongs to the field of cable technology, and specifically relates to a heating cable based on skin effect and a processing technology thereof, wherein the cable comprises a first signal line, a second signal line, and a third signal line, and the peripheries of the first signal line, the second signal line, and the third signal line are provided with a first insulating layer, a heat-conducting layer, a first flame-retardant layer, a second insulating layer, and a shielding layer in sequence from the inside to the outside, and the three points formed by the projection of the center lines of the first signal line, the second signal line, and the third signal line on the cross section are the vertices of an equilateral triangle, and the heating cable also comprises an inner sheath layer, a second flame-retardant layer, and an outer sheath layer that simultaneously covers the first signal line, the second signal line, and the third signal line, and the heat-conducting layer comprises a heat-conducting outer film, a central heat-conducting pipe, and a heat-conducting inner film that connects the outer wall of the central heat-conducting pipe and the inner surface of the heat-conducting outer film and has a circumferential array angle of 60°, and a heat-conducting liquid is sealed in the heat-conducting pipe. The cable of the present invention has uniform heating temperature, good thermal insulation effect, and is suitable for low-temperature environments.

Description

Technical Field

[0001] The invention belongs to the technical field of cables, and in particular relates to a heating cable based on skin effect and a processing technology thereof. Background Art

[0002] The skin effect phenomenon is: when there is alternating current or alternating electromagnetic field in the conductor, the current distribution inside the conductor is uneven, and the current is concentrated in the "skin" part of the conductor, that is, the current is concentrated in the thin layer on the surface of the conductor. The closer to the surface of the conductor, the greater the current density, and the current inside the conductor is actually smaller. As a result, the resistance of the conductor increases, and its power loss also increases.

[0003] The pipeline skin effect electric heating technology is a new metal pipeline heating method that has emerged in recent years. It is a new technology for heating and heat preservation of heat transmission pipelines in large petrochemical and other enterprises. This heating technology has high efficiency and is suitable for heating and heating of all long, medium and short distance metal liquid transmission pipelines. It is safe and reliable, has a long service life, and is easy to install and maintain. Therefore, it is widely used in pipeline heating of various liquid substances of different properties.

[0004] Existing heating cables based on the skin effect have the problems of slow heat conduction and uneven heating. Summary of the invention

[0005] The purpose of the present invention is to provide a heating cable based on skin effect which has uniform heat transfer and is suitable for low temperature environment and a processing technology thereof.

[0006] To achieve the above-mentioned purpose, the technical solution of the present invention is: to provide a heating cable based on the skin effect, comprising a first signal line, a second signal line, and a third signal line, wherein the first signal line, the second signal line, and the third signal line are provided with a first insulating layer, a first flame retardant layer, a second insulating layer, a shielding layer, and a thermal conductive layer in sequence from the inside to the outside, and the three points formed by the projection of the center lines of the first signal line, the second signal line, and the third signal line on the cross section are the vertices of an equilateral triangle, and the heating cable also includes an inner sheath layer, a second flame retardant layer, and an outer sheath layer that simultaneously cover the first signal line, the second signal line, and the third signal line.

[0007] Preferably, the first signal line is a power line core, the second signal line is a high-frequency signal line core, the third signal line is a non-high-frequency signal line core, and the colors of the second insulating layers on the first signal line, the second signal line, and the third signal line are different;

[0008] Among them, the color of the second insulation layer on the power line core is black; the color of the second insulation layer on the high-frequency signal line core is green; the color of the second insulation layer on the non-high-frequency signal line core is red.

[0009] Preferably, the first signal line, the second signal line and the third signal line are twisted pair wires, and the twisted wires are galvanized steel twisted wires.

[0010] Preferably, an anti-corrosion filler is provided between contact surfaces among the first insulating layer, the first flame-retardant layer, the second insulating layer, the shielding layer and the heat-conducting layer, and the anti-corrosion filler is glass fiber.

[0011] Preferably, the insulating material used for the first insulating layer includes polyperfluoroethylene propylene, ethylene propylene diene monomer rubber, butyl semi-conductive tape, and polyphenylene sulfide.

[0012] Preferably, the heat-conducting layer includes a heat-conducting outer film, a central heat-conducting tube, and a heat-conducting inner film connecting the outer wall of the central heat-conducting tube and the inner surface of the heat-conducting outer film and having a circumferential array angle of 60°. The heat-conducting tube is sealed with a heat-conducting liquid. A plurality of metal fixing frames of equal length are connected axially at equal intervals between the first signal line, the second signal line, the third signal line and the central heat-conducting tube. The heat-conducting inner film is arranged between two adjacent metal fixing frames, and the metal fixing frames are grounded.

[0013] Preferably, each of the fixing frames is provided with an S-shaped groove on its side for fixing two sides of the heat-conducting inner film.

[0014] The present invention also provides a heating cable processing technology based on the skin effect, which is characterized by comprising the following steps:

[0015] Step 1, stranding: straighten the galvanized steel strands to make the diameter of the galvanized steel strands uniform and between 2-3 mm, and interweave and press two galvanized steel strands counterclockwise to form a wire core;

[0016] Step 2, coating with a first insulating layer: bonding an anti-corrosion filler to the outer periphery of the wire core and then coating with an insulating layer;

[0017] Step 3, coating with a first flame retardant layer: coating with a first flame retardant layer after bonding an anticorrosive filler to the outer surface of the first insulating layer;

[0018] Step 4, coating with a second insulating layer: the second insulating layer is woven from zirconium oxide silicate ceramic fibers with a diameter of 0.2 to 0.4 mm;

[0019] Step 5, covering the shielding layer: the shielding layer is woven with tinned copper wire with a diameter of 0.3 to 0.5 mm;

[0020] Step 6, setting a heat-conducting layer: the heat-conducting layer includes a heat-conducting outer film, a central heat-conducting tube, and a heat-conducting inner film connecting the outer wall of the central heat-conducting tube and the inner surface of the heat-conducting outer film and having a circumferential array angle of 60°. The heat-conducting inner film evenly divides the cylindrical inner cavity surrounded by the heat-conducting outer film into three equal-volume accommodating chambers, and the accommodating chambers include a first accommodating chamber, a second accommodating chamber, and a third accommodating chamber. Three wire cores coated with a shielding layer in step 5 are selected and respectively inserted into the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber. The outer surface of the shielding layer of each wire core is bonded with an anti-corrosion filler, and the anti-corrosion filler fills the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber;

[0021] Step 7, coating the inner sheath layer: the inner sheath layer is a low-phenyl silicone rubber layer, which is coated on the thermal conductive layer by heating the sol;

[0022] Step 8, coating the second flame retardant layer: using an extruder to extrude a flame retardant on the outer surface of the inner sheath layer to form a second flame retardant layer;

[0023] Step 9, coating the outer sheath layer: the outer sheath layer is a low-phenyl silicone rubber layer, which is coated on the second flame retardant layer by heating sol.

[0024] Preferably, the specific method of coating the second flame retardant layer in step 9 is: repeatedly stirring and mixing a certain weight portion of epoxy resin, polytetrafluoroethylene, stabilizer, compatibilizer, and active diluent at 40°C to 65°C to obtain a flame retardant, and using an extruder to extrude the flame retardant on the outer surface of the inner sheath layer at a temperature of 120°C to 150°C, and then air-cooling the flame retardant to a cooling temperature of 20°C to 30°C.

[0025] Preferably, step 10 is further provided after step 9: attaching a layer of tempered film on the outer sheath layer.

[0026] Beneficial effects of the present invention:

[0027] 1. The core of each signal line is a twisted pair structure, which can avoid interference between lines. The three points formed by the projection of the center lines of the first signal line, the second signal line, and the third signal line on the cross section are the vertices of an equilateral triangle. In this way, the electromagnetic interference generated between the first signal line, the second signal line, and the third signal line can offset each other, thereby improving the stability of signal transmission.

[0028] 2. Since the cable based on the skin effect will produce a thermal effect on the local surface of the cable, when the cable is used in a low temperature environment, it will cause a large temperature difference on the cable surface and uneven heat conduction, thereby reducing the service life of the cable. The present invention sets a thermal conductive layer to effectively improve the overall heating uniformity of the cable. The thermal conductive layer includes a thermal conductive outer film, a central thermal conductive tube, and a thermal conductive inner film connecting the outer wall of the central thermal conductive tube and the inner surface of the thermal conductive outer film and having a circumferential array angle of 60°. The thermal conductive tube is sealed with a thermal conductive liquid, and the flowing thermal conductive liquid further accelerates the heat transfer inside the cable. The thermal conductive inner film connects the three signal lines, thereby improving the heat transfer between the three signal lines and avoiding the problem of large local temperature differences between different signal lines.

[0029] 3. Several metal fixing frames of equal length are connected between the first signal line, the second signal line, the third signal line and the central heat conduction tube at equal intervals along the axial direction. The heat conductive inner film is arranged between two adjacent metal fixing frames. The metal fixing frame is grounded, which enhances the stability and bending strength of the overall structure of the cable. The metal fixing frame also plays the role of fixing the relative position between the signal lines, shielding and heat conduction, and protects the heat conductive inner film with a certain elasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the heating cable based on the skin effect of the present invention.

[0031] Figure 2 It is a cross-sectional schematic diagram of the assembly of the metal fixing frame and the heat conducting layer in the present invention.

[0032] Figure 3 It is a schematic longitudinal section diagram of the assembly of the metal fixing frame and the signal line in the present invention.

[0033] Figure 4 The figure is a process flow chart of the heating cable processing based on the skin effect of the present invention.

[0034] Figure 5 This is an analysis diagram of electromagnetic induction between the first signal line, the second signal line and the third signal line in the present invention.

[0035] Figure 6 This is a simplified diagram of the magnetic field analysis calculation between the first signal line, the second signal line and the third signal line of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0037] See also Figures 1 to 3 As shown, the present invention provides a heating cable based on skin effect, comprising a first signal line 100, a second signal line 200, and a third signal line 300. The first signal line 100, the second signal line 200, and the third signal line 300 are provided with a first insulating layer 2, a first flame retardant layer 3, a second insulating layer 4, a shielding layer 5, and a heat conducting layer from the inside to the outside. The three points formed by the projection of the center lines of the first signal line 100, the second signal line 200, and the third signal line 300 on the cross section are the vertices of an equilateral triangle. Please refer to Figure 5 and Figure 6 As shown, it is assumed that the current directions of the first signal line 100, the second signal line 200, and the third signal line 300 are perpendicular to the paper and outward, then the direction of the magnetic flux lines drawn in the magnetic field generated around each signal line is the direction of counterclockwise rotation around the corresponding single signal line. Since the three points formed by the projection of the center lines of the first signal line 100, the second signal line 200, and the third signal line 300 on the cross section are the vertices of an equilateral triangle, the areas of the overlapping parts of the magnetic fields generated by the three signal lines are the same, and the vector directions are exactly offset after superposition. Figure 6 The direction of arrow 1-1 represents the vector direction of the magnetic fields of the first signal line and the third signal line after superposition, the direction of arrow 2-2 represents the vector direction of the magnetic fields of the second signal line and the third signal line after superposition, and the direction of arrow 3-3 represents the vector direction of the magnetic fields of the first signal line and the third signal line after superposition. The angle between the three arrows is 60°, the length of arrow 1-1 represents the intensity of the magnetic fields of the first signal line and the third signal line after superposition, the length of arrow 2-2 represents the intensity of the magnetic fields of the second signal line and the third signal line after superposition, and the length of arrow 3-3 represents the intensity of the magnetic fields of the first signal line and the third signal line after superposition, and the lengths of the three arrows are the same.

[0038] See also Figures 2 to 3As shown, several metal fixing frames of equal length are connected between the first signal line 100, the second signal line 200, the third signal line 300 and the central heat pipe 10 at equidistant intervals along the axial direction, and the heat conductive inner film 13 is arranged between two adjacent metal fixing frames, and the metal fixing frame is grounded. In the actual fixing process of the signal line, it is difficult to ensure that the three points formed by the projection of the center lines of the three signal lines on the cross section of any cable are all vertices of an equilateral triangle without the help of external equipment. In the process of cable preparation and laying, the relative position movement between the internal signal lines will be caused, so that the premise of "the overlapping area of ​​the magnetic field generated by the three signal lines is the same, and the vector directions are just offset after superposition" mentioned above is changed, and the magnetic fields generated between the signal lines cannot be exactly offset after superposition, which affects the stability of signal transmission. Therefore, several metal fixing frames of equal length are connected between the first signal line 100, the second signal line 200, the third signal line 300 and the central heat pipe 10 at equidistant intervals along the axial direction, and the transverse frame 9 of the metal fixing frame is adjacent to the transverse frame on the same cross section along the axial direction of the cable. 9 is 60 degrees, and the length of each horizontal frame 9 is equal. One end of the three frames on the same cross section along the axial direction of the cable is connected to the central heat pipe 10, and the other end is respectively connected to the first signal line 100, the second signal line 200 and the third signal line 300. Since the metal fixing frame can be manufactured by a manufacturing method such as injection molding and casting that can accurately set the size and angle in advance, a number of metal fixing frames with equal lengths are connected between the first signal line 100, the second signal line 200, the third signal line 300 and the central heat pipe 10 at equidistant intervals along the axial direction. The relative positions of the first signal line 100, the second signal line 200 and the third signal line can be accurately fixed, so that the relative movement problem between the signal lines will not occur during the preparation and laying of the cable, and the effect of no electromagnetic interference between the signal lines is fundamentally achieved.

[0039] In addition, since the fixing frame is a metal fixing frame and the metal fixing frame is grounded, a shielding effect is further achieved.

[0040] The metal fixing frame is arranged between the signal line and the central heat pipe 10 , which plays a good role in further accelerating the heat transfer between the heat pipe 10 and the surface of the signal line.

[0041] The thermally conductive inner film 13 is made of elastic material. If a thermally conductive inner film 13 equal to the total length of the cable is set in a cable for long-distance transmission, it is easy to stretch or wrinkle, affecting the thermal conductivity of the thermally conductive inner film 13 and the sealing inside the cable. By setting the thermally conductive inner film 13 in sections in a fixed frame formed by the transverse frame 9 and the longitudinal frame 12 of the metal fixing frame, not only can the thermally conductive inner film 13 be protected, but the thermal conductivity of the thermally conductive inner film 13 and the metal fixing frame can be combined for use to achieve more efficient heat transfer.

[0042] An S-shaped groove 11 is provided on the side of the transverse frame body 9 of each of the metal fixing frames, which is used to fix the two sides of the heat-conductive inner film 13, so that the heat-conductive inner film 13 forms a stable curved shape inside the cable, thereby expanding the heat-conductive area. The internal space formed between the heat-conductive inner film 13 and the heat-conductive outer film 12 forms a natural insulation layer for the first signal line 100, the second signal line 200 and the third signal line 300.

[0043] The heating cable also includes an inner sheath layer 7, a second flame retardant layer 8, and an outer sheath layer 1 that simultaneously cover the first signal line 100, the second signal line 200, and the third signal line 300. The heat conductive layer includes a heat conductive outer film 12, a central heat conductive pipe 10, and a heat conductive inner film 13 that connects the outer wall of the central heat conductive pipe 10 and the inner surface of the heat conductive outer film 12 and has a circumferential array angle of 60°. The central heat conductive pipe 10 is sealed with a heat conductive liquid.

[0044] The central heat conducting tube 10 is filled with heat conducting liquid, which contains the following components in percentage by weight: 20% to 90% glycerol, 0.1% to 4.0% organic acid, 0.05% to 5.0% polyol stabilizer, 0.5% to 2.0% diethanolamine, and 0.5% to 70.0% deionized water. The addition of glycerol to the heat conducting agent greatly increases the freezing point of the heat conducting agent, and the heat conducting agent can still flow even at a low ambient temperature, thus achieving a good heat conducting effect. The heat conducting liquid used in the cable has strong corrosion resistance and antifreeze performance.

[0045] Since the cable based on the skin effect will produce a thermal effect on the local surface of the cable, when the cable is used in a low temperature environment, it will cause a large temperature difference on the cable surface and uneven heat conduction, thereby reducing the service life of the cable. The present invention provides a thermal conductive layer to effectively improve the overall heating uniformity of the cable. The thermal conductive layer includes a thermal conductive outer film 12, a central heat conductive tube 10, and a thermal conductive inner film 13 connecting the outer wall of the central heat conductive tube 10 and the inner surface of the thermal conductive outer film 12 and having a circumferential array angle of 60°. The thermal conductive tube 10 is sealed with a thermal conductive liquid. The flowing thermal conductive liquid further accelerates the heat transfer inside the cable, and the thermal conductive inner film 13 connects the three signal lines, thereby improving the heat transfer between the three signal lines and avoiding the problem of large local temperature differences between different signal lines.

[0046] The first signal line 100 is a power line core, the second signal line 200 is a high-frequency signal line core, and the third signal line 300 is a non-high-frequency signal line core. The colors of the second insulating layer 4 on the first signal line 100, the second signal line 200, and the third signal line 300 are different; the second insulating layer 4 on the power line core is black; the second insulating layer 4 on the high-frequency signal line core is green; and the second insulating layer 4 on the non-high-frequency signal line core is red. When different signal lines have different functions, the colors of the outermost coating layers used are also different, so that construction personnel can make intuitive distinctions.

[0047] The first signal line 100 , the second signal line 200 , and the third signal line 300 are twisted-pair wires, and the twisted wires are galvanized steel twisted wires, which can avoid interference between the wires.

[0048] An anti-corrosion filler 6 is provided between the contact surfaces of the first insulating layer 2 , the first flame-retardant layer 3 , the second insulating layer 4 , the shielding layer 5 , and the heat-conducting layer. The anti-corrosion filler 6 is glass fiber.

[0049] The insulating material used in the first insulating layer 2 includes poly(fluoroethylene propylene), ethylene propylene diene monomer rubber, butyl semi-conductive tape, and polyphenylene sulfide.

[0050] In the present invention, a plurality of metal fixing frames of equal length are equidistantly connected along the axial direction between the first signal line 100, the second signal line 200, the third signal line 300 and the central heat conducting tube 10. The heat conducting inner film 13 is arranged between two adjacent metal fixing frames. The metal fixing frame is grounded, thereby enhancing the stability and bending strength of the overall structure of the cable. The metal fixing frame also plays the role of fixing the relative position between the signal lines, shielding and heat conduction, and protecting the heat conducting inner film 13 with a certain elasticity.

[0051] See also Figure 4 As shown, the present invention also provides a heating cable processing technology based on skin effect.

[0052] The process will be described below in conjunction with specific embodiments.

[0053] Embodiment 1

[0054] A heating cable processing technology based on skin effect includes the following steps:

[0055] Step 1, stranding: straighten the galvanized steel strands to make the diameter of the galvanized steel strands uniform and between 2-3 mm, and interweave and press two galvanized steel strands counterclockwise to form a wire core;

[0056] Step 2, coating with the first insulating layer 2: after bonding the anti-corrosion filler 6 on the outer periphery of the wire core, coating with the first insulating layer 2;

[0057] Step 3, coating the first flame retardant layer 3: coating the first flame retardant layer 3 after bonding the anticorrosive filler 6 to the outer surface of the first insulating layer 2;

[0058] Step 4, coating the second insulating layer 4: the second insulating layer 4 is woven from zirconium oxide silicate ceramic fibers with a diameter of 0.2 mm;

[0059] Step 5, covering the shielding layer 5: the shielding layer 5 is woven with tinned copper wire with a diameter of 0.3 mm;

[0060] Step 6, setting a heat-conducting layer: the heat-conducting layer includes a heat-conducting outer film 12, a central heat-conducting tube 10, and a heat-conducting inner film 13 connecting the outer wall of the central heat-conducting tube 10 and the inner surface of the heat-conducting outer film 12 and having a circumferential array angle of 60°. The heat-conducting inner film 13 evenly divides the cylindrical inner cavity enclosed by the heat-conducting outer film 12 into three equal-volume accommodating chambers, and the accommodating chambers include a first accommodating chamber, a second accommodating chamber, and a third accommodating chamber. Three wire cores coated with a shielding layer 5 in step 5 are selected and respectively inserted into the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber. The outer surface of the shielding layer 5 of each wire core is bonded with an anti-corrosion filler 6, and the anti-corrosion filler 6 fills the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber;

[0061] Step 7, coating the inner sheath layer 7: the inner sheath layer 7 is a low-phenyl silicone rubber layer, which is coated on the thermal conductive layer by heating the sol;

[0062] Step 8, coating the second flame retardant layer 8: using an extruder to extrude a flame retardant on the outer surface of the inner sheath layer 7 to form the second flame retardant layer 8;

[0063] Step 9, coating the outer sheath layer 1: the outer sheath layer 1 is a low-phenyl silicone rubber layer, which is coated on the second flame retardant layer 8 by heating sol.

[0064] The specific method of coating the second flame retardant layer 8 in step 9 is: repeatedly stirring and mixing a certain weight portion of epoxy resin, polytetrafluoroethylene, stabilizer, compatibilizer, and active diluent at 40°C to obtain a flame retardant, and using an extruder to extrude the flame retardant on the outer surface of the inner sheath layer 7 at a temperature of 120°C, and then air-cooling the flame retardant to a cooling temperature of 20°C.

[0065] In step 6, a heat transfer liquid is injected into the central heat transfer tube 10, and the heat transfer liquid contains the following components in percentage by weight: 30% glycerol, 0.1% organic acid, 0.05% polyol stabilizer, 0.5% diethanolamine, and 69.35% deionized water.

[0066] The heating cable based on the skin effect prepared by the processing technology of Example 1 was sampled and subjected to a heat preservation test in a low temperature environment. The test data is shown in Table 1. The test environment temperature is -10°C, the current is the same, and the test method is as follows: three groups of samples are taken from the cable prepared in Example 1 and the ordinary cable, the length of each group of cables is 20cm, 50cm, and 100cm respectively, the number of cables in each group is the same, and the number of cables can be set between 3-6, and the chip temperature sensors are set on the cross sections at both ends of the first signal line 100, the second signal line 200, and the third signal line 300 and the signal line cross section of the traditional cable, and the temperature data of the corresponding chip temperature sensors are recorded every 30 minutes.

[0067] Table 1

[0068]

[0069]

[0070] Table 1

[0071] Embodiment 2

[0072] Step 1, stranding: straighten the galvanized steel strands to make the diameter of the galvanized steel strands uniform and between 2-3 mm, and interweave and press two galvanized steel strands counterclockwise to form a wire core;

[0073] Step 2, coating with the first insulating layer 2: after bonding the anti-corrosion filler 6 on the outer periphery of the wire core, coating with the first insulating layer 2;

[0074] Step 3, coating the first flame retardant layer 3: coating the first flame retardant layer 3 after bonding the anticorrosive filler 6 to the outer surface of the first insulating layer 2;

[0075] Step 4, coating the second insulating layer 4: the second insulating layer 4 is woven from zirconium oxide silicate ceramic fibers with a diameter of 0.4 mm;

[0076] Step 5, covering the shielding layer 5: the shielding layer 5 is woven with tinned copper wire with a diameter of 0.5 mm;

[0077] Step 6, setting a heat-conducting layer: the heat-conducting layer includes a heat-conducting outer film 12, a central heat-conducting tube 10, and a heat-conducting inner film 13 connecting the outer wall of the central heat-conducting tube 10 and the inner surface of the heat-conducting outer film 12 and having a circumferential array angle of 60°. The heat-conducting inner film 13 evenly divides the cylindrical inner cavity enclosed by the heat-conducting outer film 12 into three equal-volume accommodating chambers, and the accommodating chambers include a first accommodating chamber, a second accommodating chamber, and a third accommodating chamber. Three wire cores coated with a shielding layer 5 in step 5 are selected and respectively inserted into the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber. The outer surface of the shielding layer 5 of each wire core is bonded with an anti-corrosion filler 6, and the anti-corrosion filler 6 fills the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber;

[0078] Step 7, coating the inner sheath layer 7: the inner sheath layer 7 is a low-phenyl silicone rubber layer, which is coated on the thermal conductive layer by heating the sol;

[0079] Step 8, coating the second flame retardant layer 8: using an extruder to extrude a flame retardant on the outer surface of the inner sheath layer 7 to form the second flame retardant layer 8;

[0080] Step 9, coating the outer sheath layer 1: the outer sheath layer 1 is a low-phenyl silicone rubber layer, which is coated on the second flame retardant layer 8 by heating sol.

[0081] The specific method of coating the second flame retardant layer 8 in step 9 is: repeatedly stirring and mixing a certain weight portion of epoxy resin, polytetrafluoroethylene, stabilizer, compatibilizer, and active diluent at 65°C to obtain a flame retardant, and using an extruder to extrude the flame retardant on the outer surface of the inner sheath layer 7 at a temperature of 150°C, and then air-cooling the flame retardant to a cooling temperature of 30°C.

[0082] In step 6, a heat transfer liquid is injected into the central heat transfer tube 10, and the heat transfer liquid contains the following components by mass percentage: 90% glycerol, 4.0% organic acid, 5.0% polyol stabilizer, 0.5% diethanolamine, and 0.5% deionized water. A large amount of glycerol is used to increase the freezing point of the heat transfer liquid, which is beneficial to heat conduction and further improves the cold resistance of the cable.

[0083] The heating cable based on the skin effect prepared by the processing technology of Example 2 was sampled and subjected to a heat preservation test in a low temperature environment, and the test data is shown in Table 2. The test method is the same as the test method of Example 1.

[0084] Table 2

[0085]

[0086] Embodiment 3

[0087] Step 1, stranding: straighten the galvanized steel strands to make the diameter of the galvanized steel strands uniform and between 2-3 mm, and interweave and press two galvanized steel strands counterclockwise to form a wire core;

[0088] Step 2, coating with a first insulating layer 2: bonding an anti-corrosion filler 6 to the outer periphery of the wire core and then coating with an insulating layer;

[0089] Step 3, coating the first flame retardant layer 3: coating the first flame retardant layer 3 after bonding the anticorrosive filler 6 to the outer surface of the first insulating layer 2;

[0090] Step 4, coating the second insulating layer 4: the second insulating layer 4 is woven from zirconium oxide silicate ceramic fibers with a diameter of 0.3 mm;

[0091] Step 5, covering the shielding layer 5: the shielding layer 5 is woven with tinned copper wire with a diameter of 0.45 mm;

[0092] Step 6, setting a heat-conducting layer: the heat-conducting layer includes a heat-conducting outer film 12, a central heat-conducting tube 10, and a heat-conducting inner film 13 connecting the outer wall of the central heat-conducting tube 10 and the inner surface of the heat-conducting outer film 12 and having a circumferential array angle of 60°. The heat-conducting inner film 13 evenly divides the cylindrical inner cavity enclosed by the heat-conducting outer film 12 into three equal-volume accommodating chambers, and the accommodating chambers include a first accommodating chamber, a second accommodating chamber, and a third accommodating chamber. Three wire cores coated with a shielding layer 5 in step 5 are selected and respectively inserted into the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber. The outer surface of the shielding layer 5 of each wire core is bonded with an anti-corrosion filler 6, and the anti-corrosion filler 6 fills the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber;

[0093] Step 7, coating the inner sheath layer 7: the inner sheath layer 7 is a low-phenyl silicone rubber layer, which is coated on the thermal conductive layer by heating the sol;

[0094] Step 8, coating the second flame retardant layer 8: using an extruder to extrude a flame retardant on the outer surface of the inner sheath layer 7 to form the second flame retardant layer 8;

[0095] Step 9, coating the outer sheath layer 1: the outer sheath layer 1 is a low-phenyl silicone rubber layer, which is coated on the second flame retardant layer 8 by heating sol;

[0096] Step 10: A layer of tempered film is attached to the outer sheath layer 1 to further improve the waterproof performance of the cable.

[0097] The specific method of coating the second flame retardant layer 8 in step 9 is: repeatedly stirring and mixing a certain weight portion of epoxy resin, polytetrafluoroethylene, stabilizer, compatibilizer, and active diluent at 55°C to obtain a flame retardant, using an extruder to extrude the flame retardant on the outer surface of the inner sheath layer 7, the extrusion temperature is 140°C, and then the flame retardant is air-cooled to 25°C. The use of self-extinguishing polytetrafluoroethylene prevents the cable from catching fire easily, the use of epoxy resin ensures the ductility of the cable, the mixing of epoxy resin and active diluent is conducive to the atomization molding of the raw materials, the flame retardant has very low water solubility and better stability, and has a good flame retardant effect when applied to the cable.

[0098] In step 6, a heat transfer liquid is injected into the central heat transfer tube 10, and the heat transfer liquid contains the following components in percentage by weight: 20% glycerol, 3.0% organic acid, 5.0% polyol stabilizer, 2.0% diethanolamine, and 70.0% deionized water.

[0099] In step 3, a plurality of metal fixing frames of equal length are arranged between the first signal line 100, the second signal line 200, the third signal line 300 and the central heat conducting tube 10 at equal intervals along the axial direction. The angle between adjacent transverse frames 9 presented by the transverse frame bodies 9 of the metal fixing frames on the same cross section along the axial direction of the cable is 60 degrees, and the length of each transverse frame body 9 is equal. One end of the three frames on the same cross section along the axial direction of the cable is connected to the central heat conducting tube 10. An S-shaped groove 11 is arranged on the side of the transverse frame body 9 of each of the metal fixing frames for fixing the two sides of the heat conducting inner film 13.

[0100] The heating cable based on the skin effect prepared by the processing technology of Example 3 was sampled and subjected to a heat preservation test in a low temperature environment, and the test data is shown in Table 3. The test method is the same as the test method of Example 1.

[0101] Table 3

[0102]

[0103] The test results of Table 1, Table 2 and Table 3 show that the cable of the present invention prepared by the cable processing technology of the present invention is more suitable for cold environments than traditional cables, and the cable of the present invention has good thermal insulation performance. According to the surface temperature data of the three signal lines on the cable of the present invention, the surface temperatures of the three signal lines are the same, and there is no temperature difference on the axial surface of each signal line at different distances, which means that the cable of the present invention has good thermal conductivity and uniform thermal conductivity, and makes full use of the thermal effect of the skin effect and conducts it evenly to the surface of each signal line.

[0104] In the present invention, a plurality of metal fixing frames of equal length are equidistantly connected along the axial direction between the first signal line 100, the second signal line 200, the third signal line 300 and the central heat conducting tube 10. The heat conducting inner film 13 is arranged between two adjacent metal fixing frames. The metal fixing frame is grounded, thereby enhancing the stability and bending strength of the overall structure of the cable. The metal fixing frame also plays the role of fixing the relative position between the signal lines, shielding and heat conduction, and protecting the heat conducting inner film 13 with a certain elasticity.

[0105] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A heating cable based on skin effect, characterized in that: The heating cable comprises a first signal line, a second signal line, and a third signal line, wherein the first signal line, the second signal line, and the third signal line are provided with a first insulating layer, a first flame retardant layer, a second insulating layer, a shielding layer, and a heat conducting layer in sequence from the inside to the outside, and three points formed by the projection of the center lines of the first signal line, the second signal line, and the third signal line on the cross section are the vertices of an equilateral triangle, and the heating cable further comprises an inner sheath layer, a second flame retardant layer, and an outer sheath layer that simultaneously cover the first signal line, the second signal line, and the third signal line; The first signal line, the second signal line and the third signal line are twisted pair wires, and the twisted wires are galvanized steel twisted wires; The processing technology of the heating cable comprises the following steps: Step 1, stranding: straighten the galvanized steel strands to make the diameter of the galvanized steel strands uniform and between 2-3 mm, and interweave and press two galvanized steel strands counterclockwise to form a wire core; Step 2, coating with a first insulating layer: bonding the anti-corrosion filler to the outer periphery of the wire core and then coating with the first insulating layer; Step 3, coating with a first flame retardant layer: coating with a first flame retardant layer after bonding an anticorrosive filler to the outer surface of the first insulating layer; Step 4, coating with a second insulating layer: the second insulating layer is woven from zirconium oxide silicate ceramic fibers with a diameter of 0.2-0.4 mm; Step 5, covering the shielding layer: the shielding layer is woven with tinned copper wire with a diameter of 0.3-0.5 mm; Step 6, setting a heat-conducting layer: the heat-conducting layer includes a heat-conducting outer film, a central heat-conducting tube, and a heat-conducting inner film connecting the outer wall of the central heat-conducting tube and the inner surface of the heat-conducting outer film and having a circumferential array angle of 60°. The heat-conducting inner film evenly divides the cylindrical inner cavity surrounded by the heat-conducting outer film into three equal-volume accommodating chambers, and the accommodating chambers include a first accommodating chamber, a second accommodating chamber, and a third accommodating chamber. Three wire cores coated with a shielding layer in step 5 are selected and respectively inserted into the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber. The outer surface of the shielding layer of each wire core is bonded with an anti-corrosion filler, and the anti-corrosion filler fills the first accommodating chamber, the second accommodating chamber, and the third accommodating chamber; Step 7, coating the inner sheath layer: the inner sheath layer is a low-phenyl silicone rubber layer, which is coated on the thermal conductive layer by heating the sol; Step 8, coating the second flame retardant layer: using an extruder to extrude a flame retardant on the outer surface of the inner sheath layer to form a second flame retardant layer; Step 9, coating the outer sheath layer: the outer sheath layer is a low-phenyl silicone rubber layer, which is coated on the second flame retardant layer by heating sol.

2. A heating cable based on skin effect according to claim 1, characterized in that: The first signal line is a power line core, the second signal line is a high-frequency signal line core, the third signal line is a non-high-frequency signal line core, and the colors of the second insulating layers on the first signal line, the second signal line, and the third signal line are different; Among them, the color of the second insulation layer on the power line core is black; the color of the second insulation layer on the high-frequency signal line core is green; the color of the second insulation layer on the non-high-frequency signal line core is red.

3. A heating cable based on skin effect according to claim 1, characterized in that: An anti-corrosion filler is provided between contact surfaces among the first insulating layer, the first flame-retardant layer, the second insulating layer, the shielding layer, and the heat-conducting layer, and the anti-corrosion filler is glass fiber.

4. A heating cable based on skin effect according to claim 1, characterized in that: The insulating material used in the first insulating layer includes poly(fluoroethylene propylene), ethylene propylene diene monomer rubber, butyl semi-conductive tape, and polyphenylene sulfide.

5. A heating cable based on skin effect according to claim 1, characterized in that: The heat-conducting layer includes a heat-conducting outer film, a central heat-conducting tube, and a heat-conducting inner film connecting the outer wall of the central heat-conducting tube and the inner surface of the heat-conducting outer film and having a circumferential array angle of 60°. The central heat-conducting tube is sealed with a heat-conducting liquid. A plurality of metal fixing frames of equal length are connected axially at equal intervals between the first signal line, the second signal line, the third signal line and the central heat-conducting tube. The heat-conducting inner film is arranged between two adjacent metal fixing frames, and the metal fixing frames are grounded.

6. A heating cable based on skin effect according to claim 5, characterized in that: An S-shaped groove is provided on the side of each fixing frame for fixing the two sides of the heat-conducting inner film.

7. A heating cable based on skin effect according to claim 1, characterized in that: The specific method of coating the second flame retardant layer in step 8 is: repeatedly stirring and mixing a certain weight portion of epoxy resin, polytetrafluoroethylene, stabilizer, compatibilizer, and active diluent at 40°C~65°C to obtain a flame retardant, and using an extruder to extrude the flame retardant on the outer surface of the inner sheath layer at a temperature of 120°C~150°C, and then air-cooling the flame retardant to a cooling temperature of 20°C~30°C.

8. The heating cable based on skin effect according to claim 1, characterized in that: After step 9, step 10 is further provided: attaching a layer of tempered film on the outer sheath layer.

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