RU176852U1 - ELECTRIC FIRE RESISTANT CABLE - Google Patents

Abstract

The invention relates to fire-resistant electric cables, characterized by the material and location of the insulation, as well as the use of flame-retardant insulation materials. An electric flame-retardant cable, the insulation system of which includes a thermal barrier layer containing the first helically applied mica tape, characterized in that said layer contains a second spirally superimposed mica tape with mutual partial overlapping of said mica tape with the formation of a virtual m entes, each mica-containing tape has a width N and is superimposed in increments of Z, and the virtual tape has a width of H, so that the following relations are true: Z> N> (Z-N), 2N> H> N.

Description

The technical field to which the utility model relates.

The utility model relates to fire-resistant electrical cables characterized by the material and location of the insulation, as well as the use of flame-resistant insulation materials.

State of the art

Known fire-resistant cable, including one or more conductive cores with flame retardant and polymer insulation, as well as a protective sheath; the fire-resistant insulation of each core is made in the form of an extruded continuous concentric layer of composite material, which subsequently turns into ceramic when exposed to high temperature, and the polymer insulation and protective sheath are made of a halogen-free polymer composition (Patent RU No. 58777 U1, IPC Н01В 7/02 Published: 11/27/2006 Bull. No. 33).

Signs of a known cable that coincide with the features of the claimed technical solution are that it contains one or more conductive conductors with combined (fireproof and polymer) insulation, as well as a protective sheath.

The reason that prevents obtaining a technical result in a known cable, which is provided by the claimed technical solution, is that the composite material of which the flameproof insulation of the core is made subsequently turns into ceramic when exposed to high temperature.

The closest analogue (prototype) is an electrical fire-resistant (power) cable, which contains from one to five twisted conductive copper conductors, a thermal barrier made of at least one mica-containing tape, spirally applied with at least 40% overlapping over the conductive copper cores, cross-linked polymer insulation, located on top of the thermal barrier, extruded inner shell of thermoplastic polymer composition, superimposed with filling the gaps between the insulated laminate, and the outer shell of a thermoplastic polymer composition, wherein said insulation is made of cross-linked polyethylene or an extruded cross-linked polymer composition based on a halogen-free polyolefin with an oxygen index of at least 30, the inner extruded shell is made of a thermoplastic polymer composition that does not contain halogens, with an oxygen index of at least 45, and the outer shell is made of extruded thermoplastic polymer composition that does not contain halogens, with oxygen one index of at least 45 (Patent RU No. 40527 U1, IPC Н01В 9/00, published September 10, 2004 Bull. No. 25).

Signs of the known cable, coinciding with the features of the claimed technical solution, are that its insulation system includes a thermal barrier layer containing one spirally superimposed mica tape.

The reason that prevents obtaining a technical result in a known cable, which is ensured by the claimed technical solution, is that said mica tape is applied with an overlap of at least 40%.

The technical problem that the utility model addresses is the need to reduce the formation time of the mentioned thermal barrier at a fixed (i.e., without increasing) wrapping speed. Obviously, this reduction in time can be achieved by increasing the width of the tape. However, on the other hand, for technological reasons, the width of the tape cannot be increased, since this leads to a decrease in the quality of the thermal barrier. Thus, the technical problem lies in the conflicting requirements for the width of the tape: the width of the tape must be increased to reduce the time of formation of the thermal barrier and the width of the tape cannot be increased, as this will lead to a decrease in the quality of the thermal barrier.

Utility Model Disclosure

The technical result, which mediates the solution of this technical problem, is to use a virtual tape of width H, consisting of two mica-containing (physical) tapes of the same width N, superimposed with partial mutual overlap, so that 2N> H> N. Moreover, each physical tape is imposed spirally with a gap, while a virtual tape is imposed spirally with an overlap (usually 40% or more), which, combined with the condition expressed by the inequality 2N> H> N, leads to the desired reduction in the time of formation of the thermal barrier without increasing the width of the mica tape and without increasing its consumption.

A technical result is achieved in the claimed technical solution by the fact that the cable insulation system includes a thermal barrier layer containing first and second helically superimposed mica tapes with mutual partial overlapping of said mica tapes with the formation of a virtual tape, with each mica tape having a width N and is applied in increments Z, and the virtual tape has a width of H, so that the following relationships are true:

Z> N> (Z-N),

2N> H> N.

Brief Description of the Drawings

In FIG. 1 schematically shows an example of a three-core cable (longitudinal section); in FIG. 2 schematically shows a rectified fragment of one layer of a thermal barrier.

Utility Model Implementation

The cable contains one or more copper conductive conductors 1 (for example, three conductors twisted into a core, as shown in Fig. 1), as well as an insulation system including a thermal barrier 2 and insulation 3 of each core, an inner sheath 4 of a thermoplastic polymer composition, superimposed on insulated conductors with filling the gaps between the conductors, as well as the outer sheath 5. The insulation system may, in addition, contain a screen 6 in the form of a winding made of copper foil or copper tape, superimposed overlapping on top of the inner sheath 4 (or, screen, armor 6 of two steel strips of not less than 0.3 mm in thickness, superposed over the inner shell 4), and a coil 7 formed of at least one glass tape or mica tape having a basis weight of at least 160 g / cm ^2, superimposed on top inner shell 4.

Thermal barrier 2 includes at least one layer. In this case, it is optimal to perform a thermal barrier of two layers when the second layer is directly superimposed on the first (Fig. 2 shows an embodiment of a thermal barrier of one layer).

Layer 2 of the thermal barrier is made of two mica-containing tapes 8 and 9, superimposed spirally on the conductive core 1 (Fig. 2). In this case, the mica-containing tapes 8 and 9 are superimposed with their mutual overlapping to form a virtual tape 10. Each mica-containing tape 8 and 9 has a width N and is superimposed in increments of Z, and the virtual tape 10 has a width H, so that the following relationships are true:

Z> N> (Z-N);

2N> H> N.

The ratio Z> N> (Z-N) means that each mica-containing tape 8 and 9 is superimposed with a gap (Z-N)> 0 and with a partial mutual overlap [2N- (Z-N)]. The ratio 2N> H> N means that a virtual tape 10 of width H formed by mica-containing tapes 8 and 9 is superimposed overlapping.

Information confirming the possibility of manufacturing a cable. In the manufacture of the cable, a thermal barrier 2 is initially formed over the conductive core 1. For this purpose, two mica-containing tapes 8 and 9 are installed in the wrapper, which are then synchronized with the mutual partial overlap of both mica-containing tapes and with gaps for each mica-containing tape laid on the conductive core 1 to form virtual tape 10. In this case, the latter is laid with an overlap of at least 40%. As a result, the first (possibly the only) layer of the thermal barrier is formed. If necessary, a second thermal barrier layer can be formed on top of the first layer of thermal barrier formed in this way using the same process steps. Sequential formation of more than two layers is possible. Then, other insulation elements are formed, which may have different designs. So, as the insulation material 3, a cross-linked polyethylene or a cross-linked polyolefin-based halogen-free polymer composition with an oxygen index of at least 30 can be used. A halogen-free polyolefin-based polymer composition can be used as the material of the inner shell 4, with an oxygen index of at least 45. As a material of the outer shell 5, a halogen-free polyolefin-based polymer composition with an oxygen index of at least 45 can be used. Using The polymer compositions used to make such a cable are manufactured by domestic industry. As for the conductive conductors 1, they are made of copper or aluminum wire, traditional for electric cables, and the twisting of insulated conductors of a multicore cable is carried out using ordinary twisting equipment. To apply insulation 3, inner 4 and outer 5 shells use extrusion equipment. The imposition of the screen 6 of copper tape or copper foil (or armor 6 of galvanized steel tape) is carried out on known equipment traditionally used in the cable industry.

Claims (3)

Fire-retardant electrical cable, the insulation system of which includes a thermal barrier layer containing a first spirally superimposed mica-containing tape, characterized in that said layer contains a second spirally superimposed mica-containing tape with mutual partial overlapping of said mica-containing tapes with the formation of a virtual tape, each mica-containing tape has a width N and superimposed in increments of Z, and the virtual tape has a width of H, so that the following relationships are true: Z> N> (Z-N), 2N> H> N.

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