RU242527U1 - Fire-resistant marine cable - Google Patents

Abstract

This utility model relates to fire-resistant marine cables that meet increased fire safety requirements. The technical result consists of increasing the cable's fire resistance. This is achieved by the cable comprising insulated conductive cores or a strand of insulated conductive cores. The core insulation itself is made of a thermosetting polymer-based composite. Moreover, over the conductive core insulation itself or the strand of conductive core cores, each of which is covered by its own insulation, there is an additional protective covering formed in the form of a winding of flame-retardant synthetic film made of a thermosetting polymer containing at least 30% polyimide, corresponding to plastic flammability class FV(PV)0. 2 .

Description

The utility model relates to the field of marine electrical equipment, namely, to fire-resistant marine cables that meet increased requirements for cable fire safety, in particular, in terms of flame propagation, formation of burning particles, formation of smoke during combustion and smoldering, smoke toxicity, and the absence of halogens.

The "Combustion-Retardant Power Cable" is known under Russian Federation Patent for Utility Model No. 71,024. The problem addressed by the group of claimed utility models is to create a power cable design that meets fire safety requirements for non-flammability in category (A), which allows it to be used when laid in bundles.

The power cable according to the specified patent contains one aluminum or copper conductive core, on top of which is applied a screen of conductive paper, paper insulation, a screen placed on the insulation, made of conductive paper, which is impregnated with a viscous or non-flowing impregnating composition, an aluminum or lead sheath, and also includes a protective covering, which is placed between the different layers of the cable.

The protective covering according to the said utility model is a fire-resistant barrier, which is made of at least one glass-mica tape, on top of which an outer shell of flame-retardant polyvinyl chloride plastic compound with low smoke and gas emission and an oxygen index of at least 35 is applied.

This utility model relates to the design of power cables with impregnated paper insulation, which are intended for the transmission and distribution of electrical energy in stationary installations at an alternating voltage of 10 kV and a frequency of up to 100 Hz.

These cables do not meet the requirements for marine cables. Furthermore, the protective covering, made of at least one glass-mica tape overlaid with a PVC outer sheath, does not fully provide protection against smoke and gas emissions in the event of a cable fire or smoldering.

The closest in technical essence to the claimed utility model is the “Ship Cable” according to the Russian Federation Utility Model No. 217589.

This cable contains conductive conductors made of copper or tinned copper wires, each covered with insulation and twisted into a core. On top of the core are inner layers and an outer sheath.

The insulation of each core itself is made of a thermosetting polymer, for example, a cross-linked compound in which the elastomer may be ethylene-propylene or ethylene-propylene rubber, or propylene, or polyethylene, or ethylene vinyl acetate, or an equivalent synthetic elastomer.

The use of such a thermosetting polymer as insulation for conductive cores reduces the thermal impact on the conductive cores or on the core at high temperatures, increasing their reliability and durability by eliminating the possibility of oxygen entering into a chemical reaction with the core material and the insulation material; however, this solution does not fully meet the fire resistance requirements of the cable.

The problem, which the claimed utility model is aimed at solving, is to increase the fire resistance of ship cables in terms of smoke formation indicators and to eliminate the appearance of molten droplets or hot particles during combustion or smoldering of the cable by increasing the proportion of flame-retardant materials with low smoke emission in the design of the fire-resistant ship cable.

The technical result that ensures the solution of the set task is achieved by forming a protective covering over the single-core cable's own insulation or over a strand of cores covered with their own insulation, twisted into a core, which increases the cable's fire resistance.

To solve the problem, the fire-resistant marine cable contains single insulated conductive cores and/or a twist of insulated conductive core cores, the insulation of which is made from a composition based on a thermosetting polymer.

On top of the individual insulation of the conductive cores and/or on top of the winding of the conductive cores of the core covered with their own insulation, a protective covering is additionally formed, on top of which the inner layers and outer sheath are placed.

The protective covering is made of one or more flame-retardant synthetic films made of a thermosetting polymer containing at least 30% polyimide. These synthetic films must comply with the FV(PV)0 flammability rating of plastics according to UL Standard 94 (USA), which classifies plastics based on their combustion behavior at various thicknesses (hereinafter referred to as the Protective Cover).

When the cable heats up above the permissible values (emergency situation), the protective covering turns into a solid shell (coke residue) on the surface of the insulation of a single core or on the surface of the winding of the conductive core cores covered with their own insulation, impermeable to smoke, molten drops, and hot particles.

This property of the protective covering, formed on the insulation of individual conductive cores or on the surface of the winding of the conductive cores of the core, covered with their own insulation, in a fire-resistant marine cable, allows:

- prevent the appearance of molten drops or hot particles of insulation during combustion of ship cable (compliance with fire hazard class “O1” according to GOST 31565);

- significantly reduce the formation of smoke during combustion and smoldering of ship cable;

- increase the reliability of ship cables by eliminating the possibility of oxygen entering into a chemical reaction with the insulation material at high temperatures;

- ensure longitudinal gas tightness of the cable core;

- localize cable damage during a short circuit without damaging the entire cable route.

In addition to the above-mentioned advantages of the Protective Cover, which are evident in an emergency, during trouble-free operation of the cable, the Protective Cover enhances the following characteristics of the insulation of the conductive cores, made of thermosetting polymer:

- reduction of mutual harmful effects of cable layers with different properties on each other;

- preventing or slowing down the penetration of gases (e.g. oxygen, water vapor), liquids (water, electrolyte solutions) or aggressive substances into the cable structure;

- preservation of dielectric properties, as it prevents water from penetrating into insulating materials, which leads to a decrease in their resistance and breakdown;

- increasing the durability of the product, due to the slowing down of the aging processes of the polymeric materials that make up the cable layers, due to oxidation and hydrolysis;

- protection from chemical aggression, due to blocking the diffusion of aggressive substances (salts, acids, alkalis) from the environment.

What is new in the proposed utility model is

- formation of a protective coating in a marine cable over single conductive cores covered with their own insulation made of thermosetting polymer, or over a layer of conductive core cores covered with their own insulation made of thermosetting polymer;

- the production of a protective covering in the form of a winding of one or more flame-retardant synthetic films made of a thermosetting polymer containing at least 30% polyimide, corresponding to the flammability class of plastics FV(PV)0 in accordance with Standard UL 94 (USA), which classifies plastics depending on how they burn at different thicknesses.

The design of a fire-resistant marine cable, additionally including a protective covering, is explained by drawings.

Fig. 1 shows a cross-section of the conductive core of a fire-resistant marine cable, which includes copper wires 1, the space between which contains a filler 2, and a heat-resistant barrier 3 formed on top of the filler 2, made in the form of a winding of several electrical insulating films. On top of the heat-resistant barrier 3, proper insulation 4 made of a thermosetting material is applied, and on top of the proper insulation 4, a protective covering 5 is formed, made in the form of a winding of one or more flame-retardant synthetic films made of a thermosetting polymer containing at least 30% polyimide, corresponding to the flammability class of plastics FV(PV)0.

Fig. 2 shows a cross-section of a twisted current-carrying core of a fire-resistant marine cable, which includes three twisted current-carrying cores 6, each of which is covered with its own insulation 4. On top of the twisted current-carrying cores 6, each of which is covered with its own insulation 4, a protective covering 5 is formed, made in the form of a winding of one or more flame-retardant synthetic films made of a thermosetting polymer containing at least 30% polyimide, corresponding to the flammability class of plastics FV(PV)0.

Films made of thermosetting polymer containing at least 30% polyimide, corresponding to the plastics flammability class FV(PV)0, were subjected to various tests.

The results of a comparison of the fire safety indicators of polyethylene terephthalate films, established by the current standard GOST 24234-80 "Polyethylene terephthalate film", and films with polyimide allowed us to obtain the following results:

Fire safety index of films Values of polyethylene terephthalate films Test results of polyimide films 1. Oxygen index, % vol. 20 39 2. Flammability group flammable, difficult to ignite difficult to burn 3. Loss of mass during smoldering and combustion, % 99 35 4. Flammability class FV(PV)2 FV(PV)0 5. Temperature, °C
- ignition
- self-ignition, 390
440 555
575 6. Smoke formation, ^m2 /kg
- decay
- combustion 1550
1100 <100
<100 7. Toxicity of HCl ₅₀ smoke, g/ ^m3 35 ≥50

A comparison of the results of tests conducted on the fire safety indicators of synthetic polymer films allows us to establish significant advantages of a thermosetting polymer containing at least 30% polyimide corresponding to the flammability class of plastics FV(PV)0, compared to known synthetic polymer films.

The tests carried out on polymer films containing at least 30% polyimide, corresponding to the flammability class of plastics FV(PV)0, allow us to conclude on the industrial applicability of the Protective Cover for this utility model application.

Claims (1)

A fire-resistant marine cable containing insulated conductive cores or a strand of insulated conductive cores of a core, the insulation of which is made from a composition based on a thermosetting polymer, and on top of the conductive cores or core cores, internal layers and an outer cable sheath are placed, characterized in that on top of the insulation of the conductive cores or on top of the strand of conductive core cores, each of which is covered with its own insulation, a protective covering is additionally formed, made in the form of a winding of a flame-retardant synthetic film made of a thermosetting polymer containing at least 30% polyimide, corresponding to the ignition class of plastics FV(PV)0.