The working principle of the fire alarm cable
The fire alarm cable adopts a new type of oxygen isolation
Flame retardant and refractory materials have the properties of non melting, non dissolving, non delayed combustion, low smoke, low halogen and low toxicity. When the cable encounters a flame, the previously soft metal compounds will be transformed into insoluble metal oxides and water, which blocks the invasion of hot oxygen on the internal insulation layer, so that the internal insulation layer cannot burn, and the oxygen insulation layer will be heated to separate the crystalline water, Absorb a large amount of latent heat of evaporation, which will greatly reduce the temperature of combustible materials in the outer layer. The cable on fire will extinguish itself (the flame is 950-1000 ℃).
Flame retardant and fire-resistant wires and cables commonly used in fire distribution lines
Under fire conditions, the fire-fighting electrical equipment must ensure a certain working time to facilitate personnel escape and fire fighting, which is beyond doubt. The national building code of Canada stipulates that in buildings with a height greater than 18m, emergency power supply that can work for 2h under full load shall be provided, and the cable for alarm and communication system shall be able to directly withstand fire attack for 1H. Australian as2293 standard requires that the main feeder and branch feeder cable for emergency evacuation lighting shall be able to operate for 2h, and the last branch circuit shall reach 15min. When ordinary cables, flame-retardant cables and fire-resistant cables are laid in the open and through steel pipes and applied with fire-retardant coatings, their continuous power supply time does not reach 30min, which is unfavorable to the power supply of fire-fighting equipment with long power supply time, such as fire control room, fire water pump, fire elevator, smoke control facilities and so on.
What is flame retardant wire and cable
Flame retardant wires and cables are wires and cables with the ability to prevent or delay the occurrence or spread of flame, that is, under the specified test conditions, wires and cables are burned. After removing the fire source, the spread of flame on wires and cables is only within the limited range and can be extinguished by itself. Flame retardant wires and cables are not non combustible cables, but flame retardant materials are added to the insulating layer and sheath layer, so that the cable will not delay combustion in the fire. When the external fire source disappears, it will self extinguish after a period of time. The grade of flame-retardant wires and cables is divided into four grades: flame-retardant grade I, flame-retardant grade II, flame-retardant grade III and flame-retardant grade IV. each grade is divided into class A, class B and class C according to the category of flame-retardant samples, hereinafter referred to as Za (flame-retardant class a), ZB (flame-retardant class B) and ZC (flame-retardant class C)
What is fire resistant wire and cable
Fire resistant wires and cables are tested for fire resistance under the specified fire source and time, and have the ability of power transmission and operation under the specified state, that is, they can ensure the integrity of the line. Fire resistant cables can maintain the normal operation of the line for a certain time, and are mainly used in important occasions where the normal transmission of power must be guaranteed under fire conditions. Fire resistant cables must adopt copper conductors with a rated voltage of 0 . 6 / 1.0kv and below, the insulating layer has fire resistance characteristics, otherwise a fire-resistant layer shall be set on the conductor or cable core. The fire-resistant layer is usually directly wrapped with multi-layer fire-resistant mica tape, which is an inorganic insulating material composed of glass fiber, mica powder and silicate. The material can be sintered into a hard and dense insulator attached to the surface of the conductor in case of fire So as to ensure the normal operation of the line under fire conditions.