Cable flame retardant performance standards, grades and tests

1. The fire safety technical indicators of flame-retardant cables are different from those in Europe and America

The main technical indicators of cables related to fire safety are the flame retardancy of the CO2 cable, the density of smoke and the toxicity of the gas. American fire protection standards pay more attention to the first two issues, but Europe and the United States have completely different views on fire safety.

American traditional fire protection concept:

The root of the fire lies in the production of carbon monoxide (CO) poisonous gas and the heat release from the conversion of CO to CO2 in the subsequent combustion process. Therefore, controlling the heat release during the combustion process can reduce the hazard of the fire.

Traditional European fire protection concept:

The amount of halogen acid (HCL) released during combustion, gas corrosivity, smoke concentration and gas toxicity are the main factors that determine whether people can safely escape from the fire scene.

2. The cable flame retardant performance standard

 A. IEC60332 flame retardant standard and combustion test

In order to evaluate the flame retardant performance of cables, the International Electrotechnical Commission has formulated three standards: IEC60332-1, IEC60332-2 and IEC60332-3:

 (1) IEC60332-1, IEC60332-2 flame retardant grade

IEC60332-1 and IEC60332-2 are used to evaluate the flame retardant ability of a single cable when placed in an inclined and vertical position (corresponding to the standards of GB12666.3 and GB12666.4 in China).

IEC60332-1/BS4066-1 Single wire or cable vertical burning test

(Flame Test On Single VerticalInsulated Wires/Cables)

Test content:

A 60cm-long sample is vertically fixed in the metal box opened on the front wall. A propane burner with a flame length of 175mm is in contact with the cable at a 45-degree angle from the position 450mm away from the upper fixed end of the sample. The distance between the damaged part of the sample and the lower part of the fixed end is not more than 50mm, and the test passes.

(2) IEC60332--3 flame retardant grade

  IEC60332-3 (corresponding to GB12666.5-90 in China) is used to assess the flame retardant ability of bundled cables when burning vertically. In contrast, the requirements for flame retardant ability of bundled cables when burning vertically are much higher.

IEC60332-3/BS4066-3 Bundle wire or cable vertical burning test

(Flame Test On Bunched Wires/Cables)

Test content:

     Fix a bundle of 3.5m long cable samples on a trapezoidal test frame with iron wires. The number of samples is determined by the non-metallic materials required by different classifications. The sample is hung vertically on the back wall of the combustion furnace, and the air is introduced into the combustion furnace through the air inlet on the bottom plate.

    The propane plane burning furnace is in contact with the sample with a flame at 750°C. The sample must not burn within 20 minutes of vertical combustion under forced air blowing (air discharge 5m3/min, wind speed 0.9m/sec), and the cable spreads in the flame. It will extinguish itself within 2.5 meters.

B. UL flame retardant standards and testing of cables

(1) UL flame-retardant standards for cables: If any cable listed by UL has been tested and verified to meet a certain fire rating, the UL identification, fire rating and approval number can be printed on the cable.

(2) Supercharged cable-CMP UL test

Supercharged-CMP level air supply combustion test/Steiner air duct test

(Plenum Flame Test / Steiner Tunnel Test)

This is the most demanding cable (PlenumCable) in the UL fire protection standard. The applicable safety standard is UL910. The experiment stipulates that it should be laid on the horizontal air duct of the device.