For flame retardant cables cited combustion test method standard we are more familiar with GB/T18380-2008 or GB/T18380.34-2008 (IEC60332-3-23), the two standards for the description of the test method and the evaluation of test results and other aspects of the differences.
In this paper, TST CABLES will compare the two standards, so that readers can better understand the differences between the two standards, and as a basis for future product selection and acceptance.
First, the name of the indicators and requirements are different
There are some differences between GB 31247-2014 and GB/T18380-2008 in the names and requirements of the indicators of the combustion test methods, with the former requiring 8 items and the latter only 1 item.
Note: Flame spread FS is the maximum charring height.
GB 31247-2014 standard requires the following 8 items:
a. Flame spread FS≤1.5m;
b.Heat release rate peak HRR peak ≤ 30kW;
c.Total heat release within 1200s by fire THR1200≤15MJ;
d. Combustion growth rate index FIGRA ≤ 150W/s;
e. Peak smoke production rate SPR peak ≤ 0.25m2/s;
f. Total smoke production within 1200s of fire TSP1200≤50m2;
g. Smoke density (minimum transmittance) It ≥ 60% (based on GB/T17651.2 test method)
h. Vertical flame spread height H ≤ 425mm (based on GB/T18380.12 test method)
And in GB/T18380-2008 standard flame spread FS≤1.5m.
Second, the test method is different
- Sample burning root number is different
GB31247-2014 standard B1 flame retardant cable or fiber optic cable test requirements:
Calculate the number of burning roots is only related to the outer diameter of the cable, and has nothing to do with the non-metallic volume in the cable, the specific calculation method refers to the formula in GB/T31248-2014;
GB/T18380.34-2008 (IEC60332-3-23) Test requirements for Class B flame retardant cables or fiber optic cables:
The total number of cable specimen segments should be the total volume of the specimen contained in the volume of non-metallic materials in the number of 3.5L/m, through this requirement can be calculated by the number of cables need to burn.
- Samples tied in different ways
GB31247-2014 standard B1 flame retardant cable or fiber optic cable test requirements:
Cable OD greater than or equal to 20 mm, cable spacing is 20 mm.
Cable outer diameter between 5 mm and 20 mm, cable spacing for cable diameter.
Cable outer diameter is less than or equal to 5 mm, the cable is installed according to the cable bundle, the diameter of each cable bundle is about 10 mm, the cable bundle shall not be twisted between the cable bundle, the spacing of the cable bundle is 10 mm.
GB/T18380.34-2008 (IEC60332-3-23) Class B flame retardant cable or fiber optic cable test requirements:
For samples in which at least one metal conductor cross-section exceeds 35mm2 , using a standard steel ladder, the number of cables shall be no more than the following number, i.e., constituting a single layer of 300mm width, with the spacing between each cable equal to 0.5 times the diameter of the cable but not exceeding 20mm (spaced arrangement of the ligatures).
For samples in which none of the metal conductors exceeds 35mm2 in cross-section, standard steel ladders are used, the specimens are closely spaced, and multi-layer arrangements are permitted.
- Burning time is different
GB31247-2014 standard B1 flame retardant cable or fiber optic cable test requirements:
The fire time is 20min, and after the end of the fire, if the cable continues to remain burning or burning and glowing, it should be extinguished.
GB/T18380.34-2008 (IEC60332-3-23) Test requirements for Class B flame-retardant cables or optical fiber cables:
Fire time is 40min, after the end of the fire, the air flow through the test box to maintain the cable to stop burning or glowing, up to 1h, and then forced to extinguish the burning or glowing.
- Determination based on different
GB31247-2014 standard B1 flame retardant cable or fiber optic cable test requirements: flame spread FS ≤ 1.5m;
GB/T18380.34-2008 (IEC60332-3-23) B class flame retardant cable or fiber optic cable test requirements: flame spread FS ≤ 2.5m;
With regard to GB/T18380-2008 or IEC60332-3 and GB31247-2014 two standards similar to an assessment index, charring height and flame spread FS, it seems that the assessment of the sample combustion parts and measurement of the length of the same way, but the sample tying method, the number of samples of combustion roots and combustion time are not the same, you can not simply help which standard is more stringent, the method is not the same. It can not simply say which standard is more strict and the method is not the same.
GB31247-2014 standard on flame retardant assessment requirements are more concerned about the combustion process of the flame (samples in the ignition source under the action of the flame) state, the smoothness of the flame, the flame intensity, the smoothness of the smoke production, etc., is not entirely the assessment of the sample burns how long.
In short, there are many differences between the two standards, so it is recommended that we believe in the product selection or acceptance of the specific conditions to choose the reference standard requirements to ensure product safety.
