PROTECTION AGAINST HEAT AND FIRE TEST METHOD: EVALUATION OF MATERIALS AND ASSEMBLIES OF MATERIALS WHEN EXPOSED TO A SOURCE OF RADIANT HEAT
Radiant heat protective clothing is worn in different circumstances and because of this, the intensity of radiation that falls on the material of the clothing can vary over a wide range.
Industrial workers or firefighters may be exposed to intense radiation.
This standard comprises two test methods: Method A is used for the visual assessment of changes in the material after the action of heat radiation. Method B determines the protective effect of the materials. Materials can be tested by both methods or by only one of them relatively low over a long period of time.
Heat Transfer Levels:
Time t12: time in seconds, expressed as a decimal place, to obtain an increase in the calorimeter temperature of (12 ± 0.1) ºC.
Time t24: time in seconds, expressed as a decimal place, to obtain an increase in the calorimeter temperature of (24 ± 0.2) ºC.
Thermal Transmission Factor (TF): A measure of the fraction of heat transmitted through the sample exposed to a radiant heat source. It is numerically equal to the ratio between transmitted and incident heat flux densities.
The radiant heat level is set by adjusting the distance between the sample and the source of thermal radiation. After the exposure, the sample and its layers are examined to determine any visible changes.
After irradiation, the sample or individual layers of the Multi-layer set. It is annotated, for the sample or for each individual layer of the set multilayer, any changes (e.g., discoloration, fouling, ember, charring, breaking, melting, shrinking, sublimation, etc.) that it is observed.
One side of the test specimen is attached to one of the side plates of the B sample support, and the sample is kept in contact with the surface of the calorimeter, by applying a force of 2 N. The movable screen is removed and the records the onset of irradiation. The mobile screen closes the moment you it reaches a temperature increase of about 30 ºC.
The times t12 and t24 are determined, expressed in seconds with a decimal place, to obtain a calorimeter temperature increase of (12 ± 0.1) °C or (24 ± 0.2) ºC, respectively. As required in the specific standard, it is calculated and Write down the result of the difference between T24 and T12.
TF (technical transition) Q0 and RHTI12 and RHTI24 are determined, a time measure t12 or t24 expressed in 0.1s for the calorimeter temperature increase of 12ºC or 24ºC respectively. The radiant heat transfer index, RHTI24-RHTI12 (Q0) for the incident heat flux density is determined RHTI24 minus RHTI12.
TF (technical transition) Q0 and RHTI12 and RHTI24 are determined, measure of time t12 or t24 expressed in 0.1s for the increase in temperature of the calorimeter of 12ºC or 24ºC respectively. The radiant heat transfer index, RHTI24-RHTI12 (Q0) for the incident heat flux density is determined RHTI24 minus RHTI12.
TEST EQUIPMENT :
For both methods, the following are used:
TEST EQUIPMENT:
For both methods the following is used:
– Radiant heat source
– Test frame
– Sample support
It is added for method B:
The radiant heat source consists of 5 SiC heating bars with an electrical resistance of 3.6 Ω ± 10% at 1070ºC.
Heat flux density:
Calibration of the radiant heat source is essential prior to the test.
Added for method B:
– Calorimeter
– Temperature measurement and recording device
The radiant heat source consists of 5 SiC heating rods with an electrical resistance of 3.6 Ω ± 10% at 1070ºC.
The heat flux density:
– Low levels: 5kW/m² to 10 kW/m²
– Medium levels: 20 kW/m² to 40 kW/m²
– High levels: 80 kW/m²
Essential calibration of the radiant heat source prior to the test.
For tests performed by method A, one sample should be used, and for tests performed by method B, at least three samples should be used for each heat flow level. If the material to be tested is not very homogeneous, at least three samples should be tested by method A and five by method B.
Samples should have dimensions of 230 mm X 80 mm. Composite samples should reproduce multi-layer clothing sets as they are used in practice. If the material supplier does not indicate the external surface, tests should be carried out on both sides.
Test conditions: room temperature between 15-35ºC and the calorimeter must be cooled to room temperature ±2ºC before each test.
The composite samples should reproduce the multi-layer clothing ensembles as they are used in practice. If the supplier of the material does not indicate which is the external surface, the tests must be carried out on both sides.
Test conditions: room temperature between 15-35ºC and the calorimeter has to be cooled to room temperature ±2ºC before each test.
RANKING OF RESULTS ACCORDING TO EN11612
| HTI VALUE RANGE 24 (s) |
| Class 1 7<20 |
| Class 2 20<50 |
| Class 3 50<95 |
| Class 4 95 |
RANKING OF RESULTS ACCORDING TO EN11611
| HTI VALUE RANGE 24 (s) |
| Class 1 ≥7” |
| Class 2 ≥ 16” |
– Make reference to the ISO 6942 standard
– Description of the test material (commercial name, fabric face, color, layers…)
– Temperature and Humidity of the test atmosphere
– Number of samples tested
– Method A: skin change description
– Individual values Q0, TF, t12, t24, RHTI12, RHTI24 and RHTI24-RHTI12
