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UNE-EN 16689:2017
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RIS-3279-TOM ISS 2

UNE-EN ISO 6942:2023

PROTECTION AGAINST HEAT AND FIRE. TEST METHOD: EVALUATION OF MATERIALS AND ASSEMBLIES OF MATERIALS WHEN EXPOSED TO A RADIANT HEAT SOURCE. Equivalence with EN ISO 6942:2022 & ISO 6942:2022.

OBJECT

PURPOSE

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 relatively low-intensity radiation over a long period of time. Industrial workers or firefighters may be exposed to medium-intensity radiation for short periods of time, or to high-intensity radiation for very short periods.

This regulation specifies two complementary 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 one method only.

Since the tests are carried out at room temperature, the results are only suitable for predicting the performance of protective clothing.

DEFINITIONS:

Heat Transfer Levels:

Time t12: time in seconds, expressed to a decimal place, to obtain a calorimeter temperature increase of (12 ± 0.1) °C when tested with method B

Time t24: time in seconds, expressed as a decimal place, to obtain a calorimeter temperature increase of (24 ± 0.2) °C when tested with method B

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.

Radiant Heat Transfer Index (RHTI): A number calculated from the time measured in seconds with a decimal place, necessary to obtain a specified increase in the temperature of the calorimeter when tested with this method and at a specified incident heat flux density.

MATERIALS AND EQUIPEMENT

TEST EQUIPMENT:

-For both methods the following are used:

-Radiant heat source consists of SiC heating bars with an electrical resistance of 3.6 Ω ± 10% at 1070ºC.

-Test frame

-Sample Stand

It is added for method B:

-Calorimeter

-Temperature Recording and Measurement Device

SAMPLES

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.

PROCEDURE AND RESULTS

METHODS

TEST CONDITIONS:

-Condition the samples at least 24 h at 20 ± 2 ºC and 65 ± 4% RH. The trial should be started within 3 min after conditioning.

-The tests will be carried out in a room free of air currents and protected from any parasitic radiation that could be recorded by the calorimeter. The temperature of the room between 15-35ºC and the calorimeter has to be cooled to room temperature ± 2 ºC before each test.

-Heat flux density:

  • Low levels: 5kW/m² to 10 kW/m²
  • Average levels: 20 kW/m² to 40 kW/m²
  • High levels: 80 kW/m²

-Calibration of the radiant heat source prior to the test is essential.

METHOD A: A sample is fixed to a vertical frame by applying a voltage of 2 N and exposed to a set level of radiant heat for a set amount of time.

The radiant heat level is fixed by adjusting the distance between the sample and the thermal radiation source. After the exposure, the sample and its layers are examined to determine any visible changes.

Evaluation: After irradiation, the sample or individual layers of the multilayer assembly are inspected. Any changes (e.g., discoloration, fouling, ember, charring, breakage, melting, shrinking, sublimation, etc.) that are observed are noted for the sample or for each individual layer of the multilayer assembly.

METHOD B: A sample is attached to a vertical frame (sample holder) by applying a voltage of 2 N and exposed to a set level of radiant heat. The times needed to obtain a temperature increase in the calorimeter of 12 ºC and 24 ºC are determined and expressed as radiant heat transfer indices. The percentage thermal transmission factor is calculated from the increase in temperature, and is also noted in the report.

The times t12 and t24, expressed in seconds with a decimal place, are determined to obtain an increase in the calorimeter temperature of (12 ± 0.1) ºC or (24 ± 0.2) ºC, respectively. As required in the specific standard, the result of the difference between t24 and t 12 is calculated and recorded.

Evaluation:

-The transmitted heat flux density QC is determined in Kw/m2

-The thermal transmission factor TF (Q0)

-Radiant heat transfer index RHTI12 (Q0, time measurement t12, expressed in 0.1 s for the calorimeter temperature increase of 12 ±0.2 ºC

-Radiant heat transfer index RHTI24 (Q0), time measure t24 expressed in 0.1 s for the calorimeter temperature increase of 24 ±0.2 ºC

-The radiant heat transfer index, RHTI24-RHTI12 (Q0) for the incident heat flux density is determined RHTI24 minus RHTI12.

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