15.4.2 Thermal tests
15.4.2.1 Test procedure
The enclosure, with the device(s) fitted, shall be tested in accordance with the method 15.4.3.1
but with the ignition source only in the position giving the most unfavourable thermal results.
The temperature of the external surface of the device(s) shall be monitored during the test. The
test shall be carried out five times. The test mixture to be used shall be (4,2 ± 0,1) % propane
in volumetric ratio with air and at atmospheric pressure. Additionally, for devices intended for
use in acetylene, (7,5 ± 0,1) % acetylene in volumetric ratio with air and at atmospheric
pressure shall be used.
In an enclosure where there is the possibility of a forced or induced flow of a potentially
dangerous gas, the enclosure shall be arranged during the tests so that the gas can flow
through the device(s) and the enclosure.
Any ventilation or sampling system shall be operated as specified in the manufacturer's
documentation. After each of the five tests, the external explosive mixture shall be maintained
for a sufficient time to allow any continuous burning on the face of the device to become
evident (for example, for at least 10 min so as to increase the temperature of the external
surface of the device or to make heat transfer to the outer face possible).
15.4.2.2 Acceptance criterion
No continuous burning shall be observed. No flame transmission shall occur. The measured
external surface temperature rise of the device shall be multiplied by a safety factor of 1,2 for
the determination of the temperature class of the electrical apparatus.
15.4.2 Thermal tests15.4.2.1 Test procedureThe enclosure, with the device(s) fitted, shall be tested in accordance with the method 15.4.3.1but with the ignition source only in the position giving the most unfavourable thermal results.The temperature of the external surface of the device(s) shall be monitored during the test. Thetest shall be carried out five times. The test mixture to be used shall be (4,2 ± 0,1) % propanein volumetric ratio with air and at atmospheric pressure. Additionally, for devices intended foruse in acetylene, (7,5 ± 0,1) % acetylene in volumetric ratio with air and at atmosphericpressure shall be used.In an enclosure where there is the possibility of a forced or induced flow of a potentiallydangerous gas, the enclosure shall be arranged during the tests so that the gas can flowthrough the device(s) and the enclosure.Any ventilation or sampling system shall be operated as specified in the manufacturer'sdocumentation. After each of the five tests, the external explosive mixture shall be maintainedfor a sufficient time to allow any continuous burning on the face of the device to becomeevident (for example, for at least 10 min so as to increase the temperature of the externalsurface of the device or to make heat transfer to the outer face possible).15.4.2.2 Acceptance criterionNo continuous burning shall be observed. No flame transmission shall occur. The measuredexternal surface temperature rise of the device shall be multiplied by a safety factor of 1,2 forthe determination of the temperature class of the electrical apparatus.
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