15.2.1.3 The test in 15.2.1.1 or 15.2.1.2 shall be made five times. The test result is
considered satisfactory if the ignition is not transmitted to the test chamber.
15.2.2 Electrical apparatus of Group lIC
The following methods can be used for this test.
15.2.2.1 First method
All gaps of joints other than threaded joints shall be increased to the value
iE = 1,5 × iC
with a minimum of 0,1 mm for flanged joints
where
iE is the test gap;
iC is the maximum constructional gap, as specified on the manufacturer's drawings.
The following explosive mixtures, in volumetric ratio with air and at atmospheric pressure, are
to be used in the enclosure and in the test chamber:
– (27,5 ± 1,5) % hydrogen, and
– (7,5 ± 1) % acetylene.
Five tests shall be made with each mixture. If the apparatus is intended for use solely with
hydrogen or solely with acetylene, the tests shall be made only with the corresponding gas
mixture.
15.2.2.2 Second method
The enclosure shall be tested with a test gap iE according to the following formula:
0,9 iC ≤ iE ≤ iC
The enclosure and the test chamber are filled with one of the gas mixtures specified for the
first method at a pressure equal to 1,5 times atmospheric pressure.
The test shall be carried out five times with each explosive mixture.
Alternatively, if the gaps of a test specimen do not fulfil the above condition, by agreement
between the testing station and the manufacturer, the following method may be used.
Precompression of the normal test mixtures according to the following formula:
where Pk is the precompression factor.
15.2.2.3 Electrical apparatus which are single constructions shall be tested five times with
unaltered gaps and with each of the explosive mixtures specified in 15.2.2.1 at atmospheric
pressure.
15.3 (Reserved for future use)