10/10
A 200
About leak detection
GB 04269 - Edition 05 - July 12
Hydrogenated nitrogen
If Hydrogen (H
2
) and Oxygen (O
2
) are mixed and heated, they react
and create water vapor (H
2
O). During this process more heat is
generated which may (if the concentration is high enough) ignite
the surrounding gas. If this process propagates, the gas explodes.
At low concentration of Hydrogen (< 4 % in air) the generated heat
is not enough to ignite the surrounding gas.
At concentrations in the range 4 to 12 % the combustion may
spread only if actions are taken to prevent the generated heat
from dissipating. It is a common misconception that hydrogen will
explode as soon as the concentration exceeds 4 %. It may explode
only if conditions are favorable for spontaneous propagation of
combustion.
Never use pure hydrogen or a mixture with a hydrogen concentration
higher than 10 % to realize a "hydrogen" test as tracer gas.
If you use the recommended tracer gas of 5 % H
2
/ 95 % N
2
and
mix it with air there will either be too little hydrogen or too little
oxygen to constitute a combustible gas mixture. Hence this gas
mixture is classified as non flammable. The actual limit is 5.7 %.
The mixture 10 % H
2
/ 90 % N
2
is commonly used in the industry
because it is flammable only under certain conditions. This mixture
is however classified according to ISO 10156 as Flammable Gas and
should only be used after due safety considerations and approvals.
adixen Vacuum Products - ASM 380 Operating instructions
Summary of Contents for adixen ASM 380
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