10 Breathing and draining devices which form part of a flameproof enclosure
Breathing and draining devices shall incorporate permeable elements which can withstand the
pressure created by an internal explosion in the enclosure to which they are fitted, and which
shall prevent the transmission of the explosion to the explosive atmosphere surrounding the
enclosure.
They shall also withstand the dynamic effects of explosions within the flameproof enclosure
without permanent distortion or damage which would impair their flame-arresting properties.
They are not intended to withstand continuous burning on their surfaces.
These requirements apply equally to devices for the transmission of sound but do not cover
devices for
– relief of pressure in the event of internal explosion, or
– use with pressure lines containing gas which is capable of forming an explosive mixture
with air and is at a pressure in excess of 1,1 times atmospheric pressure.
10.1 Openings for breathing or draining
The openings for breathing or draining shall not be produced by deliberate enlargement of gaps
of flanged joints.
NOTE If for technical reasons, breathing or draining devices have to be provided, they should be so constructed
that they are not liable to become inoperative in service (for example, because of the accumulation of dust or paint).
10.2 Composition limits
The composition limits of the materials used in the device shall be specified either directly or by
reference to an existing applicable specification.
The elements of breathing or draining devices for use in an explosive gas atmosphere
containing acetylene shall comprise not more than 60 % of copper by mass to limit acetylide
formation.
10.3 Dimensions
The dimensions of the breathing and draining devices and their component parts shall be
specified.
10.4 Elements with measurable paths
Interstices and measurable lengths of path need not comply with the values given in Tables 1
and 2, provided that the elements pass the tests of Clauses 14 through 16.
Additional requirements for crimped ribbon elements are given in Annex A.