Seals
Limit the Explosion
to an Area Close to the Source |
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There are many enclosures, devices, and fixtures suitable for all three
classes. A Class I device which can contain an explosion of a specified gas also has to
prevent dust from entering the enclosure to be suitable for Class II. The close tolerance
of the flame path which cools the burning gases is also close enough to exclude explosive
dust so that a gasket would not be needed.
Proper installation of hazardous location equipment calls for the use of seals. Special
fittings are required to keep hot gases from traveling through the conduit system and
igniting other areas if an internal explosion occurs in a Class I device. They are also
needed in certain situations to keep flammable dusts from entering dust-ignition-proof
enclosures through the conduit.
As shown to the left, when arcs and sparks cause ignition of flammable gases and vapors,
the equipment contains the explosion and vents only cool gases into the surrounding
hazardous area.
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