 General Recommendations
When possible, locate the pressurizing system right next to the proteced enclosure(s)
Install the pressurizing system at eye level in a prominent location for convenient viewing
DO NOT install valves between the pressurizing system and the protected enclosure(s)
The reference connection from the protected enclosure(s) should be installed where it is not directly affected by air flow through the protected enclosure(s)
Be sure that tubing, piping and connection fittings are suitable for the location in which they are installed and are protected against mechanical damage
Multiple Enclosure Recommendations
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The NFPA recognizes the use of electrical conduit or wireways as a part of an "approved system". The NFPA term "approved system" refers to a complete purged assembly that has been approved by the authority having jurisdiction |
Connect protected enclosures from the smallest to largest enclosure in a series of enclosures
Size connections to allow proper operation of the pressurization system
Conduit or wireways may be utilized as protected enclosures or as connections between protected enclosures.
Class I Area Recommendations
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These Class I area recommendations exceed the requirements of NFPA 496. They are presented by Pepperl+Fuchs BebcoEPS as a method to enhance the removal of flammable gases by the use of gravity. These Class I area recommendations only apply to enclosure volumes exceeding two cubic feet.
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All pressurized conduit and wireways should be sized to allow proper protective gas flow through the protected enclosures.
If flammable gases are lighter than air, the supply connection to each enclosure should enter near a bottom corner and the connection for an optional vent or piping to the next protected enclosure should exit near an extreme opposite top corner.
If flammable gases are heavier than air, reverse these connections.
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