AMCA 99-0401 addresses the choice of materials
only in terms of ferrous or non-ferrous. It is generally accepted practice
that ferrous materials are those whose iron content is 5% or greater. The
standard further addresses spark resistance in terms of assembly of fan
components. The result is three types of spark resistant construction:
Type A:
Offers the highest degree of spark resistance,
requiring that the fan components be constructed of non-ferrous material and
that they be assembled in a manner such as to reduce the possibility of
contact between any stationary and rotating component.
Type B:
Offers a medium level of spark
resistance, requiring that the impeller be constructed of non-ferrous
material, and that the fan components be assembled in a manner such as
to reduce the possibility of contact between any stationary and rotating
component.
Type C:
Offers the "entry
level" degree of spark resistant construction, requiring that the fan
components be assembled in a manner such as to reduce the possibility of
contact between any stationary and rotating component.
These classifications were
developed in response to equipment users' need for a way to achieve spark
resistance for varying degrees of ignition hazard. The specific level of
resistance necessary is one which only the purchaser can evaluate. The choice of
any level of spark resistance should be determined in consultation with the fan
manufacturer. A fan can then be engineered and constructed to meet the
required service level.
