The AMCA (Air Movement and Control Association International) has put forth a standard for construction equipment (SRC, Spark Resistant Construction) used for potentially explosive airstreams. These standards are divided into three categories: AMCA Type A Spark, Type B Spark, and Type C Spark.
AMCA Standards For Spark Resistant Construction
AMCA Type A Spark
Type A provides the highest degree of spark resistance, requiring that all fan components in the airstream 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. The most common practice to meet Spark A requirements is to construct all of the fan’s airstream components from aluminum. This includes the housing, wheel, inlet cone, and any fasteners used in the airstream. In addition, the fan shaft needs to have a sheath to cover the steel, or the shaft is to be constructed from monel. Of the three spark-resistant options, spark A is typically the most expensive.
AMCA Type B Spark
Type B requires that the impeller be constructed of non-ferrous materials and that the fan components in the airstream be assembled in a manner that reduces the possibility of contact between any stationary and rotating component. Typically, this is satisfied with the use of an aluminum wheel and an aluminum rub ring. If there is a mechanical failure of the fan, the aluminum wheel will contact a steel inlet cone. Similar to Spark C construction, the aluminum rub ring will protect against contact between the steel fan shaft and steel fan housing. Spark B falls between Spark A and C with regards to pricing.
AMCA Type C Spark
Type C offers a minimal level of spark resistance and only requires that possible contact between stationary and rotating components be reduced. Typically, this construction includes the use of an aluminum inlet cone and an aluminum rub ring. The aluminum inlet cone will be the first point of fan wheel contact if there is a mechanical failure. The aluminum rub ring placed at the opening of the housing where the shaft passes protects against contact between the steel fan shaft and steel fan housing. Spark C is the least expensive alternative.