Decoding "efficiency" for mechanical draft fans.

The article discusses what efficiency means in terms of mechanical draft fans. It says that these fans are used for moving fluid medium from one point to another by creating a draft in an industrial process system. The article describes and explains several efficiency ratings offered by equipment manufacturers and provides some working guidelines for assessing fan efficiency based on the ratio of theoretical air horsepower (AHP) to the actual brake-horsepower (BHP) input to the fan shaft.