The fan frame is desiened as a combined structure with the parts formed by special moulds punching and imported hi-precision metal plates machining. The housing plates have two types, the single-layer and the double-layer. The PU foam, PEF(with function of heat preservation and noise elimination), superfine glass fibers or other soundproofing are used as the middlelayer material of the double-layer plates. The connection of frame and housing plates is firm and airtight with the perfect performance of thermal insulation and sound proof.

The double iniet forward curved multi-blade centrifugal fan (A type drive), with the impeller which has been proved by high speed dynamic balanced test, has the feature of stable operation without vibration. The pressure and airfiow volume of fan are comprehensively calculated by precise data acquisition system, which ensures the high guality of each fan. The vairlable air flow volume is adjuested by (1)voltage regulation; 2) frequency conversion.