SM7-31 centrifugal fan for a single suction centrifugal, machine number NO.6,8,10,12. Transmission mode for the V belt drive. There are two types of rotation and reverse rotation. The fan consists of impeller, chassis, air inlet and transmission parts. The transmission part of the machine on the basis of 4-72-11 fan to be improved, the shaft with a thrown oil ring, bearing side cover silk has oil return groove, to prevent oil spills. Mainly used for textile industry-specific material handling machinery, cotton spinning system and cotton filter system to transport cotton and other fibers, shavings, wood chips and other debris material.