The causes of pulverized coal entering into the gear box of classifier in MPS212 medium speed coal pulverizer have been analysed.It is believed from analysis that the main causes are as follows:un-tight seal at sealing ring under lower frame of the classifier

at sealing place of mill rollers

at sealing place of pull rod

and at sealing place of six coal feeders;the gap between coal-dropping pipe and central barrel in the classifier

and between conical hopper and central barrel in the classifier is greater than that of the specified ones;the sealing washer between sealing end cover of classifier’s oil basin and rotational pedestal body

and sealing washer between the rotational pedestal body and the case body of driving mechanism are un-tightly pressed

and being crimped etc..Through adding seal-ring between the coal-dropping pipe and the central barrel in classifier

as well as between the conical hopper and the central barrel in classifier

retrofitting the pipeline of sealing air for gear box of the classifier

and replacing the sealing method of rotational pedestal body

the above-mentioned problems all have been solved.