Abstract: The structure of HP type mediumspeed mill was introduced. The defects of HP type mediumspeed mill in operation, such as the serious wear of the scraper, the coal contained in discharged gravels, the decreased oil viscosity in lubricatingoil station, the jamming of slag discharging pneumatic gate, the air leakage in primary hot air regulating gate, the larger dust concentration during slag discharging, the falling off fault of the wearresisting scaleboard and others, were analyzed. The feasible preventive measures were formulated; the defects of the equipment were eradicated completely, and the operation reliability of the mill was enhanced.

Key words: medium-speed mill, scraper wear, oil viscosity, jamming, air leakage