The object of this research is to prevent the industrial accidents which frequently occurred in breaking the coating in cement silo. Research was conducted to identify the cause of the coating formation, and the model experiment of aeration system was done to investigate the effect of moisture air on the coating formation. The results show that dehumidification of supply air in aeration system is the most important factor to suppress the coating formation, and the refrigerated low pressure air dryer applicable to the aeration system of cement silo was newly designed and developed. When this air dryer is applied to the cement silo, 88% of the moisture component of supply air can be reduced. Therefore the cleaning cycle extends over twice, and it contributes to the decrease of industrial accidents and cleaning cost.