Abstract: The lower sealing air pressure of the mill of directfired pulverizing system in a power plant was analyzed. It was found that the openings in the connections of the sealing air main pipe and its branches are too small, and this is the main reason of lower sealing air pressure. During an overhaul period, the tee openings had been enlarged to normal size; the sealing air pressure returned to normal; and the safe and stable operation of the mill was ensured.

Key words: direct-fired pulverizing system, medium-speed mill, sealing air, air pressure