Sector plate automatic control system fault and large air leakage rate occurred on four LAP13494/2200 type rotary air preheaters equipped on phaseⅡ 2×600 MW units in Nanyang Yahekou Power Plant.The sealing gap device existing in high temperature zone for long time and the sector plate regulation device equipped on air preheater is out of control were considered as the major reasons.By applying the three sealing technology

Joe drag seal technology

and new type of radial seal structure

and combining with the automatic control system

the sealing clearance system was optimized.The tests after the optimization showed that

the air leakage rate decreased from 10% to below 5%

which satisfied the design requirement.The automatic control quality and safe economy of the system was greatly improved.