The pulverized-coal downcoming pipes in coal-pulverizing systems of ball mills for 4 boilers installed at Thermal Power Plant under Qilu Petrochemical Co. have been retrofitted

changing original vertical downcoming pipes into declinated ones

and erecting a self-designed multi-functional pulverized-coal screen at each crossing location

so that mutual alternation of the two sides can most conveniently be realized. The practice in time of more than two years shows the effectiveness was fully perfect.