Could you please provide a brief description of the system and symptoms to help understanding the problem? I’d like to know if Fractionator bottom nozzle for fines removal system is of a typical vortex braker or stand-pipe? is the coke fines stream pumped back to fractionator bottom or to heaters charge pump suction? how big are your filters? are you catching any coke? has frequency being reduced? what evidences do you have for coke buildup inside the tower?