Abstract: The boiler parts interior in the fist 1000MW ultra-supercritical units are not clean enough and for other reasons, which it is easy to block the tubes, and the tubes are exploded during commissioning. After analyzed the causes of #1 unit several tubes exploded, the method that installing the orifice ring in the pipe interior so as to get the balance of water and substance speed was implemented. Further more, by adopting checking the cleanness of header and pipe interior, which decreased the tube explosion phenomenon, and enhanced the unit security.

Key words: ultra supercritical boiler, orifice ring, tube explosion analysis, cleanness