Damage at a superheater in a combined cycle plant due to insufficient phase separation in the drum

摘要

In spring 1999 severe wear was detected at the internal wall of firmed tubes in the first of two HRSG of the newly constructed combined cycle plant of the Mitte station of Bewag. The damage occurred at the entrance of the HP superheater and resulted in wall fractures. The laboratory examination revealed insufficient phase separation in the drum resulting in boiler water entering the superheater tubes. Due to the concentration of water constituents this process led to increased hot water oxidation. The root cause identified was confirmed by an examination of the drum/demister design. As precautionary measure the active area of the demister was enlarged by 50% and the inspection possibilities in the critical area were improved.