Boiler tube failures (BTFs) in natural circulation high pressure drum boiler of a power station

Abstract

This paper assesses boiler tube failures (BTFs), especially in boiler water wall tubes (BWWTs) for a natural circulation high-pressure fossil (natural gas) drum boiler unit (TIME-COB-206, Russia). Metallographic (micro and macrostructural) examinations of BWWTs materials (carbon steel, Russia) were carried out extensively. Analyses of carbon (mild) steels (0.22% C) revealed distinctive changes in ferrite-pearlite distribution, might be due to decarburization. Huge pits, few grooves followed by flow lines were observed on internal surfaces of BWWTs with respect to length of power plant operation. Corrosions or scaling in BWWTs depicted one of the major causes of BTFs in fossil units with drum boilers usually treated by coordinated phosphates.