Cause Analysis and Improvement Measures for Superheated Platen Tubes Failure of a 580 t/h CFB Boiler

Abstract

Superheaters are crucial components of boilers operating under high temperatures and pressures. Understanding potential damages, especially in components like superheaters, is essential for enhancing boiler, turbine, and overall power plant productivity. This paper highlights a study for the failure investigation of platen superheater tube in Unit 2 of a 2x150 MW coal-fired power plant in South Sumatra. Various tests including chemical composition, hardness, tensile, metallography, SEM fracture surface examination, and XRD compound analysis were conducted to assess the failure of the platen superheater tube. The investigation revealed that the failure of platen superheater tube was initiated by the plugging of the tube elbow due to deposits and ashes adhering to the tube's interior. This obstruction prevented saturated steam flow inside the tube, leading to overheating and a subsequent drop in mechanical strength. Overheating was confirmed by the presence of spheroid particles in the ferrite matrix. Prolonged overheating resulted in the formation of microvoids, leading to creep failure and crack formation in the tube. Following improvements made during Unit 2 maintenance outage, which involved adding refractory material inside the furnace on the platen superheater panel, positive results were observed. The platen superheater tubes, which previously exceeded temperature limits, now operate within normal range temperatures. This improvement also reduced spray water consumption and significantly increased boiler efficiency from 83.19% to 83.54%.