Failure analysis of reheater tubes in a 350 MW supercritical circulating fluidized bed boiler. (July 2022)

• Record Type: Journal Article
• Authors: Li, Jian; Cao, Tieshan; Zhang, Conghui; Cheng, Congqian; Zhao, Jie
• Is Part Of: Engineering failure analysis. Volume 137(2022)
• Publication Date: 2022-07
• Subjects: Failure analysis -- Austenitic stainless steel -- Reheater tube -- Stress corrosion cracking; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2022.106285
• Languages: English
• ISSNs: 1350-6307

Abstract

Highlights: The failure of reheater tubes in a supercritical circulating fluidized bed (CFB) boiler was analyzed. The cracks were initiated at the HAZ under the combined effects of tensile stress and high-temperature environment. A multilayered structure was formed in the cracks due to the effect of preferential oxidation and the thermal cycle. The failure mechanism of the reheater tubes was identified as stress corrosion cracking. Abstract: This work aimed to analyze a failure that occurred on the TP347H reheater tube in a supercritical circulating fluidized bed boiler from a thermal power plant. Optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron probe micro-analysis (EPMA), digital microhardness tester (DMT), X-ray fluorescence spectroscopy equipment (XRF), and carbon sulfur analyzer (CSA) were used to characterize the failed tubes. The results show that the cracks originated in the heat-affected zone and simultaneously propagated in the circumferential and radial directions. There is a multilayered structure in the crack under the effect of the thermal cycle and preferential oxidation. The failure mechanism was identified as stress corrosion cracking (SCC). The cracks were produced under the combined effects of the tensile stress and the high-temperature flue gas environment. Related improvement measures have been implemented to prevent further failures.