The breakdowns of recovery boilers occur due to defects located in Field tubes approximately once in two years periods. The Field tube (diameter 50 x 3.5, Russian steel 15ChM) after 9 years of its exploitation in gaseous flow (T= 1000 - 1050 deg C, p= 3 MPa) has been investigated. The macroscopic and metallographic investigations have been carried out using computer aided image analysis system. X-ray structural analysis has been used for the determination of surface structure and microstresses level of the Field tube. Microhardness measurements have been done to investigate changes of metal properties in different locations of the tube wall. The investigations of the Field tube revealed defects formation under the centering props mechanism. This paper gives a description of the investigation methodology, explains key processes causing defects initiation and growth and gives recommendations for the implementation of other construction of centering props.
Through-wall defects formation in the field tubes of recovery boilers
1999
6 Seiten, 2 Bilder, 8 Quellen
Conference paper
English
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