Root Cause Analysis of Superheater Tubes Failure

abstract

English

Superheater tube failure is listed among major causes of fossil fuel fired boiler outage, therefore, it is necessary not only to identify and repair it in case of failure but also to eliminate the root cause of this problem. As there may be multiple reasons of failure in such exposed equipment as superheater, thorough investigation of more than one probable cause is usually required. This article is focused on failure analysis of the boiler located in the chemical plant. After a leakage was discovered, several cracks on the superheater tubes were identified as its main cause. It was necessary to assess the extent of the damage, to detect the root cause of this damage and to propose corrective actions. Two problematic locations with cracks were identified during the visual inspection; the first at the superheater tube bends and the second in a weld joint between the superheater and a transfer pipe. As a first step, material microstructure and composition analyses of tubes were carried out in those critical locations. Even though small weaknesses in microstructure were found, the main cause of the tube failure was not identified. As the next probable cause, thermal dilatation stresses were investigated using finite element analysis (FEA). The support system, consisting of fixed, spring and sliding supports as well as the compensator were included in the analysis that confirmed the thermal dilatation stresses as the major cause of the failure. Based on the results, a new technical solution of supports was suggested and verified by FEA.

corrosion, weldment cracks, superheater supports, thermal dilatation

NAĎ, M.; LÉTAL, T.; LOŠÁK, P.; BUZÍK, J.

28. 9. 2016

9789619408803

Program in knjiga povzetkov / Program and book of abstracts

161

161

1

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