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Session: DA-08-03 Practical Applications of FFS
Paper Number: 106381
106381 - Hot Spent/waste Heat Boiler Tube Sheet Reliability Analysis
The tube sheet and several tube-to-tube sheet joints at the flue gas inlet of a hot spent boiler experienced failures in a sulfur processing unit. To address this, plugging of tubes that failed at the joint locations, weld repair on the tube sheet, and post weld heat treatment (PWHT) were performed to bring the boiler back to operation. In addition, a few more tubes were also plugged. In these applications, the selection of tubes to be plugged is based on operator’s historical experience-based information. However, such an approach may not adequately address the mechanical integrity of the unplugged tube-to-tube sheet joints and the tube sheet itself. The repair process adds complexity to the problem that already involves numerous parameters that affect this region of the subject boiler. In this work, a case study involving the subject boiler presents a systematic approach involving advanced analytical tools that provided insights into the historical reliability issues and a solution to address tube plugging for continued service. It is demonstrated that such engineering approaches can minimize further failures, repair costs, and loss of production time/costs. It is important to note that many of these boilers were designed to ASME Section I, and may benefit from approaches prescribed in ASME Section VIII, Division I and design by analysis approaches.
