Key Findings

• FAST operations concluded for 2024 with a total of 31 weld breaks, 24 of which were EFB welds with accumulated tonnages varying between 51 and 145 MGT. The remaining seven weld breaks were thermite welds and three of them broke within the first 25 MGT of service since installation as replacement welds.
• More than 90 percent of the EFB failures were due to fatigue cracks originating from stress risers that existed due to the lack of pre- or post-weld grinding.
• A metallurgical analysis revealed five of the seven thermite breaks showed the presence of voids and shrinkage porosity due to lack of solidification. Two thermite breaks were caused by cracks initiating from areas where slag or impurities consisting of alumina particles were trapped inside the fusion zone during the welding process. These thermite failures underscore the importance of heat before and during the thermite welding process to ensure complete solidification.