Case #4
Tube Sheet
We were requested to determine the cause of failure.  The part was received and photographed. There were four holes present which was indicated that they were used as receivers for lifting lugs. Cracks were observed in only one of the four holes. The other three holes did not appear to be damaged or deformed. A section of the fracture surface was removed for analysis by optical and Scanning Electron Microscopy (SEM).  A section of the fracture surface was also removed in order to perform metallography.  Optical Emission Spectroscopy (OES) was performed to determine the chemical composition of a sample removed from the tube sheet.  
Based on the evaluation, we concluded that the tube sheet was fractured in an overload type failure, perhaps as a result of uneven load distribution during handling.  The morphology exhibited on the fracture surface, as viewed by SEM, and on the outside surface, as seen in the photos, is consistent with failure due to overloading the part in a direction perpendicular to its outside diameter. During the course of this investigation we found no metallurgical evidence to indicate any manufacturing or material defects.