New Build Welding
After a few years in service a 100,000DWT ship developed cracks in erection joint welding on deck and inner bottom. Root cause was failure of a new build welding procedure. An extensive NDE program, covering sister ships, was started and a defect map produced. Subsequent analysis (strength and fatigue) guided the repair and the ships returned to service
Poor Edge Preparation
A seies of 150KDWT ships from a European builder developed cracks in butt welds of bulb flats at block joints. Each and every similar joint on the series of ships was examined. The defects were sufficiently large to cause cracking in the main deck. Fatigue analysis and crack propgation calculations supported by TWI guided the repair process. There were no further difficulties with those locations in that series of ships
A series of longitudinal cracks at the toe of fillet welds of sideshell longitudinals to side shell was allowing water to enter ballast spaces. Testing and fatigue analysis showed that this problem ran the length of the ship. The solution was rewelding and the fitting of carlings to sideshell. This cured the problem.