A Continuous Ship Unloader (CSU) is a facility in which multiple buckets rotate to excavate cargo from a ship to land. It is typically designed to have a lifespan of 20 years. However, fatigue damage is likely to occur before the end of its designated lifespan. This study aims to examine the possibility of extending the component"s lifespan by evaluating the remaining useful life of L-holder, a part of CSU, that has been in use for 20 years. Fatigue load history was predicted by measuring the strain with or without strain at the L-holder part requiring periodic replacement. Through tensile and fatigue tests, the remaining life was evaluated when cracks were not present. In addition, the remaining life in the presence of cracks was evaluated through destructive toughness test and fatigue crack propagation test. Life prediction results based on test cycles were obtained. The proposed guidelines are expected to be helpful for preventing CSU accidents.

The CSU (continuous ship uploader) is one of the most advanced and high-tech machines among the logistics facilities. It is giant heavy equipment and has a number of driving systems compared to a general crane. In general, CSU is designed to have a life of 20 years, but recently it has been increased up to 30-50 years or is being used as a semi-permanent facility. In this study, based on the structural analysis and the elasto-plastic fracture mechanics, fracture toughness test was performed on the front tension bar, which is the main load bar of the CSU machine. The J-integral analysis was performed on the front tension bar. Based on the results of the J-integral analysis and fracture resistance test, the critical crack length without instantaneous fracture was calculated and analyzed for each operating load.