Metallurgical Investigation of the Collapsed Front Structure of a Dragline in a Coal Mine

A dragline is the largest mobile equipment on earth, and it is called the “kingpin” of any mine site. In this present investigation, a case of premature failure of a coal-handling dragline is discussed. Failure occurred in a linked component known as “thimble,” which connects the A-frame and the vertical mast of the dragline. The thimble was broken into two halves and caused the entire front structures of the dragline to collapse. Failure investigation was performed through visual examination, chemical analysis, metallography, mechanical property evaluation and fractography.