Failure analysis of a ball mill located in a cement's production line

The work herein presented aims to analyse an existing failure in a ball mill of a cement production line. This equipment has the function of grinding the mixture of clinker and selected additions to produce cement. The ball mill understudy has a length of 16.2 m between supports, and the formation of cracks was noticed approximately midspan near a maintenance manhole. The failure is recurrent and responsible for reducing the period between overhauls. The cracks were detected using dye penetrant liquids and repaired by a rewelding procedure using PERMA E622 electrode. Numerical simulations were carried out using the Finite Element Method, and displacements and stresses induced in the structure were calculated. The maximum stress values were registered in the region where the failure occurred, near through-holes used to bolt the ball mill's cladding plates. The ball mill was redesigned to ensure high endurance for the equipment. Therefore, internal and/or external reinforcement rings were inserted in the structure, and the maximum stresses calculated were reduced by 32%, increasing approximately five times the fatigue life predicted for the ball mill.