Van Ngan Lê and Henri Champliaud
Horizontal mills, manholes, reinforcement pads, fatigue cracks, finite element model
Horizontal mills for crushing materials are cylindrical steel vessels slightly tilted for allowing materials to slowly flow by gravity from feed end to discharge end. With continuous rotation and bending moments due to weight, the shell is subjected to severe fatigue conditions. Cracks in shell have been observed around manhole reinforcement plates after few years of operation of mills due to ineffective design of manholes with the absence of fatigue analysis. Finite element models have been carried out for analysing three different manhole designs of horizontal mills and following conclusions are observed : The worst manhole design for horizontal mills uses overlap and fillet welded reinforcement plate which create too high stress raisers at weld toes; A better manhole design for mills is using tapered thicker plate and butt welded to shell because they present lower stress raisers on weld lines and could prolong the fatigue life of mills; It is found that the best and most economical manhole design is simply cutting manhole openings into shell with two half circles in the longitudinal direction without reinforcement plate and without weld.
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