Hydrostatic shoe bearing eliminates problems for large mills

CIM Bulletin, Vol. 75, No. 841, 1982

BO TRYGG Product Manager, Hydrostatic Bearings, SKF - Sweden, BRIAN MclNTYRE, Segment Manager - Heavy Industry, SKF Canada Limited

The need for grinding mills of ever increasing capacity and greater feed openings has tended toward mill trunnion diameters being beyond the size limits for roller bearings.Hydrodynamic plain bearings need to be wide enough to achieve the necessary bearing pressure in order to obtain an oil film with sufficient carrying capacity at low rotational speeds. This greater width increases edge loading resulting from the deflection of the mill under load.Because of the high surface pressure involved, the life of support rollers and girth rings is often inadequate—fatigue leads to flaking on the contact surfaces. Heat treatment of the girth rings also has its problems.The hydrostatic shoe bearing permits unlimited trunnion diameter and a high carrying capacity. The self-aligning shoes compensate automatically for radial deviations and large deformations can be tolerated at the girth ring.The sliding surfaces are completely separated by oil under pressure, enabling negligible starting torque and good damping capacity to be achieved together with low rotational speeds.
Keywords: Bearings, Hydrostatic bearings, Shoe bearings, Mills, Trunnions, Grinding mills, Girth rings, Lubrication, Safety devices.