Some Factors Affecting the Design of Spring Supported Thrust Bearings in Hydroelectric Generators

A size effect exists for thrust bearings, requiring increasing attention to the control of deformation as the size is increased. One method of controlling deformation is to mount the pad on a set of closely packed springs. The extent (or proportional area) of spring support is important for thin pads. Support over the whole back face of the pad causes a concavity due to elastic deformation. The bearing must then run sufficiently hot so that this is countered by thermal deformation, which always acts to produce a convexity. The effects on performance of pad thickness, the thermal gradient in the pad and the extent and pattern of the springs is described. Two case studies are presented using a 3-D thermoelastic analysis. The use of comparatively thick pads is recommended.