Q. Maintenance of steel bearings?
Cleaning and greasing of bearings is one of the important maintenance works to avoid premature failure of bearings and reduce recurring heavy repair cost of bed block and masonary below bed block. Steel bearing strip resting on steel base plate has a tendency to stick together on account of corrosion, and cease the movement of bearings. This is called as Frozen Bearing. Sliding bearings of plate girders are generally designed keeping both ends free. When bearings are frozen, a large amount of longitudinal force is transferred to the substructure for which the substructure may not have been designed. Upon introduction of RBG, MBG and HM loadings on the Indian Railway, longitudinal forces have increased considerably whereas the old substructures had been designed without considering such large longitudinal forces.
Sometimes, even repairs will not hold good if cause of frozen bearings is not eliminated by greasing. It has been laid down that the steel bearings of all girder bridges should be greased once in 3 years to ensure proper movement of bearing plates. This should be done once every two years when track consisting of LWR is continued over bridge span.