Application of tribology for enhancing the life of sugar mill roll bearing and journal

摘要

Sugar mill roll top journal bearing functions predominantly under boundary lubrication regime due to heavy load and small sliding velocity. This bearing is prone to ingress of juice/bagasse and other contaminants due to their floating condition. In many cases, the design of the mill roll top journal bearings and their lubricating grooves happen to be insufficient to reduce the temperature rise and consequently thermal expansion of the mating components. This leads to premature failures of roll top journal bearings. Thus, an attempt has been made herein to design and develop an improved sugar mill roll top journal bearing by application of tribological skills for enhancing the life and reliability of the sugar mill roll system. This paper reports the overall study carried out for the development of new design of bearing. It comprises of computation of possible loads on the bearing, experimental evaluation of tribological parameters at the mating surfaces in presence of lubricating oil using 3 pins-on-disc tester and 4 balls tester, development of shapes and sizes of lubricating grooves at bearing surfaces, computation of temperature rise and thermal expansion at the bearing and journal interface in order to determine the radial clearance between the journal and bearing, finite element analysis (FEA) of the grooved journal bearing assembly for assessing the strength and deformation under various operating conditions, and field's trials for the roles of new grooved journal bearing. The new developed journal bearing (for O1020 × 2030 mm size four-roll mill) was put on real time field trials for the two consecutive sugar crops of year 2010-11 and year 2011-12 at crush rate of 200-230 tonne of sugar cane/hour. Substantial reduction in the operating temperature is noticed with new design of journal bearing in comparison to conventional bearing. An examination of the bearing and journal surfaces after the closure of crop year 2011-12 showed negligible wear. In fact almost the original surface finish has been found on the journal bearing surface. Moreover, the overall lubricant consumption reduced to 10 L/day/mill from 15 L/day/mill i.e. about 33％ saving in lubricant.