Part 2 bearings 02 2004

Analysis and Findings: Review of Bearing Costs And Frequency of Replacement Rotor dynamic analysis to calculate bearing reaction forces and shaft flexure from fiber band load Review of the bearings specified 19 Bearing Failures Per Year 60 50 40 30 20 10 1994 1995 1996 1997 1998 1999 2000 2001 Y ear 20 The shaft-roll was modeled to calculate: The rotor natural frequencies Deflections from the fiber band loading Bearing reaction loads (for bearing calculations) ! 21 " ! # $ % & ! % " ' # % ( )% " & * 22 +' + & , )* & + ) * 23 Corrosion between rollers and the bearing outer race The flaw initiator was identified as high water content in the oil 24 Severe fretting corrosion of the bearing bore had occurred due to a loose shaft to bearing bore fit 25 Typical bearing failure • Bearing housing bore was worn oversize 0.026 inch • Severe damage to the bearing races • There was fretting corrosion of the shaft fit and scoring of the shaft fit due to the race turning on the fit The race was cracked during disassembly 26 Sludge buildup in bearing oil feed groove Two oil holes blocked One open oil inlet hole Three holes are equally spaced around the bearing 27 Shaft Roll Reliability Problem Areas Bolts & Joint Integrity Bearings Shaft Repair Process 28 Typical Bearing Fit Damage Caused By Bearing-Shaft Fretting 29 In this bearing fit failure, the fit was under size 0.075 Inch The metalizing material had completely failed Turned out to be common to find metalizing material with poor bonding to shafts (Which launched a search for a better repair process) 30 Shaft Roll Reliability Problem Areas Bolts & Joint Integrity Bearings Shaft Repair Process Roll Repair Process 31 Working with the repair shop resulted in much improved finish and machining accuracy of the roll mating surfaces and roll OD 32 Mating Face of roll shows improved machined surface finish 33 Shaft Roll Reliability Problem Areas Bolts & Joint Integrity Bearings Shaft Repair Process Roll Repair Process Condition Monitoring and testing to identify existing and developing problems 34