Bearings -Disassembly &Assembly Nizwa College of Technology

Inspection of Bearings Bearings are machine elements  support a rotating member called as shaft  Transmit the load from a rotating member to a stationary member  Performance of the system depends on condition of bearings  Continuous monitoring of condition of bearings is essential  If bearings found faulty it must be replaced

Maintenance of Bearings Mechanical maintenance of bearings involve the following steps Disassembly Cleaning Inspection Replacement or Reconditioning (servicing) Reassembly

Block Diagram-Maintenance of Bearings

Disassembly of Bearings Disassembly Steps Use the correct removal tool Use the recommended removal method Do not distort or damage the bearing

Disassembly of Plain Bearings Plain bearings are interference fit in the housing i.e. housing retained, force is needed to remove the sleeve A rod made of copper, brass, nylon is used with hammer to drive away the bush from housing If housing is small mechanical or hydraulic press may be used to apply the force.

Assembly of Plain Bearings Procedure of assembling plain (Sleeve/Bushed Bearings) Clean housing bore Use assembly tool to insert sleeve bearing with hammer force, If housing can be removed to the bench use mechanical or hydraulic press Ream out bore of sleeve to required diameter if necessary

Disassembly of Rolling Bearings The basic mounting conditions of rolling bearings are: Shaft retained bearing (Shaft rotates) A shaft retained inner race has an interference fit on the shaft and a clearance fit in the housing. Housing retained bearing (Housing rotates) A housing retained outer race has a clearance fit on the shaft and an interference fit in the housing Sleeve mounted bearing (Sleeve removable)

Shaft retained bearing A - The clearance for interference fit on the shaft B - The clearance for clearance fit in the housing (Fit- Refers to the permissible clearances between mating parts in a mechanical device) B B Shaft rotation Bearing Dia A A

Housing retained bearing Shaft rotation Dia Bearing Dia A - The clearance for clearance fit on the shaft B - The clearance for interference fit in the housing

Disassembly procedure  Inner race of the bearing has an interference with the shaft or the outer race has an interference fit in the housing.  When removing a bearing with interference fit either on the inner or outer race, force has to be used. This force can be applied by: Mechanical or hydraulic pullers Mechanical or hydraulic presses Hammer and suitable driver

Using mechanical pullers Mechanical pullers

Using a hammer Using hammer & drift Using hammer & sleeve

Cleaning and Inspecting bearings Cleaning Soak in a solvent for several hours to remove lubricant and dirt Rinse in a chemical solvent Dip in a suitable bearing lubricant Inspection Visual inspection for damage or wear Rotating slowly to see if any 'clicking' sounds or -'Sticking' found

Bearing Failures

Assembly of Rolling Bearings Pressing a bearing into a housing by hydraulic or mechanical press Using a sleeve for applied the outer race

Heat Expansion Method When the bearing and the housing is comparatively large. For shaft retainedthe outer member is bearing inner race For housing retainedthe outer member is housing The heat can be applied to the outer member several ways, and the methods can be used are: Heated oil bath Induction heating ring Temperature controlled electric furnace Lamp or electric resistance heating element

Heating methods Heated oil bath Electric induction heating ring Temperature controlled furnace

Freeze contraction This method can be used when heating methods are not suitable For shaft retained bearings the shaft has to be 'shrunk' by freezing. For housing retained bearings the bearing has to be frozen.