Bearings -Disassembly &Assembly

Nizwa College of Technology

Inspection of BearingsBearings 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 BearingDia

Dia

A

A

Housing retained bearing

Shaft rotation

Dia

BearingDia

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

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

Bearing Failures

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 iscomparatively large.• For shaft retained the outer member is

bearing inner race• For housing retained the outer member is

housingThe 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.