Part 2 bearings 02 2004

Review of Bearing Costs And Frequency of Replacement Analysis and Findings: Review of the bearings specified Rotor dynamic analysis to calculate bearing reaction forces and shaft flexu

Review of Bearing Costs And Frequency of Replacement

Analysis and Findings:

Review of the bearings specified

Rotor dynamic analysis to calculate bearing reaction forces and

shaft flexure from fiber band load.

Bearing Failures Per Year

0

10

20

30

40

50

60

1994 1995 1996 1997 1998 1999 2000 2001

Y e a r

The shaft-roll was modeled to calculate:

The rotor natural frequencies

Deflections from the fiber band loading

Bearing reaction loads (for bearing calculations)

!

" #

$

%

&

!

" &

- &

Corrosion between rollers and the bearing outer race The flaw initiator was identified as high water content in the oil

Severe fretting corrosion of the bearing bore had occurred due to a

loose shaft to bearing bore fit

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

Sludge buildup in bearing oil feed

groove

Two oil holes blocked

One open oil inlet hole

Three holes are equally spaced around the

bearing.

1 Bolts & Joint Integrity

2 Bearings

3 Shaft Repair Process

Shaft Roll Reliability Problem Areas

Typical Bearing Fit Damage Caused By Bearing-Shaft Fretting

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)

1 Bolts & Joint Integrity

2 Bearings

3 Shaft Repair Process

4 Roll Repair Process

Shaft Roll Reliability Problem Areas

Working with the repair shop resulted in much improved finish and machining accuracy of the roll mating surfaces and roll OD

Mating Face of roll shows improved machined surface

finish.

1 Bolts & Joint Integrity

2 Bearings

3 Shaft Repair Process

4 Roll Repair Process

5 Condition Monitoring and testing to identify existing and

developing problems

Shaft Roll Reliability Problem Areas