CV102 Report 281015a

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Source: S. Sharma, C. Cole, M. Rasul, C. Galeotti, CRE, CQUniversity, Australia, 2015
BMA – Broadmeadow CV102
A RCA review of recent conveyor pulley
bearing failures
Report Number: CRE R 286 BMA-01/15

Date: 27 October 2015
Submitted by:
Dr Subhash Sharma, Mr Chris Galeotti, Associate Prof Mohammad
Rasul and Prof Colin Cole
School of Engineering and Technology (SET)
Central Queensland University

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Rockhampton
Document Record

Document Title: BMA – Broadmeadow CV102

Report Number: R 286 BMA-01/15
Industry Partner: Australian Conveyor Engineering Pty Ltd

First Results & Draft Issued: 26 October 2015
First Revision Issued:

Final Issued:

Controlled Report Distribution

Copy Type Copy Held By Copy Issued This Copy
Original No
E-Copy-1 Yes
E-Copy 2 Yes

Report Source and Release Information

DISCLOSURE RESTRICTIONS

Any release to a third party to be approved by Australian Conveyor Engineering Pty Ltd and School of
Engineering and Technology, CQUniversity.

Contribution Name Signatures
Report Details Chris Galeotti and Subhash Sharma
Text Authorship Chris Galeotti and Subhash Sharma
Simulation and Data Analysis Subhash Sharma and Chris Galeotti
Review & Report Release Colin Cole, Mohammad Rasul

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Table of Contents
BMA – Broadmeadow CV102 ................................................................................................................ 1
Executive Summary ........................................................................................................................... 5
1. Introduction ................................................................................................................................... 8
1.1 Purpose ................................................................................................................................ 10
1.2 Scope ................................................................................................................................... 10
2. Data Collection and analysis ........................................................................................................ 11
2.1 Data collection ........................................................................................................................... 11
2.2 Problem Solving ......................................................................................................................... 16
2.2.1 RCA Approach ..................................................................................................................... 16
STEP 1 - Problem Definition ............................................................................................................. 16
Step 2 - FOCUS ................................................................................................................................. 17
Step 3 – Extent and Impact .............................................................................................................. 18
Step 4 - Containment ........................................................................................................................... 18
Step 5 -Take A Good Practical Look ..................................................................................................... 19
a) SKF Bearing Inspection Report - VB0045 ................................................................................. 21
b) SKF Bearing Inspection Report - VB0046 ................................................................................. 24
c) RCA of CV102 Bearing Failure - AXYS Consulting ..................................................................... 24
d) Observations of failed bearing in MCE workshop .................................................................... 26
Step 6- Patterns and Comparisons ....................................................................................................... 28
Step 8 - Fault tree analysis ................................................................................................................... 34
i) Standstill Corrosion ................................................................................................................... 34
ii) Seals and Lubrication ............................................................................................................... 36
iv) Bearing Housing ...................................................................................................................... 40
v) Conveyor Alignment ................................................................................................................ 42
vi) Bearing Fitment ...................................................................................................................... 43

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2.2.2 Vibration Analysis ............................................................................................................... 44
Step 9 - Proposed Solutions ................................................................................................................. 50
Step10-12 ............................................................................................................................................ 51
3. Results ......................................................................................................................................... 55
3.1 Summary Tables .................................................................................................................. 56
4. Discussion .................................................................................................................................... 57
5. Conclusions .................................................................................................................................. 63
5.1 Recommendations ..................................................................................................................... 63
6. Bibliography ..................................................................................................................................... 65
7. Appendix .............................................................................................. Error! Bookmark not defined.

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Executive Summary
BMA – Broadmeadow Coal Mine located in Moranbah, approached CQUniversity (CQU) to analyse a
number of unexpected pulley bearing failures on their CV102 Conveyor, these failures are
understood to have taken place with little or no warning from Vibration Analysis (VA) surveys CV102.
BMA’s main request of the CQU team, was to identify the root cause of the failure, potential actions
to prevent recurrence including a review of the failure of VA to provide adequate forewarning of the
potential failure.
The CQU team collected required data from a variety of sources for this purpose and a team visited
the Mackay Conveyor Engineering (MCE) workshop, and BMA Broadmeadow mine-site where
CV102 Conveyor is in operation. During the BMA visit the team has also organised a group discussion
(brainstorming/RCA session) with the BMA team associated with the CV102 operation. BMA
provided three reports i.e. SKF- VB0045, SKF VB 0046 and AXYS Consulting related to recent (since
September 2014) pulley failures on the CV102 conveyor.
Data collected from the above sources was thoroughly analysed using two approaches; a Lifecycle
approach secondly objects base approach. In the Life cycle approach each stage of bearing life
starting from its design (OEM), Transport/ storage, installation to operation and maintenance has
been examined carefully and factors influencing the bearing life have been identified. In the second
approach analysis is based on an Ishikawa/herring-bone diagram with the main branches
represented by Man, Machine, and Process & Environment causal factors. Both the approaches
were integrated with each other. Three reports provided on three different bearings were useful
however in determining a Root Cause Analysis (RCA) they could have minimum contribution because
these pertains to three different bearings used in CV102 conveyor system.
The data available from different bearings does not help finding a single cause of failure; however an
RCA was carried out, based on which final conclusions have been drawn:
1- Schaeffler Online Calculator (FAG Bearings) indicates the lubricant used in the bearing has
low viscosity and bearing supplier must be consulted to choose the right grease that has
higher viscosity and contains at least EP and anticorrosion in the additive package. (OEM,
Design issue)

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2- Static corrosion indicates poor storage. Thus storage and transportation of the bearing
pulley needs better care to prevent corrosion and to prevent any type of fretting during
transportation. Products from the static corrosion are thought to have introduced solid
contaminants inside the bearings ultimately contributing to the failures; as all bearings were
stored in the open for approximately 9-12 months, this is seem as a potential common cause.
(Transport and storage issue)
3- The bearings in question are mounted via tapered sleeves, in one instance the inner was
found to have an axial crack, most likely caused by incorrect fitment. Thus Installation of
bearings requires a standard practice to ensure there is no undue preloading occurs on the
bearing.
4- The conveyor belt was observed to be tracking off to one side which according to site
personnel was a result of structural movement since commissioning.. The “tracking off”
indicates there is axial force acting on the bearing that is likely due to structural movements.
The extent and significance of this structural movement has not been assessed in this report
(indicated by the BMA Team), static corrosion and misalignment of pulley shafts.
(Installation issue)
5- The location of a number of greasing points was observed to be different and possibly hard
to access given the conveyor guarding in place. Lubrication process needs improvements,
Labyrinth seals were found dry in some cases shows purging is not efficient, only two grease
nipples are used third one is left dry. SKF have recommended using a “Kobra” seals to
reduce the ingress of contaminants. The greasing system needs to be improved to ensure
consistent lubrication. A standardized lubrication point design with correct labeling is
recommended to reduce human error. (Operation and maintenance issue)
6- Marks on one of the failed bearings indicate probability of current discharge; voltage drop
should also be measured to eliminate current leakage in the bearing. Earthlings of the
structure must be verified. (Maintenance issue)
7- MCE report shows the housing tolerances are not within the required limits. It is hard to
image the housings wearing out of spec in the short period since commissioning; hence one
could assume that the oversized housing was present at time of assembly. The OEM should

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ensure standard practices are adopted for manufacture and assembly to ensure QA/QC
compliance.
8- The premature failure clearly indicates that the VA technique used on site was not effective.
This is mainly due to the reason that vibration energy and hence signal at low speed (69 RPM
for CV102) is too weak to generate a signal that stands out against other background noise
(signal to noise ratio) and be used to confidently predict the bearing condition. The correct
selection of filters and other signal processing techniques are required to ensure that low
frequency defects are identified. Bearing manufacturer SKF suggested the use of magnetic
accelerometers should to be avoided. However the literature does not show such evidence.
CQU team suggests that various options can be tried such as using waveform, using
displacement or velocity transducer, mounting with glue, and analysing the basic data. Over
and above CQU recommends that the BMA site engage an expert Vibration Analysis service
provider to trial various techniques and equipment (including differing mounting devices) to
establish a standardized VA procedure specific for CV102 (and similar conveyor) and train
site ConMon personnel in the use of this procedure and interpretation of the results
( Maintenance issue)
9- Since VA is not effective, Wear debris analysis and particle counting in the grease will be
helpful if data is collected over a period of time and a trend is setup. It is likely that more
information is revealed that otherwise could not be detected by VA. (Maintenance Issue)

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1. Introduction
The BHP Billiton Mitsubishi Alliance operates the Broadmeadow Mine amongst a number of other
mines in the coal mining area of the Bowen Basin in Central Queensland. The Broadmeadow Mine is
located some 30km north of Moranbah and 190km south west of Mackay.
The CV102 input conveyor system shown in Figure 1.1 was commissioned in March 2013, it is 2170m
long with a belt width of 2000mm and is driven by two pulleys each of which is in turn driven by 2 x
1MW electric motors (making a total of 4 x 1MW drives), total material lift is 89.6m with a nominal
material flow of 2045t/hr. (Max Design flow 6400t/hr.)
Starting in September of 2014, there have been a number of failures to drive and snubber pulleys on
the CV102 system, at least one failure has been in a repeat location (i.e. the initial failure occurred in
September 2014 and then again in April/May of 2015). Current site strategy to contain failures
includes the pre-emptive change-out of pulleys that are indicating any signs of defects as picked-up
in Condition Monitoring VA (Vibration Analysis) inspections; this however is not a desirable long
term strategy. In at least two instances the failures have been of catastrophic nature in that the
outer ring was found to have suffered axial fractures.
Compounding the failures themselves is the perceived failure to adequately discover the onset of
potential failure and provide a roughly accurate prediction of remaining life (time to functional
failure) from VA inspections. In one instance the VA advice indicated a window of action in the order
of weeks, yet only days later audible noise and a significant temperature rise necessitated an
unscheduled replacement.
The pulley is manufactured and supplied by TEFCO Engineering Pvt Limited (TEFCO). BMA engaged
CQUniversity team to investigate the cause of failure and recommendations for implementation to
prevent such premature failures in future. The design life of these bearings is more than 18 years but
failing within 2 years’ time and the total down time cost of a bearing pulley is approximately $5m.

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Figure 1.1 CV102 Conveyor System

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This report presents an RCA of bearings failed based on the previous reports and data provided by
BMA Broadmeadow. The purpose of this report is to:
• Analyse the output from a number of individual bearing failure reports, information
gathered during a site visit to Broadmeadow, which include a brainstorming session with
BMA personnel and a visit/inspection of a failed CV102 pulley/bearing assembly in MCE
workshop in Mackay. From this analysis the report will attempt to identify if there are
common modes of failure present and recommend a range of actions for BMA personnel to
consider to potentially reduce/eliminate future failures of a similar nature.
• Provide commentary and a course of actions on the perceived gaps in site VA diagnosis
1.1Purpose
The purpose of this project is to investigate failed bearings in a CV102 Pulley and to make
recommendations based on a Root Cause Analysis.
1.2Scope
The scope of the project is to make recommendations based on the review of reports available on
failures of bearings in CV102 Pulleys and data collected from the workshop, pulley site and people
associated with the conveyor operation.

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2. Data Collection and analysis
Data was collected form the following sources on different bearings this includes 2 reports from the
bearing supplier SKF, one report from a consultant and other data from the site and people
associated with conveyor operation.
2.1 Data collection
This data was carefully analysed independently and also in conjunction with one another. Since data
belongs to different bearings used in the conveyor system at different location at different times
their failure patterns are different. The main objective of the study was to find out a root cause but
this may differ for each one of the 3 failures common factors was identified to establish the cause or
causes for failures.
Two approaches were used to identify cause of failures, firstly by Object based approach and
secondly Life Cycle approach such that common factors responsible for failures could be identified
and cross checked for their dominance in the failure mechanism.
A Root Cause Analysis (RCA) has been carried out step by step where different failure analysis tools
have been used such as Fishbone diagram, Object base and Asset Management Life Cycle approach
have been used. In this analysis lubricant selection was verified using Schaeffler calculation chart
and Vibration data has been analysed consulting three experts in the area at different stages.
Main Data collected from the above sources has been used for the analysis often in this report in
different context and has been shown in Table 2.1.
2.1.1 Object based Approach:

In this approach People –Process- Equipment and Environment. This process has been shown in
Figure 2.1 which has been developed as Brain storming session or Group discussion with the BMA
staff engaged with CV102 operation. In this the three main questions asked were:
Question 1: Why most floating end or western side bearing fail and not the Eastern side or Fixed end?
Question 2: Why does CV102 and why not CV101 bearings fail so prematurely at BMA Broadmeadow
only?

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This cause of failure was targeted at People, Process, environment and Equipment and a group
discussion was directed to a brain storing session where BMA staff participated.

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Table 2.1 CV102 Frequently used data

Bearing Data Value Comments
Bearing Shaft Diameter 400 mm With sleeve
Bearing housing CSD3184
Bearing OD 700 mm
Seal TACOM
Bearing Number 23184K MB C3
Adapter sleeve OH 3184 H
Bearing Dynamic Rating 5600 kN
Bearing calculated life 628327 Hrs
Load on each bearing 597000N
Bearing Grease CASTROL BRB572 Appendix-C
L10 Life 635000 hrs
Actual Life 16000 hrs
Load 1184/2 592kN
Speed 69 rpm
Bearing Grease CASTROL BRBF572
SEAL Brand TACOM
Viscosity 220 cSt
Prescribed Viscosity 143 cSt
Schaeffler Lube FAG Load Arcanol 400 Appendix B (Proposed
grease)
Shaft Speed 69 rpm
Belt length 217 m
Belt Width 200mm
Electric motors (4) 2X2X1 MW
Material Lift 89.6m
Flow Rate 2045 t/hr below the capacity

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Figure 2.1 Object based failure Analysis

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2.1.2 Asset Management Life Cycle Based Approach:

In this approach each stage of life cycle was observed carefully and failure symptoms from the
data were correlated to establish the cause. This has been shown in Figure 2.2. Similar to that
of Failure Mode Effect Analysis (FMEA) at each Life Cycle stage failure types have been
identified such that these could be taken into account as part of RCA,

Figure 2.2 Asset Management Life Cycle Approach
Asset%Management%Lifecycle%
Plan%&%Design%
• Inadequate%design%
• Failure%to%observe%
engineering%
standards%
• Build%to%cost%
• Incorrect%design%
data,%i.e.%service%
life,%duty%cycle,%
operaBng%
condiBons%
Acquire%&%
Commission%
• Manufacturing%defects%
• Packaging,%handling,%
transport%%and%storage%
defects%
• ConstrucBon%defects%
• Precision%InstallaBon%
lacking%
• QA/QC%lacking%
Operate%&%
Maintain%
• OperaBng%
procedures%not%
followed%
• Signs%of%failure%not%
reported,%i.e.%leaking,%
noise,%warning%signs%
• Maintenance%not/
incorrectly%%
performed%
Improve%
• ModificaBons%
compromise%design%
intent%
• ModificaBons%
compromise%
statutory%
requirements%
Life%
Extension/
Decommission%
•  Grease/lubricaBon%
specificaBon%
•  Spillage%protecBon%
•  Stability%of%
structure%O%
foundaBons%
General%Defects%Specific%Defects%
•  Bearing%housing%
oversized%
•  Pulleys%stored%
incorrectly%
•  Alignment%not/
performed%
incorrectly%
•  ShaQ%Adapter%
sleeve%installed%
incorrectly%
•  Lube%points%not%
consistent%
•  IniBal%lube%qty%
incorrect%
•  Lube%not%
performed%(at%
least%for%one%seal)%
•  Product%Spillage%
over%bearing%
housings%
•  Tracking%not%
corrected%

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2.2 Problem Solving
One of the main purposes of this project is to find the root cause of failures. The evidence provided
by BMA related to 3 different failures, albeit on the same pieces of equipment, each failure should
be viewed and analysed in its own right in order to arrive at a unique root cause for each failure; in
this case the RCA approach in combination with a Fishbone (Ishikawa) diagram to identify if any
common threads existed across the 3 separate failures. During this analysis variety of tools have
been used at different steps of this analysis such as; Fishbone diagram, Fault tree analysis and
viscosity check using Schaeffler calculator and approximate calculations using Dowson Higginson’s
formula for Elastohydrodyanamic lubrication of line contacts.
The other objective of this project is to find out why Vibration Analysis was not able to predict the
bearing failure. This issue is addressed by taking a close look of the data. Since low frequency VA
involves complex condition monitoring techniques, it was found to be out of scope of this project
and the process was reviewed by seeking opinion from experts about the equipment and the
procedures used for the analysis.
The above objectives have been achieved through an RCA where above tools and techniques have
been used as a part of an RCA as and when required.
2.2.1 RCA Approach
Data collected from various sources as discussed in the previous section was analysed and based on
the information provided by BMA Broadmeadow an RCA is carried out as per the ISO 15243. The
chosen method of analysis for this project is RCA-RT 12-Step approach. In this analysis only 9 steps
have been used; another 3 steps out of 12 are the part of the implementation phase of this model.
The remaining steps of the analysis could be completed when this RCA plan is implemented by BMA.
STEP 1 - Problem Definition
The problem definition is developed by first understanding the difference between the desired state,
i.e. “the Should”, the actual or present state i.e. “the is” and thereby develop the Gap in expected
performance. The problem definition is then derived from these statements.
In the case of CV102 the following statements were developed;

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• IS
o A number of bearing failures have occurred on the CV102 Conveyor system since
commissioning in circa 2013. Bearing life based on L10 is 635,000hrs, in some cases
only ~160000 hours have been achieved.
• SHOULD
o Bearing life has been estimated to be in the order of 635,000hrs.
• GAP
o L10 life can be regarded as life in perfect conditions, but even is a real industrial
environment one would reasonably expect this class of bearing and the application
to have 20year + life. Hence, gap is 18years MTBF.
• Event
• Series of events. The question here though is how are they related.
Based upon the above one could conclude that the problem statement should read as follows;
“Premature failure of CV102 pulley bearings”
Step 2 - FOCUS
o One Plant
o BMA- Broadmeadow
o One Process
o In-pit conveyor CV102
o One Problem
o Drive and Snubber pulley Bearings.
Normally one would examine each failure by itself and not group a series of failures together as the
exercise can become too large and potentially confusing, but in this case we are dealing with failures
that have occurred back in September 2014 and in some cases the evidence trail and reports form
those events are incomplete; indeed the only formal reports that have been used to compile this
report are SKF bearing inspection reports VB0045 & 46 and an AXYS Consulting report AR1740and
while the latter attempts to arrive at a root cause, the former two are limited to the actual bearings
rather than examining the underlying causal factors.

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Step 3 – Extent and Impact
The extent of the problem at this stage appears to be confined to the bearings in the March 2015
Condition Monitoring report for CV102, which identifies 6 bearings with defects. All defects are on
the Left hand (Western/Floating) bearing and 3 bearings have failed (2 of them being on the floating
side); considering that the calculated L10 life is of the order of 635,000hrs then failure of any of
these bearings at this stage i.e. less than 16000hours is considered unacceptable. The financial
impact considering only the potential opportunity loss of production is at least $5M.
Significance against KPI’s is estimated as below:
o Safety – Nil
o Environmental – Nil
o Production – Conservatively, site personnel have placed an estimate of 50,000tonnes
production opportunity between September 2014 and May 2015 due to production
downtime required to replace CV102 Pulleys.
o Maintenance – Each pulley rebuild is estimated to cost between $100,000-$200,000 and
there have been at least 3 failures in the period under examination.
o Revenue Cost – TSI (The Steel Index) prices for coking coal for Q2 2015 are in the order of
US$100/tonne, hence the 50,000tonne estimated production opportunity loss equates to
US$5M.
The present bearings installed in the CV102 conveyor are being monitored and pre-emptively
changed out at the first sign of fault as previous functional failures have occurred only days after a
potential failure was flagged by VA.
Step 4 - Containment
Containment up to this point in time has been the immediate change out of any pulley/bearing
assembly that has an indicated VA fault. This containment measure is in response to the perceived
lack of adequate formatting of functional failure by present VA methods. One aspect of this exercise
apart from determining the root cause/s of the bearing failures is also to determine why the present
VA processes have not given enough indication to operational personnel and if there are any other
techniques that can be used to determine the onset of a potential failure and more accurately
forecast a "time to failure" severity rating.

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Step 5 -Take A Good Practical Look
There are a number of reports and updates that have been provided that describe the status,
condition an apparent failure modes of the CV102 pulley bearings, they include;
1. BMA update on Condition of Pulleys (Nigel Wooldridge)
2. SKF Bearing Inspection Report - VB0045
3. SKF Bearing Inspection Report - VB0046
4. RCA of CV102 Bearing Failure - AXYS Consulting
5. Initial observations of failed bearing in MCE yard Mackay by CQU personnel
Each of these will be detailed to summarise relevant points.
BMA update on Condition of Pulleys:
The CV102 Conveyor has in recent times due to previous catastrophic bearing failures undergone
increased scrutiny, in response to this heightened awareness a summary of the present condition for
CV102 bearings was compiled by Nigel Wooldridge – BMA, as per the following
• Jib Pulley - LHS bearing minor fault
• HT Bend Pulley - LHS minor fault
• Drive Snub Pulley - LHS minor fault - low level demodulated spectra only
• Inbye Drive Pulley - LHS New Fault, trending is stable - this bearing subsequently failed
• Take-up Pulley - LHS Minor Fault - comes and goes, indicative of bearing spinning in housing
• Tail Pulley - LHS minor fault
All above items were raised on sites CMMS as notifications to replace as per Table 2.2

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Table 2.2 Inpit CV102 Conveyor Condition Monitoring Report ( Nigel Wooldridge)

It was further noted that tracking of the conveyor off to the LHS (Fig. 2.3) and uneven wear on the
pulley lagging were issues and potentially contributing to the failures. A recommendation to survey
pulleys and confirm/correct parallelism was noted. One other failure was noted on a RHS bearing,
but this was attributed to water ingress and deemed not related to the above faults. VA surveys are
conducted fortnightly.

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Figure 1.3 CV102 showing tracking
With respect to conveyor alignment, it is noted that, "Except for special purpose applications (such
as turnover exit) all conveyor pulleys shall be set level and the centreline set perpendicular to the
centreline of the belt. Misalignment should be measured to ascertain its severity as significant
departure in alignment will result in unnecessary thrust load on bearings, accelerated and uneven
lagging wear and belt tracking problems" (Belt Conveyors for Bulk Materials - CEMA 5th edition
p.411)
a) SKF Bearing Inspection Report - VB0045
VB0045 summarises the bearing failure from the No.2 drive pulley of CV102, which was removed
from service in April 2015. The bearing in this instance was a FAG 23184 K MB C3. The report notes
that the precise cause of failure cannot be determined due to the extent of damage, however the
most likely cause is given as being related to ineffective lubrication film. This particular bearing was
in service for approximately 24months, well short of the 635,000hr L10 life. A number of defects
were noted against the following items (Fig. 2.4 and 2.6 );
• Outer ring - Fracture and cracking, fretting and moisture/ standstill corrosion
• Inner Ring - Surface initiated fatigue and plastic deformation

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• Rolling Elements - moisture corrosion, plastic deformation and abrasive wear
• Cage - Abrasive wear
• Adapter sleeve - Fretting corrosion and fracture
• Bearing Housing - Fretting corrosion Bearing Journal - Fretting Corrosion

Figure 2.4. Outer ring spalling

Figure 2.5. Outer Ring Fracture
Of particular note in this report is the assessment of the moisture corrosion which is surmised to

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have occurred on two occasions, once during storage and then when installed in position this
suggests that storage and delivery practices may have allowed moisture to enter the bearing.
Anecdotal evidence from site personnel interviews during the CQU visit also suggests that bearings
were delivered to site with missing grease nipples.
The fractured adapter sleeve is clear evidence of fitting/clearance issues.

Figure2.6. Outer ring, standstill corrosion

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b) SKF Bearing Inspection Report - VB0046
VB046 summarises the bearing failure from CV102 Drive Snub Pulley, which was removed from
service in May 2015 after approximately 24 months in service. The bearing in this instance was a FAG
23192 K MB C3 and the NTE (floating bearing was noted to have early signs of failure in the form of
heavy fretting and evidence of moisture ingress specifically the report notes the following defects:
• Outer ring - Adhesive wear, Fretting, circumferential marks indicating loose fitting in the
housing (and possible rotation), moisture corrosion, standstill/contact corrosion and plastic
deformation
• Inner Ring - Abrasive wear, plastic deformation and moisture corrosion
• Rolling Elements - moisture corrosion, standstill/contact corrosion
• Cage - Abrasive wear
c) RCA of CV102 Bearing Failure - AXYS Consulting
AXYS Consulting compiled a RCA report on the failure of CV102 Drive Pulley No 1 bearing after it had
failed in September 2014 after possibly only 18months in service. Both bearings were examined
although there is no corresponding SKF Bearing inspection report for this particular failure as
submitted evidence. The report concludes that there was significant evidence of water/moisture
ingress and subsequent corrosion, but also noted the following specific defects
• Fixed End Bearing - this being was giving the poor VA readings, which precipitated the
change-out.
o Outer ring - Crack across the face of the bearing and chips missing from along the
outer face. Corrosion/etching marks visible on outer race, deep spalling evident.
Rollers were not running centrally indicating axial loading
o Rolling elements -Corrosion/ etching marks
o Bearing Housing - Water inside housing,
o Labyrinth seals - Identified as being dry.
• Floating End Bearing
o Outer ring - Corrosion present
o Bearing Housing - Corrosion observed, Water present, postulated that this limited
axial movement and would have applied great load to Fixed end bearing.
o Labyrinth seals -identified as being dry.

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o Bearing Journal - Grooves present indicating labyrinth seals running dry
The AXYS report identifies 3 probable causes and areas for corrective actions:
• Water Ingress - the source of the water is from the conveyor itself as wash water spills off
the conveyor, this has been recognised by site and a number of corrective actions in the
form of guarding and conveyor skirting (containment devices) have already been installed to
reduce the spillage of process water (containing contaminants i.e. coal dust).
• Maintenance - Identification and review of Lube points on each bearing to ensure the
correct quantity of grease is applied at the right frequency
• Storage - The AXYS report notes standstill corrosion as being present, this condition was also
noted in VB0045 & VB0046 so this must be viewed as highly credible. Site personnel
interviewed during CQU visit also provided a back story that may explain the presence of
standstill corrosion, in that pulley components for CV102 were delivered and remained on
site in the open for a period of time before construction commenced; It is also likely that
once installed, the pulleys remained stationary for a period of time before commissioning
and commencement of routine operation. This possibility was also commented on by site
personnel who in understanding the impact of standstill corrosion have assessed in hindsight
that these bearings were destined to premature failure even before the commencement of
operations.

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Figure 2.7. Typical Pulley/bearing arrangement
d) Observations of failed bearing in MCE workshop
A bearing from CV102 as shown in Figure 2.7 was cleaned and made available for initial inspection by
S. Sharma and CJ Galeotti from CQU. Special features related to failures in these bearings that have
been observed are shown in Figures 2.8 to Figure 2.10. Bearing observed Initial observations include
fluting, pitting and corrosion are shown in these figures.
• Floating end
o Outer race - pitting/spalling and possible brinelling marks on outer race (also visible
fluting [Fig. 2.8] that could indicate that electric arcing has occurred TBC), corrosion
marking evident on outside of outer race
o Rolling Elements - minor pitting present on a number of rollers.
o Fixed end Outer race - False Brinelling present. Load zone was quite evident
o Outer ring fluting also indicates skidding which could be due to poor lubrication

Figure 2.8. Outer ring, fluting

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Figure 2.9. Outer ring pitting

Figure 2.10. Outer ring, standstill corrosion

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Step 6- Patterns and Comparisons
CQU Team has visited the CQU visited BMA - Broadmeadow site to see firsthand the CV102
installation and the conditions/environment in which it was operating and to hold discussions with
site personnel to gain an understanding of the potential causal factors.
CV102 – Field Inspection
Site inspection of the CV102 conveyor area noted the following observations:
Coal dust residue/product spillage was clearly present in varying degrees over all conveyor pulley
bearings.  Significant effort had already been undertaken to reduce water and material spillage
directly onto the bearing areas of the conveyor, some in recent time such as the diversion of the
drain from the spillage wash trays under the discharge end of the conveyor and the installation of
skirting (Fig. 2.11 and Figure 2.12) along the inclined section of the conveyor to contain otherwise
fugitive material.
There were noted a number of inconstancies with respect to grease nipple locations. The conveyor
was noted to be tracking off to the western (floating side) by an estimated 150mm+. Site personnel
indicated that despite a number of attempts they were unable to correctly centralise the belt.  The
conveyor structure appears to have moved as evidenced by beams attached to adjacent ground level
concrete walkways in an effort to stabilise the area.

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Figure 2.11. CV102, typical spillage over bearing housing

Figure 2.12 CV102, skirting installed by site to control spillage

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Group discussion and Brainstorming session
Personnel from BMA - Broadmeadow, BMA Broadmeadow and CQU then adjourned to one of the
sites meeting rooms to conduct a group discussion leading to a brainstorming session on the
conveyor bearing failures and see if there were any patterns or relationships between failures.
As previously stated, RCA exercises are best done on individual failures rather than trying to tie a
series of failures (some for different reasons) together in this case although it was the only option
available, so data regarding previous failures is missing or has not been supplied as requested and
other data is subject of anecdotal evidence, hence a definitive root cause will be hard to guarantee,
but overall with the evidence provided and the ensuing fault tree that has been constructed a
number of reasonable recommendations will be made in an effort to provide a pathway of
corrective actions to reduce repeat early life bearing failure on this conveyor.
The brainstorming session used a Ishikawa diagram (also known as fishbone or Cause & Effect
diagram, (Fig. 2.13) to examine the main causal factors in order of People, Process, Equipment and
Environment (Figure 2.1) on order to categorise the evidence at hand, be it in the form of SKF
bearing failure reports, or anecdotal storytelling, the main points for each causal factor being:
• People :
o Lubrication errors - human error or the ability of the designated lube person to
skip/miss lube points on the bearings. There are approximately 16 pulleys on the
CV102 conveyor each pulley having two bearings, which in turn have 3 lube points,
one for the W33 groove and an inboard and outboard point for purging of the
labyrinth seals (no outboard point on non-drive pulleys). In a couple of instances
there appeared to be an inconsistency in the lube points and site personnel agreed
to conduct an audit to ensure all necessary points existed and were accessible. Given
the AXYS report noted and includes a photo showing a lack of lube to the labyrinth
seals and SKF reports VB0045 & 46 noted the presence of moisture inside the
bearings then there is a reasonable cause to assume that lubrication has not been
effective on all occasions.

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Premature(Bearing(
Failure(
5.6(Fracture((axial(crack)(
5.6.3(Fa8gue((pi:ng/
spalling(in(load(zone(
Contaminants(present(
Product(of(stands8ll(
corrosion(
Pulleys(stored(in(the(
open(
Lack(of(QA/QC(on(
storage(&(handling(
Entered(via(seals(
Seals(design(not(
adequate(
Seal(not(installed(
correctly(
Seal(not(Lubricated(with(
correctly(
(lube(film(thickness(
insufficient((
Site(spec(used(for(grease(
selec8on(
Rolling(elements(running(
on(outboard(edge(of(
outer(race(
Axial(loading(present(
Floa8ng(bearing(seized(
Rust(from(contamina8on(
Presence(of(stands8ll(
corrosion(
Or(entered(due(to(lack(of(
lube(to(seals(
Conveyor(tracking(off(Structure(has(moved(Insufficient(founda8ons(
5.6.3(Fracture(
(circumferen8al(crack(
Insufficient(support(on(
bearing(
Bearing(Housing(
oversized(
Check(QA/QC(procedure(
for(bearing(assembly(
VA(tes8ng(did(not(give(
enough(warning(of(
imminent(failure(
VA(technique(employed(
did(not(account(for(low(
speed/low(energy(signal(
Site(developed(own(
technique(
Figure 2.13 Simplified RCA Fault tree

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o Wash-down Practices - In operations such as Broadmeadow, it is common for
production personnel to be charged with basic operator/maintenance tasks such as
equipment wash down, overzealous or misdirected wash down practices can result
in high pressure water being directed at bearing housings. The presence of moisture
corrosion was noted in all three source reports; the source of the water ingress
could come from a number of possibilities i.e. whilst stored out in the weather for an
extended period, process material/water spillage from the conveyor and/or wash
down practices.
o Installation error - Bechtel were the EPCM on the CV102 construction and hence
with any installation there exists the potential for error in alignment of the pulleys
although one would expect a thorough QA/QC process would prevent this from
occurring.
• Process :
o PM incorrect - It was revealed that BMA personnel identified a error in the
recommended grease quantity for CV102 bearings, this error has subsequently been
corrected, but the effects of this error could be a reason for the premature bearing
failures
o Storage and Handling practices - In all 3 reports submitted as evidence for this
investigation the presence of standstill corrosion was observed suggesting that
pulley components remained out in the weather for a period prior to installation and
commissioning of the conveyor. Site personnel back up this claim, along with
feedback from TEFCO (OEM) who confirmed ex works dates (March-May 2012) well
in advance of site commissioning in March 2013. This occurrence of standstill
corrosion suggests that packaging of the pulleys was not sufficient to prevent
moisture ingress, which raises a QA/QC question on the part of the OEM and
acceptance criteria on the part of the EPCM.
• Equipment
o Alignment of the Belt - It was clear from observing the CV102 in running state that
tracking is a problem with the belt running off to the western (floating side) by
approximately 150mm. Site personnel agreed and confirmed that a number of
attempts have been made to correctly centralise the belt to no avail. An engineering
survey performed on site indicates the conveyor structure has moved, further

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evidence of this movement is given by the fixture of at least one steel beam to
concrete walkways adjacent to the conveyor to stabilise the concrete. Also of note is
the nearby CV101 conveyor, which appears also to have some alignment problems
with the tracking of the belt and general observation of the conveyor structure.
o Lubrication points not consistent - As stated in the people branch lubrication points
were not uniform and a conveyor audit has been suggested to correct any anomalies
o Spilltray/drain design causing splashing over bearings - Again this item is in the
process of being corrected by site personnel
o Bearings,
§ Housing quality - One OEM bearing housing was found to have been welded
together i.e. a weld repair of a crack which would cast some doubt on the
QA/QC controls employed by the OEM
§ One housing found to be oversized which is unexpected for the life of the
units, hence one could conclude this was in error at time of assembly
o Sealing system - Labyrinths not lubricated the ability to fit the seals in a manner
where they do not run concentric to the shaft, the failure of V-seals and at least one
OEM housing was found to be oversized and out of acceptable tolerance.
The lubrication defect is already mentioned in respect to the ability to grease all necessary points;
the seals on bearings being rebuilt by MCE are now being converted to SKF Kobra seals which appear
to be superior to the present labyrinth seals used on the OEM bearings. The oversized housing
would potentially allow the outer bearing ring to rotate which in itself is no major defect, but
considering the age of the components the oversized dimensions would most likely have been
present at time of manufacture which again casts some concern over the QA/QC processes
employed by the OEM.
BMA are presently having the failed pulleys repaired by MCE out of Mackay and there has been a
conscious switch to SKF components in the rebuild process including the aforementioned Kobra
seals.
• Environment:
o Spillage -As previously noted it was apparent that spillage of product (coal dust/fines &
water) from the conveyor does rain down on the bearings and drive areas in general.
The extent of the spillage is thought to have come from the usage of water sprays to

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suppress dust within the mining areas, but is exacerbated by the fact that the sprays are
not turned off when coal is not being loaded, leaving an excessive amount of water on
the belt which mixes with coal residue and spills off the belt when approaching the
inclined section of the conveyor. Site personnel have already attempted a remedial
action by installing a conveyor skirting system along most of the inclined section of
CV102, but in addition to this the inclusion of some form of water spray interlock to
minimise water addition to this conveyor when coal is not being loaded should be
considered.
Step 8 - Fault tree analysis
The fault tree constructed to represent the series of failure presented to the site working group and
CQU personnel has been compiled using the fault code nomenclature under ISO 15243 - Rolling
bearings - Damage and Failures - Terms characteristics and causes. Elements from the Ishikawa
diagram were used to compile the fault tree diagram by including those items generated from the
site brainstorming session a simplified Fault Tree diagram is shown in Figure 2.20.
It was clear once causal factors were labelled that at least one common theme was apparent and
this was the presence of corrosion, more specifically the report all mention the evidence of standstill
corrosion, i.e. corrosion caused by inadequate storage and handling practices for the completed
conveyor pulley/shaft/bearing assemblies. Anecdotal evidence and despatch records from the OEM
indicate the items were delivered to site and remained in the open for a pressed of time before
being installed and the again remaining in the open until commissioning and the commencement of
normal operations.
i) Standstill Corrosion
Standstill corrosion is most likely the initiator of contaminants in their bearings that have led to
surface initiated fatigue /spalling at an early stage in the bearings life, and ultimately led to the
creation of stress raisers in the locations where the axial cracks developed. SKF Bearing failure
guidelines note;
“Rust will form if water or corrosive agents reach the inside of the bearing in such quantities that the
lubricant cannot provide adequate protection for the steel surfaces. This process will soon lead to

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deep-seated rust. This produces greyish black streaks across the raceways, mostly corresponding to
the rolling element distance.
The risk of corrosion is highest in non- rotating bearings, such as during standstill”.
(http://www.skf.com/binary/86-62751/RTB-1-06-Bearing-investigation.pdf)
As the presence of standstill corrosion was observed in all 3 source reports and there is a clear
causal link between the corrosion, the subsequent spalling and the final axial fractures it is most
likely that this defect i.e. corrosion is the most likely and significant cause. The underlying cause for
the presence of the standstill corrosion is the lack of or failure to observe storage & handling
standard. One would imagine though no evidence has been gathered to prove or dispute that the
EPCM (understood to be Bechtel) for this project would have a comprehensive suite of standards
that would safeguard the packaging, transport and storage of materials for CV102. The storage of
the pulley assemblies in the open for extended periods would allow for the ingress of moisture
simply from overnight condensation and or seasonal precipitation. Storage of these assemblies
under-cover and out of the weather should have been specified and adhered to as part of the
EPCM's QA/QC responsibilities to ensure no degradation or damage to delivered
material/components occurs. The bearing OEM, Schaeffler was contacted to provide input on
storage practices, advice received based upon the 3 reports and included photographs lead the OEM
to also conclude that the most likely defect at play in these series of failures was the initial presence
of corrosion from poor site storage practices, advice also included the need to ensure 100% fill on
the bearing housings and the selection of a storage type grease that absorbs moisture rather than
repelling it as an improved state for consideration.
Standstill corrosion noted in AR1740 is thought to have also had an effect on the ability of the
bearing housing to allow free axial movement of the shaft in that the corrosion would have
effectively caused the floating housing to experience a higher level of friction than would normally
be expected and therefore allowed the rolling element to run further outboard on the outer bearing
race. This is thought to have led to, but also in combination with the presence of standstill corrosion
to pitting and subsequent higher stresses on the outboard edge of the outer race; resulting in the
chipping of the outer face and the final axial fractures.

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ii) Seals and Lubrication
Together with the standstill corrosion, the ongoing lubrication of these bearings showed a number
of potential defects, including;

Seal design
The present seals rely on a V-seal to separate the main housing from the taconite seals used for
purging, repair personnel noted that in instances the V-seals were found to be in a failed state when
the bearing was disassembled. SKF have recommended the use of “Kobra” Seal system to reduce the
ingress of contaminants which differs in the orientation of the seal grooves and is claimed to have
reduced contaminants in an iron ore environment by a significant amount.
Seal Lubrication
Quantity of Grease - Site personnel note that in the initial operating period of this conveyor, the
quantity of grease recommended well below OEM spec, this has since been rectified in site CMMS,
but highlights that for a period of time, the purging of contaminants would have been inadequate.
The purpose of the seals is to contain the lubricant and prevent ingress of moisture and
contaminants; the seals can only perform this function when they are purged at the correct
frequency and using the right quantity of grease. AR1740 notes that a dry seal (Fig. 2.14) was
discovered during the disassembly of the Drive pulley no 1.

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Figure 2.14 AR1740 observations of dry seals
ite observations noted that a couple of lube points at least were not all that visible and that a
mistake could be made; for this reason it is considered appropriate to survey all lube points and
standardise the layout such that for all 3 points on each bearing (2 points on non-drive), are
connected to hoses that are run to a clearly visible point near each bearing housing with a label/sign
on each point showing the type and quantity of lube for each point as per Figure 2.15. Alternatively
remote auto grease units could be considered.

Figure 2.15 Typical lube point
AR1740 noted that the taconite seals were dry; this alone would have allowed the entry of
contaminants/spillage thereby contributing to premature bearing failure as per fig 13. The presence
of the dry seals at least in this instance shows this location was not greased for a period of time.
iii) Lubricant Quality/Suitability
Lubricant keeps two bearing surfaces apart during motion while machine components transfer
forces from one to the other. Viscosity plays a vital role in forming an oil film between these parts.
Rolling element bearings are Suitability of Grease – The grease used by site in the lubrication of
Grease&type:&XYZ&grade&220&
5" 5"10"Qty"(>"

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these bearings is BP Energrease FPG which has a base oil viscosity of 220cSt. According to TEFCO this
was chosen by site, but interestingly enough a drawing of these pulleys notes a lube spec of Castrol
BRB572, which has a base oil viscosity of 143cST. The question of lubricant suitability is therefore
worth exploring and as noted by AST Bearings, the lubricant plays a number of roles in bearing
service; “The most important task of the lubricant is to separate parts moving relative to one another
(balls or rollers and raceways) in order to minimize friction and prevent wear. A lubricant that is
designed for specific operating conditions will provide a load bearing wear protective film. The ideal
condition is when the friction surfaces are separated by this film. In addition to providing this load
bearing film, the lubricant should also allow for the dissipation of frictional heat thus preventing
overheating of the bearing and deterioration of the lubricant and provide protection from corrosion,
moisture, and the ingress of contaminants.”(http://www.astbearings.com/bearing-lubrication.html)
The lubricant viscosity was crossed checked by two methods firstly using a Schaeffler Calculator and
secondly using an analytical approach where by calculating oil film thickness using well known
Dowson Higginson’s non dimensional formula for Elastohydrodynamic lubrication (EHL) of line
contacts.
• Viscosity Check by Chaeffler’s Calculator:
Using Asset management Life Cycle approach one of the crucial factor responsible for bearing
lubrication is base oil viscosity . With the above in mind the bearing OEM (Schaeffler/FAG) was
consulted to provide some thoughts on lubricant suitability, firstly by just using the Schaeffler/FAG
online calculator which when using the resolved loading conditions (1184KN/2), speed 69RPM and
grease viscosity of 220cSt advised an increase in grease viscosity as the Kappa value (Actual
viscosity/Required viscosity) was 0.7; any Kappa value less than one indicates that a higher viscosity
should be considered. To prove a point, the calculator was run again with the viscosity changed to
400cSt, the results this time indicated the grease viscosity was acceptable with the Kappa value
exceeding unity at 1.43. This result in itself should not be taken as gospel as other factors such as the
presence of EP (Extreme Pressure) additives in the grease may influence these results; however,
when the Schaeffler representative was consulted he did agree with the calculated results and
supported a change to higher viscosity grease.
To confirm the above consideration for a change to higher base oil viscosity of the grease SKF should
also provide their recommendations.

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• Oil film thickness Calculations
In a rough estimate of minimum oil film thickness film thickness was calculated using Dowson
Higginson formula for elastohydrodynamic lubrication (Figure 2.16) of roller bearings in this case
certain assumptions were made such as standard pressure viscosity coefficient, roller dimensions
and assuming there are 24 rollers, bearing material. The non-dimensional form of the equation is :
Hc = 1.6 U0.7 G0.6 W-0.13.R
Where:
Hc = center line film thickness and R is the reduced radius of roller and the inner race radius
Hmin = minimum oil film thickness which is 0.75 hc
U= non dimensional rolling speed ( η U/E’.R)
G= material parameter (E’. α )
W = non dimensional load per unit length (w/l.E’.R )
Here speed U is presumed to be the combined roller and inner race speed at the PCD in pure rolling)
and E’ is the reduced Elasticity modulus. E’= E/ (1-ν2) where E1=E2=E and ν1= ν2 = ν
The center line film thickness value is 9.7 microns in other words minimum oil film thickness which is
about 25% small the value is about 7 microns. This value is conservative and hence for given
viscosity 220 cSt appears to be too low in two respects firstly the value is too small and secondly its
an application where environment is heavily contaminated, misalignments expected and foundation
movement is anticipated the film thickness is too low. Thus viscosity calculations using Schaeffer’s
procedure appears to be safe and higher viscosity base oil with 400 cSt must be considered in
consultation lubricant supplier and bearing manufacturer. Please note that these calculations have
been made based on certain assumptions such as roller geometry and assuming only 20% rollers
take the load therefore cannot be quoted as actual oil film thickness. The purpose is to compare the
trend of oil film thickness with the Schaeffer’s calculator.

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Figure 2.16 Elastohydrodynamic lubrication
iv) Bearing Housing
The AR1740 report also notes a circumferential crack on the outer ring (Fig. 2.17), which according
to the FAG rolling bearing damage guide is indicative of poor support of the rings in the housing.
Further evidence to support this as a mode of failure come from the MCE workshop rebuild Work
Order 4180 which notes that the bearing housing is oversized and has evidence of fretting;
specifically the size tolerance on the housing is 700mm -0.00/+0.125 where measurements in a
number of locations exceeded 700.200mm, well outside the considered tolerance (Fig.2.18). What
this means in practical terms is that the oversized housing does not correctly support the outer
bearing ring and the load applied to the bearing is in fact distributed over a smaller area, resulting in
higher stresses (Figure 2.19). The circumferential cracking is a result of these stresses.
It is unclear how this housing has become oversized in such a short operating timeframe, it may be
the case that it was oversized at the time of manufacture in which case it falls upon the OEM to
demonstrate a QA/QC procedure was followed for this particular housing and any other housings
that are supplied.
hmin

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Figure 2.17 AR1740 report - circumferential crack

Figure 2.18 Excerpt from MCE WO 4180

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Figure 2.19 Stress distribution in oversized housing
v) Conveyor Alignment
Whilst it is most likely that contamination as a result of standstill corrosion is the most significant
causal factor in the premature failure of the CV102 bearings based upon the fact that the 3 reports
all mention the presence of this type of corrosion the one concern of site personnel is that the
failures appear to be occurring almost exclusively on the floating side bearing. Corrosion by itself is
unlikely to result in this sort of bias unless of course we take into account the proposed failure mode
indicated in AR1740 whereby the corrosion locks increases the friction in the bearing housing on the
float side and prevent free axial movement to the extent that the rolling elements run on the
outboard edge of the bearing. The presence of solids and contaminants from standstill corrosion and
indeed from any product ingress would combine with the outboard running to possibly create the
pitted/spalled surface in the load zone which contributed towards the final fatigue induced axial
crack.
Alternatively, if the corrosion was not enough to lock the floating end bearing, then another factor
may be present that is causing the failures to favour the floating side of the conveyor. It was
suggested and it strongly believed among the group of site personnel gathered that the CV102
Load%Distribu-on%in%correctly%sized%housing%
Load%Distribu-on%in%oversized%housing%

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structure has moved and that site surveys had recorded this fact. Structural movement will result in
the misalignment of pulleys, which will directly affect tracking and possibly allow for an increase
axial load to be placed on the bearings. The conveyor structural survey is in the hands of site
engineering personnel who need to be able to assess, the degree of movement, whether the
movement if likely to continue, the impact of the movement, likely cause of the movement and what
remedial measures may be available and at what cost.
The alignment question is also supported by field observations in Step 6 and discussed in the
brainstorming session. Given that there is presently no feedback/assessment from site engineering
as to the impact of structural movement it is difficult to devise a corrective action, but as a
containment measure site should measure and correct any deviation in alignment on a 6monthly
basis to ensure the belt runs centrally and does not apply any unnecessary axial loads on the
bearings. It is essential that pulleys are aligned and parallel with each other and a routine PM should
be established to monitor this movement; if successive inspections find no appreciable movement
then the task can be reduced in frequency.
vi) Bearing Fitment
VB0045 notes that a stress fracture is also present on the adapter sleeve; there is a high likelihood
that it comes from a fitment issue as the bearing has been driven too far on to the tapered sleeve. In
this instance, the OEM should be questioned to review the QA/QC procedures used in assembling
this and any other bearing to ensure the correct clearance reduction & bearing installation has been
achieved. Incorrect fitment can lead to bearing pre-stressing which may lead to misalignment and
cracks under cyclic loading.

Figure 2.20 Complete Fault tree

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2.2.2 Vibration Analysis
Vibration Analysis is a useful and proven Condition Monitoring technique that has found its way into
the standard suite of Asset Management practices in a number of industries over the last few
decades. While on the surface the techniques may appear simple, ie we are just inspecting for
vibration; in reality the collection and analysis of vibration data can be somewhat of a black-art.
Machines like CV102 conveyor have their own peculiarities, most significant being the relatively low
operating speed of 69rpm. The data shown in Figure 2.21 has been analysed that did not give
adequate warning to bearing failure. As explained earlier low frequency vibration measurement and
analysis is a complex process. Data provided by ACE is analysed and was further discussed with
experts from Vipac, Australia, Arms reliability, Applied Technologies Australia and with one of Our
Rail engineering expert team member. Each of them has their own opinion and considering their
views it is found that it is beyond the scope of this project and an expert needs to be hired to set up
a robust VA system and BMA staff should be trained to use it later. Opinions of these experts are
presented in this investigation.

Figure 2.21 Vibration data that did not predict the failure
Data summary is as below:
06/03/15 – Routine fortnightly survey, No Change.
13/03/15 – Routine Survey, Increase in vibration levels
17/03/15 – Surveyed due to Temp Increase, further increase in Vibration levels

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19/03/15 – Further increase in temp and Vibration levels. Call made to replace pulley.

Current overall vibration level is 1mm/s. This does not exceed any ISO vibration levels, but the rate
of deterioration is of particular concern and this is the bases for replacing the pulley ASAP. At the
current rate of deterioration (from data collected over the last few days) the bearing could reach
critical levels within a few days. Importantly the rate of deterioration makes bearing life
unpredictable.

Saavedra and Estupinan (2003) noted the difficulties in measuring vibration in low speed machines
(for the purpose of the article they defined low speed as being 6-300rpm
“Using spectral analysis of vibration to predict the presence of defects in the bearings of low-speed
machines can be difficult. The vibrations generated by these machines are of low amplitude com-
pared with the level of electrical noise, and in many cases this prevents the detection of defects in the
bearings.
The monitoring of the vibration of low-speed machines requires that strict attention be paid to the
selection and use of vibration measurement equipment. Concerted efforts to improve the signal-to-
noise ratio of the measurement are required. If special attention is not paid to analyzer and
transducer operating characteristics as well as to the vibration analysis techniques used, potentially
serious problems on these machines will often go undetected.” (The Journal of Process Mechanical
Engineering. Vol. 215, No. 4, 200, pp. 245 – 271):
"At over 100 rpm, it is easy to diagnose the condition of degradation and damage using vibration
analysis. This is because vibrations have a great amount of energy and occur over a short period. On
the other hand, with a rotating machine working at less than 100 rpm, it is difficult to diagnose
damage or degradation because of the small amount of energy and the vibrations occur over a
longer period"

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a) Opinion of Martin Wilson, Vipac Australia:
Martin Wilson from VIPAC was also consulted with respect to this bearing and the spectra captured
by site personnel, his comments based on data shown in Figure 2.19 and a conversation with BMA
Broadmeadow representative:
• I would not use an ISO standard to qualify or quantify any machine or shaft condition that is
doing 1.15Hz (speed as stated in one of the plots), as there is almost no dynamic energy in the
rotating components. My experience is that ISO and AS standards can be very wrong in some
circumstances. Experience is much more reliable on slow speed machinery;
• The vibration characteristic seen in spectra from the pulley is of concern as it indicates a distinctly
non-linear and non-synchronous source of energy;
• The characteristics seen in spectra is typical of a bearing fault on a large slow speed bearing,
based on my experience of see hundreds of this type of bearing;
• The harmonics series looks to be about 10X RS, which is about right for an outer race fault
frequency on the type of bearing that would be on the pulley (assuming the speed is 1.15Hz,),
however the immediate environment should be inspected to identify any potentially intrusive
vibration sources that could be contaminating the spectra. A high range acceleration spectra (0-
500- or 0-1000Hz would give more weighting to the higher harmonics and potentially allow
better identification of any intrusive vibration as the higher vibration frequencies will not travel
far, unlike the lower frequency components;
• A total spectral energy value of 1mm/s from only fault indicators is of concern.
• The total energy in the harmonics looks to be increasing, which indicates the fault is progression
and the bearing is deteriorating. This is of concern.
• A key issue with bearing wear on slow speed machines is that the outer race can wear evenly
without producing a change in the texture of the race surface, i.e. no pitting, spalling etc. is
present, just an even removal of metal for some distance around the load zone on the outer
race. This poses a problem from a detection point of view as conventional CM relies upon the
presence of bearing fault indicators generated by rolling elements contacting damage on the
race and producing an identifiable regular event, which produces the identifiable fault
frequencies. In the case of even wear, the clearances in the bearing can increase without fault
indicators being apparent. If clearances increase too much the seal can be compromised
allowing dust/debris into the bearing, which would cause a quick failure. As such if significant
fault indicators are present on a pulley (which there looks to be in this case) I would recommend

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removal of the bearing at the next convenient opportunity – just to be sure, since our job is
reliability. A feeler gauge can be used to check clearances if the bearing cannot be replaced for
some time;
• Lubricating can be an issue on pulley bearings, i.e. someone is not doing it. This could be the
reason for failures on one side of the conveyor. Also there is likely to be a thrust bearing on only
one side of each pulley. This side may be the side that the bearings are failing on, in which case
axial loading may be an issue.
•
b) Opinion of Deslie Haliday, Applied Technologies
Deslie Halliday from Applied Technologies (SKF agent) has also been able to supply some
commentary;
At 69 rpm the following race defect frequencies will be produced if there is a defect on a 23184CC
bearing.
BPFI - 13.54 Hz
BPFO - 10.61 Hz
REDF - 9.15 Hz
FTF - 0.5 Hz
Our recommendations for VA settings would be as follows:
10 kHz Acceleration 1600 lines
100 Hz gE3 800 lines
200 Hz Velocity 800 lines
1 kHz Velocity (ISO) 1600 lines
First indications of race problems such as the scalloping (sic) will show up earliest in the baseband
(either the 200 or 1kHx spectra). gE is unlikely to see this sort of fault until there is spalling present. In
effect the envelope data (gE) becomes a late stage indicator rather than an early warning.
Standard 100mV/g accelerometers with an amplitude deviation of +- 3dB from 2 to 10 kHz. No
requirement for higher sensitivity accelerometers
The accelerometer should be mounted either as close as possible to the load zone or 180 degrees to
the load zone. Glue on mounting studs is a minimum requirement. Magnetic mounts should not be
used.”

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Given the above opinions and in light of the fact that site diagnosis did not seem to yield a correct
forecast in terms of severity of the fault an immediacy of the need to replace, then it is
recommended that site Condition Monitoring personnel contact a provider of Vibration Analysis
techniques and engage them to provide a specific procedure and advice when inspecting these type
of bearings on slow moving machinery. The procedure should be specific on type and mounting of
accelerometer, type of leads, analyser settings, signal processing and interpretation.
c) Magnetic accelerometer mounting Literature search
Available literature was reviewed and more information about magnetic mount is gathered
understand the effect of Magnetic mounting of accelerometers to understand Deslie’s
opinion as stated below from two internet sources:
Source 1 :
https://archive.org/stream/evaluationofmagn00coll/evaluationofmagn00coll_djvu.txt
VIII. RECOMMENDATIONS

1 . The investigation should be continued to determine whether high frequency
components of machinery motion would have an adverse effect on the ability of a
magnetic clamp to reproduce the lower frequency spectrum.

2 . The use of an oil or silicone grease film for mounting magnetic accelerometer
clamps is recommended.

3. When mounting magnet clamps, great care should be taken to exclude foreign
matter between magnet and surface.

4. When possible, multiple readings should be obtained at each point of
attachment, carefully remounting the magnetic clamp for each run.

Source 2: https://www.google.com/patents/US4771637

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“A permanent magnet is the simplest method when the location to be measured is a flat ferro-
magnetic surface. Typically, the magnet is carried by an adapter, which is provided with a stud
opposite that surface which is to be attached to the structure the accelerometer then being screwed
onto the magnet. As the mass of the accelerometer will then be substantially increased, it can
therefore only be used for relatively stiff and large objects without affecting the results. Additionally,
when adding a magnet to an accelerometer or even when adding an adhesive mounting base, it is
necessary to recalibrate the accelerometer assembly due to changes in the mass and mounting”.
d) Opinion of Philip Sage, Arms Reliability
Philip has analyzed the data shown in Figure 2.21 provided by BMA Broadmeadow and gave
his opinion as below:
• 10.41 orders "should" correlate to a known geometry or fault frequency of a specific
bearing.
• In order to generate considerable harmonics, as this case does, we need a component
that is most likely damaged.
• Which component is the question, and often that can be identified by its fault frequencies
or geometry.

• What is unclear from the data is whether or not there is a 1X or a 2X peak in this data but
filtered by the instrument. This relates to the instrumentation issue I noted.

• I might suggest - ruling out what it cannot be, so that you are left with what it must be.
Given the conveyor shaft speed of 1.15 Hz, I would start by asking, what are all of the
bearing fault frequencies of the bearings that are turning at that speed on that shaft?

During a verbal communication Phil also suggested, “to avoid complicacies low frequency
range up to 500 Hz Velocity and displacement transducers can also be used to collect in
the wave form rather than a spectrum to get better results”.

e) Opinion of Prof Colin Cole:
Professor Cole looks at this problem with a simple approach and states as below:

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• The problem is not only the accelerometer. Accelerometers can detect low frequency and
can be purchased with low frequency range. The problem is they sense high frequency
better and with larger magnitudes Xw^2.
• Quite simply the signal needs a low pass filter – so you can see the low frequency, smaller
and more important signals. You can guess the low frequency you need to pick up by
multiplying number of rollers by rps. All frequencies of major interest will be below this
value as this will pick up the cycle due to passing a single surface defect.
• I recommend you still retain analysis of all frequencies in a separate channel as well to
pick up single roller defects.
After considering the opinion of the above experts and the literature search, it is concluded that the
further investigation analysis of the data is out of scope of this project and as Martin of Vipac’s
stated this is not a rocket science it needs a practical look which may require few hit and trials to
fixing the problem on the site itself. Thus it needs a VA expert’s service for proper investigation and
setting up a new procedure for a VA system.
Step 9 - Proposed Solutions
In this step defects are looked at with a solution point of view. The defects discussed earlier have
been presented as a typical asset Lifecycle model; the purpose being to illustrate how a practical
example such as the CV102 Pulley bearings under examination fits the theoretical model.
Furthermore, this example shows that like the model suggests, the defects are not limited to one
stage or one area of responsibility and that defects were present even before the asset was
commissioned.
Specifically, from the materials presented defect have been discovered in the Plan & Design, Acquire
& Commission and Operate & Maintain phases and while it is still surmised that the original
Standstill Corrosion defect is the most predominant and only common factor, the other specific
defects would also be a detriment to the bearing practically achieving a reasonable percentage of
the forecast L10hr Life. Factors associated with different stages of Asset life are shown in Table 2.3.
In this case, it is not surprising that there is no one unique solution given that a number of failure
have been investigated and the detail provided is still somewhat lacking in specific robust evidence.
Patterns and comparisons have largely been used to identify common factors and probable

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underlying causes, actions to correct and further investigate these causes and noted in the below
Table 2.3;
Step10-12
The remaining steps can be completed by the vendor after implementing the RCA findings. These
steps are as below:
• Step 10 - prepare and execute (the changes)
o Develop a plan for implementation which may include soft changes to maintenance
or operating procedures, or more complex equipment changes that may require
CAPEX, design, procurement, scheduling into planned shutdown windows.
o Approval is required to proceed with changes. A value/ease chart is useful in this
stage to identify any quick wins
• Step 11 - Did it work (monitor the system after the change)
o Monitor the changes to ensure they achieved the desired effect
• Step 12 - Make it stick
o Updating systems to reflect the changes, i.e. alarm limits, spare parts lists, P&ID’s,
Maintenance procedures in CMMS etc.)

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Table 2.3 Corrective measures
Item Problem Description Priority Status
1 Standstill
Corrosion
Establish/review QA/QC standards for the
packaging, handling, transport and storage
of pulley/bearing assemblies to ensure that
the occurrence of standstill corrosion cannot
take place. Standard should be applied to
ongoing maintenance and Capex works.
Suppliers need to demonstrate compliance.
1
2 Lubrication Ensure lubrication points are clearly
identified and labelled to “mistake proof”
lube process as per example in fig. 11
2
2a Lubrication Ensure SAP and associated lube route
instructions for CV102 have correct details
for type, quantity and frequency of
lubrication
1
2c Lubrication Consult SKF (considering new pulley are
being assembled using SKF components) for
suitable lube given loading and speed
conditions (69rpm) – Request advice in
writing
Schaeffler tool advises 400+ grade grease
1
3 Alignment Given the assertion that CV102 has moved,
consult site engineering to determine
appropriate course of action. Assessment
needs to determine;
1. The extent of movement
2. Whether the movement will continue
2 Site engineering
has apparently
surveyed the
structure;
Assessment
required

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3. What can be done to stabilise the
structure
4. Potential costs
5. Alternatives action if costs to stabilise
prove to be prohibitive (ie if structure
cannot be stabilised, routine PM to re-
align pulleys)
3b Alignment Survey pulleys, note deviations and correct
alignment (deliberate overlap action for
above action). May need to include this as
routine PM task
2
4 Spillage Audit CV102 area for spillage and devise
appropriate diversion/ containment/
protection measures to reduce product &
water spillage on CV102 components
1 In progress –
site already
undertaking
5 Oversized
Housing
TEFCO to be asked to comment on oversized
housing as per MCE WO4180, i.e. why?
3
7 Fluting SKF to confirm nature of fluting observed on
bearing in MCE Yard July 2015. If electrical
discharge is thought to be evident, then site
to inspect/measure CV102 for potential
current discharge.
*As this observation has now been clarified
by SKF as likely to be skidding caused by
incorrect clearance specification, then SKF to
be engaged to specify correct clearance for
drive and idler & snubber pulleys
3
6 VA
Procedure
Vipac to be contracted to provide specific
instruction to site on collection and analysis
1 BMA to contact
Vipac (Martin

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of Vibration data from CV102. Details to
include type of probes, mounting, sampling
techniques, duration and analysis.
A used grease analysis for wear debris and
particle count should be a regular condition
monitoring activity and data should be
trended to monitor the bearing
performance. ASTM 1404, NLGI
recommends DIN 51813 tests could be
useful for these analysis.
Wilson)

A simple lab
test can be
developed for
counting
ferrous
particles in the
grease sample.

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3. Results
In this report results have been included in the RCA in the form of Fault tree analysis, Fishbone diagram
and viscosity calculation.
However the analysis shows that there is no single cause that could be held responsible for bearing
failures. It could be a cumulative effect or all factors acting at the same time and depending upon the
location and condition of fitment, or condition of the bearing prior to fitment. One or the other cause
could be dominant and that becomes the major cause of failure. In general all the factors identified
needs to be addressed to minimise the cumulative effect.
• There common factors responsible for bearing failures have been identified. These must be
addressed simultaneously or by giving a priority:
• Correct packaging that suits pulley transport conditions and storage system be developed.
BMA should use correct practices for bearing storage. Water spillage needs to be controlled
at the same time ensure grease contains anticorrosion and antiwear additive.
• Alignment of shafts needs to check before fitting the labyrinth seal. If SKF recommended
Kobra seals are used there fitment and alignments must be taken into care.
• Select oil with higher viscosity with superior EP and anticorrosive additives in the additive
package these should be selected in consultation with the bearing supplier and lubricant
suppliers. FAG Schaeffler agrees with Viscosity 400 cSt FAG Load ARCANOL 400 grease.
• Foundation movement and pulley alignment needs to be checked if need be it should be
fixed.
• A standard method of mounting bearings using taper sleeve be developed and be practiced.
• Current leakage needs to be checked, if needed proper grounding must be done.
• Standard housing must be used and OEM should ensure the tolerances are within the
prescribed limits.
• If there is doubt as to the style and mounting of vibration probes, a variety of trials can be
conducted as part of the engagement of a Vibration Analysis expert in the development of a
specific procedure for CV102 and similar conveyors.
• BMA should seek expert service for VA and establish a correct VA practice.
• Results:
• The results have been summarized based on the review of the reports and data collected
from variety of sources. These have been recorded in the Table 3.1.

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3.1 Summary Table
Table 3.1 Results obtained of review of reports and data provided by BMA
No Cause source Remedy
1 Base oil viscosity Design aspect Choose higher viscosity close to 400 cSt
2 Static corrosion Storage Use proper sealing with desiccant
3 Contamination spillage Use protection and use rust inhibitors in the a
additive package
4 Taper sleeve Mounting
procedure
Use standard practice described by the OEM or
bearing manufacturer
5 Pulley Track off Misalignments Check foundation movement and fix it if needed.
6 Lubrication Greasing points use a redesigned configuration
7 Seals Dry labyrinth
seals
Replace them with Kobra seals and check the
alignments of shafts
8 Current Leakage Marks on one of
the bearings
Check voltage drop if need be use proper earthing
9 Fluting Fretting marks Use proper restrains during transport, turn pulley 6
times if stored for long poor lubrication could also
contribute fluting
10 Current Leakage Marks on one of
the bearings
Check grounding and measure voltage drop ensure
proper grounding
11 Housing, Tolerances are
high
OEM should ensure a standard housing is supplied
with standard tolerances
12 VA measurements Low speed signal
is not detected
confidently

13 Oil Analysis No other CM
technic to verify
the defects
Use grease analysis for wear debris analysis and
particle counting or cleanliness to compliment VA
technique

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4. Discussion
There are two questions needs to be addressed out of this study. The first question is; why premature
failures are taking place in CV102 BMA location only and second question is why vibration analysis
could not pick up the failure symptom at the early stage. Thus discussion is presented in two stages.

Root cause of bearing failure:

The investigation is required based on the review of three reports (2 from SKF and one from AXYS),
data collected from MCE, Mackay workshop, and BMA site as well as a discussion with the BMA staff
and stakeholders.

The reports provided by BMA Broadmeadow for failed bearings are for three different bearings used in
different locations in the CV102 Pulley system thus finding a root cause is not an easy task. Because
failure mechanism could have been different for different bearings and as stated failures are not taking
place in other conveyor systems CV 101, it is envisaged that operating condition and factors influencing
failures are changing from one location to other over the period of time. Dominance of one factor over
the other that changes from location to location and also the condition of the bearing prior to fitment is
not the same for all bearings.

In this study an attempt has been made to analyse data collected from various sources such that the
common factors responsible for failures could be identified. To make this study systematic, two
approaches have been used to identify these factors firstly, Object based approach where a brain
storming session was conducted during the discussion with the BMA staff asking answer to two basic
questions a) why failures occur in CV102 and not in CV101 and what are the factors responsible for the
failures. The causes of failures were connected to people, process, equipment and environment as
shown in Figure 2.1 and that was used as a road map for this study. In order to cross match the root
cause Asset management life cycle approach was used where origin of failure is connected to different
stages of life cycle of the bearing.

During the group discussions few factors that were found out using object based (OB) approach had no
documented proof but verbal statements of the workers. These discussions revealed useful information
such as: 1) bearings stored in open for several months without giving them six rotations as

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recommended by OEM. 2) It is reported that even weld joint were found in the bearing housing. 3)
Structural movements were noticed in the past and site engineers prepared a report. This information
indicates that there could be one or several such factors that might have been overlooked. To cite an
example if foundation is moving, then it will have an impact on the bearing performance and no matter
what lubricant is used it may not be effective similarly other factors such as corrosion, lubricant
viscosity will add fire to the fuel including undue vibration transmission which may affect bearing
performance.

CQU team could not access to Site engineer’s report about structure movement, therefore it severity
cannot be predicted. So is the case with the misalignments of pulley shafts.

Corrosion is found to be a common factor that affects the bearing performance corrosion occurs due to
poor storage practices as well as due to spillage during the operation. This affects lubrication and
deteriorates bearing mating surfaces and defects grow more and more. Corrosion changes the surface
topography; it acts as a third body causing abrasive wear. It is also noticed that bearings were not
rotated 6 times during the long period of storage as advised by the OEM. Proper packaging of bearings
is demanded to protect them from moisture that may require an additive that absorbs moisture at the
same time protects against corrosion.

There are fluting marks in the bearing appears to be due to skidding of the rollers which means poor
lubrication can cause high friction and phenomenon similar to stick-slip occurs. In MCE workshop other
failed bearing inner ring also showed equidistant roller marks that appears to be due to brinelling.
There are contradictory opinions about these types of marks which could be brinelling, skidding or
current discharge. A discussion with bearing users and manufactures indicated that due to discoloration
it may be difficult to distinguish between the brinelling and current discharge through the contact and
it is likely both defects co-exist. In case of brinelling proper packing should restrain movements. The
simple test to eliminate current discharge is to measure the voltage drop across the bearing and if it
occurs then proper grounding is required. The CQU team feels proper lubrication will ensure rolling
action of rollers without skidding.

Cause of cracks is always associated with the excessive loading. In this application bearings are
operating below the design load. The only possibility of axial forces could be due to misalignments,
structural movements or due to preloading of bearings. Since misalignment and structure movements

CV102 Report 281015a

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