lubrication failure analysis
TRANSCRIPT
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Lubrication
Bearing Failure Patterns and Trouble-shooting
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
Holcim Group Support
Symptoms
RemediesCauses
Bearing Failure analysis
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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False Brinelling
Symptoms
Elliptical wear marks in
an axial direction ateach ball position with
a bright finish and
sharp demarcation
Often surrounded by a
ring of brown
debris
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Causes
Vibrations in stationary
machines leading to
micro motion between
rolling elements &
raceways
When the bearing is notturning, an oil film
cannot be formed to
prevent raceway wear
False Brinelling
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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False Brinelling
Remedies
eliminate or absorbexternal vibration
use lubricants containing
anti-wear additives
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Overheating
Symptoms
Discoloration of the rings,
rolling elements and
cages from gold to blue
Temperatures in excess
of 200C can anneal ring
and rolling elementmaterials, reducing the
bearing capacity and
causing early failure
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Symptoms
In extreme case, the
bearing components will
deform
Temperature rise can
also degrade or destroy
lubricant
Overheating
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Causes
Heavy electrical heat
loads
Inadequate heat paths
Insufficient cooling or
lubrication when loads
and speed are excessive
Overheating
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Overheating
Remedies
Thermal or overload
controls
Adequate heat paths
Supplemental cooling
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Symptoms
Typically a crack spreads
evenly in the
circumferential direction,
with several fractured
pieces often originating
With axial load, fracturesusually occur a little
beyond the middle of the
raceway
Outside outer ring shows
irregular load pattern
Outer Ring Fracture
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Causes
Poor support of the rings
in the bearing housing
Outer Ring Fracture
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Outer Ring Fracture
Remedies
Improvement in bearing
mounting
Follow mounting instructions
for appropriate
recommendations
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Misalignment
Symptoms
A wear path not parallel
to raceway edges on the
raceway of the no
rotating ring
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Causes
Bent shafts
Burrs or dirt on shaft orhousing shoulders
Shaft threads that are not
square with shaft seats
Locking nuts with faces
that are not square to the
thread axis
Misalignment
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Misalignment
Remedies
Inspect shafts and
housings for run-out of
shoulders and bearing
seats
Use single point-turned
or ground threads onnon-hardened shafts and
ground threads only on
hardened shafts
Use precision
grade locknuts
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Symptoms
Spotted smear marks
Roughening of rollingelements or raceways
Slippage Tracks
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Slippage Tracks
Causes
Rolling elements slide on
the raceways when the load
is low and lubrication ispoor
Occasionally occurs if load
zones are too short, causing
rolling elements to
Also, fast changes in speed
brake in the unloaded zone
and accelerate again when
entering the load zone
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Slippage Tracks
Remedies
Select bearings with
lower load carrying
capacity
Preload bearings
Reduce bearing
clearance
Improve lubrication
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Tight Fits
Symptoms
A heavy rolling element
wear path in the bottom
of the raceway
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Causes
Excessive loading of the
rolling elements when
interference fits exceed
the radial clearance at
operating temperatures
Continued operationunder such conditions
leads to rapid wear and
fatigue
Tight Fits
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Tight Fits
Remedies
Decrease total
interference with better
matching of bearings to
shafts and housings
Consider operating
temperatures
Increased radial
clearance in bearing
selection
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22Bearing failure & Troubleshooting M25_Lubrication Management
DEAHolcim Group Support
Axial Cracks
Symptoms
Inner ring partly orcompletely cracked in the
axial direction
Slightly rounded fracturededges indicate that thefracture originated during
operation and was cycled(cracked edges may breakoff after prolongedoperation)
Sharp edged cracks indicatefracture during dismounting
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Axial Cracks
Causes
Bearing slippage
Rotation of inner ring onthe shaft
Inadequate lubrication
Too tight of fit to shaft
Grooved shaft
Out-of-roundness
Grazing against
surrounding parts
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Axial Cracks
Remedies
Improve lubrication with
additives or increased oil
quantities
Select suitable fit
Avoid grazing
Provide for better seating
conditions
Consider special heat
treatment for rings
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DEAHolcim Group Support
Symptoms
Often referred to as spalling;
indicated by the fracture of
the running surfaces andsubsequent removal of small
discrete particles of material
from the inner ring, outer ring
or rolling elements Spalling is progressive, and
once initiated will spread with
continued operation
Always accompanied by a
noticeable increase in
vibration
Normal Fatigue
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Causes
Bearing has remained in
operation beyond its
calculated fatigue life
Normal Fatigue
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Remedies
Replace the bearing
and/or consider
redesigning to use abearing with a greater
calculated fatigue life
Normal Fatigue
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True Brinelling
Symptoms
Brinell marks appear as
indentations in the
raceways, increasingbearing vibration (noise)
Severe brinell marks can
cause premature fatiguefailure
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True Brinelling
Causes
Static overload of the
bearing
Severe impact to the
bearing
Using a hammer to install
the bearing Dropping or striking
assembled equipment
Pressing a bearing onto the
shaft by applying force
to the outer ring
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Remedies
Observe static load
ratings in making bearing
selection
Install bearings using
appropriate equipment
and by applying forceonly to the ring being
press-fitted
True Brinelling
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Contamination
Symptoms
Denting of rolling
elements and raceways,
causing vibration
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Contamination
Causes
Air-born dust, dirt or
abrasive substances
from contaminated workareas
Dirty hands or tools
Foreign matter inlubricants or cleaning
solutions
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Remedies
Clean work areas, tools,
fixtures and hands reduce
the risks
Isolate bearing assembly
area from any grinding
operations
Leave bearings in their
original packaging until time
of installation
For contaminated operatingenvironments,sealing
arrangements should be
considered
Contamination
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Symptoms
Discolored rolling
elements (blue/brown)
and rolling elementtracks
Excessive wear of rolling
elements, rings, andcages follow, resulting in
overheating and
catastrophic
failure
Lubricant Failure
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Lubricant Failure
Causes
Restricted lubricant flow
Excessive temperaturesthat degrade the lubricant
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Lubricant Failure
Remedies
Use of the appropriate
and correct amount of
lubricant
Ensure proper bearing fit
Control preload to reduce
bearing temperatures
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Corrosion
Symptoms
Corrosion results from the
chemical attack on bearing
materials by hostile fluids oratmospheres
Red/brown stains or
deposits on rolling
elements, raceways orcages
Increased vibration followed
by wear
Increase in radial clearance
or loss of preload
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Causes
Exposing bearings to
corrosive fluids or
atmospheres
Corrosion
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Corrosion
Remedies
Divert corrosive fluids
away from bearing areas
Use integrally sealed
bearings
Consider external seals
for particularly hostileenvironments
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Fluting
Symptoms
Brownish marks parallel
to the axis on a large part
of the raceway, orcovering the entire
raceway circumference
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Fluting
Causes
Electrical Fluting occurs
when a current is passed
through the bearing,instead of to a grounded
source.
Constant passage ofalternating or direct
current
Even low currents
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Fluting
Remedies
Prevent currents from
flowing through the
bearing by means ofgrounding or insulating
Use current insulated
bearings
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Excessive Loads
Symptoms
Heavy rolling element wear
paths
Evidence of overheating
Widespread fatigue areas
(spalling)
Symptoms are the same asnormal fatigue, although
showing heavier ball wear
paths, greater evidence of
overheating, and a morewidespread and deeper
spalling (fatigue area)
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Causes
Excessive loading of the
bearing
Excessive Loads
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Excessive Loads
Remedies
Reduce the load
Redesign using a bearingwith greater capacity
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Lip Fractures
Symptoms
Supporting lips are partly
or completely broken off
or cracked
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Lip Fractures
Causes
Axial load unacceptably
high
Lip insufficiently
supported
Axial shock load
Mounting damage
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Lip Fractures
Remedies
Ensure good lip support
design
Keep load within
specified limits
Observe appropriate
mounting instructions& procedures
F tti
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Fretting
Symptoms
Fretting, the generation
of fine metal particles
which oxidize, leaving adistinctive brown color
Wear at the fitting
surfaces causing noise &runout problems
Possible fatigue fracture
Possible disturbance offloating bearing function
F tti
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Fretting
Causes
Micro motion between
fitted parts where the fits
are too loose in relationto the acting forces
Fretting
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Fretting
Remedies
Follow mounting
instructions for
appropriate fitrecommendations
S i
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Seizure
Symptoms
Partial or large-area
welding and deep
scratches in the lip androller face areas
Also lubricant coking in
this area
Seizure
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Seizure
Causes
Inadequate lubrication
with high loads and high
speeds (quantity oroperating viscosity of
lubricant too low)
Inadequate lubricationwith high loads
and low speeds (when
there is no hydrodynamic
lubricating film betweenthe roller face and lip)
Seizure
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Seizure
Causes
Detrimental preload due
to heat expansion
Skewing of rollers due to
raceway wear or ring
tilting
Axial load too high oncylindrical roller bearings
Axial preload too high for
out-of-square matingsurfaces
Seizure
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Seizure
Remedies
Improve lubrication
(increase viscosity, EP
additives, increasequantity)
Ensure correct
adjustment of bearings
Reverse Loading
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Reverse Loading
Symptoms
Balls will show a grooved
wear band caused by the
ball riding over the outeredge of the raceway
Failure mode is very
similar to that of heavyinterface (tight) fits.
Reverse Loading
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Reverse Loading
Causes
Angular contact ball
bearings are designed to
accept an axial load inone direction only
When loaded in the
opposite direction, the
elliptical contact area on
the outer ring is truncated
by the low shoulder on
that side of the outer ring
Reverse Loading
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Reverse Loading
Causes
Result is excessive
stress and an increase in
temperature, followed byincreased vibration and
early failure
A thrust load applied to
the wrong bearing face
results in a wear band on
the balls.
Reverse Loading
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Bearing failure & Troubleshooting M25_Lubrication ManagementDEA
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Reverse Loading
Remedies
Ensure proper installation
of angular contact
bearings