[PDF] - Outline Outline Fluid Film Thrust Bearings: Fluid Film Thrust PDF Document

SLIDE 1

Fluid Film Thrust Bearings: Fluid Film Thrust Bearings: Fundamentals, Damage Fundamentals, Damage Evaluation, & Repair Evaluation, & Repair

Pioneer Motor Bearing Pioneer Motor Bearing May 2006 May 2006

VIBRATION INSTITUTE MEETING VIBRATION INSTITUTE MEETING CHARLOTTE, NC CHARLOTTE, NC

Outline Outline

n nBasic Design Criteria

Basic Design Criteria

n nThrust Bearing Monitoring

Thrust Bearing Monitoring

n nDamage investigation

Damage investigation

n nDamage mechanisms

Damage mechanisms

n nInspection

Inspection

n nRepair

Repair

History History

n n Without question

Without question the most the most significant significant mechanical mechanical invention in the invention in the world was: world was:

The The Wheel Wheel

History History

n n However, almost

However, almost immediately upon immediately upon discovery of the discovery of the wheel, the need wheel, the need for bearings was for bearings was also discovered: also discovered:

History History

n n Which has

Which has led to one led to one

f the most
f the most

elusive elusive searches in searches in human human history history

History History

n n As one can

As one can

bserve from this
bserve from this

wooden wheel wooden wheel dating to 2700 dating to 2700 BC, axels where BC, axels where used to allow used to allow support by radial support by radial and thrust and thrust bearings: bearings:

SLIDE 2

Load Orientations: Load Orientations: radial/thrust

radial/thrust

Slide Slide 8 8

Thrust Bearing Thrust Bearing

n nSupport axial load from the process

Support axial load from the process

n ne.g. Water or steam pressure

e.g. Water or steam pressure

n nThrust runner surface

Thrust runner surface

n nGenerally flat

Generally flat (<13

(<13 µ µm = 0.0005 m = 0.0005” ”) )

n n 16

16 µ µin RMS in RMS n nThrust bearing

Thrust bearing

n nGenerally circumferential segments

Generally circumferential segments

n nTend to be

Tend to be “ “square square” ” -

length=width

length=width

n nTrade

Trade-

off
ff

n nLarger loaded area gives more friction loss

Larger loaded area gives more friction loss

Thrust Clearance Thrust Clearance

n nTypical operating clearance

Typical operating clearance

Human hair about Human hair about 75 75 µ µm (0.003 m (0.003” ”) diameter ) diameter

Typical operating clearance Typical operating clearance about 25 about 25 µ µm (0.001 m (0.001” ”). ).

Thrust Load Thrust Load

n n Load capacity based on

Load capacity based on

n n Hydrodynamic pressure profile

Hydrodynamic pressure profile

n n Pad area

Pad area

n n Nominally

Nominally

n n Reduced by grooving

Reduced by grooving

( )

2 2

* * 25 . ID OD Area − = π

Thrust Bearing Designs Thrust Bearing Designs

n nFlat Washer

Flat Washer

n nFlat

Flat Babbitted Babbitted Face With Grooves Face With Grooves

n nTaper

Taper-

Land

Land Babbitted Babbitted Face Face

n nTilting Pad Thrust Bearing

Tilting Pad Thrust Bearing

n nEqualized Tilting Pad Thrust

Equalized Tilting Pad Thrust Bearing Bearing

Flat Washers Flat Washers

n n Simple but useful

Simple but useful

nly with minimal
nly with minimal

speed and load speed and load conditions conditions

n n Grease lubricated

Grease lubricated

SLIDE 3

“ “Bumper Bumper” ” Thrust Thrust

Babbitted Babbitted axial surfaces to resist motion of shaft collars. axial surfaces to resist motion of shaft collars. Babbitted Babbitted surface may have radial pockets or grooving. surface may have radial pockets or grooving.

Flat Flat Babbitted Babbitted Thrust Face Thrust Face with Grooves with Grooves

n n Useful as a bumper,

Useful as a bumper,

r locating bearing
r locating bearing

n n Oil or grease

Oil or grease lubricated lubricated

n n No theoretical load

No theoretical load capacity capacity

n n Practical capacity

Practical capacity around 50 to 75 PSI around 50 to 75 PSI

“ “Bumper Bumper” ” Thrust Thrust

Radial Radial grooves grooves enhance load enhance load capacity. capacity.

Taper Taper-

Land Thrust Bearing

Land Thrust Bearing

n n Optimized for only

Optimized for only

ne speed and load
ne speed and load

combination combination

n n Taper for oil wedge

Taper for oil wedge formation is formation is machined into the machined into the bearing surface bearing surface

n n Alignment is critical

Alignment is critical to operation to operation

n n Practical load limit

Practical load limit 150 to 225 PSI 150 to 225 PSI

Simple Tapered Simple Tapered-

Land Thrust

Land Thrust

Compound Tapered Compound Tapered-

Land Thrust

Land Thrust

Taper is steeper Taper is steeper at the inner at the inner diameter than diameter than at the outer at the outer diameter. diameter. Taper is Taper is generally generally 0.003 0.003” ”-

0.007

0.007” ”. . Land region is Land region is visible. visible.

SLIDE 4

Fluid Fluid-

film Thrust Bearing

film Thrust Bearing

n nAnnulus controls axial position.

Annulus controls axial position.

n nMaximum load capacity

Maximum load capacity

Tilting Tilting-

pad

pad bearing bearing

Tilting Pad Thrust Bearing Tilting Pad Thrust Bearing

n n Self Optimizing based

Self Optimizing based

n applied load and
n applied load and

speed speed

n n Maximum Flexibility

Maximum Flexibility re: potential re: potential modifications modifications

n n Alignment is critical

Alignment is critical

n n Load Capacity in

Load Capacity in excess of 600 PSI excess of 600 PSI

Tilting Pad Thrust Bearings Tilting Pad Thrust Bearings

Equalizing linkages correct for housing skew. Equalizing linkages correct for housing skew. Equalizing linkages do not correct for rotating collar skew. Equalizing linkages do not correct for rotating collar skew.

Ref: Kingsbury literature Ref: Kingsbury literature

Non Non-

Equalizing Support

Equalizing Support

Ref: Constantinescu, p. 354. Ref: Constantinescu, p. 354.

Non Non-

Equalized Bearing

Equalized Bearing

Self Equalizing Tilting Pad Self Equalizing Tilting Pad Thrust Bearings Thrust Bearings

n n Maximum capacity in

Maximum capacity in given space given space

n n Self optimizing oil

Self optimizing oil film film

n n Can accommodate

Can accommodate collar to housing collar to housing misalignment misalignment

n n Not designed for

Not designed for dynamic dynamic misalignment misalignment

n n Load Capacity in

Load Capacity in excess of 600 PSI excess of 600 PSI

SLIDE 5

Equalizing Linkages Equalizing Linkages

Ref: Constantinescu, p. 354. Ref: Constantinescu, p. 354.

Intent is to Intent is to equally load equally load each of the each of the thrust pads in thrust pads in spite of spite of variations in variations in pad thickness or pad thickness or misalignment of misalignment of the housing to the housing to the runner. the runner.

Anti Anti-

Rotation Pins

Rotation Pins

Provides: Provides: Locates shell in housing Locates shell in housing

Circumferential

Circumferential Prevent rotation of the cage Prevent rotation of the cage in the housing. in the housing.

Combined Journal Thrust Combined Journal Thrust

Lobed journal Lobed journal bearing bearing Tapered thrust Tapered thrust bearing bearing

Oil Distribution Geometry Oil Distribution Geometry

OIL INLET OIL INLET HOLE HOLE

Radial groove Radial groove Axial groove Axial groove

Bleeder Bleeder Bleeders Bleeders

Thrust Bearing Flows Thrust Bearing Flows

Ref. Kingsbury
Ref. Kingsbury

sales literature, sales literature, EQH EQH-

1.

1.

Rotation Rotation

Tilting Pad Thrust Bearings Tilting Pad Thrust Bearings

Ref: Kingsbury literature Ref: Kingsbury literature

SLIDE 6

So, how much load can So, how much load can my my bearing take? bearing take?

n n This depends

This depends

n where you
n where you

are operating are operating within the within the regime of the regime of the bearing bearing performance performance parameters parameters

n n No, I am not a

No, I am not a lawyer lawyer

What can be done to What can be done to increase load capacity? increase load capacity?

n nFirst, understand the shortcomings

First, understand the shortcomings

f the existing bearing
f the existing bearing

n nSecond, consider modifications to

Second, consider modifications to the operating parameters the operating parameters

n nThird, consider an upgrade to the

Third, consider an upgrade to the basic bearing design basic bearing design

Deal with low speed wear Deal with low speed wear

n n Hydrostatic lift system to provide

Hydrostatic lift system to provide hydrostatic oil films where hydrodynamic hydrostatic oil films where hydrodynamic

il films may not otherwise be present
il films may not otherwise be present

n n Start up operation

Start up operation

n n Turning gear operation

Turning gear operation

n n Some emergency conditions

Some emergency conditions

n n Per DIN 31652 part 3 consider hydrostatic lift

Per DIN 31652 part 3 consider hydrostatic lift where startup loads exceed 2.5 where startup loads exceed 2.5-

3.0

3.0 MPa MPa (363 (363-

435

435 psi psi) )

n n May be required for lower loads

May be required for lower loads

Hydrostatic Lift Systems Hydrostatic Lift Systems

n nInject high pressure oil (typically >

Inject high pressure oil (typically > 1000 1000 psi psi) at the location of the ) at the location of the highest loading highest loading

n nHydrostatic film is developed

Hydrostatic film is developed through pressure, film thickness is through pressure, film thickness is controlled by flow controlled by flow

n nQuite often, many bearings are fed

Quite often, many bearings are fed by a common high pressure header by a common high pressure header

Hydrostatic Lift System Hydrostatic Lift System

n nIntroduce externally

Introduce externally-

pressurized oil

pressurized oil into bearing cavity for operation at into bearing cavity for operation at low surface speeds and high loads low surface speeds and high loads

n n Forms hydrostatic bearing on lower half

Forms hydrostatic bearing on lower half

Hydrostatic Lift System Hydrostatic Lift System

Hydrostatic lift in tilting pad thrust shoes. Hydrostatic lift in tilting pad thrust shoes.

SLIDE 7

Sample Hydrostatic Lift Oil System Sample Hydrostatic Lift Oil System

Schematic of Schematic of Turbine Turbine-

Generator

Generator Hydrostatic Hydrostatic Lift System Lift System

Each radial bearing #3 Each radial bearing #3-

8 has a

8 has a separate pressurized hydrostatic separate pressurized hydrostatic-

lift supply (1500 psig), separate

lift supply (1500 psig), separate supply pump with a gravity (or supply pump with a gravity (or slight vacuum) drain back to the slight vacuum) drain back to the reservoir. reservoir.

OK smart guy, I OK smart guy, I’ ’ve already got ve already got a tilting pad thrust bearing, a tilting pad thrust bearing, Now what? Now what?

n nConsider upgrading specific design

Consider upgrading specific design features of the assembly features of the assembly

n nDirected lubrication

Directed lubrication

n nAlternative materials

Alternative materials

n nOffset pivots

Offset pivots

Effect of Pivot Offset Effect of Pivot Offset

Effect of Chrome Effect of Chrome-

Copper Alloy

Copper Alloy Backing Material Backing Material

Thrust Bearing Monitoring Thrust Bearing Monitoring

n nTemperature

Temperature

n nLoad

Load

n nThrust Collar Position

Thrust Collar Position

Thrust Temperature Thrust Temperature Monitoring Monitoring

n nEmbedded Sensors

Embedded Sensors

n nThermocouples

Thermocouples

n nRTD

RTD’ ’s s

n nOil Inlet and Exit Temperature

Oil Inlet and Exit Temperature

SLIDE 8

Tilt Tilt-

Pad Thrust Profiles

Pad Thrust Profiles

Ref. Kingsbury
Ref. Kingsbury

sales literature, sales literature, EQH EQH-

1.

1.

Temperature profiles Temperature profiles show influence of show influence of pressure peak over the pressure peak over the pivot (dashed circle), as pivot (dashed circle), as well as radial and well as radial and circumferential flow. circumferential flow.

Embedded Sensors Embedded Sensors

n n Proper Location

Proper Location

Thrust Load Measurement Thrust Load Measurement

n n Basic Bearing

Basic Bearing Design Design

Thrust Load Measurement Thrust Load Measurement

n n Leveling Plates

Leveling Plates

Thrust Load Measurement Thrust Load Measurement

n n Strain

Strain Gage Gage Load Cell Load Cell

Thrust Position Measurement Thrust Position Measurement

n nEddy Current Probes

Eddy Current Probes

n nDual Voting

Dual Voting

SLIDE 9

Thrust Position Measurement Thrust Position Measurement

Damage Investigation Damage Investigation

n nGeneric Elements

Generic Elements

n nVisual examination

Visual examination

n nBackground information

Background information

n nPhotographic records

Photographic records

n nEvent reconstruction

Event reconstruction

n nLaboratory analysis

Laboratory analysis

Damage Investigation Damage Investigation

n n Visual

Visual Examination Examination

“ “Say, is all that Say, is all that babbitt supposed babbitt supposed to be on the to be on the bottom of the bottom of the bearing housing bearing housing like that? like that?” ”

Damage Investigation Damage Investigation

n nGeneric Elements

Generic Elements

n nVisual examination

Visual examination

n nBackground information

Background information

n nPhotographic records

Photographic records

n nEvent reconstruction

Event reconstruction

n nLaboratory analysis

Laboratory analysis

Visual Examination Visual Examination

Where is the damage? Where is the damage?

n nBabbitt Surface

Babbitt Surface

n nCentered over pivot

Centered over pivot

n nMore toward trailing edge

More toward trailing edge

n nMore toward leading edge

More toward leading edge

n nSupporting structure

Supporting structure

n nLeveling plates

Leveling plates

n nThrust collar

Thrust collar

SLIDE 10

Babbitt Surface Damage Babbitt Surface Damage

Damage located primarily along the trailing edge is indicative o Damage located primarily along the trailing edge is indicative of debris, f debris, electrolysis, or other trauma that occurred while the bearing wa electrolysis, or other trauma that occurred while the bearing was s

therwise operating in a normal condition
therwise operating in a normal condition

Babbitt Surface Damage Babbitt Surface Damage

Damage located primarily opposite the pivot is indicative the be Damage located primarily opposite the pivot is indicative the bearing aring

perating in an overloaded condition
perating in an overloaded condition

Babbitt Surface Damage Babbitt Surface Damage

Damage located primarily along the leading edge is indicative of Damage located primarily along the leading edge is indicative of a lack a lack

f lubrication, either during start up, or during operation
f lubrication, either during start up, or during operation

Support Structure Damage Support Structure Damage

n nDamage to the leveling plates, base

Damage to the leveling plates, base ring, or other support structure is ring, or other support structure is usually indicative of thrust collar usually indicative of thrust collar runout runout problems problems

n nCollar may be installed improperly,

Collar may be installed improperly,

r may have come loose in service
r may have come loose in service

Collar Damage Collar Damage

n nCircumferential scoring or

Circumferential scoring or scratching of the thrust collar is scratching of the thrust collar is usually indicative of debris in the oil usually indicative of debris in the oil system system

Damage Mechanisms Damage Mechanisms

n nMechanisms are the same as those

Mechanisms are the same as those covered earlier by Dr. Branagan covered earlier by Dr. Branagan

n nSpecific thrust bearing photographs

Specific thrust bearing photographs may help may help

SLIDE 11

Minor Overload Minor Overload

Babbitt Fatigue Babbitt Fatigue

Overheating Overheating

Gross Overheating Gross Overheating

Anisotropy Anisotropy

Tin / Copper Migration Tin / Copper Migration

SLIDE 12

Pivot Fretting Pivot Fretting

Leveling Plate Fretting Leveling Plate Fretting

Babbitt Erosion Babbitt Erosion

Bearing Inspection Bearing Inspection

n nBearing Surface

Bearing Surface

n nBearing Subsurface

Bearing Subsurface

n nThrust Collar

Thrust Collar

n nAssembled End Play

Assembled End Play

Thrust Bearing Surface Thrust Bearing Surface

n nPortion of bearing designed to carry

Portion of bearing designed to carry the load must be clean and flat the load must be clean and flat

n nInspect for embedded debris with a

Inspect for embedded debris with a single edged razor blade single edged razor blade

n nInspect surface with straight edge

Inspect surface with straight edge

n nInspect contact with Prussian

Inspect contact with Prussian bluing with a calibrated plate and bluing with a calibrated plate and finally with the mating thrust collar finally with the mating thrust collar

Thrust Bearing Subsurface Thrust Bearing Subsurface

n nUltrasonic Inspection

Ultrasonic Inspection

n nDye Pen Inspection

Dye Pen Inspection

n nBrass Dowel Ring Test

Brass Dowel Ring Test

SLIDE 13

Thrust Collar Inspection Thrust Collar Inspection

n nSurface finish 16 RMS or better

Surface finish 16 RMS or better

n nSurface flatness less than .001 inch

Surface flatness less than .001 inch

n nAssembled

Assembled runout runout less than .001 less than .001 TIR TIR

Assembled Assembled Runout Runout Check Check

n nCan not be measured with a single

Can not be measured with a single indicator as rotor float will impact indicator as rotor float will impact measurement measurement

n nTemporary blocking may be

Temporary blocking may be required to limit rotor float during required to limit rotor float during inspection inspection

n nRequires 2

Requires 2 Mag Mag base indicators with base indicators with sufficient travel to stay in contact sufficient travel to stay in contact with collar face with collar face

Indicator position Indicator position

Typical Measurement record Typical Measurement record

0.0010 0.0020 0.0030 360 0.0000

0.0010
0.0010

315

0.0010
0.0010
0.0020

270

0.0020

0.0025 0.0005 225

0.0010

0.0020 0.0010 180 0.0000 0.0030 0.0030 135 0.0010 0.0050 0.0060 90 0.0020

0.0005

0.0015 45 0.0010

0.0010

0.0000 A-B B A Rotation

Column of calculated A Column of calculated A-

B values gives twice the

B values gives twice the TIR TIR runout runout readings for the thrust collar. In readings for the thrust collar. In this example, the collar is running out .002 TIR this example, the collar is running out .002 TIR

Assembled End Play Assembled End Play

n nBest to first measure available

Best to first measure available space and stacked height of the space and stacked height of the bearing assemblies bearing assemblies

n nDifference should be the assembled

Difference should be the assembled end play end play

n nAfter assembly, bump test the rotor

After assembly, bump test the rotor to confirm measurement to confirm measurement

Repairs Repairs

n nMany minor thrust bearing repairs

Many minor thrust bearing repairs can be accomplished on site can be accomplished on site

n nThe level of repair that should be

The level of repair that should be attempted is directly proportional to attempted is directly proportional to the experience level of the the experience level of the technicians available technicians available

SLIDE 14

Babbitt Surface Repairs Babbitt Surface Repairs

n n Minor imperfections

Minor imperfections can be removed by can be removed by lapping or scraping lapping or scraping

n n Larger scratches can

Larger scratches can be repaired by first be repaired by first locally locally puddling puddling babbitt and followed babbitt and followed by by peening peening and then and then lapping or scraping lapping or scraping

Babbitt Babbitt Puddling Puddling

Hand Scraping Hand Scraping

Power Scraping Power Scraping

Thrust Collar Repair Thrust Collar Repair

n nMinor damage and glazing can be

Minor damage and glazing can be repaired by hand stoning repaired by hand stoning

n nUse a fine 600 grit oil stone

Use a fine 600 grit oil stone

n nMore serious repairs can be

More serious repairs can be corrected by turning, lapping, or corrected by turning, lapping, or grinding grinding

n nMany of these operations can be

Many of these operations can be conducted in place conducted in place

Conclusions Conclusions

n nRemember that that the babbitt

Remember that that the babbitt surface is a SOFT, sacrificial layer. surface is a SOFT, sacrificial layer.

n nLook at your babbitt surface to

Look at your babbitt surface to better understand the likely cause better understand the likely cause

f the bearing damage and reduce
f the bearing damage and reduce

re re-

occurrence.
ccurrence.

n nRemanufacture (repair) or redesign

Remanufacture (repair) or redesign bearing depending on the nature, bearing depending on the nature, severity, and probability of future severity, and probability of future damage. damage.