wear mechanisms applied to lifeboat slipway...

Wear Mechanisms applied to Wear Mechanisms applied to

Lifeboat Slipway LaunchesLifeboat Slipway LaunchesB. Thomas*B. Thomas*aa, M. , M. HadfieldHadfieldaa, S. , S. AustenAustenbb

Sustainable Product Engineering Research Centre, Sustainable Product Engineering Research Centre,

Bournemouth University, Bournemouth University, UKUK

aa Bournemouth University, Bournemouth University, bb Royal National Lifeboat InstitutionRoyal National Lifeboat Institution

* Corresponding author. * Corresponding author. thomasb@bmth.ac.ukthomasb@bmth.ac.uk

Presentation StructurePresentation Structure

�� Overview of lifeboat slipway launchingOverview of lifeboat slipway launching

�� Friction and Wear problems on lifeboat launch Friction and Wear problems on lifeboat launch slipwaysslipways

�� Experimental MethodologyExperimental Methodology

�� Test rig designTest rig design

�� Tests ScheduleTests Schedule

�� ResultsResults

�� ConclusionsConclusions

�� Recommendations & future workRecommendations & future work

Tamar Class LifeboatTamar Class Lifeboat�� The Tamar slipThe Tamar slip--launched lifeboat is designed as a launched lifeboat is designed as a

replacement to the Tyne class lifeboat. It is significantly replacement to the Tyne class lifeboat. It is significantly larger and heavier than the Tyne and this has meant new larger and heavier than the Tyne and this has meant new slipways and boathouses have had to be built to slipways and boathouses have had to be built to accommodate it.accommodate it.

�� The Tamar currently operates from new boathouses and The Tamar currently operates from new boathouses and slipways at Tenby, Padstow and Cromerslipways at Tenby, Padstow and Cromer

20061982Year Introduced

7

240n. miles

Steel

26 - 27 tonnes

17.6 knots

1.26m

4.48m

14.3m

Tyne Tamar

6Crew

250n. milesRange

FRPConstruction

~ 35 tonnesDisplacement

25 knots Speed

1.35mDraught

5mBeam

16mLength

Slip-launched Lifeboats

Lifeboat Slipway LaunchLifeboat Slipway Launch

Typical Slipway Typical Slipway --

PadstowPadstow

19mm Jute/Phenolic composite panels

Steel rollers

�� Padstow has recently received Padstow has recently received a new boathouse in order to a new boathouse in order to accommodate the new Tamar accommodate the new Tamar class slipclass slip--launched lifeboatlaunched lifeboat

�� The slipway layout is typical of The slipway layout is typical of the next generation boathouses the next generation boathouses and slipways being built for the and slipways being built for the TamarTamar

�� The slipway consists of an The slipway consists of an upper section of steel rollers upper section of steel rollers and a lower section lined with and a lower section lined with lowlow--friction 19mm thick friction 19mm thick Jute/Graphite infused Phenolic Jute/Graphite infused Phenolic resin Composite panelsresin Composite panels

Slipway Lining MaterialsSlipway Lining Materials

�� Weather Treated Weather Treated Wood Wood –– Traditional Traditional c.1850c.1850

�� Nickel/Chromium Nickel/Chromium carbide coated Steel carbide coated Steel –– c.1980c.1980

�� Jute/Graphite Infused Jute/Graphite Infused Phenolic Resin Phenolic Resin Composite Composite –– c.1996 c.1996

Jute/Graphite Infused Phenolic Resin CompositeJute/Graphite Infused Phenolic Resin Composite

- Alignment ropes - Winch cableLifeboat alignment and attachment of winch cable – alignment ropes and winch cable indicated

Lifeboat Slipway RecoveryLifeboat Slipway Recovery

Lifeboat Slipway RecoveryLifeboat Slipway Recovery

- Quarter stop ropes - Winch cableFig. 3.1.2i: Haul Stage – Rope quarter stops and winch cable keel attachment position shown

Problems..Problems..

�� High friction is often present along the slipway panels High friction is often present along the slipway panels ––this is particularly apparent as high winch loading during this is particularly apparent as high winch loading during lifeboat recoverylifeboat recovery

�� Currently marine grease or in some cases other Currently marine grease or in some cases other lubricants, are manually applied to the slipway before lubricants, are manually applied to the slipway before each launch and recoveryeach launch and recovery

�� Due to the exposed nature of the slipway and the Due to the exposed nature of the slipway and the unpredictable intervals between lifeboat launches the unpredictable intervals between lifeboat launches the lubricant grease can be washed away, dry out or lubricant grease can be washed away, dry out or become contaminated with wind blown sand etc. become contaminated with wind blown sand etc. resulting in unpredictable friction coefficientsresulting in unpredictable friction coefficients

�� Severe cracking and wear of composite slipway panels Severe cracking and wear of composite slipway panels has been observed at both Tenby and Padstow requiring has been observed at both Tenby and Padstow requiring regular replacementregular replacement

TE92 Rotary Tribometer TE92 Rotary Tribometer -- SchematicSchematic

TE92 Rotary TribometerTE92 Rotary Tribometer

�� Original geometry is designed Original geometry is designed to measure wear in ball to measure wear in ball bearingsbearings

�� Geometry is modified to a Geometry is modified to a ring/disc arrangement to mirror ring/disc arrangement to mirror the slipway/keel situationthe slipway/keel situation

�� New geometry design features New geometry design features a self levelling pin to ensure a self levelling pin to ensure even contact through strokeeven contact through stroke

�� Tests are designed to Tests are designed to incorporate dwell effects to incorporate dwell effects to simulate launch intervalssimulate launch intervals

Tests ScheduleTests Schedule

801000DryCR4

601000DryCR3

401000DryCR2

201000DryCR1

Contact Pressure (N)

Test Duration (#passes)

LubricantTest ID

Contact Force Tests

Wear Tests

201000Biogrease #1LR6

201000Silicon Microsphere Lub.LR5

201000Marine GreaseLR4

201000FreshwaterLR3

201000SeawaterLR2

201000DryLR1

Contact

Pressure (N)

Test Duration

(#passes)LubricantTest ID

TE92 Jute/Phenolic Composite: Wear Volume vs. Contact Pressure

0

5

10

15

20

25

30

35

40

20 40 60 80

Contact force (N)

We

ar

Vo

lum

e (

mm

3)

TE92 Jute/Phenolic Composite: Wear Coefficient vs. Contact Pressure

1E-12

1E-11

20 40 60 80

Contact force (N)

Wear

Co

eff

icie

nt

TE92 Jute/Phenolic Composite: Wear Volume vs. Lubricant Regime

0

5

10

15

20

25

30

35

40

45

50

Seawater Freshwater Silicon

Microball

Lub.

Marine

Grease

Biogrease Dry

We

ar

vo

lum

e (

mm

3)

TE92 Jute/Phenolic Composite: Wear Coefficient vs. Lubricant Regime

0

1E-12

2E-12

3E-12

4E-12

5E-12

6E-12

7E-12

8E-12

9E-12

Seawater Freshwater Silicon

Microball

Lub.

Marine

Grease

Biogrease Dry

We

ar

Co

eff

icie

nt

Case studiesCase studies

�� Slipways were examined at Selsey, Tenby, Slipways were examined at Selsey, Tenby, SwanageSwanage, Padstow, , Padstow, Bembridge, Sennen Cove and The LizardBembridge, Sennen Cove and The Lizard

�� Jute/Phenolic composite sections at Selsey, Bembridge, Padstow, Jute/Phenolic composite sections at Selsey, Bembridge, Padstow, Tenby and Sennen Cove were all found to have similar wear Tenby and Sennen Cove were all found to have similar wear patternspatterns

BembridgeBembridge SelseySelsey

PadstowPadstow TenbyTenby

Case StudiesCase Studies

Fig #: Wear map for 1mm angled offset – Original panel (top), Chamfer panel (bottom)

1.287E-03 8.579E-04 4.289E-04 1.072E-04

1.072E-03 6.434E-04 2.145E-04 4.289E-05

�� Slipways panels were found to be longitudinally misalignedSlipways panels were found to be longitudinally misaligned

�� Misalignment ranged up to 4mm with an average of 0.88mmMisalignment ranged up to 4mm with an average of 0.88mm

�� FEA simulations were conducted to show the effects of FEA simulations were conducted to show the effects of panel misalignment on panel stress concentrationspanel misalignment on panel stress concentrations

Fig #: Parallel Panel Misalignment Model

Offset Distance

0.E+00

1.E+06

2.E+06

3.E+06

4.E+06

5.E+06

6.E+06

0 1 2 3 4 5

Offset Distance (mm)

Vo

n M

ises M

ax

. S

tress (

N/m

2)

0.E+00

1.E+05

2.E+05

3.E+05

4.E+05

5.E+05

6.E+05

7.E+05

8.E+05

0 1 2 3 4 5

Offset Distance (mm)

Fri

cti

on

Fo

rce

Ma

x.

(N)

0.0E+00

5.0E-04

1.0E-03

1.5E-03

2.0E-03

2.5E-03

3.0E-03

0 1 2 3 4 5

Offset Distance (mm)

We

ar

Ma

x.

(mm

/m s

lid

e)

Chart #: Parallel Panel Offset Comparison

FE AnalysisFE Analysis

FEA simulation vs. typical worn and misaligned jute fibre/phenolic resin composite lining section from Tenby slipway

FE AnalysisFE Analysis

84.58Dry

56.30Biogrease

49.88Marine Grease

22.65Silicon Microball Lub.

18.66Freshwater

16.80Seawater

Eq. No of Launches & Recoveriesfor 19mm Wear Scar Depth

Lubricant

Equivalent number of lifeboat launches/recoveries required to generate a 19mm wear scar on a 4mm parallel offset misaligned slipway panel by lubricant used

FE AnalysisFE Analysis

Concluding RemarksConcluding Remarks�� Under ideal conditions the wear coefficients between slipway panUnder ideal conditions the wear coefficients between slipway panels and els and

lifeboat keel are not sufficient to cause failure during the explifeboat keel are not sufficient to cause failure during the expected 2ected 2--year year lifespan of the panel.lifespan of the panel.

�� Real world slipways often exhibit misalignment between slipway pReal world slipways often exhibit misalignment between slipway panels.anels.

�� FEA shows that there a significant stress concentrations and FEA shows that there a significant stress concentrations and correspondingly wear, at these misalignments.correspondingly wear, at these misalignments.

�� This increase in wear due to stress concentrations is sufficientThis increase in wear due to stress concentrations is sufficient to explain to explain the high wear observed at Tenby and Padstow.the high wear observed at Tenby and Padstow.

�� The use of lubricants along the slipway should again have littleThe use of lubricants along the slipway should again have little effect effect under ideal conditions according to the test data. However, withunder ideal conditions according to the test data. However, with panel panel misalignment included the choice of lubricant may become more misalignment included the choice of lubricant may become more significant.significant.

�� Previous work has indicated that lubricants are necessary to meePrevious work has indicated that lubricants are necessary to meet the t the friction specification of the slipway.friction specification of the slipway.

�� It is therefore recommended to review and reIt is therefore recommended to review and re--fit the affected slipways to fit the affected slipways to reduce slipway panel misalignment.reduce slipway panel misalignment.

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