IO Mooring Intro

Mooring Design: Minimizing Failures

Pacific Marine Environmental Pacific Marine Environmental LaboratoryLaboratoryA leader in developing ocean observational systems to address NOAA’s mission

Overview:


• Scientific Mission?

• Pick a Platform Design

• Site Assessment: ‘The Big Three’

• Pick a Mooring Design

• Iterate on Mooring Design

• Mooring Modeling

• Bending

• Shock Loading

• Mooring Performance?

Designing for Success : Scientific Payload


Designing for Success : Site Assessment


The ‘Big’ Three:• Water Depth

• Currents

• Wave Conditions (slope)

Designing for Success : Water Depth


Designing for Success : Currents


Designing for Success : Waves


Designing for Success : Site Assessment


The ‘Big’ Three:•Water Depth

• Currents

• Wave Conditions (slope)

Other Considerations:• Site specific

(vandalism, wind, ice ,

marine life, etc)

Designing for Success: Picking a Mooring Design

Taught Line• ~0.985% of water depth

• Low Current Areas

• High Waves (minimizes shock Loading)

• Scientific Benefits: Instrument depth accuracy

• Requires very accurate water depth information

Designing for Success: Picking a Mooring Design

Slack Line• ~1.14 – 1.4 of water depth

• High Current Areas

• Waves: Issue with Shock Loading

• Large Watch Circle

Designing for Success: Mooring Modeling


WHOI CABLE• Freeware program: www.gobatconsulting.com/Cable

• Both Static and Dynamic Outputs

• ONLY as accurate as the data you input

• Accurate to ~10% if Currents are well known.

• NOT SUPPORTED

OrcaFlex• Expensive

• Supported

•ONLY as accurate as the data you input

http://www.gobatconsulting.com/Cable

Tools for Design: WHOI CABLECABLE Predicted Tension to Actual Deployment Tension @ KEO Buoy

9/27/2007 @ 0800

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2200

0 100 200 300 400 500 600 700 800 900 1000

Time

Tens

ion

(lbs) CABLE Predicted Data

Recorded Mean TensionRecorded Min TensionRecorded Max Tension

Need Material Data for Mooring ModelingPhysical Line Testing

Raw Tension-Strain

y = 3E+11x5 - 3E+10x4 + 1E+09x3 - 2E+07x2 + 225274x + 102.77R2 = 0.9976

y = 1E+11x5 - 1E+10x4 + 6E+08x3 - 1E+07x2 + 175886x + 123.42R2 = 0.999

y = 5E+10x5 - 7E+09x4 + 4E+08x3 - 9E+06x2 + 146163x + 93.145R2 = 0.9993

y = 6E+10x5 - 8E+09x4 + 4E+08x3 - 1E+07x2 + 155640x + 81.365R2 = 0.9994

y = 4E+08x5 - 1E+08x4 + 1E+07x3 - 1E+06x2 + 74358x + 95.943R2 = 0.9999

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-0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Strain (dL/L)

Load

Out

put (

lbs.

)

Test 1 Test 2 Test 3 Test 4 Test 5 Poly. (Test 3) Poly. (Test 5) Poly. (Test 4) Poly. (Test 2) Poly. (Test 1)

WHOI CABLE: Bali Site Study


Bali Current Profiles

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-0.2 0 0.2 0.4 0.6 0.8

Current Speed (m/s)

Wat

er D

epth

(m)

August 1989 @ 11.4 Deg. South

March 1992 @ 11.10 Deg. South

Bali Study Predicted Catenary

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Horizontal Distance frm Anchor (m)

Wat

er H

eigh

t (m

)

Currents: March 1992 @11.10Currents: August [email protected] Surface

Bali Study Static Tension Predictions (D-3 Buoy Displacement: ~1525 lbs)

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Tension @ Buoy (lbs)

Wat

er H

iegh

t (m

)

Currents: August 1989 @11.40

Currents: March 1992 @ 11.10

Bali Study Dynamic Tension Predictions

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Time (s)

Tens

ion

@ B

uoy

(lbs)

Currents: August 1989 @11.40

Currents: March 1992 @ 11.10

D-3 Buoy Displacement

WHOI CABLE: Alaska 2007 Site Study


Alaska 2007 Study Current Profiles

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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Speed (m/s)

Dep

th (m

)

2.5 knt25%-25%JKEO 2006

Alaska 2007: D-3 Mooring Catenary Standard 2.5 knt Current is: (0, 1.25) (400, 0.3125) (1500, 0.156) (4900, 0)

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0 1000 2000 3000 4000 5000

Horizontal Distance From Anchor (m)

Hei

ght a

bove

the

Bot

tom

(m)

2.5 Knt Current Catenary

2.5 Knt Current, No Nylon Catenary

2.5 Knt Current + 25% Catenary

2.5 Knt Current - 25% Catenary

4900m Mean Water Depth

JKEO 2006 Current - 30% Catenary_1.14ScopeJKEO 2006 Current - 30% Catenary

Alaska 2007: Static Tension Standard 2.5 knt Current is: (0, 1.25) (400, 0.3125) (1500, 0.156) (4900, 0)

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Tension (lbs)

Hei

ght a

bove

the

Bot

tom

(m)

2.5 Knt Current Static Tension

2.5 Knt Current, No Nylon Static Tension

2.5 Knt Current + 25% Static Tension

2.5 Knt Current - 25% Static Tension


JKEO 2006 Current - 30% Static Tension_1.14ScopeJKEO 2006 Current - 30% Static Tension

Alaska 2007: Dynamic Tension 1.675m wave every 6s, Standard 2.5 knt Current is: (0, 1.25) (400, 0.3125) (1500, 0.156) (4900, 0)

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0 200 400 600 800 1000

Time

Tens

ion

@ B

uoy

(lbs)

2.5knt Current Dynamic Tension

2.5knt Current , No Nylon Dynamic Tension

2.5knt Current +25% Dynamic Tension

2.5knt Current -25% Dynamic Tension


JKEO 2006 Current -30% DynamicTension_1.14 ScopeJKEO 2006 Current -30% DynamicTension

Dynamic Tension at the Anchor 1.675m wave every 6s, Standard 2.5 knt Current is: (0, 1.25) (400, 0.3125) (1500, 0.156) (4900, 0)

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Time

Tens

ion

@ B

uoy

(lbs) 2.5knt Current , No Nylon Dynamic Tension

2.5knt Current +25% Dynamic Tension

2.5knt Current -25% Dynamic Tension

JKEO 2006 Current -30% DynamicTension_1.14 Scope

Designing for Success: Best Practices


• Bending regions:• Mooring Components

• Instruments near the surface

• Shock Loading

• Properly Sized Components:• 3 strand nylon: ~11% RBS

• 12-strand polyester: ~20% RBS (10% RBS for shock loading)

Best Practices: Mooring Component Bending Stiffness


Thinking about Bending


Designing for Success: Best PracticesInstrument Loading

Slack Line Mooring Considerations:Shock Loading

Using Cable to Reduce Shock Loading

Data for Engineering: KEO Load Cell

• Tension Load Cell• Does Engineering Data Match Model?• Visual inspection & Line Break Testing• Detailed Failure Analysis

KEO 2007 Loadcell Data Bracketing Deployment

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9/25/2007 9/25/2007 9/26/2007 9/26/2007 9/27/2007 9/27/2007 9/28/2007 9/28/2007 9/29/2007

Time

Tens

ion

@ th

e B

uoy

(lbs)

KEO Mean Loadcell Data

KEO Mininium Loadcell Data

KEO Maximium Loadcell Data


Overview:


• Scientific Mission?

• Pick a Platform Design

• Site Assessment: ‘The Big Three’

• Pick a Mooring Design

• Iterate on Mooring Design

• Mooring Modeling

• Bending

• Shock Loading

• Mooring Performance?

WHOI CABLE: Example


Documents

IO Mooring Intro