OMAE 2011-50298 Presentation

OMAE2011-50298

Murphy Thunder Hawk:New Findings on Polyester and

Chain Mooring SystemsPresented by

Jonathon D. Miller P.E.

OMAE2011-50298

Murphy Thunder Hawk:New Findings on Polyester and

Chain Mooring SystemsPresented by

Jonathon D. Miller P.E.

OverviewOverviewOverview

• Thunder Hawk Platform• Inspection Findings• Conditions for Corrosion• Steel Corrosion Model• Bio-film formation• Rusticles – Composition• Rusticles – Structure• Rusticles – Other vessels• Conclusions • Acknowledgements

Thunder Hawk PlatformThunder HawkThunder Hawk PlatformPlatform

• 45,000 BOPD Oil• 70,000,000 CFPD Gas• 71 x 71 x 52 m hull• 10,250 tons operating wt• Murphy (37.5%) • ENI (25%)• StatOilHydro (25%)• Marubeni Oil (12.5%)

Thunder Hawk PlatformThunder Hawk Thunder Hawk PlatformPlatform


• Insert Drawing of Mooring Leg




~2m

~2.5m


Inspection FindingsInspection FindingsInspection Findings

• Top Chains – Twist Free• Fairleads – Intact• Fairlead Chains – Intact• Polyester Ropes – Intact• H-link hardware – Intact• Ground Chain – Intact • Ball-grab connectors – Not visible• Anchors – Intact

Year 1 Inspection-Mooring LinesYear 1 InspectionYear 1 Inspection--Mooring LinesMooring Lines

• Topside Chains +15m


• Fairlead Chains – 26m


• Upper Chain to Polyester H-Link – 117m


• Polyester Insert – 142m


• Upper Polyester to Polyester H-Link – 144m


• Lower Polyester to Polyester H-Link – 147m


• Upper Polyester Segment – 700m


• Middle Polyester to Polyester H-Link – 960m


• Lower Polyester Segment – 1462m


• Lower Polyester to Chain H-link – 1717m


• Lower Chain Segment – 1751m


• Driven Piles – 1870m


• Marine Life Highlights

The Subsea Environment – ReinhartThe Subsea Environment The Subsea Environment –– ReinhartReinhart

Surface

300

600

900

1200

1500

1800

2100

6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2

33.0 33.2 33.4 33.6 33.8 34.0 34.2 34.4 34.6 34.8

0 1 2 3 4 5 6

0 2 4 6 8 10 12 14 16 18

pH

Salinity

(ppt)

Oxygen

(mL/L)Temperature

(°C)

Steel Corrosion Model – MelchersSteel Corrosion Model Steel Corrosion Model –– MelchersMelchers

Corrosion Loss

ra rs

ro

ca

cs

ta

Localized anaerobic conditions have developed

Exposure Period

Phase 0Phase 1

Phase 2Phase 3

Phase 4

Water Temperature Impact – MelchersWater Temperature Impact Water Temperature Impact –– MelchersMelchers

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

00 1 2 3 4 5 6

Exposure Period (years)

Cor

rosi

on L

oss

(mm

) 20°C28°C

10°C4°C

Bio-film Formation – DreeszenBioBio--film Formation film Formation –– DreeszenDreeszen

Bio-film Formation – BorensteinBioBio--film Formation film Formation –– BorensteinBorenstein

(1)= O2 + 2H2O + 4e- → 4OH- (cathodic)

(2)= Fe → Fe++ + 2e- (anodic)

(3)= 4Fe++ + O2 + 10H2O → 4Fe(OH)3 + 8H+

(tubercle formation)

Rusticles – Titanic - Droycon BioConcepts Inc.Rusticles – Titanic - Droycon BioConcepts Inc.

Rusticles – Composition – Pellegrino et. al.Rusticles Rusticles –– Composition Composition –– Pellegrino et. al.Pellegrino et. al.

• Titanic Rusticles – 20-35% Iron• Other Shipwrecks – 79.7-92.2% Iron

Rusticles – Structure – Cullimore et. al.Rusticles Rusticles –– StructureStructure –– CullimoreCullimore et. al.et. al.

Central Water Channel

Rusticles – Structure – Cullimore et. al.Rusticles Rusticles –– Structure Structure –– CullimoreCullimore et. al.et. al.

γFe3+O(OH)

αFe3+O(OH)

Rusticles – Structure – Frankel et. al.Rusticles Rusticles –– Structure Structure –– Frankel et. al.Frankel et. al.

What Do Rusticles Do? – Ray et. al.What Do Rusticles Do?What Do Rusticles Do? –– Ray et. al.Ray et. al.

(Pitting)

After

Before

• Corrosion occurs in a hypoxic environment?

ConclusionsConclusionsConclusions

• Does corrosion occur at 1800m depth?

• Is corrosion life predictable?

),,,( 2 pHvOTfr oo

•

• Rusticles evidence of steel corrosion?

• Should corrosion allowances be maintained?

• Synthetic Rope Moorings corrosion solution?

AcknowledgementsAcknowledgementsAcknowledgements

• Co-Authors– Luc Chabot– Jim Jenkins– Brett Warren

• Conference Reviewers and Administrators– Ron Riggs– René Huijsmans– Joel Witz– Johann Wichers

• American Society of Mechanical Engineers• Kivi Niria• OMAE 2011

E x p e c t M o r e . . . G e t M o o r .

QUESTIONS?QUESTIONS?

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OMAE 2011-50298 Presentation

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