subsea hyperbaric welding for pipeline repair

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Neil Woodward

Subsea Hyperbaric Welding Trials for Pipeline Repair Applications

Neil Woodward B. Eng, PhD, FWeldI, C.Engnjw@isotek.co.uk

Isotek & Oil Gas Ltdwww.isotek.co.uk

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Neil Woodward

Content

1. Application2. Technology Background3. Repair Method4. Remote Welding System5. Subsea Hyperbaric Weld Results6. Conclusions

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APPLICATION:Pipe Damage to be repaired by new pipe section (Spool Piece)>180msw Diver Depth Limit>30” Pipeline Diameter

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Hyperbaric Welding Qualification performed in Pressure Chambers

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250bar & 400bar Hyperbaric Welding Chambers>10 Years Understanding Mechanical Properties (CTOD, Sour Service Corrosion etc.), Heating Level & Cooling Rate, Humidity Levels, Hydrogen Assisted Cracking, Consumables, Parameters etc. Welding Parameters to 2,500msw, Qualification to 1,000msw

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Welded Sleeve: Joint Design

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Spool side 1-Atm welded during onshorefabrication

Pipe inserted into sleeve subsea

Pipe side dry hyperbaric weld subsea

Tolerance to ovality and misalignment

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Remote Welding SystemMain modules

Remote Welding Habitat Remote Welding Power and Control (POCO) Remote Welding Tool

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Remote Welding Habitat

Providing a dry, gas filled habitat for the welding operation

Support and stabilise the pipes by a claw system

Based on seawater hydraulics Direct vertical landing interface of

Remote Welding POCO Remote Welding POCO recovery

possible without flooding the habitat Dry weight 90ton Launch and recovery by vessel crane

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Contains the most critical systems most likely to fail during operation

Gas filled container: 0.4 bar overpressure Permanent umbilical connection Easy launch and recovery from vessel using

module handling tower through moon pool or by A-frame over vessel side

Welding & Pre-Heat Power Sources Dry weight 25ton Provide a dry transfer «garage» for the

Remote Welding Tool

Remote Welding POCO

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Remote Welding Tool

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Contains all functions for subsea welding: Welding head Torch tip changer Welding consumable (bulk storage) Pre- and Post-Heating Sleeve & Pipe Coils Survey head Service head

Extensive 1-Atm Robustness Testing

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1-Atm Welding TestsPost-Weld Inspect, Service Head Cutter, Close Inspect

Service Head CuttingRoot Weld Review Sensor Head Close Inspect

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Deep Water Test October 2014REM OCEAN Vessel

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Deep Water Test October 2014: Habitat Deployment

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Vessel Crane Over-BoardingArgon Purge, Blow-Down, IR Heating, De-humidify for Welding Atmosphere

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Deep Water Test October 2014: Remote POCO Launch & Recovery via Vessel Moon Pool

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Argon Purge on Deck prior to Launch

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Deep Water Test October 2014: Remote POCO Dock at 400 and 1,000msw

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Remote Welding SystemHyperbaric MIG welding process48 Hours Arc-On Time at Depth, 60kW Heating Power Used Subsea

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Weld QA QC Summary400msw: Arc Voltage & Welding Current

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Remote Welding SystemHyperbaric MIG Welding Results

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1,000msw Hyperbaric MIG Welds

Visual Appearance at 1:30 and 6 o’clock

Acceptable:

Visual & NDT Multiple Macros HV10 Hardness All-Weld Tensile Charpy V Notch

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Remote Welding SystemHyperbaric MIG Welding Results

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Mechanical Properties at 1,000msw: Acceptable Visual & NDT, Multiple Macros Checks for H.A.C. (High Restraint, Moisture), Chemical Analysis, Oxygen Content

HV10 Hardness Peak HV10 Hardness is 276HV10 (Pipe Cap HAZ) and 260 HV10 (Pipe Cap HAZ)

All-Weld Tensile 564MPa 0.2% PS, 632MPa UTS 27.5% El. 563MPa 0.2% PS, 626MPa UTS, 27.6% El.

Charpy V Notch (Full Set at -20⁰C) FL+5: >Capacity of Machine FL+2: 316J Minimum Fusion Line: 173J Minimum Weld Metal: 123J Minimum

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Chemical Analyses

Weld Metal Oxygen Levels comparable with Lab. results

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The future….

STATUS OF TECHNOLOGY

Remote welded sleeve repair method is implemented for the large diameter pipelines in deep waters; 30” to 42” in water depths 180-1,300meters

Remote Welding System is qualified and approved by DNV-GL and in accordance with Statoil corporate requirements

Technology is available via Pipeline Repair and Subsea Intervention (PRSI) Pool

FUTURE DEVELOPMENT

Extend pipeline dimension range downwards to 10” – 30” pipelines Extend depth range to 3,000meters Develop method for bi-metallic materials like clad and lined pipelines

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