The document discusses subsea hyperbaric welding trials conducted by Neil Woodward for pipeline repair applications, focusing on a remote welding system designed for deep-water environments. Key components include a remote welding habitat, power control system, and tool, all tested for operation at depths up to 1,000msw. Results indicate successful welding processes and mechanical properties, with future developments aimed at extending the capabilities to smaller pipelines and greater depths.

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Neil Woodward
Subsea Hyperbaric Welding Trials for
Pipeline Repair Applications
Neil Woodward B. Eng, PhD, FWeldI, C.Eng
njw@isotek.co.uk
Isotek & Oil Gas Ltd
www.isotek.co.uk
EuroJoin 9, 21st May 2015

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Neil Woodward
Content
1. Application
2. Technology Background
3. Repair Method
4. Remote Welding System
5. Subsea Hyperbaric Weld Results
6. Conclusions
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Neil Woodward
APPLICATION:
Pipe Damage to be repaired by
new pipe section (Spool Piece)
>180msw Diver Depth Limit
>30” Pipeline Diameter
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Neil Woodward
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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Neil Woodward
Welded Sleeve: Joint Design
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 Spool side 1-Atm welded during onshore
fabrication
 Pipe inserted into sleeve subsea
 Pipe side dry hyperbaric weld subsea
 Tolerance to ovality and misalignment

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Neil Woodward
Remote Welding System
Main 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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Neil Woodward
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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Neil Woodward
1-Atm Welding Tests
Post-Weld Inspect, Service Head Cutter, Close Inspect
Service Head CuttingRoot Weld Review Sensor Head Close Inspect

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Deep Water Test October 2014
REM OCEAN Vessel
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Deep Water Test October 2014:
Habitat Deployment
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Vessel Crane Over-Boarding
Argon Purge, Blow-Down, IR Heating,
De-humidify for Welding Atmosphere

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Neil Woodward
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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Neil Woodward
Deep Water Test October 2014:
Remote POCO Dock at 400 and 1,000msw
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Neil Woodward
Remote Welding System
Hyperbaric MIG welding process4
8 Hours Arc-On Time at Depth, 60kW Heating Power Used Subsea
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Neil Woodward
Weld QA QC Summary
400msw: Arc Voltage & Welding Current

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Neil Woodward
Remote Welding System
Hyperbaric 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 System
Hyperbaric 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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Neil Woodward
Chemical Analyses
 Weld Metal Oxygen Levels comparable with Lab. results

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Neil Woodward
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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