robotic inspection of subsea assets - idt expo
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Copyright © Sonomatic 2017www.vsonomatic.com
Robotic Inspection of Subsea Assets
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Copyright © Sonomatic 2017
Subsea Inspection
Many assets installed in the Gulf of Mexico are going to
require significant investment in life extension programs in
the next 10-20 years. Regulators are insisting that purely
theoretical modeling will not be enough to justify life
extension. Inspection will be required to validate theoretical
calculations.
This highlights the importance of Subsea inspection.
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Inspections By Asset TypeSubsea Pipelines
• Unpiggable Pipelines• ILI Verification • Dead Legs• Risers• Steel Cantenary Riser touch
down point
Structural
• Tension Leg Platform Girth weld inspection• Merlin Connectors in situ inspection• SPAR Ballast Tanks• Caissons
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Subsea Robotic ToolsROV-ITNautilus
Mag Rover
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Subsea Pipeline Inspection• Diver and ROV Deployed tools make it possible to carry
out fully automated inspections to depths of 9500ft• ILI Verification of critical indications • Sampling inspection of unpiggable pipelines make it
possible to justify continued operation of pipelines.• Factors which can make lines difficult to pig, Low
flow conditions, Wax buildup• Acquisition of high quality quantitative data allows
for use of statistical methods as part of Fitness for service evaluations
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Channeling corrosion Interacting
corrosion pits Knife edge corrosion
Preferential weld corrosion
Spurious:Cliff-edge effects
Overstated: 12% → 60%Calibration errors
Calibration flaws:Representative?
Interpreted as needle pits
Imaging Degradation Mechanisms
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• Subsea dead legs often experience degradation because inhibitors cannot be used effectively
– Corrosion is unpredictable and often random.
• Often present challenging inspection geometries.
Dead Legs
Modified Nautilus Scanner
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Caisson and Risers
Circ weld at -12.5M
Circ weld at -9.5M
This section is 680mm
Circ weld at -6.5M
This can measures
2.93 metres long
This can measures
3 metres long
3 o’clock
9 o’clock
9 o’clock
6 o’clock
12 o’clock
• Robotic tools allow inspection of Caissons and Risers to confirm extent of corrosion/preferential weld corrosion.
• Risers are often subject to stresses which can lead to stress corrosion cracking in weldments
– ROV deployed tools can be used to deploy fully automated Phased Array and TOFD inspection of Welds
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Life Extension Tension Leg Platforms• Inspection Challenges include Inspection of Critical girth welds on TLP• Inspection of critical welds on Steel Centenary riser touch down points• Inspection required to depths of 5000ft
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MAG-Rover Case Study
Structural Inspection
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MAG-Rover Case Study
mm 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700
mm0.0
18.226.032.037.241.946.250.354.157.861.3
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Life Extension Spar platform ballast-
tank• Two Primary Inspection challenges
– Tracking Location of Tool on Tank
– Locating and Tracking internal fillet welds
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Navigation
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Weld TrackingThe 0° ultrasonic phased array data provides valuable information for tracking welds during data collection. Example: Stiffener fillet weld. •Currently the welds can be imaged ultrasonically which allows manual adjustments to scanner heading to be made in real time during data collection. •It is possible to detect the fillet weld through automated signal processing. Currently this is done post data collection. •This may be used to trace the fillet weld, straighten the collected data or be used to provide feedback for close loop drive control and automated weld following during data collection.
0° Phased Array Data - As Collected 0 Phased Array Data – Straightened
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Inspection of Merlin Connectors
Inside Gravity base structure
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Subsea roboticsChallenging Access Application
• Inspection of critical welds on conductors inside a gravity base structure
• Depth 140 m• Only accessible through 625 mm diameter
openings• Up to 60 m travel past openings• Deployed to the entrance to the gravity base by
work class ROV (provides power and comms)• Mini ROV for deployment through openings into
each compartment for conductor inspection• 230 welds inspected (TOFD and PE)• Weld misalignment inspection (0 deg)
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Merlin connectors
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