Robotic Inspection of Subsea Assets - IDT EXPO

Copyright © Sonomatic 2017www.vsonomatic.com

Robotic Inspection of Subsea Assets

www.sonomatic.com

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.


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


Subsea Robotic ToolsROV-ITNautilus

Mag Rover


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


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


• 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


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


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


Life Extension Spar platform ballast-

tank• Two Primary Inspection challenges

– Tracking Location of Tool on Tank

– Locating and Tracking internal fillet welds


Navigation


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


Inspection of Merlin Connectors

Inside Gravity base structure


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)


Merlin connectors


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Robotic Inspection of Subsea Assets - IDT EXPO

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