Conference and workshop - · PDF fileConference and workshop Underwater robots ... Increasing activities in installations: • Offshore structures ... rotary dryer. Welding lifters

Esbjerg, Friday 8th February 2013 Conference and workshop Underwater robots

Offshore structures and structural behavior due to biofouling

www.aau.dkwww.esbjerg.aau.dk

Presentation• Anders Schmidt Kristensen• M.Sc. in Mechanical Eng. from Aalborg University in 1993• Ph.D. in Mechanical Eng. from Aalborg University in 1997• Consultant for PTC Denmark 1997-1998 – implementation

of Pro/ENGINEER• 1998 to pt. Associate Prof. at Aalborg University Esbjerg in

Mechanical Engineering• Associate Prof. Mechanical Engineering, Ph.D., M.Sc. (ME),

Department of Civil Engineering, Aalborg University Esbjerg

• 2010 Head of Campus Esbjerg


Finite Element Modelling


Aalborg University (AAU)

AAU-Esbjerg

AAU-Cph

197.426 mennesker i Aalborg Kommune pr. 1 januar 2010

115.114 mennesker i Esbjerg Kommune pr. 1 januar 2010


Offshore structures and structural behavior due to biofouling

• Motivation• Offshore structures

• Examples• Structural behavior

• Loads• Fatigue

• Biofouling or marine growth

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Motivation

• Biofouling or marine growth is found to influence loading of offshore structures by increasing tube diameters, drag coefficient, mass and hydrodynamic added mass and structural weight.

• Biofouling or marine growth obstruct service and inspection of offshore structures.

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Motivation - continuedObjective 2.1: Cognitive Systems and Robotics

Target outcomesa) Robotic systems operating in real-world environments: Expanding and improving the functionalities of robotic systems and further developing relevant features, such as autonomy, safety, robustness, efficiency, and ease of use. As appropriate, work will include exploring ways of integrating, in robotic systems, new materials and advanced sensor, actuator, effector and leading edge memory and control technologies.

Expected impact

• Integrated and consolidated scientific foundations for engineering cognitive systems under a variety of physical instantiations.

• Significant increase in the quality of service of such systems and of their sustainability in terms of, for instance, energy consumption, usability and serviceability, through the integration of cognitive capabilities.

• Innovation capacity in a wide range of application domains through the integration of cognitive capabilities.

• Improved competitive position of the robotics industry in existing and emerging markets for instance in the following sectors: manufacturing; professional and domestic services; assistance and co-working, production, logistics and transport, construction, maintenance and repair, search and rescue, exploration and inspection, systems monitoring and control, consumer robotics, education and entertainment.

• Consensus by industry on the need (or not) for particular standards. More widely accepted benchmarks. Strengthened links between industry and academia.

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Motivation

Increasing activities in installations:• Offshore structures• SubSea systems and installations• Deep Sea/Deep Water systemsServices:• Surveillance• Maintenance• Inspection• Decommissioning

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Subsea systems and installations

• API RP 17N, Recommended Practice for Subsea Production System Reliability and Technical Risk Management.

• API RP 17A 4th Ed 2006 - Recommended Practice for Design and Operation of Subsea Production Systems equal to ISO 13628-1

• API RP 17B 4th Ed 2008 - Recommended Practice for Flexible Pipe equal to ISO 13628-11• API RP 17C 2nd Ed 2002 - Recommended Practice on TFL (Through Flowline) Systems equal to ISO 13628-3• API SPEC 17D 1st Ed 1992 - Specification for Subsea Wellhead and Christmas Tree Equipment• API SPEC 17E 3rd Ed 2003 - Specification for Subsea Production Control Umbilicals• API SPEC 17F 1st Ed 2003 - Specification for Subsea Production Control Systems equal to ISO 13628-6• API RP 17G 2nd Ed 2006 - Recommended Practice for Design and Operation of Completion / Workover Riser Systems• API RP 17H 1st Ed 2009 - Recommended Practice for Remotely Operated Vehicles (ROV) Interfaces on Subsea equal to

ISO 13628-8• API RP 17I 1st Ed 1996 - Installation Guideline for Subsea Ambilicals• API SPEC 17J 2nd Ed 1999 - Specification for Unbonded Flexible Pipe equal to ISO 13628-2• API SPEC 17K 1st Ed 2001 - Specification for Bonded Flexible Pipe equal to ISO 13628-10• API RP 17M 1st Ed 2009 - Recommended Practices on Remotely Operated Tool (ROT) Intervention Systems equal to ISO

13628-9• API RP 17N 1st Ed 2009 - Recommended Practice for Subsea Production System Reliability and Technical Risk Management• API RP 17O 1st Ed 2009 - Recommended Practice for Subsea High Integrity Pressure Protection Systems (HIPPS)

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SubSea systems and installations

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OFFSHORE STRUCTURES

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Terminology

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Offshore systems

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Offshore systems

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WILL ALSO AFFECT INFRASTRUCTURE


Offshore systems

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Offshore structures- Jacket foundation

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Offshore structures

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Offshore structures

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Offshore structures

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Offshore structures

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Installation

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Offshore structures

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Offshore structures

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Offshore structures – monopile foundation

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Offshore structures – monopile foundation

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Offshore structures

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STRUCTURAL BEHAVIOR

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Residual stress are built-in or introduced (typically during manufacturing) to an unloaded part.

Residual stresses can be the cause of crack initiation and, therefore, fatigue failure

Source: ASM International

Example: rotary dryer. Welding lifters to a rotary shell

Residual stresses introduced during welding caused crack initiation

Fatigue failure Residual stresses


Fatigue failures

Samlinger

Alexander L. Kielland (1980)Accomm / drilling rigLess than 2 years oldCapsized when member failed due to fatigueCapsized in under 20min123 died


Fatigue failures

Samlinger


Offshore wind energy systems

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Loads

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Loads

• Random loads can be described in the Time or Frequency domain:

Introduction

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Introduction

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Characterization of Fatigue

• Fatigue - a distinct failure mode:• Apparently brittle even in ductile materials• Sudden and catastrophic• Result of initiation and propagation of a crack• Fatigue is failure due to time-varying stresses


Introduction

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Fatigue failure

• Fatigue failures more common than static• Due to multiple loadings of material• Always begins at crack• Occurs in three stages

• Crack initiation• Crack propagation• Fracture


Introduction

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Fatigue failure


Damage ratio D

Stress-life


Introduction

5x105 = 500.000 cykler 2x106 = 2.000.000 cykler


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Fatigue issues


Fatigue issues

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Offshore structural components

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TOWER = 150.000kg

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En reduktion afgodstykkelsen på1 mm betyder envægt besparelsePå 2 tons

En reduktion afgodstykkelsen på1 mm betyder envægt besparelsePå 3,8 tons

34m

17m

Estimated 16 mill dkr saved for 90 OWT



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BIOFOULING OR MARINE GROWTH

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Problem description:

• Biofouling/marine growth is an accumulation of microorganisms, plants, algae, and/or animals on wet or wetted surfaces.

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Marine growth can increase the radius of a windturbinefoundation upto 25cm. This results in:

- Inspection is made difficult, i.e. fatigue, corrosion- Loads are increased, i.e. hydrodynamics forces- Corrosion is increasedResulting in:- Increased costs of systems production- Increased costs of maintenance/operation- Increased costs of inspection


Problem description:

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Citations from Offshore Windturbine regulations:

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Definitions:

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Basic components in an Autonomous Underwater Vehicle (AUV)

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FRAME

BUOYANCYCONTROLSYSTEMS

PROPULSIONSYSTEMS

DEPLOYMENTSYSTEM

DOCKINGSYSTEM

MANIPULATORSYSTEM

BIOFOULING

Need: Biofouling causes an increase of loads on an offshore windturbine, i.e. increased costs.

Problem: Can an offshore structure be kept free of biofouling using an AUV system?


Example on an Offshore Wind Farm:

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AUV visiting all Wind turbinesto remove marine growth


Example - cost

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Issues to be solved:

• Deployment – How do we put/install the system in the water?• Buoyancy – How do we design a buoyancy system without affecting the

hydrodynamics of the vehicle/vessel?• Docking – How do we supply the vehicle/vessel with energy during operation?• Propulsion – How do we design the propulsion system to allow minimum use of

power and to maximize maneuvering?• Frame - How do we design a frame without affecting the hydrodynamics of the

vehicle/vessel?• Manipulator – How do we design a system which allows us to hook on/off the

offshore structure and remove/clean biofouling with a minimum use of power?• Control – How do we navigate between several offshore structures, how do we

navigate into the docking unit and dock/undock, how do we operate the cleaning process?

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Thank you for your attention

Documents

Conference and workshop - · PDF fileConference and workshop Underwater robots ... Increasing activities in installations: • Offshore structures ... rotary dryer. Welding lifters