Data Collection and Analysis for the Creation of a Digital Shadow During the Production of Thermoplastic Composite Layers in Unbonded Flexible Pipes

Unbonded flexible pipes present a mature technology for the efficient recovery and transport of hydrocarbons offshore. The substitution of metallic reinforcement layers in the multi-layered structure by thermoplastic fiber-reinforced polymer (FRP) presents a solution for self-weight issues of especially long pipes, as FRP materials display high specific strength and modulus while being resistant to external pressure and corrosion. The production of these layers is automated by the laser-assisted tape winding process without the need of additional curing steps. During the manufacturing process, several data like process temperature and consolidation pressure are continuously monitored by non-contact sensors to ensure process stability without interfering in the consolidation process. To gain additional information about the temperature distribution within the multi-layered laminate, contact temperature sensors were introduced in the tape winding process. By this method the temperature of subjacent tapes can be assessed during the continued winding process. Additionally, this paper features a new approach of utilizing winding path data for relating the time-dependent sensor data to the exact position on the produced part. The visualization of path-dependent sensor data opens up possibilities of linking quality monitoring results to manufacturing insufficiencies and potential part defects.

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Controlling Factors of Carcass Fatigue in Unbonded Flexible Pipes

Volume 5A: Pipelines, Risers, and Subsea Systems ◽

10.1115/omae2019-96310 ◽

2019 ◽

Author(s):

Upul S. Fernando ◽

Andrew P. Roberts ◽

Michelle Davidson

Keyword(s):

Fatigue Failure ◽

Failure Modes ◽

Dynamic Stress ◽

External Pressure ◽

Controlling Factors ◽

Flexible Pipe ◽

Flexible Pipes ◽

Innermost Layer ◽

Key Features ◽

Unbonded Flexible Pipes

Abstract Carcass, the innermost layer of a flexible pipe structure is designed to prevent the collapse of the pressure sheath due to external pressure. Weakness, damage or failure of the carcass layer can result in collapse with associated loss of production and potentially serious risk to pipe integrity and hydrocarbon leakage to the environment. Avoiding carcass failure in service is therefore an essential consideration during the design of unbonded flexible pipes. Carcass failure is rare in service. This paper highlights the three possible failure modes and presents further analysis on the fatigue failure mode, relevant to dynamic service. Two key features of carcass manufacture are identified as causes for dynamic stress; locking of the carcass profile due to extended pitch and polymer ingress within the carcass cavity. Guidelines for the design of carcass profiles, setting safe pitch limits and appropriate barrier profile controls to mitigate carcass fatigue failure in dynamic service are presented.

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Calculation Methods of the Local Structure Behavior of Unbonded Flexible Pipes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.658.481 ◽

2013 ◽

Vol 658 ◽

pp. 481-486

Author(s):

Zhi Bo Li ◽

Hui Xu ◽

Gui Zhen Zhang

Keyword(s):

Local Structure ◽

Axial Load ◽

Bending Moment ◽

External Pressure ◽

Nonlinear Relationship ◽

Calculation Methods ◽

Flexible Pipes ◽

Bending Load ◽

Unbonded Flexible Pipes ◽

Moment Load

In this paper, the nonlinear relationship between the bending moment and curvature of non-bonded flexible pipes was studied. It was found that the relation was a function of internal and external pressure, axial force, and bending moment load. The model used in this paper took into consideration of the flexural, tensile and torsional strength of layers as well as the frictions between them. Symmetrical axial load was first applied, and then the bending load. Due to friction, the response of the unbonded flexible pipes is hysteretic to the loads. In conclusion, the response of unbonded flexible pipes are both related to its own structural properties and external loads.Coupling factors of different conditions should also be considered.

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Local Stress Assessment of Flexible Unbonded Pipes Using FEA

Volume 3: Pipeline and Riser Technology ◽

10.1115/omae2012-84248 ◽

2012 ◽

Cited By ~ 2

Author(s):

Ben Edmans ◽

Giulio Alfano ◽

Hamid Bahai ◽

Lakis Andronicou ◽

Ali Bahtui

Keyword(s):

Linear Models ◽

Local Stress ◽

External Pressure ◽

Flexible Pipe ◽

Flexible Pipes ◽

Finite Element Package ◽

Bending Radius ◽

Unbonded Flexible Pipes ◽

The Individual ◽

Computational Resources

Detailed stress analysis of unbonded flexible pipes has always been a challenging exercise which requires significant amount of computational resources and state of the art knowledge of flexible pipe modelling techniques. Lloyd’s Register EMEA and Brunel University have embarked on the development of a model which captures the response of the individual unbonded layers of flexible pipes using the ABAQUS finite element package employing 3D explicit and 3D implicit integration rules. The model accounts for nonlinear interaction between layers and provide the hysteresis response. The use of periodic boundary conditions to eliminate boundary effects at the pipe ends has also been investigated. The model predicts stress and strain conditions in metallic and plastic layers. These FEA predictions of the 3D non linear models are compared with the results of analytical methods for axisymmetric loads. This verification is carried out for three basic cases as follows: i) axial tension ii) internal/burst pressure iii) radial external pressure. Good agreement has been shown for stiffness and stress values predicted by the FEA and analytical formulations. Some initial results are presented for the bending behaviour in which the hysteresis obtained in the case of cyclic application of the design minimum bending radius is simulated.

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Non-metallic Unbonded Flexible Pipes for Deepwater

10.2118/108473-ms ◽

2007 ◽

Cited By ~ 1

Author(s):

Mike Bryant ◽

Shankar U. Bhat ◽

Bin Chen

Keyword(s):

Flexible Pipes ◽

Unbonded Flexible Pipes

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A Theoretical and Experimental Analysis of the Bending Behavior of Unbonded Flexible Pipes

Volume 6B: Pipeline and Riser Technology ◽

10.1115/omae2014-24247 ◽

2014 ◽

Cited By ~ 1

Author(s):

Tatiana Vargas-Londoño ◽

José Renato M. de Sousa ◽

Carlos Magluta ◽

Ney Roitman

Keyword(s):

Internal Pressure ◽

Cross Section ◽

Structural Response ◽

Experimental Tests ◽

Theoretical Models ◽

External Pressure ◽

Local Behavior ◽

Flexible Pipes ◽

Floating System ◽

Bending Loads

Due to its compound cross-section, the prediction of the structural response of flexible pipes to loads such as their self-weight, internal and external pressure, movements imposed by the floating system and environmental loads such as currents, waves and wind is quite complex. All these loads generate stresses and strains in the cross section of the pipe that have to be properly evaluated in order to ensure integrity of the line. Research has been done on the local behavior of flexible pipes under combined axisymmetric loads as well as under bending loads. However, there is a lack of research combining both axisymmetric and bending loads, as also in the study of the strains in the tensile amour layers of the pipes, aspects which are important for the calibration of theoretical models to predict such behavior. Based on that, this study aims to evaluate the local behavior of flexible pipes under combinations of axisymmetric (tension, and internal pressure) and bending loads via a series of experimental tests in a 9.13″ I.D pipe. In the experimental tests, the behavior of the pipe was studied for three load combinations: i) bending combined with tension; ii) bending combined with internal pressure; and iii) bending combined with tension and internal pressure. Based on these tests, the authors obtained the strains in the tensile armor layer, axial elongation due to tension, axial reaction forces due to internal pressure, and deflection due to bending. These measurements were used to calibrate a theoretical model devoted to simulate the pipe’s response, getting accurate results for stiffness and stresses of the pipe in each scenario.

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An Analytical Model to Predict the Bending Behavior of Unbonded Flexible Pipes

Journal of Ship Research ◽

10.5957/jsr.2013.57.3.171 ◽

2013 ◽

Vol 57 (03) ◽

pp. 171-177

Author(s):

Leilei Dong ◽

Yi Huang ◽

Qi Zhang ◽

Gang Liu

Keyword(s):

Bending Moment ◽

Bending Stiffness ◽

Nonlinear Formulation ◽

Flexible Pipe ◽

Flexible Pipes ◽

Bending Behavior ◽

Interlayer Slip ◽

Unbonded Flexible Pipes ◽

Relationship Of ◽

Theoretical Results

Analytical formulations are presented to determine the bending moment-curvature relationship of a helical layer in unbonded flexible pipes. Explicit expressions describing the variation of both bending stiffness and moment as a function of the applied curvature are given. The approach takes into account the nonlinearity of the response caused by the interlayer slip. The contribution of local bending and torsion of individual helical elements to the bending behavior of helical layers is included. Theoretical results for a typical unbonded flexible pipe using the nonlinear formulation for helical layers are compared with experimental data from the available literature. Encouraging correlations are found and the importance of the initial interlayer pressures is seen. The influence of local bending and torsion of individual helical elements on the bending behavior of the entire pipe is also evaluated. The results show that the inclusion of this local behavior significantly influences the full-slip bending stiffness.

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Qualification Approach to Unbonded Flexible Pipes With Fibre Reinforced Armour Layer

23rd International Conference on Offshore Mechanics and Arctic Engineering, Volume 2 ◽

10.1115/omae2004-51175 ◽

2004 ◽

Author(s):

Jan Rytter

Keyword(s):

Offshore Structure ◽

Flexible Pipe ◽

Load Bearing ◽

Compression Load ◽

Metal Parts ◽

Analysis Tools ◽

Industry Standards ◽

Flexible Pipes ◽

Unbonded Flexible Pipes ◽

Load And Resistance Factor

The future water depth capabilities for unbonded flexible pipes is being pushed by NKT Flexibles I/S through the development of an innovative flexible pipe structure, taking full advantage of the material characteristics of metallic, polymeric and fibre reinforced materials. The fluid tight liner and possible insulation of this pipe structure are supported by an inner armour, capable of carrying the external hydrostatic pressure, clamp and crushing loads, as well as axial compression load, and an outer armour, consisting of two cross wound layers of carbon/epoxy composites, carrying the internal pressure as well as end cap forces and applied tension. A permeable and radially flexible outer layer protects the composite armour. Combining known and well-proven flexible pipe technologies and new solutions for materials, structure and functionality of the flexible pipe, positions this future product outside the present industry standards for flexible pipes, e.g. API-17J. The analysis tools used for the conventional flexible pipes are validated by NKT according to the API-17J specification. The API-17J describes load cases and corresponding allowable utilization ratios, stated as design criteria. However, this approach is not directly applicable to the composite pipe, where the same analysis tools will be used, but the material in one of the two primary load bearing layers is made of fibre reinforced polymer, a material class not covered by the API allowable utilization factors. The DNV offshore standard DNV-OS-C501 considers any offshore structure in which the load bearing material is a composite. An accompanying Recommended Practice DNV-RP-F202 for composite risers has also been issued, but is not applicable to the composite flexible pipe. The design equations of the DNV standard are formulated in the so-called Load and Resistance Factor Design (LRFD) format, where partial safety factors are applied to the load effects and to the resistance variables that enter the design equations. The DNV standard DNV-OS-C501 covers composite materials and composite metal interfaces of a structure, metal parts should be designed according to other relevant standards. The API standard can therefore be used for the metal parts. One of the challenges in using this combined approach is the different ways loads are defined in the two standards. In short, this will result in a conventional API design check of the inner armour, the polymer layers, and the secondary layers, whereas the composite tensile armour, special intermediate layers and the interfaces will be analyzed with composite specific tools based on the criteria derived from the DNV standard. The qualification procedure is described and exemplified in the following.

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Characterizing the Wave Environment in the Fatigue Analysis of Flexible Risers

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.2185129 ◽

2005 ◽

Vol 128 (2) ◽

pp. 108-118 ◽

Cited By ~ 15

Author(s):

John M. Sheehan ◽

Frank W. Grealish ◽

Annette M. Harte ◽

Russell J. Smith

Keyword(s):

Cost Effective ◽

Critical Issue ◽

Fatigue Analysis ◽

Flexible Pipes ◽

Water Developments ◽

Key Issues ◽

Flexible Risers ◽

Offshore Industry ◽

Unbonded Flexible Pipes

As the offshore industry moves towards deeper water developments and continues to embrace harsh environments, unbonded flexible pipes are increasingly being utilized as a cost effective riser solution. Furthermore, with the advent of issues such as nonpristine annuli environments, the fatigue performance of these flexible risers is becoming a critical issue. This paper presents an overview of the comparisons between deterministic and stochastic global fatigue analysis techniques. Methods used to perform both deterministic and stochastic analyses are outlined, from performing the global analyses to using local models to generate armor wire stresses and subsequent fatigue damage. The paper identifies the key issues in the analysis performed and presents key results and conclusions with regard to the characterization of the wave environment in the global fatigue analysis of flexible risers.

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