Annulus Testing for Condition Assessment and Monitoring of Flexible Pipes

2004 ◽  
Author(s):  
Jon Olav Bondevik ◽  
Sigmund Lunde ◽  
Rune Haakonsen
Keyword(s):  
Barrier Layer ◽  
Nitrogen Pressure ◽  
Condition Assessment ◽  
Reliable Operation ◽  
Flexible Pipe ◽  
Flexible Pipes ◽  
Assessment And Monitoring ◽  
Flexible Risers ◽  
Paper Address ◽  
Vacuum Testing

The Norwegian operator Norsk Hydro has more than 80 flexible dynamic risers and service lines in operation at different platforms. Riser integrity monitoring programs have been established for the flexible risers in order to ensure safe and reliable operation. SeaFlex has performed annulus testing on a large number of these risers as a part of the programs. The free annulus volume of a flexible pipe is defined as the volume between the extruded internal pressure barrier layer and the extruded external sheath subtracted the volume occupied by pressure- and tension armor, tape and eventual other layers. Two methods are presently used by the industry for annulus free volume testing of flexible pipes, namely nitrogen pressure testing and vacuum testing. Both methods identify trends of volume reduction with time and to detect annulus flooding. Annulus testing has proven to be an efficient and reliable tool for detecting annulus flooding, blocked vent ports and outer sheet damages. This paper address the challenges related to annulus testing of flexible pipes, advantages, experiences and how such tests and the results are used for condition assessment and monitoring of the risers.

Cathodic Protection Design Consideration for an Offshore Flexible Riser Connected to an Impressed Current System

2021 ◽  
Author(s):  
Thierry Dequin ◽  
Clark Weldon ◽  
Matthew Hense
Keyword(s):  
Cathodic Protection ◽  
Sacrificial Anode ◽  
Flexible Riser ◽  
Flexible Pipe ◽  
Linear Resistance ◽  
Flexible Pipes ◽  
Flexible Risers ◽  
Impressed Current ◽  
Host Structure ◽  
Impressed Current Cathodic Protection

Abstract Flexible risers are regularly used to produce oil and gas in subsea production systems and by nature interconnect the subsea production system to the floating or fixed host facilities. Unbonded flexible pipes are made of a combination of metallic and non-metallic layers, each layer being individually terminated at each extremity by complex end fittings. Mostly submerged in seawater, the metallic parts require careful material selection and cathodic protection (CP) to survive the expected service life. Design engineers must determine whether the flexible pipe risers should be electrically connected to the host in order to receive cathodic protection current or be electrically isolated. If the host structure is equipped with a sacrificial anode system, then electrical continuity between the riser and the host structure is generally preferred. The exception is often when the riser and host structure are operated by separate organizations, in which case electrical isolation may be preferred simply to provide delineation of ownership between the two CP systems. The paper discusses these interface issues between hull and subsea where the hull is equipped with an impressed current cathodic protection (ICCP) system, and provides guidance for addressing them during flexible pipe CP design, operation, and monitoring. Specifically, CP design philosophies for flexible risers will be addressed with respect to manufacturing, installation and interface with the host structure’s Impressed Current Cathodic Protection (ICCP) system. The discussion will emphasize the importance of early coordination between the host structure ICCP system designers and the subsea SACP system designers, and will include recommendations for CP system computer modeling, CP system design operation and CP system monitoring. One of the challenges is to understand what to consider for the exposed surfaces in the flexible pipes and its multiple layers, and also the evaluation of the linear resistance of each riser segment. The linear resistance of the riser is a major determinant with respect to potential attenuation, which in turn largely determines the extent of current drain between the subsea sacrificial anode system and the hull ICCP system. To model the flexible riser CP system behavior for self-protection, linear resistance may be maximized, however the use of a realistic linear resistance is recommended for evaluation of the interaction between the host structure and subsea system. Realistic flexible linear resistance would also reduce conservatism in the CP design, potentially save time during the offshore campaign by reducing anode quantities, and also providing correct evaluation of drain current and stray currents.

Tie-in of a Rigid Pipeline to a Flexible Rise: Design and Installation — Challenges and Lessons Learnt

2019 ◽  
Author(s):  
Gianbattista Curti ◽  
Francois Lirola ◽  
Gianluigi Pirinu ◽  
Diego Pavone ◽  
Frederic Perrin
Keyword(s):  
West Africa ◽  
Bearing Capacity ◽  
Water Depth ◽  
Lessons Learned ◽  
Analysis Approach ◽  
Capacity Analysis ◽  
Flexible Pipe ◽  
Horizontal Connection ◽  
Flexible Pipes ◽  
Flexible Risers

Abstract This paper presents the experience made with the engineering and execution of the tie-in of flexible risers to rigid pipelines on a project recently completed in West Africa. Five production and injection pipelines (10” and 6”) were tied back to the host platform with flexible risers, in Lazy wave configurations, in ∼600m water depth. The risers are directly connected to the terminations structures (PLETs) of the rigid pipelines, through horizontal connection systems. The structures forming the tie-in (risers, PLETs and pipelines) have been designed to accommodate axial displacements of the pipelines in the range 0.3m to 1.0m, as positive displacements (expansions) and −0.1m to −0.7m as negative displacements (contractions) of the pipelines, respectively towards and away from the risers, due to pipelines thermal expansions and pipe walking. Note that along some of the lines anchoring structures have been installed to control pipe walking. The tie-in interface loads were to be limited, in order not to threaten the flexible pipe, the PLETs and the connectors, and, despite the small pipeline end displacements, keeping the interface loads within allowable values, was a challenge. The positive displacements were causing interface loads as high as 80% of the allowable values, while the negative displacements were causing up to 90% utilization of the capacity of the connectors and 95% of the allowable loading of the foundations of the PLETs. The main drivers of such high loadings are the stiffness of the flexible pipe, combined with the layout of the tie-in. Extensive in place analyses were done to simulate the effects of progressive displacements of the pipelines, the pipe-soil interactions and the specifics of the behaviour of the flexible pipes (hysteretic stiffness). Full 3D FE analyses of the foundations (mud mats) of the PLETs were done, to circumvent the limitations of a classical bearing capacity analysis approach. As built information were also used, to remove some conservatisms in the assumptions initially taken in the design. A special installation procedure was implemented, to achieve a layout of the riser at the approach of the pipeline capable to better relieve the displacements of the pipelines and reduce interface loads. Feedbacks from the installation are given in the paper. The lessons learned are also presented: a “flexible” pipe is a “stiff” structure and a direct tie-in to the pipeline may become an issue, if not addressed early enough during the execution of the project, when it can be too late to add mitigation structures, like intermediate tie-in spools, or to change significantly the routing of the risers and pipelines.

Flexible and Rigid Pipe Solutions in the Development of Ultra-Deepwater Fields

2003 ◽  
Author(s):  
Adriano Novitsky ◽  
Fin Gray
Keyword(s):  
Oil Industry ◽  
Technical Cooperation ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Collapse Resistance ◽  
Flexible Pipes ◽  
Campos Basin ◽  
Flexible Risers ◽  
Girth Welds ◽  
Full Scale Tests

The development of the offshore segment during the last three years was remarkably important for the oil industry due to some major achievements observed in the technical area, more specifically on the development of pipe solutions for ultra deepwater (UDW) applications. Brazil and Gulf of Mexico (GoM) have lately been the two main regions for application of proven pipe solutions in UDW. In Brazil, flexible pipes have been widely used in the development of UDW fields by Petrobras, while in the GoM, rigid pipelines and SCRs have been used for the majority of deepwater field developments. The main advances in flexible pipe technology are linked to the development of two major Petrobras fields located in the Campos Basin named Roncador and Marlim South. Technip-Coflexip has, through Technical Cooperation Agreements with Petrobras, designed, tested and installed flexible pipes, proving the fitness of this kind of product to UDW applications. The qualification of flexible risers for 1500m WD and flexible flowlines for 2000m WD are highlighted as being the main achievements. Extensive testing programs including, collapse, fatigue and offshore full scale tests have been put in place in order to simulate the design conditions to be seen by the pipes during installation and operation phases. The main design aspects in UDW like collapse, radial and lateral buckling of tensile armours, fatigue and thermal insulation will be covered in this paper and the current available technologies to tackle these issues will be presented. Similar design and qualification issues exist for rigid pipelines and risers (SCRs). The following three areas are specifically covered in this paper: collapse resistance of steel pipe; fatigue strength of plastically strained girth welds: and qualification of pipe-in-pipe thermal performance. These are some of the key areas of reeled pipe in deepwater applications that require successful project qualification. Technip-Coflexip has performed internal R&D programs on these areas as well as project specific qualifications. Both will be addressed by the paper.

scholarly journals Burst pressure prediction of fiber-reinforced flexible pipes with arbitrary generatrix

2021 ◽  
Vol 16 ◽  
pp. 155892502199081
Author(s):  
Guo-min Xu ◽  
Chang-geng Shuai
Keyword(s):  
Transfer Matrix ◽  
Linear Equations ◽  
Burst Pressure ◽  
Fiber Reinforced ◽  
Flexible Pipe ◽  
Theoretical Derivation ◽  
Design And Optimization ◽  
Flexible Pipes ◽  
Novel Method ◽  
Winding Angle

Fiber-reinforced flexible pipes are widely used to transport the fluid at locations requiring flexible connection in pipeline systems. It is important to predict the burst pressure to guarantee the reliability of the flexible pipes. Based on the composite shell theory and the transfer-matrix method, the burst pressure of flexible pipes with arbitrary generatrix under internal pressure is investigated. Firstly, a novel method is proposed to simplify the theoretical derivation of the transfer matrix by solving symbolic linear equations. The method is accurate and much faster than the manual derivation of the transfer matrix. The anisotropy dependency on the circumferential radius of the pipe is considered in the theoretical approach, along with the nonlinear stretch of the unidirectional fabric in the reinforced layer. Secondly, the burst pressure is predicted with the Tsai-Hill failure criterion and verified by burst tests of six different prototypes of the flexible pipe. It is found that the burst pressure is increased significantly with an optimal winding angle of the unidirectional fabric. The optimal result is determined by the geometric parameters of the pipe. The investigation method and results presented in this paper will guide the design and optimization of novel fiber-reinforced flexible pipes.

Creep Analysis for an Unbonded Flexible Pipe Barrier

2006 ◽  
Author(s):  
Lun Qiu ◽  
John Zhang
Keyword(s):  
Finite Element ◽  
Creep Behavior ◽  
Barrier Layer ◽  
Polyvinylidene Fluoride ◽  
Element Model ◽  
Polymer Materials ◽  
Flexible Pipe ◽  
Internal Fluid ◽  
Creep Analysis ◽  
Parameter Matching

The fluid barrier in an unbonded flexible pipe seals the pressure from the internal fluid. Since the barrier is usually made of polymer materials, it is unable to hold the pressure by itself. A metal reinforced hoop layer is usually needed outside the barrier layer in order to resist the pressure. The hoop layer is usually a steel bar with a cross-section of an irregular shape. It is helically wrapped at the outside of the barrier layer. When the pipe is pressurized, the barrier will be supported by the hoop reinforcement layer from outside. However, at the gap between the steel wraps where the barrier layer bridges, material of the barrier will be forced to extrude into the gap. The amount of the extrusion is a function of many parameters such as temperature, material property, and internal pressure and so on. In addition, it is time dependent. The creep effect needs be considered. It is critical to have a proper barrier design for a flexible pipe structure. This article presents a practical finite element method for evaluation of the barrier/gap design. The creep behavior of the polymers is multi-parameter related. Therefore, a series of material tests has been conducted under various stresses and temperatures for nylon, polyethylene and Polyvinylidene Fluoride. In this work a method is given to determine the creep behavior parameters through parameter matching based on the tests. The creep deformation of barrier was analyzed with a finite element model using these parameters.

A practical approach for supporting decisions in bridge condition assessment and monitoring

2019 ◽  
Author(s):  
Dániel Honfi ◽  
John Leander ◽  
Ivar Björnsson ◽  
Oskar Larsson Ivanov
Keyword(s):  
Measurement Techniques ◽  
Condition Assessment ◽  
Illustrative Case ◽  
Public Authorities ◽  
Daily Work ◽  
Rational Decision Making ◽  
Bridge Condition Assessment ◽  
Assessment And Monitoring ◽  
Illustrative Case Study

<p>In this contribution a practical and rational decision-making approach is presented to be applied for common bridges typically managed by public authorities. The authors have developed a model with the intention to be applicable for practical cases for common bridges in the daily work of bride operators responsible for a large number of assets, yet still maintain the principles of more generic frameworks based on probabilistic decision-theory.</p><p>Three main attributes of the verification of sufficiency of structural performance are considered, namely: 1) the level of sophistication of modelling performance, 2) the degree of verification and acceptance criteria in terms of dealing with uncertainties and consequences, 3) the extent of information is obtained and incorporated in the verification.</p><p>The simplicity of the approach is demonstrated through an illustrative case study inspired by practical condition assessment decision problems. It is argued that in practical cases it may be desirable to utilize less advanced methods owing to constraints in resources or lack of reliable data (e.g. based on structural health monitoring or other on-site measurement techniques).</p>

Optimization of Flexible Pipes Dynamic Analysis Using Artificial Neural Networks

2016 ◽  
Author(s):  
Victor Chaves ◽  
Luis V. S. Sagrilo ◽  
Vinícius Ribeiro Machado da Silva
Keyword(s):  
Dynamic Analysis ◽  
Fem Simulation ◽  
Training Data ◽  
Local Analysis ◽  
Flexible Pipe ◽  
Nonlinear Fem ◽  
Irregular Wave ◽  
Flexible Pipes ◽  
Artificial Neural ◽  
Hybrid Methodology

Irregular wave dynamic analysis is an extremely computational expensive process on flexible pipes design. One emerging method that aims to reduce these computational costs is the hybrid methodology that combines Finite Element Analyses (FEA) and Artificial Neural Network (ANN). The proposed hybrid methodology aims to predict flexible pipe tension and curvatures in the bend stiffener region. Firstly using short FEA simulations to train the ANN, and then using only the ANN and the prescribed floater motions to get the rest of the response histories. Two approaches are developed with respect to the training data. One uses an ANN for each sea state in the wave scatter diagram and the other develops an ANN for each wave incidence direction. In order to evaluate the accuracy of the proposed approaches, a local analysis is applied, based on the predicted tension and curvatures, to calculate stresses in tension armour wires and the corresponding flexible pipe fatigue lifes. The results are compared to those from full nonlinear FEM simulation.

Investigation on Mechanical Properties of Fibreglass Reinforced Flexible Pipes Under Torsion

2018 ◽  
Author(s):  
Pan Fang ◽  
Yuxin Xu ◽  
Shuai Yuan ◽  
Yong Bai ◽  
Peng Cheng
Keyword(s):  
Mechanical Behavior ◽  
Torsion Angle ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Load Condition ◽  
Element Model ◽  
Flexible Pipe ◽  
Torsional Load ◽  
Flexible Pipes ◽  
The Impact

Fibreglass reinforced flexible pipe (FRFP) is regarded as a great alternative to many bonded flexible pipes in the field of oil or gas transportation in shallow water. This paper describes an analysis of the mechanical behavior of FRFP under torsion. The mechanical behavior of FRFP subjected to pure torsion was investigated by experimental, analytical and numerical methods. Firstly, this paper presents experimental studies of three 10-layer FRFP subjected to torsional load. Torque-torsion angle relations were recorded during this test. Then, a theoretical model based on three-dimensional (3D) anisotropic elasticity theory was proposed to study the mechanical behavior of FRFP. In addition, a finite element model (FEM) including reinforced layers and PE layers was used to simulate the torsional load condition in ABAQUS. Torque-torsion angle relations obtained from these three methods agree well with each other, which illustrates the accuracy and reliability of the analytical model and FEM. The impact of fibreglass winding angle, thickness of reinforced layers and radius-thickness ratio were also studied. Conclusions obtained from this research may be of great practicality to manufacturing engineers.

Mechanical Behaviors of Steel Strip Reinforced Flexible Pipes Under Bending

2018 ◽  
Author(s):  
Shan Jin ◽  
Shuai Yuan ◽  
Ting Liu ◽  
Peihua Han ◽  
Yong Bai
Keyword(s):  
Steel Strip ◽  
Practical Application ◽  
Pure Bending ◽  
Flexible Pipe ◽  
Four Point Bending ◽  
Offshore Engineering ◽  
Flexible Pipes ◽  
Proposed Model ◽  
Composite Pipe ◽  
Good Coincidence

Steel strip reinforced flexible pipe (SSRFP) is a kind of unbonded composite pipe, which has more application foreground in offshore engineering due to its excellent mechanics and the considerable flexibility. In practical application, SSRFP will inevitably experience bending during reeling process and installation. In this paper, the mechanical behavior of SSRFP subjected to pure bending are studied both experimentally and numerically. A four-point bending equipment is utilized to conduct the full-scale laboratorial tests of SSRFP. Furthermore, the commercial software ABAQUS is employed to simulate its ovalization instability. The results acquired from the ABAQUS simulation are compared with the ones from verification bending experiment, which are in good coincidence with each other. The proposed model and the relative results may be of interest to the manufacture factory engineers.

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

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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