A Knn Based Collapse Methodology and Recent Qualification of Flexible Pipes in Deepwater Application

2021 ◽  
Author(s):  
Linfa Zhu ◽  
Victor Nogueira ◽  
Zhimin Tan
Keyword(s):  
Flexible Pipes

Artificial mixing to reduce growth of the blue-green alga Microcystis in Lake Nieuwe Meer, Amsterdam: an evaluation of 7 years of experience

2001 ◽  
Vol 1 (1) ◽  
pp. 17-23 ◽  
Author(s):  
E. Jungo ◽  
Petra M. Visser ◽  
Jasper Stroom ◽  
Luuc R. Mur
Keyword(s):  
Water Body ◽  
Bubble Plume ◽  
Annual Fluctuation ◽  
Algae Biomass ◽  
Mechanical Parts ◽  
Living Space ◽  
Artificial Mixing ◽  
Flexible Pipes ◽  
Nitrogen Concentrations ◽  
Extensive Growth

The problem of Lake Nieuwe Meer (area = 1.3 km2, max. depth 30 m, Ptot = 500 mg/m3) was extensive growth of Microcystis with disturbing scum forming. Since 1993 the lake has been artificially mixed in summer by a bubble plume installation. The result is quite successful since the mass of Microcystis is up to 20 times lower than in the years before mixing and no scum is present any more. The study in Lake Nieuwe Meer showed a shift from cyanobacterial dominance (mainly Microcystis) to flagellates, green-algae and diatoms when artificial mixing was applied. Total phosphorus and nitrogen concentrations did not change as a result of mixing and had apparently no effect on the shift in the phytoplankton composition. The chlorophyll-a concentration was much lower in the mixed lake as a result of dilution. The total algae biomass decreased. The transparency did not improve. The total heat energy of the lake is slightly higher than before mixing but still remains in the range of annual fluctuation. The temperature on the surface is approximately 2°C lower. In the whole water-body oxygen was always higher than 5 mg/l. Living space for fish is therefore wider. The installation in Lake Nieuwe Meer consists of flexible pipes near the sediment, built in a way to prevent sediment erosion and transport into the water. There are no constructions in the water-body. All mechanical parts are on land. The layout of the installation is shown in Fig. 1. Installed compressor energy is 85 kW. This is equivalent to an upper middle-class motor-car. The design was made specifically for this problem. It is based on the physical data of the algae and the plant. It would be beneficial to use this 7 year's experience for further applications e.g. elimination of toxic algae in drinking-water reservoirs.

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.

Torsion Failures in Handling Operations for Power Cables, Umbilicals and Flexible Pipes

2021 ◽  
Author(s):  
Philippe Mainçon ◽  
Vegard Longva
Keyword(s):  
Failure Modes ◽  
Compressive Load ◽  
Qualitative Description ◽  
Power Cables ◽  
Knowledge Gaps ◽  
The Past ◽  
Flexible Pipes ◽  
Systematic Nomenclature ◽  
Component Failures ◽  
Flexible Products

Abstract Over the past 10 years, SINTEF has investigated, or been informed about, a range of torsion failures in cables, umbilicals or flexible pipes. These failures have occurred while the flexible products were being transported along a route during production, loadout, installation. One failure occured during operation. There are no guidelines on how to minimize the risk of such failures. This may be attributed to a lack of knowledge in the industry about the mechanisms that cause torsional moments to appear. Further, some buckling patterns of the components of a flexible product under excessive torsion, closely resemble patterns caused by excessive bending or compressive load, so that some torsion-induced failures are wrongly attributed. Hence, there is a need to increase the knowledge and awareness of torsion failures in the industry. Previous papers by the authors have considered some of the mechanisms that lead to the appearance of torque in handling operations. The present paper is a continuation which focuses on torque-induced failure modes. It begins by providing a systematic nomenclature for the description of torsion kinematics. It then provides a qualitative description of known torque-induced failure modes. The literature provides some models for torque-induced failures, as well as models of component failures due to excessive bending or compression of the flexible product, which are also relevant for the study of torsion. These are reviewed, and their relevance to torsion-induced failures are discussed. Knowledge gaps and challenges are highlighted.

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.

Experimental Study on Flexible Bare Pipe Arrays Undergoing Vortex-Induced Vibrations

2018 ◽  
Author(s):  
Y. Liu ◽  
C. Shi ◽  
Z. Liu ◽  
J. Wang ◽  
X. Bao
Keyword(s):  
Fatigue Damage ◽  
Dynamic Responses ◽  
Array Configuration ◽  
Damage Rate ◽  
Flexible Pipes ◽  
Vortex Induced Vibrations ◽  
Helical Strakes ◽  
Preliminary Study ◽  
Single Pipe ◽  
Center Distance

Vortex-induced vibration (VIV) excited by current is a major contributor to the fatigue accumulation of marine risers. For deepwater operations, several risers are often arranged together in an array configuration. In this study, a set of four identical flexible pipes of a rectangular arrangement were tested in a water tunnel. By comparing the dynamic responses of a pipe in an array with that of a single isolated pipe, the effects of the current speed and the center-to-center distance between the up-stream and downstream pipes on their dynamic responses were investigated. Fatigue damages accumulated on each pipe in an array was calculated and a factor, termed “fatigue damage amplification factor”, was defined as a ratio between the fatigue damage rate of pipe in an array and the fatigue damage rate of a single pipe at a same current condition. The results showed that for bare pipes (i.e., without helical strakes), the downstream pipes in an array configuration may have larger dynamic responses and fatigue damage rates than those of a single pipe; and, it is not always conservative to assume that the fatigue damage rate estimated for a single pipe can be used to represent the fatigue damage rates of pipes in an array. This preliminary study provided some meaningful results for the design, analysis and operation of marine riser arrays.

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.

Development and operation of a fiber Bragg grating based online monitoring strategy for slope deformation

Sensor Review ◽  
2015 ◽  
Vol 35 (4) ◽  
pp. 348-356 ◽  
Author(s):  
Yongxing Guo ◽  
Dongsheng Zhang ◽  
Jianjun Fu ◽  
Shaobo Liu ◽  
Shengzhuo Zhang ◽  
...  
Keyword(s):  
Real Time ◽  
Online Monitoring ◽  
Deformation Monitoring ◽  
Slope Deformation ◽  
Remote Access ◽  
Monitoring Strategy ◽  
Content Type ◽  
Flexible Pipes ◽  
Sensor Structure ◽  
Distributed Strain

Purpose – The purpose of this paper is to investigate an online monitoring strategy that incorporates fiber Bragg gratings (FBGs) for deformation displacement detection, with the background that slope deformation monitoring is crucial to engineering safety supervision and disaster prevention. Design/methodology/approach – A “beam element” method has been proposed, introduced and experimentally verified in detail. The deformation displacement along a flexible bar can be obtained based on this method, using the distributed strain detected by the FBGs embedded in the bar. A novel sensor structure containing inclinometer casings and a series of connected flexible pipes with FBGs embedded has been proposed. Based on the features of this structure, two FBG deformation sensors have been manufactured and installed into a slope. A matched monitoring station which permits real-time supervision, warning and remote access across the Internet was established and operated. Findings – Displacement data from September 2013 to August 2014 are obtained, which is basically consistent with the practical situation. Originality/value – The FBG deformation sensors demonstrated a robust and reliable measurement performance, which is promising for real-time disaster warning in slope engineering.

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.

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