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The connectors on an umbilical system are critical components that are subjected to high tensile loads. To ensure tension resistance to an umbilical cable connection, its structural elements must be properly anchored to the armor pot. One way to provide that connection is the use of the adhesive properties of an epoxy resin. In that context, it is necessary to perform a series of pull out tests in order to verify if the resin is capable of withstanding the tensile loads transmitted by the tensile armor layers or the steel tubes. For that purpose, a series of tridimensional finite element models are being developed to represent, as realistic as possible, the interaction between metallic layer and resin. These models allow a fully helical tensile armor to interact with a resin substrate. For this article, an early stage model considering bonded contacts is presented and the adhesion of the tensile armor tendons is evaluated in terms of the shear stresses in the contact regions.

At the end of flexible pipe manufacturing, the assembly of end fittings ancillaries is necessary to provide the connection with the platform and the subsea systems. The assembly process uses epoxy resin to ensure the holding of the tensile armor layers inside the end fitting. The anchoring system has great importance in the integrity of the flexible pipes system, since their failure causes the separation between the flexible pipe and ancillaries, what can put on risk the production and the environment. During the qualification tests of new structures were observed that some variables of the process could be determinant on the mechanical strength resistance required for the product. One of these known variables is the ratio resin/hardener. Resin supplier specifies at the datasheet the proper ratio to obtain the full cure, but it was observed that small variations in the concentration alters the maximum tensile anchoring strength supported by the structure, as well the minimum curing time that should be obeyed, so it can be better used regarding their mechanical properties. In this way, laboratorial tests were conducted to enhance the performance of this resin in the tensile anchoring system, according to Prysmian Surflex products’ necessity. Compression tests varying the resin/hardener ratio were done to evaluate the resistance as a function of curing time. Besides this, tensile tests (tensile wire pulls over from resin) were conducted to establish a relation between maximum tensile load and the resin ratio, and so provide enough data to control the best proportion of resin during the end fitting assembly phase.Copyright © 2015 by ASME

Umbilical cables are essential elements of offshore floating production systems. Due to their complexity, the offshore industry regularly counts on numerical tools to perform design assignments. One of these assignments is to evaluate strains and stresses states in all components due to distinct sets of external loads. The main purpose of this paper is to present a numerical model for prediction of the stress and strain fields in the umbilical cable components under crushing loads. Such loads, outcoming from the laying operation, comprise the caterpillar shoes load and the squeezing effects, associated not only to the tensile armours, but also to helical components under tension. The referred model comprises a joint analysis using a two-dimensional Finite Element Method (FEM) fed by an analytical model, which represent three-dimensional effects. A combined analytical-numerical approach is much easier to implement than a complete fully three-dimensional one and it is meant to obtain results efficiently, without the need of a large computational capacity. The paper presents and discuss modeling hypotheses and methodology, describing in which way three-dimensional effects and interactions among cable components were treated. Case studies with three umbilical cables are presented.Copyright © 2015 by ASME

In the design of flexible pipes, predict the anchoring behavior on end fittings is always challenging. In this sense, Prysmian Surflex has developed a finite element model, which should help the end fitting design as well the prediction of the structural behavior and the acceptable maximum loads. The current model considers that the contact between armor-resin is purely cohesive and has been suitable for the design of end fittings [1] and [2]. But tests and new studies [3] and [4] indicate that only cohesive assumption would not be the best approach. Experimental data from prototype tests also show that the current model would not predict acceptable results for loads higher than those used in previous projects. This document will describe a study developed considering the friction and thermal contraction, instead of the cohesive phenomenon in the anchoring behavior analysis. Small scale tests were conducted in order to understand the anchoring relation between the resin and the wire used in the tensile armor. For this purpose, a special test device was developed to simulate an enclosure system. A parametric study was also performed to identify the cooling temperatures, coefficients of friction and contact properties parameters taken from small scale tests. The finite element model considers the thermal effects during exothermic curing. Using the new parameters obtained, a second model was developed. This model consists of only one real shaped bended wire inside an end fitting cavity. To validate the model, samples were tested on laboratory according anchoring design. The results of this round of tests were studied and corroborate the argument that use friction and thermal effects is better than use only the cohesive condition.

This paper presents a numerical 3D finite element model to simulate a flexible pipe under crushing-traction condition, which is a typical situation found during its laying operation. This model considers the geometry of some layers from the flexible pipe, responsible of providing the most contribution to its radial strength (e.g., interlocked carcass, internal polymeric layer, pressure armor, and external polymeric layer) and geometry of laying system shoes. It also considers the flexible pipe initial ovalization and the squeezing effect due to the tensile armor layers under traction. A numerical-experimental comparison is presented, in order to show the model validity.Copyright © 2013 by ASME

Accurate prediction of the load capacity of the constituent components of flexible risers and flowline structures is critical in demonstrating fitness for purpose, particularly as the envelope of application of flexible pipe is being extended to incorporate higher flow rates, greater water depths, more aggressive fluid contents and challenging installation conditions. Analytical techniques and numerical solid modelling methods have evolved significantly in recent years as a means of improving the ability to accurately predict flexible pipe load capacity. Due to the complexity of the flexible pipe structure and the load sources and load paths to which it can be subjected, different analysis methods are required, depending on the type of response being evaluated. Specific effects can be difficult to simulate using analytical approaches and require local stress analysis using numerical techniques. This paper presents numerical approaches to two such effects, the extreme loading of tensile armour wires within a flexible pipe end fitting and the stability of tensile armour wires in axial compression.

This paper discusses a nonlinear analytical model for flexible pipe crushing analysis, improving analytical models previously published in OMAE2003, 2010 and 2011. Following that path, and still based on the concept of equivalent pipes and rings, the present model discusses a strategy to cope with an elastic-to-plastic analysis. Such a model considers the combined action of squeezing and concentrated loads applied as representing those due to the caterpillar shoes. Experimental results and finite element analysis are used to assess the pertinence of analytical modeling hypotheses.Copyright © 2012 by ASME

During installation and operation a flexible pipe may be subjected to high compressive forces, high cyclic curvatures and external pressures leading to high reverse end-cap loads. Under such loading conditions, which occur particularly in the touchdown region for deep water applications, the limiting condition for the flexible pipe can be the compressive stability of the tensile armour wires. Two potential instability modes are possible: radial mode (birdcaging) and lateral mode (lateral wire disorganization). Previous work on the subject has established the key factors which influence the onset of each buckling mode [1],[2],[3] and [4]. In order to ensure the feasibility of flexible designs for applications with increasing water depth, it is important to improve the knowledge of the mechanisms which can lead to instability of armour wires and enhance the ability to predict with greater assurance, the particular conditions which increase the risk of wire instability. The focus of this work is the comparison of finite element prediction of radial buckling (birdcaging) with physical testing results under loading states that lead a pipe to birdcaging failure. The numerical model incorporates all tensile armor wires and their interactions with each other and adjacent layers. The outer sheath and reinforcing tape layers are explicitly represented, while the inner layers of the pipe (pressure armour and carcass sheath) are idealized using a homogeneous representation. The model also incorporates the effects of manufacturing pre-tension and hoop strength in the anti-birdcaging tape layers which are critical determinants for the onset of buckling. A key aspect of the method presented is the means by which the loading is applied. Specifically, the modeling handles the simultaneous and controlled application of end rotations, axial compression and radial resistance of the tapes through to the point of tape failure, pipe ovalisation and subsequent radial displacement and buckling of individual wires. In summary, in this paper a solid modeling approach is presented, which is compared with full a scale sample test data, that enables the simulation of a flexible pipe undergoing large combined compression, curvatures and pressure loading.