The Analysis of Mechanical Properties and Lightweight Design of Nonmetallic Armored Umbilical Cable

Due to the development of gas and oil exploration into the deep sea, the effective tensile capacity provided by armored steel wire will decrease rapidly with the increase of the weight of umbilical cables. In this paper, two designs of lightweight umbilical cables were studied in full consideration of the geometric characteristics, and the mechanical properties were investigated under tension, bending, and torsion. The contact and friction between the components of the umbilical cables were also included in the model. Three cases are presented for validation from theoretical and finite element methods. The discussion on variables was carried out from the views of friction coefficient and helically wound angle. Compared with the steel tube umbilical model, the nonmetallic armored umbilical cable shows higher tensile strength and more flexibility. With the increase of friction coefficient, the stiffness of umbilical cable models don't change much. The helically wound angle has a great influence on the tensile stiffness and bending stiffness but little effect on the torsional rigidity. The proposed lightweight model can be applicable to 6000m water depth. This research can benefit the design of umbilical cables to achieve the goal of high tensile capacity in deepwater applications.

Electro-thermal-mechanical Coupled Analysis on Two High-Current Composite Umbilical Cable Cross-sections

A new type of umbilical cable named ‘strong-electricity composite umbilical cable’ is composed of electronic cables, optical cables, steel tubes and structural strengthening components. It can be regarded as a key piece of industrial equipment in subsea production systems that provide control functions, strong electric and hydraulic remote transmission. when it is oriented at a power supply with a relatively high rated voltage, power transmission will produce a lot of heat. Then, the cross-sectional temperature increases, which affects the performances of its material and mechanical responses. Therefore, electro–thermal–mechanical coupled analysis is critical for the cross-sectional design of the strong-electricity composite umbilical cable. Accordingly, a multi-physics coupled analysis was performed based on two typical umbilical cable cross-sections. Finite element models were established and subjected to electro–thermal analysis to obtain a temperature distribution of the two sections at different current capacities. Based on results of temperature field analysis, the section models were subjected to thermal–mechanical analysis. The results of the two types of analyses are compared and differences are discussed, which illustrate the multi-physics coupled effect cannot be neglected. The armored layers will relatively reduce the heat dissipation performance, but compared with the umbilical cable model without the armored layers, the model with double-armored layers is less affected by temperature, so its capacity of resistance external pressure is relatively better. The proposed coupled analysis methodology provides a new guidance for the design of the strong-electricity composite umbilical cables.

Propuesta de un sistema de comunicación inalámbrico para una red de sensores bajo el agua en tiempo real aplicado a un sistema ROV

This work a novel approach in radio frequency communications applied to a underwater wireless sensors network UWSN is presented. The proposal is to manipulate in a bounded and controlled environment a Remote Operated Vehicle ROV without umbilical cable through a underwater sensors network based on radio frequency communication, taking advantage of the faculties of this underwater communication in conjunction with a sensor network, furter, a dynamic redundancy is used in the transmitters towards the ROV to increasing the range and avoiding communication loss, aditional a static redundancy is applied on the receiver to increase te reliability of comunication. The part of the ROV receiving sensors is based on a statisc redundancy of 3 sensors which will apply a vote taking in order to failure tolerantce, the sensor network will applied a dinamic redundacy in the transmitters in order to follow the communication with the ROV, in case of failure, the communication loss can be compensated with another sensor of the network that will take its role.

Phenomena Analysis of Ferroresonance and Self-Excitation in Subsea Power Systems

This article addresses the study regarding the emergence of ferroresonance and selfexcitation phenomena in Subsea Power Systems - SPS, composed essentially of synchronous generators installed on a platform (Topside), a three-phase umbilical cable and the electrical loads, the latter constituted by induction machines located on the seabed and connected to the umbilical through a power transformer and power electronic converters. Such phenomena are conceptually stated and characterized in the scope of SPS and the simulations are carried out in the PSCAD/EMTDC software, in its parallel processing environment, to verify indications of the existence of problems in the base network of the subsea distribution system.

Crushing of a Steel Tube Umbilical (STU) Cable During Laying Operation: A Finite Element Method Assessment at the Entry/Exit Regions of Tensioner Shoes

Umbilical cables are fundamental equipment used in deep and ultra-deep waters oil and gas production systems. The complexity of this kind of structure leads structural analysis to be currently performed with numerical tools. This paper presents a nonlinear three-dimensional finite element model of a typical armored Steel Tube Umbilical Cable (STU) subjected to crushing loads imposed to the umbilical cable during laying operation. The study focuses on the analysis of the stress distribution in the steel tubes at caterpillar shoes, mainly at the entry/exit transition regions. With the use of a commercial software, the finite element model is constructed, considering geometric and materials nonlinearities. Crushing loads are imposed by two rigid plates. Focus is given on the duplex tubes, with the material stress-strain curve modeled from a specific crushing experiment with a single tube and by using a classic Ramberg-Osgood fitting. Firstly, comparisons at mid-length of the three-dimensional model are made with the results from a simpler and planar finite element model. Then, the localized three-dimensional effects are analyzed. The results show a considerable increase of the stress levels in the steel tubes at these transition regions, with the occurrence of stress field redistribution after the onset of plastic deformation.

Parametric Analysis of Steel-Tube Umbilical Armor Pots

Armor pots are mechanical devices employed in the offshore oil production to anchor armor wires/steel tubes of an umbilical cable. In epoxy-based armor pots, this anchoring is obtained through the interaction between the resin and the tensile armors/steel tubes and also through the capstan effect from geometric variations, such as radius and lay angle changes. In this context, friction plays a fundamental role in the anchoring capacity and is mainly affected, among other factors, by the intensity of resin thermal contraction, which generates positive pressure at the contact interfaces, and also by the friction coefficient. Therefore, this works presents an extensive parametric analysis of the resin thermal contraction and of the friction coefficient performed through the finite element method with the objective of understanding their qualitative and quantitative influence at the anchoring capacity of a steel-tube umbilical armor pot. In recent years, the authors published fully three-dimensional finite element models of armor pots. In order to accomplish the present work, several enhancements were performed in the aforementioned models. The main development is an innovative methodology for the resin mesh generation, ensuring mapped elements at the interfaces with steel tubes, resulting in a smoother contact representation. At the same time, this methodology is computationally advantageous by allowing larger element sizes at the remaining resin volume without loss of quality in the representation.