Design and Modeling of Flexible Ball Joint Pipe
Authors: Albarody Thar M. Badri , Bt Mustaffa Zahiraniza , Taufiq Mohammed Badri 
Published: June 2014

Abstract
Reel-lay process is considered the most efficient installation/construction methods for offshore pipelines and has attracted particular interest on the designing of pipe with large elastic deformation capacity. Therefore, an unbonded, flexible composite ball joints pipe is proposed. The pipe is comprising an internal composite pipe segment with its ball joining to play as liner i.e., carcass, and one or more helical wounding tape stacks applied to the internal liner for absorbing axial and bending loads. The composite tape stacks are formed from a plurality of thin tape strips. All the layers are manufactured from a lightweight composite material consisting of highly noncorrosive epoxied matrix reinforced by long continuous fibers. This paper describes the design parameters of the pipe segments (e.g., modeled as laminated composite cylindrical shell) that form the pipe and its elastic deformations capacity under pure bending conditions (e.g., typical reeling installation condition). To this aim, a straightforward treatment of the problem is presented via using Hamilton's principle and based on the first order shear deformation theories. The solution of the laminated composite cylindrical shell was formulated to follow exactly a simply supported boundary condition. The inter-laminar stresses are evaluated for wide range of orthotropy ratio.

Introduction
A large diameter, an unbonded, and flexible composite ball joint pipe may be used in particular, although not exclusive, as utility in offshore (e.g., continental shelf environments) or onshore for the transportation of petroleum oil and gas or other fluids. Given that the production of the fossil fuels in offshore fields is limited by a small diameter pipeline was selected to avoid the hydrostatic pressure. It is considered reasonable to assume that the large diameter composite pipes will yield a much higher volume of oil and gas. Thereby the pipe becomes bendable and sufficiently flexible to spool onto reel for the purpose of reeling installation. In general the anti-corrosive and flexible composite pipes are expected to have a lifetime more than 25 years in operation. Flexible pipes are well known in the art and are for example they described in the standards ANSI/API 17 B; Recommended Practice for Flexible Pipe, and ANSI/API 17J; Specification for Unbonded Flexible Pipe. In this paper the proposed flexible ball joint pipe was designed to fulfill a number of requirements:First of all the pipe was designed to have a very high mechanical strength to withstand the forces it will be subjected to during transportation, deploying and in operation.The pipe segments was designed to withstand the internal pressure that are usually considered very high and may vary considerably along the length of the pipe, in particular when applied at varying water depths. Therefore, the pipe segments will design to be stiffer enough to resist the differences in the pressure withstanding the burst and collapse.Simultaneously the flexible pipe was designed from specific composite materials to be highly non-corrosive and chemical resistance.The proposed pipe was designed to keep the weight of the pipe relatively low, both in order to reduce transportation cost and deployment cost but also in order to reduce risk of damaging the pipe during deployment.
Therefore, the present paper will emphases more on the designing of the pipe element to combined the controlled weight (i.e., depending on the buoyancy that required to keep the pipe stable at the design depth) and high strength properties.