Session: 04-01-07 Flexible Pipes & Umbilicals VII

Paper Number: 121191

121191 - Bending Stiffness of Unbonded Flexible Pipes and Its Application in Installation 

The bending hysteresis behavior of unbonded flexible pipe is well known and fully implemented in flexible riser system design and analysis, for example, extreme, interference and fatigue analysis. However, in some quasi-dynamic or quasi-static applications, the inclusion of the full bending hysteresis loop sometimes leads to noticeable deviations with respect to configurations observed in the field.

To address these, this paper intends to interpret these differences from the nature of the internal friction, which is the main mechanism governing the pipe bending hysteresis behavior. Two operation cases are presented for the study: 1) a flowline installation and 2) a flexible riser wet storage. The pipes in both cases are not subjected to any significant wave excitations, therefore are considered as quasi-dynamic or quasi-static applications. The flowline installation involves a ‘camel hump’ configuration during end fitting gooseneck connection. The riser wet storage case involves a single wave configuration with installation ballasts, considering about a 1-year wet parking period. The paper presents a configuration sensitivity study with different bending stiffnesses and identifies the one that produces the best agreement between the predicted and measured configuration in the survey. Based on the findings, the paper also recommends the most appropriate use of pipe bending stiffness in designing short quasi-dynamic or quasi-static jumpers which predicts accurate configuration and associated support interfacing loads thus avoiding excessive conservatism.

Keywords: Bending Stiffness Relaxation, Unbonded Flexible Pipes, Installation, Jumper

Presenting Author: Linfa Zhu Baker Hughes

Presenting Author Biography: Linfa Zhu is a Staff Engineer in Baker Hughes. He has over 10 years of experience in the flexible pipe industry. Dr. Zhu gained his PhD in mechanical engineering at Arizona State University.

Authors:

Linfa Zhu Baker Hughes
Yan Zhou BP
Yucheng Hou Baker Hughes
Jason Reuter BP
Jiabei Yuan Baker Hughes
Zhimin Tan Baker Hughes
Andrew Roberts Baker Hughes