When there is a failure on the external sheath of a flexible pipe, a high value of hydrostatic pressure is transferred to its internal plastic layer and consequently to its interlocked carcass, leading to the possibility of collapse. The design of a flexible pipe must predict the maximum value of external pressure the carcass layer can be subjected to without collapse. This value depends on the initial ovalization due to manufacturing tolerances. To study that problem, two numerical finite element models were developed to simulate the behavior of the carcass subjected to external pressure, including the plastic behavior of the materials. The first one is a full 3D model and the second one is a 3D ring model, both composed by solid elements. An interesting conclusion is that both the models provide the same results. An analytical model using an equivalent thickness approach for the carcass layer was also constructed. A good correlation between analytical and numerical models was achieved for pre-collapse behavior but the collapse pressure value and post-collapse behavior were not well predicted by the analytical model.

References

References
1.
Sánchez
,
S. H. A.
, and
Salas
,
C. C.
, 2006, “
Risers Stability under External Pressure, Axial Compression and Bending Moment Considering the Welded as Geometrical Imperfection
,” Proceedings of the 25th International Conference on Offshore Mechanics and Arctic Engineering, 2006.
2.
Fernando
,
S. U.
,
Sheldrake
,
T.
,
Tan
,
Z.
, and
Clements
,
R.
, 2004, “
The Stress Analysis and Residual Stress Evaluation of Pressure Armour Layers in Flexible Pipes Using 3D Finite Element Models
,” Proceedings of the 23rd International Conference on Offshore Mechanics and Arctic Engineering, 2004.
3.
Gay Neto
,
A.
, and
Martins
,
C. A.
, 2010, “
Burst Prediction of Flexible Pipes
,” Proceedings of the 29th International Conference on Offshore Mechanics and Arctic Engineering, 2010.
4.
Timoshenko
,
S. P.
, and
Gere
,
J. M.
, 1961,
Theory of Elastic Stability
,
McGraw-Hill International Book Company, Inc.
,
New York
.
5.
Bai
,
Y.
Analytical Collapse Capacity of Corroded Pipes, Proceedings of the Eight International Offshore and Polar Engineering Conference, 1998.
6.
Bai
,
Y.
,
Hauch
,
S.
, and
Jensen
,
J. C.
, 1999, “
Local Buckling and Plastic Collapse of Corroded Pipes with Yield Anisotropy
,” Proceedings of the Ninth International Offshore and Polar Engineering Conference, 1999.
7.
Martins
,
C. A.
,
Pesce
,
C. P.
, and
Aranha
,
J.A. P.
, 2003, “
Structural Behavior of Flexible Pipe Carcass during Launching
,” Proceedings of the 22th International Conference on Offshore Mechanics and Arctic Engineering, 2003.
8.
American Petroleum Institute
, 2002,
API Recommended Practice 17B, Information Handling Services
,
API
,
Washington D.C.
.
9.
De Sousa
,
J. R. M.
,
Lima
,
E. C. P.
,
Ellwanger
,
G. B.
, and
Papaleo
,
A
, 2001, “
Local Mechanical Behavior of Flexible Pipes Subjected to Installation Loads
,” Proceedings of the 20th International Conference on Offshore Mechanics and Arctic Engineering, 2001.
You do not currently have access to this content.