Flexible risers and umbilicals
Flexible risers and umbilicals are composite structures made up of components of steel, polymer and other materials. Subjected to external or internal loading the various components will interact in a complicated way. Design of flexible risers and umbilicals is based on advanced methods for structural analysis in combination with structural and materials testing. Global response and stress, strain and displacement of individual wall components are calculated by analysis. In the laboratory, the conditions within a cross section are simulated for the individual components, which are subjected to static and dynamic loading corresponding to design conditions. For new designs full scale static and dynamic testing is in general required.
MARINTEK has been focusing research on first principle methods for cross sectional strength analysis of flexible risers and umbilicals, and small scale testing for modelling of safe life of critical components. Mechanical, thermal and chemical loads have been considered, and degradation mechanisms have been identified and investigated in detail. The main objective of the work has been to contribute towards improved design and enhanced reliability for these structures. Development of efficient design methods may also reduce the need for time consuming and costly full scale tests.
BFLEX |
UFLEX |
Dynamic test rig |
The following numerical tools and test facilities have been developed:
RIFLEX:
Non-linear FE code for 3-D global analysis of pipe, static and dynamic analysis, frequency and time domain analysis, assessment of test parameters for simulation of operating conditions.
BFLEX:
Computer program for calculation of stress and displacement, fatigue and wear analysis of wall components of flexible pipes subjected to bending, torsion, tension, internal and external pressure. Detailed cross sectional analysis of tensile armour and pressure armour (Zeta, Theta, C-clip profiles).
UFLEX:
Computer program for calculation of stresses in complex umbilicals cross-sections subjected to bending, torsion, tension, internal and external pressure, and external contact forces.
DYNAMIC TEST RIGS:
Rig for full scale fatigue testing of 18 m (max.) length of flexible riser or umbilical with end terminations and bend stiffener/ bellmouth. This test is required for new designs.
As above for fatigue testing of 8 m (max.) long models. The rig is suitable for testing of smaller size umbilicals and flexible risers.
THERMAL TEST RIG:
Rig for simulation of thermal cycles caused by intermittent shut-down of flow through a flexible riser. Many operators require this test for new designs in applications with high temperature well flow.
SMALL SCALE TESTS:
Rigs for testing of fatigue, corrosion fatigue (including CO2 and H2S), friction, wear and durability at elevated temperature for materials and components in flexible risers and umbilicals. These tests provide input parameters for BFLEX and UFLEX.
Contact at MARINTEK: Oddvar Eide