RiserTec and Lankhorst Mouldings have formed a partnership for the design, manufacture, testing and commercial development of a range of Riser System Ancillary Products. The design and engineering is carried out by RiserTec who operate an ISO 9001 certified design process. The objective of the partnership is to offer a fully documented engineering solution manufactured to the highest standard and which has been rigorously tested.

One of the most demanding of these products is a Dynamic Bend Stiffener designed for operational life in excess of 20 years. The design is currently offered for risers and umbilicals with outer diameters from 60mm up to 200mm; with larger sizes planned for the future. The polyurethane profile of the bend stiffener design can be produced as part of the system global analysis or with the RiserTec RT_Bend in-house non-linear design package from typical tension angle data.

The key to the design is the interaction between the steel insert and the moulded polyurethane. RiserTec expended a considerable effort to produce an optimised insert design which we believe is “state of the art” working from basic principles and developing and testing, through axi-symmetric FEA models over 40 different geometries. The geometry has also been optimised for moulding and for long insert fatigue life and was finalised using a full 3D Finite Element Analysis with steel-polyurethane elements and riser internal contact modelled as well as the full material stress-strain curves.

Following the detailed design RiserTec and Lankhorst carried out the full-scale testing of a 3m stiffener with an ID of 90mm and 100mm as part of a design verification process. The full scale testing, at a test house facility involved dynamic cycling and bending the stiffener through 95degrees from its initial configuration to simulate the 100 year design condition. The result can be seen in the spectacular photograph below. RiserTec designed / Lankhorst manufactured dynamic bend stiffeners are currently in service. The whole process from design to manufacture, test and shipping took less than 6 weeks.

As part of the verification the load deflection was measured through the test for both stiffener types and compared with the predicted load deflection curve from the FEA model. The comparison curves are plotted below and provide adequate verification of the accuracy of prediction of the detailed FEA analysis.

The full documented design and test package is available for client inspection at RiserTec’s offices on request please contact link to sales at Lankhorst for further information.

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