Bend stiffeners are used to support flexible pipe, umbilicals and cables when connected to rigid structures or a floating production system where there is a requirement to control the minimum bend radius of the pipe. They are usually attached at either the topside or seabed connection.
In dynamic applications bend stiffeners require to have sufficient fatigue resistance to control the in-service bend radii and sustain the cyclic loads to the end of the specified life whereas in static applications they protect against gross over-bending.
Stiffeners are typically conically shaped polyurethane mouldings with a cylindrical bore that slips over the pipe, umbilical or cable.
Balmoral bend stiffeners are designed in accordance with API 17J Appendix B using specifically formulated polyurethane materials and are engineered to suit specific operational parameters.
Design analysis
Balmoral uses the proprietary package ‘Orcabend’, an industry standard for many years, to generate the profile for the active conical section of the stiffener.
Information that is critical to the stiffener design includes:
• Tension and angle data from the riser analysis
• Temperature
• Interface detail
• Riser end-fitting profile
• Diameter and stiffness
• Minimum bend radius
• Riser analysis fatigue data
Balmoral’s FEA package is used to verify the Orcabend design and analyse the end-fitting structure. This process can also provide thermal analysis if required.
A combination of Orcabend and FEA technologies allows split stiffeners to be designed for retro fitting.
Stiffener interface structure
A smooth transition is required between the rigid flange and the flexible cone of the stiffener. BOE’s design achieves this by creating both rigidly bonded and un-bonded areas that provide deflection and minimum stress in these localised areas.
