Designed as interlocking elements, bend restrictors prevent over-bending at the interface between flexible flowlines, umbilicals and cables and rigid structures such as wellhead connections, J-tube exits, rigid pipe crossovers and PLET connections by mechanically locking up.
They are normally used in static applications but, unlike bend stiffeners, only provide protection once the pipe has achieved the desired bend radius.
Designed in accordance with API 17J Appendix B, BOE bend restrictors are manufactured in rigid structural polyurethane two piece units that are bolted together around the pipe.
Design analysis
BOE restrictors are designed using ‘Orcabend’, the recognised industry standard, using the following information:
• Flexible pipe OD
• Flexible pipe if heated
• Minimum bend radius
• Service life
• Length of coverage by angle or length
• Support structure details
• Flexible pipe min and max internal temperatures; operation and installation
• Flexible pipe min and max thermal conductivity value if pipe is heated
• Min and max installation air temperature
• Min and max seawater operation temperature
• Installation and operation shear force
• Installation and operation bending moment
• Flexible pipe stiffness if not taken into consideration in the bending moment and shear force loads
