Fatigue Analysis of a 6” Flexible Pipe With Broken Tensile Armor Wires

This work focuses on a methodology to predict the fatigue life of flexible pipes with wires broken in their tensile armors. Initially, the mechanical behavior of these pipes is discussed. Relying on this discussion, a simple set of equations is proposed in order to calculate the stresses in the armors of these pipes. These equations employ pre-estimated linear coefficients to convert forces and moments that act on the pope into stresses. These stresses are then processed by well-known cycle counting methods and S-N curves are finally used to evaluate fatigue damage at several points in the pipe’s cross section. The use of this methodology is exemplified by the assessment of the fatigue life of a 6” flexible pipe in which 0 up to 5 wires of its outer tensile armor are broken. The results indicate a substantial reduction in the fatigue life of the pipe with the increasing number of wires broken.