Flexible Armor Wires: Fatigue Load Frequency Effects and an Accelerated Pitting Methodology

Corrosion fatigue in the tensile armor layer is a design consideration for both flexible risers and flowlines offshore. Recently, the industry has experienced a handful of in-service flexible pipe replacements due to corrosion fatigue of armor wires. That experience motivated the work effort summarized herein. This paper presents the preliminary results from an experimental program undertaken by ExxonMobil to evaluate and suggest improvements to the currently established fatigue testing methodology for armor wires in corrosive environments. In particular, the results from a frequency scanning test program for armor wires and a methodology for artificially generating pitted armor wire specimens for fatigue endurance tests are presented.