Subsea flowlines and risers experience fatigue cycles due to thermal and/or pressure transients or vortex induced vibration (VIV). Flowlines and risers also experience extended period of constant hold (i.e., static load) during operation. Low alloy bolts on subsea equipment also experiences constant load in addition to the fatigue loading during start up and shut down. Although there has been work on the fatigue damage of flowlines and risers, little work has been done to understand the crack growth rate (CGR) resulting from the static loading during operations in production environment. Tests were performed in this work under constant stress intensity factor (K) levels to measure the sub critical CGR associated with the constant load periods mentioned above. Tests were performed in a mildly sour environment and in seawater under cathodic protection (CP) to understand the difference in the CGR. The applicability of a crack tip strain rate based model in rationalizing the CGR vs K.

Subject
Environmental cracking, Strain rate, Crack growth, Sour environments, Metal dissolution, Corrosion cracking, Fatigue crack growth rate, Stress cracking, Constants, Crack length, Corrosion inhibitors, Fatigue, Cracks
Keywords:
Offshore, pipelines, fatigue crack growth rate, crack growth rate, fatigue, fracture, subcritical crack growth, crack tip strain rate, sour service, cathodic protection
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2018
Association for Materials Protection and Performance (AMPP)
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