Engineering Critical Assessment of nickel-based clad pipeline girth welds in a wet H2S-containing environment

• Nickel-based alloy pipeline welds were fatigue tested in H2S solution.
• Fatigue crack growth rate is about 4 times higher than the in-air values.
• Fatigue crack growth rate is higher than the BS7910 in-air data by up to 3 times.
• Diffusible hydrogen analysis were also performed.
• CRA clad layer protects the pipeline backing steel from hydrogen embrittlement.

Specimens from nickel-based clad pipeline girth welds were tested in H2S solution. The results of the fatigue crack growth rate curve at higher ΔK values were about 4 times higher than the in-air values. The rate at 180 °C was generally higher than the in-air data for flaw assessments found in the British Standard BS7910 by a factor of up to 3 times. From the analyses of the diffusible hydrogen, the backing steel of such pipelines are predominantly protected from the sour environment by the corrosion-resistant alloy clad layer. The results from this study are relevant for desktop Engineering Critical Assessment of girth welds of such pipelines.