Ultimate creep load and safety assessment of P91 steel pipe with local wall thinning at high temperature

• Ultimate creep load estimation way of pipe with LWT at high temperature is proposed.
• The most influential factor to ultimate creep load of pipe with LWT has been found.
• The relation of ultimate creep load of pipe with LWT and creep time is established.
• The assessment curves of pipe with LWT at high temperature have been proposed.
• The engineering load calculation method at different creep times has been obtained.

Safety assessment of pipe with local wall thinning (LWT) at high temperature is highly important in power and nuclear engineering. Based on strain criterion and isochronous stress–strain curves at high temperature, this paper studied the ultimate creep load of pipe with LWT under creep condition by orthogonal experimental design and finite element numerical simulation. Firstly, the influence of LWT geometries was analyzed, which indicated that relative defect depth was the most significant factor to ultimate creep load. Secondly, the ultimate creep load formulas were regressed based on the ultimate creep loads of pipe with LWT at different creep times. And safety assessment curves for the pipe with LWT at high temperature by different strain criteria were proposed. Finally, the engineering method of allowable load of pipe with LWT by different strain criteria was constructed. The research results try to improve the safety assessment and structure integrity analysis of pipe with LWT at high temperature.