A Case Study on the Effect of Peaked Pipe Welds on Piping Life Expectancy

This paper details a case study on the effect of weld peak geometry on the expected creep life of a piping system operating in a refining environment. Inspection of the 1-1/4 Cr piping system revealed significant peaked geometry at the longitudinal weld locations. A Finite Element Analysis (FEA) assessment of the remaining life was made using the Omega method of creep life assessment. The sensitivity of the results to modeled pipe geometry and assumed material properties was assessed. The variability of life prediction that was obtained indicated a necessity to perform further more detailed assessment of the pipe geometry and material properties by the removal of samples at the weld locations. The improvement obtained in the assessment accuracy and final life predictions from the sample analysis is presented in the paper and practical implications on the operation of the piping system are detailed. Suggestions and cautions for the practical assessment of similar peaked pipe problems are also discussed.