Welding SA-213-T9 to SA-213-T22 with a TP304H safeend

[metalhoosier]

Would someone mind giving their thoughts on this weld connection on a RH crossover? This was originally called out by the OEM. I would think a P5A to a P5B would last longer due to the closer coefficient of thermal expansion, especially with the fluctuation of temperature a RH can see during startup. This just seems counter-intuitive to me. Thank you.

 

[metengr]

metalhoosier;
Not necessarily, it all depends on metal temperature profiles during operating conditions. Yes, one wants to avoid dissimilar metal welds because of creep life concerns along the T22 side of the weld joint. Beyond T22, T5 and T9 offer limited creep strength without thickening the tube wall to reduce primary membrane stresses. So, it might be that 304H is needed for this thickness transition. One could push back to the OEM and inquire about swaging the material transition piece versus using 304H.