A majority of steam-methane reformers (SMRs) have hot outlet manifold systems that operate at temperatures in the range of 750 to 900 °C (1382 to 1652 °F) and internal pressures in the range of 2000 to 3500 kPag (290 to 510 psig). Under these operating conditions, the materials used in the manifold systems, including weld joints, are subject to degradation from high-temperature creep. Thus, fitness-for-service (FFS) assessment of the manifold systems requires evaluation of material degradation as a result of creep damage (voids, micro-fissures and cracks) and creep deformation (strain). This paper reviews a general approach to FFS assessment of SMR hot outlet manifold systems. Using data on operating temperature, pressure, and time in service stresses and strains in the manifold sections are calculated by the finite-element method. The calculated stress-strain data are then used to compute creep damage accumulation as a function of time in service for both base metal and weld joints using available creep-rupture data for the materials. These results are then used to predict remaining creep life and establish recommended inspection protocols.

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