The finite element software was employed to calculate the wall temperature of final superheater elbow(which using TP347Haustenitic stainless steel as the material)with different thicknesses of oxide scale inside the tubes.By the Larson-Miller formula with revised constant term

the stress-time curves of superheater tube under different confidence levels and temperatures were calculated.Then the service life of superheater tubes with different oxide scale thicknesses under a certain confidence level was predicted.The criterion of material failure was established by the Robinson method to conduct grading evaluation on the accumulation degree of oxide scale.The results showed that

with the confidence level of 0.95

when the TP347Hsuperheater tube’s oxide scale was thinner than 5mm

the service life of the material was longer than 1.0×105 hours and the blocking inside the pipe was mild;when the oxide scale was thicker than 5mm but thinner than 9mm

the service life of the material was only dozens of thousand hours and the blocking was intermediate;when the oxide scale was thicker than 9mm

the service life of the material will be shorter than 1.0×104 hours and the blocking was serious.