In N-494,by using specially defined L r as sbacissa, the scatter of FAC for piping containing circumferential crack is reduced compared to that using S r as sbacissa,especially for θ/π≤0 5.The N-494 FAC can assure the safety and reasonableness of assessment when θ/π≤0 5.But the applicable range for N-494 FAC is limited in θ/π≤0 5, otherwise the assessment accuracy is worse. Since the material stress-strain relationship used in N-494 is weaker than that of real material, so that the FAC is over conservative. Therefore, more accurate FAC for piping containing circumferential crack of any size should be developed.
