The non-destructive techniques such as the microstructural assessment are usually performed for residual creep life assessment of plant components. Since these techniques have limited accuracy, destructive assessment techniques such as uniaxial creep tests are required to improve the accuracy of the assessment. However, if this type of destructive assessment technique are applied, the sampling and the weld repair damages the material, and also the assessment will become expensive. On the other hand, small punch creep (SPC) test [1,2], which uses miniature-sized specimens, does not cause any serious sampling damages, and its assessment accuracy is high since it is a mechanical assessment technique. However, in applying the SPC test to the residual creep life assessment of the boiler in service, there are some issues to be studied [1,3,4]. In order to apply SPC test to the residual creep life assessment of the 2.25Cr-1Mo steel boiler pipe, the relationship between uniaxial creep stress and the SPC test load has been studied. And the Omega method [5] by SPC test was also studied.
