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ABSTRACT A practical procedure for predicting the remaining creep-rupture life of in-service boiler pipes under their operating conditions is proposed and discussed in this study. Tests were conducted on a coupon obtained using electric discharge sampling equipment from the outer surface of an in-service boiler pipe of modified 9Cr-1Mo steel. An ultra-miniature creep （UMC） specimen machined from the coupon was employed for the tensile creep test. Focusing on an isostress approach that has potential for the remaining life prediction using a limited test data, its suitability has been discussed. Test results indicate that the isostress approach can be applied to predict the remaining creep-rupture life using the UMC testing method with high accuracy. Furthermore, an examination of the high-temperature oxidation resistance of the UMC specimen indicated that oxidation had little influence on the rupture time.
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