A reliability study of API 530 for predicting creep life of long-service exposed 9Cr-1Mo steel tubes

Abstract

ABSTRACT API 530, entitled Calculation of Heater Tube Thickness in Petroleum Refineries; is an API standard used for the design of fired heater tubes, as well as the remaining life assessment of service-exposed heater tubes in the refining and petrochemical industry, which its seventh edition released in 2015 as the latest one. Stress- rupture master curves in the standard are the principle tools to achieve goals that were changed in the latest version compared to previous editions (5th and 6th Ed.). This study investigates how tube service exposure time could affect creep life prediction and which version of the standard could match the results more closely. Stress- rupture tests were conducted at 600 to 650 °C and stress levels ranging from 37.5 to 117.5 MPa to examine the creep behaviour of three tubes made of 9Cr-1Mo steel after service for 75,000, 150,000, and 250,000 hours, respectively. Testing varied from a short-term, under 50 hours, to a long-term, over 10,000 hours to evaluate their reliability for future service according to API 530. According to this study, the ability to accurately predict the remaining life of tubes depends on their service life. Also, the seventh edition was more consistent with results in general.