The Research Of Residual Lifetime Estimation Of (101B) Hydrogen Reformer Tubes

This paper mainly presents the research of residual lifetime estimation of hydrogen reformer tubes in service; the research conclusion has high significance on guiding our equipment management. The reformer tubes are the 3^rd generation of new type centrifugally cast reformer tubes (HPNb). The reformer tube subject to research has been in service for 11 years, which is an old tube that was replaced due to over-temperature caused by process operation and other equipment. This reformer tube was used as a specimen and a series of destructive tests were done on the samples taken from it. Sample in ring shape was taken from the representative position of the tube, and macro dye penetrant test was made in order to examine whether macro crack damage occurred on the tube or not. Based on macro dye penetrant, metallographic specimens were machined in different directions of the tube ring. The tube was observed from inner wall to outer wall to compare the changes of micro structures along the wall thickness. Meanwhile, the carburization of inner wall and oxidation of outer wall were observed to check the damage extent. Micro-hardness measurement was done on the surface of metallograph specimen and Brinell hardness measurement was done on machining surface at the same tube position, which are indications of average conditions of tube material and also references for site examinations. Samples were taken on inner and outer walls on fire facing side and rear fire side at two representative positions of the tube in order to make tensile test at normal temperature and short time mechanical properties at high temperature, and compare the measured data to the original data, so as to determinate the changes of mechanical properties of the materials after certain period of service. As to the actual high temperature components in service, it's necessary to make creep rupture evaluation and predict the residual lifetime. Since no assumption is needed for the component in service and historic conditions are available already, such research methods are rather suitable and closer to realistic situation.For estimation of residual lifetime of serviced high temperature components, the research is usually done by single shaft stress rupture test at accelerated speed on the specimen taken from real component, i.e. obtaining short term rupture time Vs stress and temperature by increasing stress and temperature, then calculating the long term rupture time Vs stress and temperature by using Larson-Miller extrapolation. Lastly, it is known that the residual lifetime of the most severe tube segment of present tubes is about 3 years by comprehensively utilizing micro structure analysis, test results of mechanical properties at normal and high temperature, hardness measurements and creep rupture tests, multi damage and lifetime estimation methods, and comprehensively studying the damage condition, distribution and lifetime. This result has important meaning on guiding the timely preparation of spare parts and replacement for relevant departments of our company.