Microstructural studies and remnant life assessment of eleven years service exposed reformer tube

Utilization of appropriate inspection during plant shut down, in combination with high temperature mechanical properties, microstructural analysis and judicious accelerated creep provided an effective strategy for short term assessment of 11 years service exposed reformer tube integrity. Barring development of corrosion cracks and decarburization of the inner and outer walls of the tube, the microstructure of the service-exposed alloy was free from any signs of deterioration like creep cavitation or voids, and the hardness was within the expected ranges; however, tensile testing revealed an apparent loss of strength from 25 °C to 900 °C. Accelerated 900–980 °C stress rupture testing of samples machined from 11 years at 950 °C and 19 MPa exposed KHR 35 CT reformer steel tubing, did not reveal any degradation of rupture behaviour compared to that of the virgin alloy. An additional life of at least 32,822 h is predicted at the operating stress–temperature conditions.