Life management of refinery furnace tubing

The 2PTR and 3PTR furnaces at the MOBIL (Altona) Refinery have tubing that have been in operation for over 20 years. API RP 530 creep rupture life cal culations showed that the tubes have limited remaining life. Therefore acce lerated creep rupture resting was undertaken of a material from the likely worst case tube sample. However, going from creep rupture test results to a ssess the remaining life of furnace tubing is complicated by the fact that the tested tubes may not have been exposed to the maximum temperature for t he life of the furnace; the test stress is different from the service stress because various pressu re and wall thickness combinations exist. To overcome such issues detailed heat transfer calculations were carried ou t to understand tube temperatures based on thermography data and assessment of consumed life fraction was undertaken. Deterministic modelling of total life based on wall thickness data and operating pressure was carried out u sing most appropriate creep rupture database. It was found that there was sufficient remaining life for tubes in 2PTR fur nace such that replacements were not required prior to the next normal outa ge. However, it is found that if high temperatures are experienced in 3PTR furnace a failure could occur in the near future. The information from the life assessment study was integrated into a risk b ased inspection program and set temperature limits to allow planned replace ment of the tubing. (C) 2000 Elsevier Science Ltd. All rights reserved.