In Service Repair Challenges With Pyrolysis and Steam Methane Reformers High Temperature Metallurgy

Abstract

The high temperature section of pyrolysis furnaces and steam methane reformers are exposed to conditions ranging from ambient temperature during shutdowns to temperatures near 1093°C (2000°F) when in service in the case of pyrolysis tubes. These conditions lead to variety of metallurgical transformation affecting material properties at different temperatures. The involved materials are exposed to internal and external environments leading to chemical and metallurgical reactions causing additional material property changes. Moreover, pressure boundary components also need to withstand other high temperature damage mechanisms including creep, stress-relaxation cracking, thermal fatigue, and thermal shock. The paper reviews high temperature metallurgy and degradation mechanisms for both pyrolysis and steam methane reformer services. Several case histories are presented. For pyrolysis service, furnace coil failures due to thermal fatigue/thermal shock, quench nozzle failures and transfer line exchanger tube failures are covered. For steam methane reformer, several failures in furnace coil tubes, reducers, pigtails, and outlet headers are covered. In order to select the suitable alloys for resistance of thermal shock and thermal fatigue, a research study has been carried out to rank the high temperature alloys’ resistance to thermal shock and thermal fatigue based on the test protocols which represent the extreme temperature conditions. General guidance on material selection, failure prevention and welding repairs are included.