HP40 Ethylene Cracker Failure Analysis of Degradation Due to Excessive Service Temperatures

Abstract Cracker furnace tubes operate under extreme temperatures and aggressive environments, making them susceptible to creep and fatigue damage. This study investigates failure mechanisms in aged HP40 cracker tubes from an ethylene facility, including oxidation, creep, and thermal fatigue. The furnace was run using natural gas and recently switched to 93% hydrogen-rich fuel after a new batch of HP40 tubes were installed. Microstructural examination revealed severe service-related damage, including carbide coarsening, internal void formation, and thick decarburization layers on both inner and outer surfaces after less than two years of service. Progressive creep damage occurred with a significant loss of ductility. Advanced degradation was associated with chromium depletion in the austenitic matrix, which reduces the ability to maintain a protective oxide layer and allows easier ferrite formation. Subsequent temperature scans showed the furnace was now operating significantly higher in temperature in some areas than it had when burning natural gas, leading to excessive operating temperatures. Ferrite formation occurred, leading to higher magnetic permeability of the tubes that correlated well to the extent of creep and decarburization. The findings demonstrate that long-term high-temperature exposure leads to combined oxidation, creep, and thermal fatigue damage that compromise the structural integrity of HP40 tubes. Recommendations are presented for improved inspection practices, control of furnace atmosphere and temperatures less than 1900 degrees Fahrenheit, and material considerations to mitigate these degradation mechanisms and extend tube service life.