The effect of carburisation on heater tube life

Carburisation and fireside corrosion - 9CrMo tube


  • 9CrMo tubes in a Platformer heater, with severe internal carburisation that had led to cracking and spalling of the carburised layer
Cracking of carburised 9CrMo tube


  • to determine the effects of carburisation on tube integrity and life
  • to predict the safe remaining life of the tubes


  • post-exposure rupture testing of tubes having a range of carburisation depths, including comparative tests on samples with the carburised material removed
  • probabilistic life assessment, following our standard method.
Effect of carburisation on creep rupture life


  • Effect of through-wall carburisation on post-exposure test life determined, for three typical tube materials
  • In the early stages of service life this strengthening effect dominates. Later, the accompanying loss of ductility leads to cracking of the carburised layer and a reduction in life.


  • Quantified model of the strengthening and weakening effects of carburisation
  • Database of in-service carburisation rates
  • Database of mechanical properties of carburised tube materials
  • A validated, improved method of heater tube life prediction


Brear, J.M. and Williamson, J.
“Integrity and life assessment of catalytic reformer units”
Chapter 2 of EFC Publication 42 ‘Corrosion in Refineries’, eds Harston, J.D., Ropital, F.
Inst Materials, Minerals and Mining, London, July 2007, pp 18-46

Franks, A.R., Bagnall, S.L., Brear, J.M., Williamson, J., Conlin, P. Reid, G.
“Carburization and Metal Dusting in Fired Heaters and Steam Methane Reformers:
Plant Integrity Issues”
NACE – AWS Conf. ‘Materials Performance and Welding Technologies’
Dammam, Kingdom of Saudi Arabia, 11-14 September 2017


Plant Integrity