Failure analysis and re-design of a boiler casing

Cracks between boiler casing and steam drum

  • Three 250MW systems generating power and process steam for a European aluminium production plant


  • Severe cracking at welds between the boiler casing and the integral steam drum, leading to loss of exhaust gas with subsequent environmental problems and high maintenance costs


  • Design review and root cause analysis
  • Transient and steady state thermal stress calculations
  • Re-design study, including heat conduction calculations to define the type and thickness of insulation required on both the inside and outside of the boiler


  • Root cause identified as severe temperature difference between steam drum and boiler casing during normal steady state operation.
  • Start up and shut down transients confirmed not to be the cause of the temperature differentials
  • An insulation blanket, attached to the inside of the boiler casing to eliminate the severe temperature differentials, designed and fitted
  • Environmental issues eliminated
  • High cost of regular strip-downs and re-welding eliminated
  • Small increase in efficiency and available process steam

Plant Integrity