Fitness for service of fire-damaged headers


  • Radiant section headers fabricated from Type 347H and operating at 650°C in a UOP charge heater in the USA


  • Following a fire in the heater, two through wall cracks and severe bulging were found in the headers. Initial impressions were that the condition was not fully compatible with fire damage


  • To determine the cause of the cracking and bulging
  • To assess whether the headers would be fit for service following repair


  • Removal of header containing cracks and worst bulges, for detailed examination
  • Site inspection of all top headers
  • Failure analysis to determine the root cause of the cracking
  • Fitness for service assessment of repaired headers


  • Site inspection revealed damage to be confined to areas around supports
  • Metallurgical examination of undamaged header indicated significant remaining life.
  • Examination of cracks and bulges reveal surface cracking on both the internal and external surfaces
  • Metallographic examination revealed the internal cracks to be due to creep, but the external cracks to be due to thermal fatigue
  • Failure demonstrated to be as a result of the ingress of large quantities of rainwater through the insulation boxes onto the hot headers around the support system
  • Full UT inspection reveals remaining header to be free of internal and external defects


  • Identification of the root cause of the problem
  • Assurance that the repaired header could be safely returned to service
  • Refurbishment of the insulation boxes eliminated the source of the rainwater ingress

Plant Integrity