The refractory lined components could be damaged during operation due to various causes such as thermal expansion and contraction from changes of the temperature in service fluids, vibration caused by internal flow, or improper refractory construction. The damaged refractory causes thermal hot spot because a hot service fluid contacts to the inside surface of the component directly and this situation leads temperature increases in the skin of the component. This temperature increases from thermal hot spot does not causes immediate failure of the component, but creep phenomenon can cause structural rupture in the long term. As one of the countermeasures against thermal hot spot, the steam cooling is used as a field practice of maintenance works to reduce elevated temperature by spraying steam onto the area of thermal hot spot. However, when steam cooling is applied, it is designed and installed based on experiences without performing proper engineering. After steam cooling is applied, it is observed that thermal hot spot is locally cooled only in the area where the steam touches, which also raises concerns about unexpected damage due to local temperature gradient from localized cooling. This paper provides the evaluation of structural integrity of an actual case of thermal hot spot subjected to steam cooling in the FCC unit and discusses the appropriate steam cooling method as a countermeasure for thermal hot spot to ensure more effective structural integrity.

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