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.

Severe vibration is observed at FRP (Glass-Fiber-Reinforced Thermosetting-Resin) bypass line connected to discharge of sea water intake pump which is installed on offshore platform. To find out characteristic of the flow, CFD (Computational fluid dynamics) analysis is conducted, and result shows that it is produced by complex pulsating two phase flow formed by the high speed water jet at the resistance orifice which passes through several elbows. After CFD analysis, the force-time history result from CFD analysis is used in transient structural analysis. Based on the numerical analysis result, mechanical response of the pipe and structure for the initial piping system and reinforced piping system are verified and compared with criteria of Energy Institute guideline and NORSOK S-002. Also in order to demonstrate a validity of the numerical analysis and check soundness of the whole reinforced piping and structure system with vibration, site measurement is performed. Moreover, in order to check the stress level of piping, dynamic strain measurement is undertaken. This paper discusses the details on history of bypass line design to avoid air entrapment not to damage on seawater pump, and how the vibration issue is approached, and finally compared with industry standard for safety. Further, the paper presents the numerical analysis result that makes design modifications implement for bypass piping and structure during a commissioning, and various evaluation method that verify the soundness of piping and structure based on field vibration measurement.

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