Pressure Boundary Inspection Quick Guide

Effective HRSG inspections focus on damage mechanisms that could affect each of the specific components; not all components are susceptible to all damage types.  Focusing an inspection only on components affected at other plants (scope defined by “industry experience”) has in some instances resulted in wasted resources or ineffective utilization of resources.  This is because high-risk locations for some mechanisms (for example, FAC) vary from plant to plant.  Blind inspections that do not consider plant specific conditions often yield sub-optimal results. The table below shows is a quick summary guide to the damage mechanisms affecting pressure parts and the most likely locations where one might look first for that type of damage, if time is limited and/or in the absence of any clear indication that this damage might have occurred in any particular area of the HRSG.  Once the pressure boundary is breached then water and steam will leak out.  If the leak is large enough, it will be detected by excessive makeup water consumption and/or by noting steam or water exiting the casing during operation. During an internal inspection, the location of leaks and the pressure boundary breach are typically identified by the presence of water traces or staining on the inside of the unit.  Nevertheless, it is important to note that the source of most staining or discoloration is not pressure boundary leaks.  Other common sources include: rainwater or vented steam/water leakage from roof, water leaks during testing and tube exposure to elements during construction