Safe Operation of a HTHA Affected DHT Reactor

High temperature hydrogen attack (HTHA) is a serious and potentially service ending damage mechanism for fixed pressure equipment in the refining industry.  During a planned routine inspection of a 30-year-old Distillate Hydrotreater reactor high temperature hydrogen attack was discovered.  This paper discusses the management of this damage to allow continued safe operation until a replacement vessel could be fabricated and installed.  The inspection techniques used, in-service monitoring program implemented as well as measures taken to mitigate the problem are discussed and explained.