This paper outlines a systematic risk based process to define the limiting
construction materials envelope for a petroleum refining unit. Operating units are subject to an ongoing evolution of feedstock changes and unit optimizations. These changes can potentially have a dramatic impact on materials degradation and are one of the leading causes of unit reliability issues and unplanned maintenance costs. This paper describes how a systematic unit materials review confirming current materials of construction and expected operating exposures, can define the key and limiting operating variables. This review can additionally identify equipment inspection and maintenance requirements needed for a long term equipment plan. The process and examples of its use in a specific
operating unit will be presented. Keywords: petroleum refining, materials envelope, risk based, unit materials review, materials integrity, corrosion monitoring, corrosion control