Experiences with Sandvik grades in oil refinery applications

Abstract

A modern refinery can have more than a thousand of heat exchangers, of which the clear majority comprises tubes made of carbon or low alloyed steel. In some special applications severe conditions can occur where the use of low alloyed steels does not give enough life time and in the worst cases causes unplanned shutdowns. Among the most problematic heat exchangers in a refinery are the overhead condensers in atmospheric and vacuum distillation units, but also others within the refineries can have highly corrosive conditions. The most common problems are condensation of hydrochloric acid, diluted chlorides in acidic water phases, deposits and formation of chloride salts such as ammonium chloride. These conditions can induce general and under deposit corrosion, pitting and stress corrosion cracking. Other units in the refineries where high alloyed stainless steel or nickel base alloys are commonly encountered are in hydrotreaters and reactor effluent air coolers (REACs). In this paper experiences from installations of high alloyed stainless steels tubes in critical refinery heat exchangers will be discussed. Comparisons of different grades, their performances and limitations depending on the environments, will also be addressed.