Cost of Corrosion in Gas Sweetening and Fractionation Plants

Abstract

Abstract In 2003, a major integrated oil & gas company initiated a study to define the cost of corrosion throughout the core operations with the objective of focusing plant, engineering, and research investment in corrosion control to the areas that had the largest economic impact on corporate performance. This paper reviews available literature on cost of corrosion, reports the methodology adopted for the study, and highlights the most important problems discovered in gas sweetening and fractionation plants. For gas sweetening plants, it was found that 25% of the maintenance budget was committed to corrosion control. For gas fractionation plants, 17% of the maintenance budget was due to corrosion. For plants that were capacity limited, deferred production represented the most significant cost. For gas fractionation plants, deferred production costs were estimated to be four times the direct maintenance costs. For a gas sweetening plant, a day of deferred production in one unit at one plant would be on the order of 47% of the annual direct cost of corrosion for that unit. Common failure mechanisms in amine units included velocity enhanced damage due to operation at throughputs in excess of the original design, selective weld grooving, hydrogen induced cracking (HIC), and on rare occasions, stress corrosion cracking (SCC). Failures in fractionation plants included HIC, sulfide stress cracking (SSC), and caustic SCC. All plants experienced corrosion under insulation, concrete degradation, and utility system corrosion, including firewater and steam generating systems. Plants with buried pipework experienced severe soil-side corrosion that necessitated day-lighting projects. Plants with marine facilities experienced atmospheric corrosion and there has been a major move towards nonmetallic materials for items such as deck grating.