Service Life, Reliability And Reparability of Systems For Preventing Corrosion Under Insulation

ABSTRACT There are currently several competitive protective coating systems commonly considered for use in hot, cyclic carbon steel operating equipment which is to be insulated (CUI, Corrosion Under Insulation Service). Performance characteristics of these different coating systems overlap, but vary significantly in ways which can become important (and costly) during the service life of a system. This paper compares the initial and long term costs, performance characteristics, expected service life as well as ease of repair of these CUI systems using lab test results and field performance experience obtained from users, third-party labs and vendors of the various systems. Service life of any CUI system is strongly affected by quality of surface preparation, quality of application, and by local conditions during the service life, but the coating system largely determines the cost of repair or replacement, and whether at initial failure the service life can be extended or the system has to be completely replaced. INTRODUCTION All refineries and most chemical plants are really just sophisticated cooking processes, where raw materials are heated under various conditions to produce higher-value mid-products or end products. Large amounts of energy input are required and energy is expensive. Insulating process vessels and piping helps reduce energy loss and improves process efficiency. There are also peripheral insulation needs, such as personnel protection and temperature stability of finished goods. Surfaces of piping and process equipment operating at elevated temperatures, whether cyclic or continuous; require specialized coating systems including appropriate levels of surface preparation, coating application, and inspection procedures. Most surfaces are insulated after coating and require even more exacting preparation, coating and inspection, since any potential coating problems will be hidden under the insulation. AGING INFRASTRUCTURE AND LIMITED BUDGETS Over the past few years there has been a new interest in high temperature coating systems to control corrosion under insulation.