Selecting construction materials in developing new and modernizing existing oil refinery equipment

Abstract

Approaches to selecting construction and gasket materials for developing new and modernizing existing oil refinery equipment and the results of corrosion-electrochemical studies are presented.Materials for building vessels and equipment are selected based on their suitability for the design, compliance with standards and norms, and assimilation in the industrial plant. In turn, the suitability of a material is determined by the resistance to overall corrosion, corrosive cracking, hydrogen sulfide embrittlement, point-pitting and crevice, intercrystallite, structurally selective, and other types of corrosion, structural strength at a given temperature, manufacturing processability of the equipment, and economy.There are two approaches to selecting construction materials in developing equipment designed to operate with aggressive media -European and American [1][2][3]. According to the European approach, the selected construction, welding, and gasket materials must ensure a defined lifetime with the minimum number of breakdowns, i.e., high reliability of the equipment. This naturally affects the cost of the equipment, since more alloyed structural materials are selected as the basic materials. The American approach consists of selecting the cheapest construction materials, even if the reliability of the equipment is lost, but costs for unscheduled repair of the equipment are included in project estimates and a given operating life is simultaneously guaranteed. The lifetimes are 20 years for towers, 30 years for reactors, 20 years for tanks, 20 years for heat-exchanger bodies, 5 years for carbon steel tube banks, and 10 years for stainless steel tube banks.The developer using the least expensive materials obtains exemptions [3].UkrNIIkhimmash Co. uses both approaches in practical selection of construction, welding, and gasket materials, giving preference to guaranteeing operability for a given lifetime, since breakdown of a reactor, tower, heat exchanger, or tank not only involves repairing the structure and correspondingly shutting down the unit and manufacturing less product, but also possible environmental damage and fire hazards. For this reason, experience in operating existing equipment, the work by VNIIneftemash, Lenneftekhim, VNIIkhimmash, and other organizations, and the results of corrosion studies are the basis in developing equipment according to the basic designs of Shell, Axens, ABB,. In recent years, customers of the developed equipment have been stipulating a maximum corrosion rate of construction materials of 0.1 mm/year.