Diagnosing air-separating units to extend the set working life

Abstract

620.179<<401.7>>In recent years, there has been a marked reduction in the upgrading of oxygen plant and catastrophic ageing in the range of air-separating equipments, which has made it particularly necessary to perform engineering diagnosis to defme the remaining working life of plant. There are many instances of safe operation for air separation plant beyond the set working life, which have led unfortunately to the view that a comparatively simple diagnostic procedure applied to the strength parameters of vessels and other plant can provide a basis for extending the established working life of the plant as a whole. There is also no shortage of firms that will perform such a diagnosis on the basis of licenses issued by the Russian Federation State Mining and Engineering Supervisory Service. There is a tendency for poorly trained staff and ill-equipped organizations specializing in other areas than cryogenic engineering to undertake examination of cryogenic plant. Naturally, they do not have all the knowledge and data on the behavior of materials, welded joints, and soldered ones in cryogenic media, nor on the changes in properties of insulating materials or the accumulation of explosive substances in equipment and failures that occur on prolonged operation; they cannot provide skilled decisions on continuing use and safe operation of equipment.We would like to draw the attention of specialists to procedures for diagnosing air separation plant that provide exact definition of the residual working life in order to extend the established period.Equipment life is limited on account of changes occurring during operation, which affect the strength, reliability, and safety parameters. The main effect comes from the cyclic loads on heat exchangers, fuel-cycle fatigue in adsorbers, pipeline vibration, insulation compaction, the accumulation of solid particles in pipes, and so on. The behavior of these effects can be incorporated in designs and into integral forms of quantitative expression for the established life. Variations in the parameters (geometrical or working ones) may affect the established working life. However, economic considerations lead one to take the working life for large air separation plant as 20 years, and in the design one provides for corresponding choice of the adjustable parameters.Explosion and fire hazards arise in the operation of air separation plant; the basic safety specifications are formulated in PBPRV-88 [1]. However, the physical mechanisms involved and the methods of meeting these requirements in calculations and design are exceptionally numerous (condensation, crystallization, adsorption, boiling, circulation, flow distribution, and so on in the presence of a wide range of hydrocarbon impurities).This company has an exceptional set of experimental data, methods, and software designed to support explosion safety in air separation plant. Prolonged experience has shown that this background, which has been realized in many types of plant, provides for their safe operation without explosions...