The necessity of determination of the condition and life of equipment operating under pressure is related to providing safe operation with prolongation of the service life beyond the standard. The system of planned preventive repairs in existence earlier made it possible to maintain equipment in satisfactory condition but did not provide sufficiently accurate information on the possibility of further service upon completion of the established service life.The high level of effective stresses and the accumulation of fatigue damage in zones of concentration and the change in microstructure of the material under low-cycle and multicycle thermal and force aetious may with the passage of time cause a reduction in allowable stresses with a simultaneous increase in the probability of brittle fracture of weld joints of metals. Taking into consideration these features in the behavior of metals, it must be pointed out that further service of equipment beyond the standard life must be only after a composite inspection using a special method, which include the following operations:-external and internal inspection of the surfaces and weld joints of the equipment; -technical impection and checking of the condition of vessels, apparatus, and piping with loading by the operating and test pressures with use of acoustic emission (AE) iuspection; -measurement of the wall thickness of metal subjected to the cryogenic action of the medium and other methods of nondestructive inspection; -a calculated evaluation of the effectiveness of the vessel with determination of the remaining life. Very pressing in diagnosing the condition is use of the acoustic emission method in combination with traditional methods of nondestructive inspection (ultrasonic iuspeetion, x-ray, penetrant inspection). The advantage of the acoustic emission method is, above all, the fact that it makes it possible to promptly record an embryonic crack and to take the necessary measures for elimination of an emergency situation.Diagnosing of the condition of a structure with use of AE inspection is done in two stages. In the f'trst stage the structure is analyzed, the most dangerous zones for placement of AE signal transducers are selected, measurements are made with loading of the object, and the measurement results are processed and documented. In the second stage the inspection results of the condition are analyzed, the strength and accumulated fatigue damages during the period of operation considered and evaluated, and a decision is made on the possibility of further, service.In the presence of dangerous defects, if necessary an inspection is made by one of the traditional methods of nondestructive inspection and repair work is done or further service of the part is prohibited.In production of vessels and parts operating under pressure for cryogenic technology, elements having a complex structure are used. In conducting acceptance tests and under operating conditions the elements of vessel structures are in the three-dimensional stressed and strained condition. Th...
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...
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