Purpose: To investigate the strength of tees with regard to their erosion wear, it is necessary to consider the complex three-dimensional geometric shape of the erosion worn inner surface of the tee. In addition, the study of the strength of the erosion worn tees of the main gas pipelines is complicated by the occurrence of additional stresses caused by changes in the direction of movement of the gas stream, resulting in an uneven pressure distribution in the inner cavity of the tee, and the temperature difference in its walls. Design/methodology/approach: Methodology for complex numerical three-dimensional simulation of the stressed state of tees of the main gas pipelines, taking into account the gas-dynamic processes that occur in the places of these defects, erosion wear of the tee wall, temperature difference in the tee walls. Findings: The acceptable parameters of erosion defects of tees of gas pipelines, and residual life of tees with erosion defects of the wall should be determined. Research limitations/implications: The developed model does not take into account internal corrosion and corrosion products as an additional erosion factor. Further studies plan to develop a model of corrosion-erosion wear of pipeline elements. Practical implications: The developed technique allows determining the location of erosion defects, estimating the strength and determining the residual life of tees with erosion wear of the wall in order to ensure their reliability, to rank such defects according to the degree of danger, to determine which of them are critical and need an immediate repair. Originality/value: Based on the gas-dynamic processes occurring in the internal cavity of the main gas pipelines’ tees, the complex three-dimensional geometric form of wall erosion defects, and temperature difference, the technique of three-dimensional simulation of stress state of the main gas pipelines’ tees is developed.
The principles of formation of mathematical models for the choice of rational modes of operation of complex gas transmission systems with multi-shop compressor stations equipped with different types of gas pumping units are given. It is proposed to optimize the modes on the basis of the use of energy-economic characteristics of the gas transmission system, which are built on the basis of the parameters of the gas transmission system taking into account the technical condition of its elements and economic performance for a certain period. This approach ensures compliance with the principle of operation of the gas transmission system in the field of permissible modes and maximum energy consumption on the one hand and minimizing the cost of gas transportation on the other. If it is possible to use the actual data on the actual technical condition of the equipment and gas pipelines of the system, this method allows to evaluate and take into account in the further procedure the parameters of gas supply reliability. An important requirement for the optimization procedure is the stability of energy efficiency characteristics, which means that in any practical changes of non-basic regime parameters, the energy efficiency characteristic should not be shifted beyond the allowable error. The problem of optimal load distribution in a complex gas transmission system is considered based on their minimum total energy costs at a given volume of gas supply and other planning and technological constraints. The task of optimizing a multiparameter object is to find the extremum of the goal function by selecting a vector of control effects that would satisfy the constraint. The distribution of loads at the highest hierarchy for the system of main gas pipelines is obtained by finding the minimum total cost of gas compression for each pipeline. The method of construction of such characteristics and the procedure of establishing their stability are shown, which allows the formalization of the construction of the criterion dependence of the regime parameters on energy economic factors. The stated basic decisions allow to formalize the function of the purpose for a choice of a rational mode of operation of gas transmission system in the conditions of its incomplete loading.
General principles of the spare parts amount selection when operating gas supply systems for renewable and non-renewable elements have been developed. Nomenclature is considered as a list of numbers and names of reserve instruments and equipment, which is compiled in accordance with a certain grouping and sequencing according to the producing plants technical documentation and which includes mechanical details, assemblies, and aggregates. The assessment criteria of the spare parts set sufficiency have been chosen based on the condition of the sufficient system operation reliability which is based on the estimates of the failure emergence probability during the period of regular element removals. The demand for spare parts and materials is of random nature and it is considered as a stable process which is described by the Poisson’s distribution. The calculation principle comes down to determining the possibility of the fact that all the service channels and waiting spaces in the mechanism will be filled in accordance with the queuing theory. The technique for spare parts amount selection when operating gas supply systems has been developed eventually.
The management process of the gas-main pipelines' technical state that includes different-type constituent elements and has a complex multihole and looped structure is considered. The task falls under the optimization category of the maintenance process. The study aims to optimize the preventive overhaul graph of the gas supply system that includes independent subsystems. An optimum schedule of maintenance service will be determined by selection condition of the timepoint values that provide with the quality indicators' extremum of the functioning of the process facility complex within a centralized service of gas supply system. It was suggested the technical-and-economic index, in particular the average summarized unit costs to system operation, be used as a criterion for the optimality of maintenance process. The characteristic curve obtained from conducted studies provides a way to estimate the maintenance states of the complicated gas supply system that includes different-type, geographically distributed but functionally interlinked process facilities of the gas supply system in the region of the central maintenance and repair base, they give an opportunity to plan an optimum schedule of the preventive overhaul of the gas supply system.
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