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.
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 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.
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.
The Soyuz, Urengoy-Pomary-Uzhhorod and Progress gas pipeline systems form the basis of the trans-Ukrainian trans-Ukrainian pipeline system. The complex gas transmission system contains a number of gas pipelines forming a linear part and several compressor stations. The amount of capacity of pipelines depends on the number and characteristics of compressor stations. Reliability of work, regulation of transit flows and ensuring uninterrupted gas supply is carried out with the help of underground gas storage facilities, which are an integral part of the GTS of Ukraine. The use of underground storage facilities is considered to be one of the most efficient ways of gas supply, improving the quality of gas supplies to consumers and the efficiency of gas sales within the country and abroad. With the use of storage, you can reduce the unevenness of seasonal consumption and ensure security of supply. The use of underground storage facilities is an integral part, as during the year the maximum daily gas extraction exceeds the minimum more than three times, and the supply of gas through the main gas pipelines is almost constant. The maximum storage capacity cannot be represented as the sum of the absolutely free flow rates of all production wells. This is explained by the fact that the productivity of the underground gas storage during the extraction period is affected by the hydraulic resistance of the gas collection system to the underground storage and its technical condition, which is determined by the coefficient of hydraulic efficiency of loops and collectors. Studies show that the location of gas storages in the system has an impact on the amount of energy consumption. Therefore, the strategy of rational use of underground gas storage facilities in pipeline transport (in terms of minimizing energy consumption) is based on the study of the impact of their location in the gas transmission system. The principle of energy efficiency of the use of underground gas storage facilities for long-distance transportation (in order to equalize the unevenness of gas consumption) is based on the sequence: the most remote UGS should be used first. These are the objects that are located at the end points of the GTS route and whose location corresponds to the proximity to consumers.
The work is devoted to establishing the regularities of the flow of technological processes in gas transportation systems to optimize the operational management of operating modes under the condition of their incomplete loading. On the basis of the study of the stationary modes of operation of the gas transportation system with changes in the volume of gas pumping, the principle of building a mathematical model based on the superposition of the characteristics of linear sections and compressor stations is proposed, which makes it possible to estimate the throughput of the system, parameters of the operating mode, and energy consumption for gas transportation. The methods of building a system of integral influence coefficients for gas transportation systems in order to evaluate the parameters of its operation in stationary modes of operation are presented. Each change in the technological parameters of the operating mode at the entrance of the gas transport system will necessarily cause a reaction of the system, which will manifest itself in a change of the corresponding parameters at its exit. It is obvious that the input and output parameters of the system are interconnected by a complex system of equations, the implementation of which requires certain time costs and the collection of additional information about the technical and hydro-gas-dynamic conditions of the system at each moment of time. In the conditions of incomplete loading of the gas transportation system, which involves frequent changes in its operation modes, the implementation of the task is not always possible. It is proposed to create a system of integral influence coefficients that characterize the ratio of input and output information in various stationary modes and to formally present it in a matrix form. On the basis of the research results, the principle of optimizing the operation modes of the gas transportation system under conditions of partial loading according to the criterion of minimum energy consumption for gas transportation at the maximum level of gas supply reliability is proposed.
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