Experimental substantiation of the corrosion rate of pipe steel

Определяющее значение в развитии дефектности металла труб имеет коррозионный фактор, а также деградация механических свойств трубных сталей в процессе эксплуатации трубопроводов. Авторами приведены результаты экспериментальных исследований по оценке скорости коррозии и склонности к трещинообразованию трубных сталей, наиболее распространенных на длительно эксплуатируемых магистральных нефте- и нефтепродуктопроводах. Разработана методика определения количественных показателей коррозионно значимых параметров для обоснования вывода в капитальный ремонт трубопроводов на основе результатов натурных экспериментальных исследований скорости коррозии фрагментов трубной стали при различных условиях поляризации и коррозионной активности грунта. Объект исследования - фрагменты труб (пластины) 50×50×3 мм, изготовленные из стали марок 09Г2С и 17Г1С. Полученные результаты позволили сформулировать рекомендации по уточнению количественных критериев коррозионно значимых факторов для обоснования вывода трубопровода в капитальный ремонт: 1) необходимо учитывать марку трубной стали (установлено, что сталь 17Г1С на 20-30 % более устойчива к коррозии, чем сталь 09Г2С, особенно в части образования локальных повреждений - язв и питтингов); 2) при значениях удельного электрического сопротивления грунта менее 20 Ом⋅м скорость коррозии возрастает примерно на порядок независимо от марки стали и наличия системы электрохимической защиты. This work presents the results of experimental studies on the assessment of the corrosion rate and the cracking tendencies of pipe steels, most common in the main oil and oil product pipelines that have been used for a significant amount of time. A methodology was developed for determining quantitative indicators of corrosion-significant parameters to justify the overhaul of main pipelines based on the results of field experimental studies of the corrosion rate of pipe steel fragments under various conditions of polarization and corrosive activity of the soil. The object of the study is pipe fragments (plates) with the dimensions of 50×50×3 mm, made of steel with the grades 09G2S and 17G1S. The results made it possible to formulate recommendations for refining the quantitative criteria of corrosion-significant factors to justify the overhaul of the pipeline: 1) it is necessary to take into account the pipe steel grade (it was found that 17G1S steel is 20-30 % more resistant to corrosion than 09G2S steel, especially in the formation of local damages - corrosion pits and pittings); 2) at values of specific soil resistance less than 20 Ohm⋅m, corrosion rate increases by about an order, regardless of the steel grade and the usage of an electrochemical protection system.

Influence of cathode and anode processes on tribocorrosion of aluminium alloy AA2024 in acid rain

The nature of cathodic processes during the frictional interaction of aluminum alloy with ball corundum in the conditions of reciprocating motion has been studied. Under conditions of anodic polarization under conditions of friction, corrosion processes are activated and their speed during friction increases many times. The potential on the surface of the alloy under acid rain shifts sharply in the negative direction. Changes in the tribopotential and coefficient of friction are characterized by a gradual shift in values ​​at the initial stage of research. The oxide film is formed on the metal surface in neutral and acidic environments. The service life of the film is increased due to electrochemical protection during cathodic polarization at the electrode potential of pure alloy without oxide film. It is proved that polarization changes the life of the film in the initial stages and the loss of material and the coefficient of friction during the entire test period. It is established that the nature of surface fracture also changes as a result of application of the polarization potential during friction. The largest surface damage is observed during anodic polarization.

Control of produced water with highly corrosive medium in oil-gas production

The construction of middle oil-gathering facility, in which technological processes are managed in a closed medium is necessary for environmental protection to control highly corrosive medium in oil and gas production. Associated gas separated from the fluid in initial separation unit within middle oil-gathering facility enters gas-gathering point with low pressure, and the liquid - into the pig of oil, water and sand, which should be constructed from iron concrete for cleaning from mechanical impurities sediments and salt as well. The liquid charge from the separation unit and pig of oil, water and sand is based upon the law of communicating vessels. To supply long-life for reservoirs, the inner and outer walls should be covered with a special coating and additionally, electrochemical protection should be provided as well.

Development and Testing of the Methodology for Assessing Features of the Operation of Long-Acting Comparison Electrodes in Electrochemical Protection Systems for Gas Pipelines in Frozen Soils

Current problem of monitoring parameters of the electrochemical protection of gas pipelines is to clarify parameters of long-acting comparison electrodes on frozen soils. The problem is the violation of the electrolytic contact between the long-acting reference electrode and the built-in potential sensor during freezing of the surrounding soil, which leads to a distortion of the data obtained or the impossibility of taking them. The article describes the study of the main operational parameters of long-acting comparison electrodes in permafrost, freezing and thawing soils.

Development of Calculation Model of the Distribution of Protective Currents of Gas Pipeline Electrochemical Protection System in Permafrost Soils

Clarification of parameters of the distribution of protective currents in permafrost soils is an urgent issue. The article describes a grid model of the soil, which differs from the generally accepted homogeneous model. Grid model of soil imitates various conditions of permafrost. Calculation model allows us to estimate parameters of the electrochemical protection of gas pipelines, taking into account the inequality of the parameters of the electrical conductivity of soils and also the transition resistance of the protective coating of the pipes along the length of the section. The model also makes it possible to estimate seasonal changes in the propagation conditions of protection currents due to periodic thawing and freezing of the soil in the conduction layer.

DEVELOPMENT OF AN OPTIMAL PLACEMENT ALGORITHM FOR ELECTROCHEMICAL PROTECTION OF UNDERGROUND STEEL GAS PIPELINES

Statement of the problem. The paper considers the process of complex periodic corrosion inspection in order to assess the effectiveness and improve the operational reliability of the corrosion protection system (CPS) using the example of on-site technological networks of the underground gas storage Elshanskaya. Results. The technical condition of the electrochemical protection means, the level of active protection and the technical condition of pipelines of the underground gas storage were assessed, the object was protected by its length and time, and zones of negative influence of constant and stray currents were identified. A method is proposed for determining the optimal number and locations of cathodic protection stations (CPS). Conclusions. Based on the research results, a commissioning method is proposed that provides the optimal technological mode of operation of electrochemical protection means (EChP), and proposals have been developed to ensure the effectiveness of diagnostics and the safety of further operation of gas distribution pipelines. The implementation of this approach in the design of EChP facilities can lead to a significant reduction in energy consumption during operation.

Development of an Optimal Placement Algorithm for Electrochemical Protection of Underground Steel Gas Pipelines

Постановка задачи. Рассматривается процесс комплексного периодического коррозионного обследования с целью оценки эффективности и повышения эксплуатационной надежности системы противокоррозионной защиты на примере внутриплощадочных технологических сетей компрессорного цеха Елшанской станции подземного хранения газа (СПХГ). Результаты. Произведена оценка технического состояния средств электрохимической защиты, уровня активной защиты и технического состояния отдельных элементов трубопроводов Елшанской СПХГ, определена защищенность объекта по протяженности и во времени, выявлены зоны негативного влияния постоянных и блуждающих токов. Предложен метод определения оптимального количества и мест размещения станций катодной защиты на примере площадки СПХГ. Выводы. По результатам исследований предложен способ наладки, обеспечивающий оптимальный технологический режим работы средств электрохимической защиты, разработаны предложения по обеспечению эффективности диагностики и безопасности дальнейшей эксплуатации газораспределительных трубопроводов. Реализация данного подхода при проектировании средств электрохимической защиты позволит существенно снизить энергозатраты при эксплуатации. Statement of the problem. The paper considers the process of complex periodic corrosion inspection in order to assess the effectiveness and improve the operational reliability of the corrosion protection system using the example of on-site technological networks of the underground gas storage Yelshanskaya. Results. The technical condition of the electrochemical protection tools, the level of active protection and the technical condition of pipelines of the underground gas storage were assessed, the object was protected by its length and time, and zones of negative influence of constant and stray currents were identified. A method is proposed for determining the optimal number and locations of cathodic protection stations. Conclusions. Based on the research results, a commissioning method is proposed that provides the optimal technological mode of operation of electrochemical protection tools. Proposals have been developed to ensure the effectiveness of diagnostics and safety of further operation of gas distribution pipelines. The implementation of this approach in the design of electrochemical protection means facilities might lead to a significant reduction in energy consumption during operation.