Improvement of the conformity assessment system for the improvement of pipe products quality

Нормирование качества трубной продукции является ключевым инструментом, влияющим на системную надежность, безопасность и эффективность функционирования объектов магистральных трубопроводов. В статье рассмотрены особенности оценки соответствия стальных труб, предназначенных для строительства, ремонта и реконструкции линейной части нефте- и нефтепродуктопроводов. Проведен сравнительный анализ технических требований к трубной продукции, установленных отраслевыми нормативными документами, международными и национальными стандартами. Выделены проблемные вопросы, связанные с оценкой соответствия труб, применяемых на объектах нефтепроводного транспорта. Отмечено, что проблема повышения качества труб актуальна как для операторов магистральных трубопроводов, так и для заводов - изготовителей трубной продукции. На основе практического опыта определено, что наилучшие результаты в области контроля и повышения качества труб обеспечивает реализация комплекса мероприятий, сочетающего «классическую» процедуру оценки соответствия (сертификации) с методической базой, позволяющей на основе статистических данных об отказах и браке в условиях эксплуатации трубной продукции эффективно решать задачи по управлению ее качеством. Standardization of the pipe products quality is a key tool affecting system reliability, safety, and efficiency of operation of main pipeline facilities. The article discusses the features of conformity assessment of steel pipes intended for the construction, repair, and reconstruction of linear sections of oil and oil product pipelines. A comparative analysis of the technical requirements for pipe products established by industry regulations, international, and national standards has been conducted. The issues related to the conformity assessment of pipes used at oil pipeline transport facilities are highlighted. It is noted that the issue of improving the quality of pipes is relevant both for operators of main pipelines and for manufacturers of pipe products. Based on practical experience, it has been determined that the best results in monitoring and improving the quality of pipes are ensured by implementation of a set of measures that combines the traditional conformity assessment (certification) procedure and a methodological base that allows to effectively solve problems of managing their quality based on statistical data on faults and defects in the operating conditions of pipe products.

Low-Frequency Dielectric Relaxation in Structures Based on Macroporous Silicon with Meso-Macroporous Skin-Layer

The spectra of dielectric relaxation of macroporous silicon with a mesoporous skin layer in the frequency range 1–106 Hz during cooling (up to 293–173 K) and heating (293–333 K) are presented. Macroporous silicon (pore diameter ≈ 2.2–2.7 μm) with a meso-macroporous skin layer was obtained by the method of electrochemical anodic dissolution of monocrystalline silicon in a Unno-Imai cell. A mesoporous skin layer with a thickness of about 100–200 nm in the form of cone-shaped nanostructures with pore diameters near 13–25 nm and sizes of skeletal part about 35–40 nm by ion-electron microscopy was observed. The temperature dependence of the relaxation of the most probable relaxation time is characterized by two linear sections with different slope values; the change in the slope character is observed at T ≈ 250 K. The features of the distribution of relaxation times in meso-macroporous silicon at temperatures of 223, 273, and 293 K are revealed. The Havriliak-Negami approach was used for approximation of the relaxation curves ε″ = f(ν). The existence of a symmetric distribution of relaxers for all temperatures was found (Cole-Cole model). A discussion of results is provided, taking into account the structure of the studied object.

Modeling the Stress-Strain Curve of Elastic-Plastic Materials

The work is devoted to the formulation of mathematical models of plastic materials without hardening. A functional is proposed, the requirement of stationarity of which made it possible to formulate the differential equation of stress as a function of deformation. On the linear deformation section, a second-order functional is proposed; on the non-linear deformation section, a fourth-order functional is proposed. A range of boundary value problems is formulated, that ensure the continuity of the function at the boundary of the linear and non-linear sections of the deformation curve. The theoretical strain curve was compared with the samples of experimental points for materials: St3sp steel, steel 35, steel 20HGR, steel 08Kh18N10, titanium alloy VT6, aluminum alloy D16, steel 30KhGSN2A, steel 40Kh2N2MA, and showed a good agreement with the experiment. Thus, a variational model is constructed, that allows one to construct curve deformations of various physically non-linear materials, which will allow one to construct further mathematical models of the resource of such materials.

Analysis of the Linear Section Risk Level Including Changes in the Pipe Material Strength Properties during Main Oil Pipeline Operations

Strength properties of the pipe material are random variables and have a statistical straggling that differs for pipe products of different grades. Distribution of these properties significantly effects on the results of calculating the current level of strength reliability and risk of linear sections for the main pipelines. The reliability of such calculations results depends not only on the distribution that obeys the strength properties of the pipe material at the surveyed section, but also on the dispersion limits of these properties. At present, the main pipelines have significant service lives. Due to this, when making assessment of the technical condition, safety, and risk level of linear sections, the issue is raised of how stable the distribution is related to the pipe steel strength properties with an increase of the service life for the main pipeline. The results of studies are presented concerning the actual distribution and limits of dispersion for the strength properties of pipe steel grade 17G1S after a long-term operation of the main pipeline. It is established that the regularities and strength properties dissipation limits for the material of a pipe made of the above steel are changing with time. Based on the results of the study, a practical example is considered related to the assessment of the effect of the identified changes on the probability of failure and the risk level for one of sections at the linear part of the main oil pipeline. The results obtained in the work substantiate the need in considering changes in the distribution of strength properties that arises with an increase in the main pipelines service life. The outlined approach allows to increase the reliability of risk assessment results for the main pipelines having long-term service life.

AFM Study of the Influence of Glycerol Flow on Horseradish Peroxidase near the in/out Linear Sections of a Coil

Flow-based coiled systems, through which a heat transfer fluid (such as glycerol) is pumped, are widely used for thermal stabilization of bioreactors and biosensor cuvettes and cells. Previously, using horseradish peroxidase (HRP) as a model protein, we have demonstrated that the incubation of a protein solution in a flow-based system over coiled pipe with flowing glycerol leads to a change in the adsorption properties of the protein macromolecules. Herein, we have studied the effect of the glycerol flow on the properties of HRP, the solution of which was placed differently: i.e., near either the inflow or the outflow linear sections of the pipe, while the coiled section of the pipe was shielded with a grounded metallic cover. Atomic force microscopy (AFM) has been employed in order to visualize the HRP protein macromolecules adsorbed from its solution onto the mica substrate surface. The quantity of adsorbed protein was estimated based on the AFM data. The enzymatic activity of HRP was estimated by spectrophotometry. We demonstrate that a change in the properties of HRP enzyme was observed after the incubation of its solution near the inflow/outflow linear sections of the pipe with flowing glycerol. Namely, after the incubation of HRP solution near the inflow section, a decrease in the protein adsorption onto mica was observed, but its enzymatic activity remained unchanged in comparison to the control sample. In another case, when the HRP solution was incubated near the outflow section, an increased protein adsorption was observed, while the enzyme exhibited considerably lower activity.

Segregation of the bulk cargo on a belt conveyor under the vibro-pulse impact

The dynamics of interaction of the large lumps of the bulk cargo with a conveyor belt while passing through roller supports of the conveyor linear sections is often a cause of damage on the conveyor belt. In order to reduce the negative impact it is proposed to isolate the conveyor belt surface from the large lumps by filling small fractions of the bulk cargo by means of adding a shock device to the conveyor structure that causes increased segregation of the bulk cargo. A mathematical model of the segregation of the bulk cargo located on the conveyor belt and in zone of impact of the shock pulses has been developed. The model considers a change in the rotation direction of the large lump when applying shock pulses to the characteristic points of the lump lower face. Herewith it takes into consideration weakening of the shock pulse by a layer of the bulk cargo small fractions. The presented model has received experimental confirmation. Analytically and experimentally the height of filling of the bulk cargo small fractions under a large lump when passing the vibrating impact device located on the conveyor belt has been determined.