SYSTEM ANALYSIS IN DEPENDABILITY AND SAFETY
Based on the theoretical findings presented in the first part of the paper, this part investigates the main characteristics of the dependability of a k-out-of-n system with arbitrary distributions of failure-free time and time to component repair. Using the marks transformations proposed in Part I of the paper and simulation, various probabilistic and temporal characteristics of the model are calculated and studied, while their sensitivity to the initial distributions and their parameters is analyzed.
Safe operation of any complex distributed systems is largely defined by the quality of the event analysis and prediction tools. Aside from the external hazards, the so-called hazardous production facilities (HPFs) pose significant threats. Accidents at such facilities are a subject of constant analysis and concern of operating organisations. At the same time, the accident statistics accumulated over the period of operation of such facilities are often heterogeneous. Accidents and incidents at HPFs occur at different times, against different forecast backgrounds, which complicates the construction and verification of digital models of such facilities. This paper proposes an algorithm for preprocessing time series of observations to extract data that can be subsequently used to build and train predictive models with the required accuracy. The proposed approach can be implemented by means of the R language, that in many respects has become a standard for statistical calculations.
STRUCTURAL RELIABILITY. THE THEORY AND PRACTICE
Aim. The paper aims to reduce the costs associated with the post-failure downtime of equipment. This is especially relevant for industries such as oil production due to the territorial distribution of the maintained facilities and remote location of spare part storage, which leads to increased time to repair due to the wait for the arrival of the right part or piece of equipment. At the same time, there may be spare parts in stock that will not prove to be useful in the near future due to the irrational content of the stock in storage. Methods. Managing equipment spare parts usually comes down to using probabilistic methods and mathematical models for solving optimization problems, but such methods require data on the technical condition of a facility, cost characteristics, etc., that may not always be available, so a method that does not use such information needs to be developed. Results. A method is proposed for defining the number of spare items using the times-to-failure of same-type items and identifying the predicted probabilities of failures, which allows, in the absence of statistical data on the technical condition of items, minimising the downtime of equipment while waiting for spare parts.
The systematically growing proportion of equipment, devices, and installations (hereinafter referred to as entities) of electrical power systems, whose service life exceeds the standard value, and the consequences of that fact, some of which are unacceptable, require decisive measures to improve their efficiency. Today, the effort is focused on improving the methods of identifying and monitoring their technical state. In other words, the matters associated with improving the reliability and safety of operation naturally come to the fore. The authors suggest monitoring the technical state of overhead lines with a rated voltage of 110 kV or higher monthly based on the operational reliability indicators. New methods and algorithms for their assessment, comparison, and ranking are presented. Since the operational reliability indicators are multidimensional, the existing methods for comparing and ranking unidimensional statistical estimates are unacceptable, as neglecting the premises of such methods causes a significantly higher risk of a wrong decision. The proposed new methods are based on the fiducially approach, simulation, and the theory of statistical hypothesis testing. The awkwardness and labour intensity of manual calculation of operational reliability indicators and the scientific complexity of the calculation methods are compensated by the migration to automated systems that provide procedures and information on the technical state of overhead lines. The recommended methods are part of the group of risk-based approaches to improving the efficiency of electrical power systems.
During transmission pipelines pressure testing, the value of the test pressure is taken to be equal to 1.1 of the working pressure for sections of the normal category and 1.25 or 1.5 for sections of higher categories. The substantiations of the above values date back to the middle of the 20-th century, and may need to be reconsidered in the light of the new-generation pipe materials implementation. This paper aims to identify the optimal safety factor for pressure testing of main pipelines, taking into account the material of the pipes, as well as the variation of the destructive power in case of multiple loading of the test objects. The findings will allow confirming or revising the existing approach to assigning the strength test pressure of main pipelines and theoretically substantiating the observed phenomena. In practice, that will allow establishing the optimal parameters for testing gas pipelines, ensuring the required dependability and safety. The research is relevant due to the continuous improvement of pipe steels, as well as in the light of innovative pipe material development. An analysis of foreign and Russian experimental studies involving double loading of steel test objects to failure indicates that – before the second loading – the destructive force can be reduced to 90% of the first loading value. The available statistical sample of foreign and Russian experiments is small, while the methodology is complex. Given the above, the authors developed an original methodology, that was used in destructive double loading experiments on steel test objects and statistical analysis of the results.
ВОПРОСЫ АВТОМАТИЗАЦИИ И УПРАВЛЕНИЯ ПРОЦЕССАМИ НА ТРАНСПОРТЕ
The paper analyses the system of standards related to the safety of railway automated process control systems, including the key trends of standardisation for the near future. The authors examine theoretical matters of functional safety, including the safety concept of the bottom-layer transportation management process and the basic safety principles.
Aim. The research aims to define and demonstrate additional expertbased methods of examining technological systems in the context of possible damage assessment, that can be used for relative comparison of designed, planned or operated objects of analysis, development of strategies and recommendations for further operation. Method. The paper uses methods of relative analysis of quantitative patterns. Result. The use of additional expert-based methods will allow building know-how to compare technological system designs in the absence of operational experience, to identify their potential capabilities in the context of further modifications and upgrades. Conclusion. The proposed method of relative analysis of quantitative patterns allows developing strategies and recommendations for choosing among competing technological solutions, system management decision-making, and planning production funding based on existing, expertdefined safety and security deficiencies and “weak links” in the technological capabilities or management of a company.
Given the rapid development of the oil and gas industry, the matter of assessment of the explosion resistance of buildings and structures at multicomponent gas mixture transportation and processing facilities remains of relevance. The paper investigates the sensitivity to the initiation of explosive transformation of methane and air mixtures of hydrogen and methane homologues depending on the component composition. Estimates were obtained of the sizes of detonation cells of methane and hydrogen mixtures, which allows for a more accurate definition of the class of sensitivity to detonation.