IMPROVEMENT OF METHODS OF TECHNICAL DIAGNOSIS OF PASSENGER RAILWAY CARS

Extension of the service life of a particular passenger railway car can be considered fully justified only if it is justified by the results of scientific and experimental research and approved by the relevant administrative documents of Ukrzaliznytsia the service life limit for wagons of this type. The existing method of technical diagnostics of passenger railway cars does not allow to fully assess the probability of extension of the service life of the car, because it does not take into account the peculiarities of damage to structural elements during operation. In the article the sequence of research of stresses in elements of a frame of a body of the passenger car of construction of KVN on the basis of standard tests is considered. The task of the study is to determine the sequence of calculation of stresses in the frame elements of the passenger car body of KСР (Kryukiv Carriage Plant) with a service life exceeding 41 years from the date of manufacture to assess strength and fatigue resistance by technical diagnostics and standard tests. It is concluded that the condition of the load-bearing metal structures of cars after long operation does not approach the limit. The residual resource was set at one of the minimum calculated values. If the results of calculations show that the resource is exhausted, the residual service life is determined by the results of bench tests for fatigue. The obtained practical and theoretical results make it possible to extend the service life of cars beyond that set by the manufacturer.

Safe operation of gas pipelines based on the control of stress corrosion cracking

PurposeThe paper is devoted to the phenomenon of stress corrosion cracking (SCC), which is an urgent problem for major operator companies that use large-diameter gas transport systems built in the second half of the last century. The aim of the study is to predict the operability of gas pipelines with SCC and ensure their safe operation.Design/methodology/approachThe methodology of the article mainly consisted of strength calculations, mathematical and analytical approaches.FindingsThe paper describes practical methods of assessing the residual service life and operability of pipes with SCC defects as part of gas pipelines, the developed approaches to assessing the point of failure of pipes, provides recommendations for developing requirements to ILI smart tools in order to detect cracks and the methods of pipe repair depending on the SCC defect parameters.Originality/valueThe originality of the study consists in the analytical description of the point of destruction of gas pipelines with SCC, assessment of their performance, as well as the definition of modern requirements for the accuracy of in-line inspection to ensure the detection of potentially dangerous SCC defects.

THE DETERMINATION OF THE RESIDUAL LIFE OF BUILDING STEEL STRUCTURES BY THE RELIABILITY INDEX INDICATORS

In order to assess the operational safety of steel constructions, the paper analyzes the principles of calculating the safety of structural steel constructions with consideration for the reliability index β at all phases of constructions operation and the design fundamentals of the reliability index β for both new constructions (at the design stage) and structural steel constructions in the conditions of the long-term operation. The task of safety and reliability calculations, first of all, consists in assigning normalized safety parameter values, i.e. normalizing the reliability index, the value of which should be strictly related to the consequence classes (CC), which are determining for setting the reliability coefficients for further calculations while designing the constructions. The article considers the calculation values β of the reliability index for constructions operated beyond the time limit for operation, with accumulated defects and damages. To improve the mechanism for calculating the reliability index value for the constructions operated beyond the maximum operating limit, with accumulated defects and damages, several tasks were set to determine such values β of the reliability index below which the construction is no longer considered to be operational and to define the reliability index values β for possible performance of renovation works (reconstruction, refurbishment) to strengthen and extend the remaining structural lifetime. Thus, emphasizing all of the aforementioned, the main conclusions to the article should be specified: at the stage of solving the issue of calculating the reliability index for structures being operated over the projected service life, with damages and initial defects accumulated during the operation period, it is required to perform their review and determine two main criteria for solving the issue of determining the reliability index, namely: to set such values of the reliability index below which the structure will be no longer operational, to define and set such values of the reliability index at which it is possible to carry out renovation works on steel structures, their reconstruction or repair. Considering the possibility of changing the reliability index compared to a new structure, given that the residual service life may be shorter than the design one, taking into account the economic factors and factors of probability of losing a person’s life, setting of such reliability index values is necessary for further possibility of the service life extension of a structure and determination of its residual life.

Development of an experimental-estimation method for estimating indices of residual life of a radio technical complex

To implement the operation of a radio technical complex according to its technical condition, it is necessary to jointly evaluate its reliability and residual life indices with required accuracy and reliability and minimization of the scope of special tests. The known methods are focused on separate solutions to the problems of estimating these indices as applied to the regulated strategy. To solve this problem, general provisions have been developed for estimating the indices of residual life of the radio technical complex including the accepted assumptions and limitations for developing the method, the estimated indices, and criteria of limiting state. The developed experiment-calculated method is a set of mathematical models of change of the reliability indices of a radio technical complex depending on calendar duration of operation or total operating time and analytical models of estimating the indices of its residual life. The mathematical models of change of mean time between failures, the probability of failure-free switching, and the parameter of the flow of failures of the radio technical complex depending on calendar duration of operation or the total operating time were presented in a form of regressive dependences. Analytical models of estimating the residual life indices are ratios for calculating the "average residual service life (resource)" according to the technical and economic criterion using regression-time dependences of the reliability indices. The developed experiment-calculated method can be used to estimate the indices of residual life of the radio technical complex with acceptable accuracy (no more than 2 quarters) and reliability (no worse than 0.8). In this case, the duration of the intervals of predicting the reliability indices should be 0.5 to 1 year and the corresponding observation intervals should be more than 1 year

INVESTIGATION OF RESIDUAL RESOURCE OF SPECIAL RAILWAY VAGON

The article examines the residual life of load-bearing metal structures (NMC) of special cars for the transportation of special contingent on the basis of the results of technical diagnostics and standard tests. Most scientific publications investigate the increase in the service life of different types of passenger cars by improving their design properties. The following methods are used in the study: resetting from wedges, resource tests for impact strength, impact tests, static strength tests. On the basis of carrying out technical diagnostics and standard tests the possibility of establishment of new appointed service life of cars is defined. The residual resource was set at one of the minimum calculated values obtained by mathematical dependence to calculate the residual service life. When determining the residual resource during the standard tests, the evaluation of the fatigue resistance margin was performed taking into account the stress of the load-bearing structures of the car during the tests. It is concluded that the condition of load-bearing metal structures of special wagons for transportation of special contingent after long operation does not approach the limit. The obtained practical and theoretical results make it possible to extend the service life of special wagons for the transportation of special contingent beyond the established by the manufacturer.

Stochastic Time-Dependent Deterioration Models for Estimating Residual Service Life of Offshore Jacket-Type Platforms

This paper presents deterioration models for maintenance planning of offshore jacket platform based on two methods: i) stochastic Markov-chain based model and ii) stochastic-mechanistic deterioration models based on steel corrosion rates. Markov-chain models require the estimation of transition probability matrix (TPM), which is typically derived from the inspection data. The global structural health condition of the jacket is computed based on the condition of individual elements and their criticality in terms of failure consequence. The criticality factors are established based on nonlinear static redundancy analyses. This method can model deterioration when routine inspection records of jacket members are available. When there is scarcity of inspection records, stochastic-mechanistic deterioration modeling approach can be used. Monte-Carlo simulations with established corrosion wastage models are utilized to estimate the time-dependent deterioration of jacket legs, horizontal and diagonal bracings in splash and immersion zones. This method is proposed when there is scarcity of inspection records. The deterioration models are further utilized to predict the timing for Maintenance, Repair and Rehabilitation (MRR) actions, and estimate the residual service life of the jacket platform. This study demonstrates the application of the proposed deterioration modeling approaches with a case study of a typical 4-legged offshore jacket platform.

Methodical approach to forecasting costs for updating and using arms and military equipment park

A methodological approach to forecasting the cost costs at the main stages of the life cycle of a sample of weapons and military equipment, as one of the most important carriers of the capabilities of military organizational-staff formations, is proposed, which is carried out when substantiating measures for developing the capabilities of troops in the course of long-term and medium-term defense planning. The methodological approach is based on the use of the concept of a typical distribution of the cost of the life cycle of a sample by stages and stages, which allows in a formalized form to link costs at each stage of the purchase price of a serial product of a sample of weapons and military equipment of a specific type and type, taking into account the choice of a specific way of obtaining weapons and military equipment. It is proposed to forecast the volume of necessary costs at the stage of operation and support, taking into account the uneven distribution of these costs during this stage of the life cycle of a separate product. For this, it is proposed to divide the entire period of the duration of the operation stage into two main parts. The first part corresponds to the operating conditions of the product with a constant failure rate of the equipment after the completion of a short running-in process, and the operating costs per unit of time on it are considered the same throughout its duration. A formalized expression is proposed for obtaining the predicted value of these costs depending on the purchase price of the product. In the second part of the period of operation and support of a product of weapons and military equipment, operating costs per unit of time change over time according to an exponential law, reflecting the fact that operating costs increase with an increase in the failure rate as it approaches the assigned service life, which corresponds to the laws, known from the general theory of reliability of technology. The specifics of forecasting the costs of operation and support of a product obtained by import and which has already been in operation and has a residual service life have been determined.