Tom 23 (2012): Zeszyt 1 (September 2012)

The high failure frequency and the resultant reliability and safety implications in recent years of transformers, in particular at nuclear power plants (NPP), required an in-depth assessment. Fires of main transformers are considered as critical because of the large quantity of oil in contact with high voltage elements. Therefore, these phenomena have been investigated in more detail using the information from the OECD FIRE database for NPP. 12.8 % of all fires and, thus, the most frequent fire source in this database are transformer fires, mainly fires of high voltage oil-filled transformers. Thus, possible diagnostic measures to avoid such events and enhance the reliability currently discussed in Germany are shortly described. Moreover, consequences of transformer failures with respect to a reliable electric power supply are addressed.

Safety culture is a well-known concept in different industries worldwide, in particular in the nuclear field. Safety culture is recognized as an important factor in achieving high levels of safety performance. Although there is a wealth of information relating to safety culture, there is still no universal definition or model. Thus, the appropriate definition for the respective area such as nuclear, aviation or maritime has to be determined. However, the essence of safety culture is the ability and willingness of the organization to understand safety, hazards and means of preventing them as well as to act safely. Safety can only be achieved through the use of reliable structures, components, systems, and procedures as well as plant personnel committed to a strong safety culture.

The paper describes an approach to the numerical analysis of response of nuclear power plant buildings including soil-structure interaction effects. A reinforced concrete structure of an NPP reactor building under operating and seismic loadings is considered. The simulated seismic load corresponds to a maximum designed earthquake of magnitude 7 (the peak ground surface acceleration is 0.12 g). The numerical analysis was performed by the finite element method in a 3D nonlinear statement using the FEM-programs ANSYS and LS-DYNA. Review of the numerical analysis results demonstrated that the presented technique can be successfully applied to seismic design of NPP structures.

The article describes numerical method of physical gas flow parameters recovery at accidents investigation, which are conditioned by guillotine rupture of a pipe in gas trunkline and distribution pipeline systems. The information about full-scale measurements of time dependences of gas flow parameters at defined points inside pipelines system and at its boundaries is the base for recovery implementation at numerical investigation of accidents. Numerical recovery is carried out by defining and solving a special identification problem

Reliability and availability of electric power system equipment (e.g., generator units, transformers) are often evaluated by defining and solving Markov models. Transition rates among the identified equipment states are estimated from experimental and field data, or expert judgment, with inevitable uncertainty. For model understanding and to guide validation and confidence building, it is of interest to investigate the effects of the uncertainty in the input transition rates on the output reliability and availability. To this aim, Global Sensitivity Analysis (GSA) can be used for defining importance (sensitivity) indexes that allow a ranking of the transition rates with respect to their influence on the uncertainty in the output. In general, GSA requires a large number of model evaluations. In this paper, a metamodel is defined to estimate the performance index of interest (e.g. reliability or availability). The metamodel is built based on polynomial chaos expansion (PCE), a multidimensional polynomial model approximation whose coefficients are determined by evaluating the model in a reduced set of predetermined values of the input. The proposed approach is illustrated on a power generating unit.

To ensure that road transport safety measures are effective and efficient, forecast tools should be applied to help with strategic decision-making. Models of road safety measures provide such tools. The paper presents a proposed macro model of road accident casualties. The proposed models of road accident fatalities are built from a database covering more than fifty countries worldwide. The concepts of model design can be used for developing factor-based models to describe strategic societal risk on the road networks of selected countries worldwide. One of the concepts was applied to model the number of road accident fatalities. The analyses used Smeed’s model and its modifications developed for the needs of this analysis.

The paper presents several issues of risk management in respect to ship collisions with bridges. Accident statistics in Poland and around the world, risk acceptance problems and two case studies for probability assessment are presented

The paper presents the methodology of numerical modelling of road crash tests based on the selected vehicle-road barrier system using the possibilities of modern CAD /CAE computing systems for a numerical simulation process of the collision. Owing to these systems, thorough analysis of the process of collision, including the analysis of the stress and strain fields and energy consumption in the tested systems, is possible. It is possible to design and redesign virtually the barriers at a relatively low cost.

Long-lasting exploitation of a machine usually brings about wear and tear of its subsystems due to deteriorated material properties and mechanical wearing, which means that all safety functions should be periodically inspected for finding any changes in parameter values that could reduce the control system capability to perform its function. Therefore in the CIOP-PIB and IBS PAN the simplified procedures were formulated that aimed at the insurance of maintaining the required availability of safety function throughout the lifetime of machinery. The paper presents practical examples of application of these procedures to different architectures of the systems. Those examples proved usability of developed procedures.

The scope of the project covers the development of a method for assessment of risk related to machinery, based on the computer-aided virtual reality technique. The investigations started with the formulation of the matrix of correspondence between the hazards and functions performed by the VR using document-based inspection method based on documentation of the 3 machines. Further investigations have been conducted by Expert Inspection method using virtual models of 3 machines. It was proved that the immersive projection technology were highly usable in the assessment of risk involved by mechanical hazards and arriving at more accurate results necessary for machine assessment in view of ergonomic then the HDM techniques. In further research the usability of the developed method will be investigated using the User Testing method.

The article deals with some problems that designers of sea waterways encounter, i.e.: interrelations between parameters of waterway, ships and positioning systems used, selection of position determination systems depending on ship's operating conditions on sea waterways, and the optimization of waterway parameters.

In the paper, the results of dependability evaluation of railbuses are presented. These results are the basis for assessment of their durability. Selected indicators and characteristics are used to evaluate the dependability of railbuses. Information about the operation and maintenance has been obtained from the railway company, which performs the passenger transport with the use of railbuses. The research analysis contains 8 single mode railbuses of type X (manufactured by the same producer).

In this paper, the authors’ research work is focused on imperfect inspection policy investigation, when not all defects are identified during inspection action performance. They are interested in Block Inspection Policy performance for multi-unit systems, the maintenance policy which is one of the most commonly used in practice. As a result, at the beginning, few words about delay time modelling approach and a brief literature overview is given. Later, the model of Block-Inspection Policy is provided. The numerical example with the use of QNU Octave program is given. In the next Section, the sensitivity analysis of the developed model is characterised. The article ends up with summary and directions for further research.

In this paper, the authors’ research work is focused on uncertainty analysis implementation in the developed DSS for transportation means’ maintenance processes performance. Thus, in the Introduction section, the transportation means’ maintenance processes issues and the uncertainty problem are described. Later, there is briefly literature overview in the research area discussed. In the next Section, the expert system for means of transport maintenance processes performance is also investigated. Following this, the uncertainty analysis is developed and the examples of expert system implementation are given. The work ends up with summary and directions for further research.