The workability of a transport system is associated with performance and operational reliability. Operational reliability provides a measure of the probability that a transport system will realize transport process as intended. Performance reliability is an adequacy measure of transport process realization under specific environmental and traffic conditions. Transport system can be modelled as repairable, multistate, non-homogenous rectangular or dendrite system. This article provides the Markov and semi Markov models for estimation of the operational and performance reliability of city transport system. The system is semi homogenous it means that serial subsystems have the same reliability function. The reliability of any serial subsystem is exponential. The distribution of the repair time is any probability distribution. In case where the probability distribution of the repair time is exponential, the Markov process is used to construct simulation model. The simulation model was applied at Microsoft Excel. Many stochastic models in engineering, logistic and even finance or insurance are setup in a spreadsheet for simulation. The semi Markov model of the multistate reliability of repaired system is applied to the street system. The embedded Markov chain was used to count stationary probabilities. The possibility of application of the results is illustrated by an example for the systems with rectangular or dendrite shaped accordingly, consist of three types of elements.
Analysis of the Influence of Carried Out Repairs Efficiency on Transport Means Operational Reliability
The Maintenance factors and destructive processes which affect systems and elements of technical objects result in undesirable changes of values of their functional features, which causes damages. A damage to a technical object has been defined as exceeding permitted boundary values by significant features characterizing their elements. On the basis of analysis results of the author's own research concerning damages to means of transport, used in real transport systems, it has been found that these damages are the effect of different forcing factors. A certain number of damages is caused by natural wear of machine elements, whereas other damages can occur in result of ineffective repair of a previous damage. Thus, the so called recurrent (secondary) damages occur in a short period of time. On the basis of literature and maintenance and operation analysis results it was found that the most frequent cause of recurrent damage occurrence is improper quality of repairs of the analyzed means of transport. Primary damages are not dependent on each other and they appear randomly, whereas recurrent damages do depend on each other and their occurrence is the conditioned by earlier occurrence of a repair, and above all, by its poor quality. In the paper, a method for evaluation the influence of carried out repairs on transport means operational reliability, has been presented On the basis of the analysis of the moments in which damages to the means of transport and of the time interval lengths between them a simulation model representing a real stream of the damages was built, which enables to evaluate influence of the efficiency of the performed repairs of the means of transport in the real transport system
The use and maintenance of technical systems throughout their lifecycle aims at achieving goals that allow for high values of productivity and availability characteristics of these systems. In the economic policy of each state or private organization or state institution, there is the right to determine the type of adequate maintenance system within the maintenance strategy adopted. Thus, the types of maintenance systems recognized in the technical domain are analyzed from the point of view of the two previously-mentioned features, productivity and availability, thus making the predictive maintenance system, derived from the preventively-planned one, advantageous for all organizations. It is obvious that the current trend is to spread this predictive maintenance system, according to which the interventions will be carried out before the malfunction occurs, depending on the periodically measured values of global pressure, flow, energy consumption, temperature, current, voltage, vibrations, etc.
The article deals with the research of operational reliability of forest felling machines with the method FMEA (Failure Mode and Effect Analysis) and its implementation for observed machines in the organization. Forwarders 810D by John Deere were chosen for this research. The research was realized in real operational conditions. Application of the FMEA method allows flexibility in case of unexpected situations and optimization of human potential abilities. FMEA tool is a tool preventing outages operational reliability and preventive tool for ensuring the maintenance of facilities. This paper explores and verifies the operational reliability theory in practical real-world conditions, resulting in a reduction in operating (variable) costs, minimization of failures and readiness and increased performance of observed machines.
The article presents the role of lubricating oils for aviation applications, along with their classification, and discusses the key physicochemical properties. It characterises engine, transmission gear, hydraulic and instrumentation oils and their impact on a device operational reliability. It also points out the requirements for these products in relation to the operating conditions and the chemical composition of a product.
The patterns of process situations play an important role in the monitoring of diagnostic processes. The adaptation of mathematical models describing the degradation processes in mechanical and electronic devices creates opportunities to develop diagnostic standards for buildings erected in traditional technology. This article presents a proposal for the prediction of building operational reliability, which is a prognostic process model within the full period of its use.
Over the course of their use, building structures are subject to constant destructive processes, which can take various courses. Over time, performance characteristics deteriorate, and can be partially restored as a result of repair works. The article presents a proposal for the prediction of changes in the performance characteristics of a building based on the adaptation of principles applied in predicting the operational reliability of technical objects.
The current maintenance system, preventively planned and applied to the military equipment according to the necessities, involves the rigorous execution of maintenance operations, which results in high costs and volume of work. These causes generally determine the formality of planned repairs and maintenance, with detrimental effects for the availability of vehicles. Moreover, the constructive-functional level of the current technical systems leads to the reorientation of adopting maintenance strategies that correspond to the availability level of the constructive kits to computerized diagnosis operations, such as the maintenance based on operational reliability. For some types of vehicles, the periodical technical inspection, besides allowing for regular traffic on public roads, can offer significant data for the managerial and technical implementation of the maintenance based on operational reliability within the military units. The paper aims at offering viable and efficient solutions for executing maintenance activities and for making vehicles available by turning to good account the data resulting from the technical diagnosis process, correlated with an optimal management of maintenance.
The Earth’s large amount of thermal energy is virtually an inexhaustible resource often placed too deep in the ground. Making use of this kind of energy is possible in limited areas. In this paper we analysed a GSHP system, in Galati city (Romania), for which we monitored the available thermal energy. For the analysis we used operational reliability theory, the concept of degradation, which in this case means a reduction of the ground’s thermal capacity as a result of continuous exploitation, meaning low temperature of the thermal agent used for transporting the heat from the ground to the primary exchanger of the heat pump. The decrease of thermal energy supply in the ground means that the heat pump wills no longer function properly in order to provide the energy for heating the building. The term time to failure refers to the time when the ground can no longer provide the minimum required energy for the heat pump operation, in terms of energy efficiency. What we want with this approach is to offer a solution in order to control and manage the heat pump operation.
Transport has always been a fundamental impulse for the development of civilization. Issues related to the regularity of operation of technical systems, in the last decade have become important issues being considered from both the point of view, as well as economics. Today the major threat in the operational reliability constitutes intensification of the machine and equipment use leading to excessive degradation. In automated manufacturing processes where the material handling operations are realized by the cranes, the safety as both devices and operating people constitute important factor. The main purpose of the article was focused on the set of issues including the material handling devices (MHD) reliability shaping problem especially presents work in progress towards development the MHD condition assessment system with using telematic approach. In the article author, special care was enclosed to MHD devices with strength human factor interaction and relatively large construction, so the overhead travelling crane was chose. The object of the statement constitutes an attempt of collecting the knowledge concerning a possibility of use modern measurement systems to monitoring crane bridge deflection. All tests and considerations were conducted on the double girder overhead travelling crane with hosting capability 1000 kg and bridge span 8000 mm.