Abstract
IEC 61508 standard could be used in the evaluation of safety of the k-out-of-n technical systems, including elements which may remain in one out of four different reliability states. Such a model leads to the huge complexity of analytical calculations and the limitations of its practical application possibilities. Therefore, a computerised method using Markov processes for estimating the reliability of k-out-of-n systems was developed. The algorithmization of the applied computational procedure was performed. It allowed one to analyse systems including a huge number of elements. An algorithm that may be applied for complex k-out-of-n systems was developed and used for exemplary calculations. The developed method was verified by comparing the obtained results with the ones obtained from analytical method as well as simulation method. The compatibility of results obtained in the two methods confirms the correctness of the developed procedure and proposed computer program which now offers the possibility of doing calculations for k-outof-n structures with more than three elements required for the system’s proper functioning and significantly accelerates calculations. Reliability and safety are priorities in the operation of technical systems. This decides of the applicability of the calculation methods described. The operational safety aspects are of particular significance in cases when the occurrence of a failure is a hazard to people’s health and life, ecological risk or considerable financial loss.
Highlights
To assess the reliability of repairable systems of complex reliability structure, whose times-to-failure and times-to-repair of technical components can be described by exponential distribution, Markov processes are successfully employed [3, 11, 14]
To verify the program written following the above algorithm six basic k-out-of-n structures were selected used in safety-related systems
The results of calculations performed after BlockSim program differ from the other two methods, but yield values of a large safety margin, which is favourable from the practical point of view
Summary
To assess the reliability of repairable systems of complex reliability structure, whose times-to-failure and times-to-repair of technical components can be described by exponential distribution, Markov processes are successfully employed [3, 11, 14]. The limitations due to the application of exponential distribution to describe failure and repair processes do not significantly affect the practical applicability of these calculation procedures. The aim of the present article is to discuss the problems related to the safety of complex technical systems and to, first, characterize the assumptions made in the calculation procedures employed in the aforementioned standards, and next to explain how these assumptions complicate the graphs of states and reliability calculations. On the basis of the analysis they have developed a calculation program which can be used successfully for the verification of the calculations done following the IEC 61508 standard
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
