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Proceedings of the Eighth International Conference on Probabilistic Safety Assessment & Management (PSAM)

Michael G. Stamatelatos
Michael G. Stamatelatos
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Harold S. Blackman
Harold S. Blackman
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ASME Press
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The article deals with selected problems, which are associated with reliability and safety assurance in the case of electromechanical systems of traction vehicles. The authors of the article have long-term co-operation with Lekov Company (Blovice, Czech Republic), which is well-known producer of electric switching and controlling components for traction vehicles. To be successful in competition and satisfy high requirements of customers (major manufacturers of traction vehicles) the company, among others, pays exceptional attention to reliability and safety of its products.

Considering the problems of reliability and safety carefully, the Lekov Company puts into practice the integrated RAMS program in the process of development, design and production. The authors of this article notably participated in the project and implementation of the program, and, moreover, they are closely co-operating on solving the concrete problems concerning high reliability and safety of the manufactured equipment.

The article presents a concise characterization of the implemented safety and reliability integrated program which ensures that in the process of development, design and production of new electromechanical equipment, the defined requirements concerning reliability, availability, maintainability and safety will be fulfilled. Regarding the limited size of this contribution, the interpretation has been reduced to the aspects of the program that lead up to reliability and safety providing.

The main methods, which are used as parts of the program, are Preliminary Hazard Analysis, Failure Mode, Effect and Criticality Analysis, Fault Tree Analysis and Reliability Diagram Analysis. The methods are used in individual steps that logically connect methods each to other. The article describes the procedures of the program in detail and brings a survey of applied methods with characterizations. Particular attention is devoted to problems that are associated with estimation of reliability measures of individual parts of systems.

The program has to allow a flexible reaction to customers' various demands that are to be met within the program. For that reason the implemented program does not represent any explicitly defined processes; it is rather a set of principles, rules, methods and procedures which are always expediently used, regarding both the nature of the product and the customer's demands. Generally, the program can be divided into three parts:

• analysis of the customer's demands

• reliability prediction of the system and its parts

• reliability demonstration.

The reciprocal link-up of the three basic parts of the program and their position in the process of development, design and production is indicated in the article. Furthermore, the principles, rules, methods and procedures applied to the individual parts of the program are characterized briefly.

The implemented reliability and safety program, even if using relatively simple methods, systematically ensures the fulfillment of the customer's requirements for reliability and safety of the system. The logically linked steps taken before the design stage ensure that the engineering design will be carried out effectively, with an emphasis on the given requirements fulfillment. The design correctness is then checked out by reliability assessment that precedes the prototype production. This procedure minimizes the possibility of producing a prototype with a structural defect. Thus the prototype reliability tests decrease the occurrence probability of the significant problems in the systems produced in series.

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