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Ohjausjärjestelmien turvallisuusvaatimukset:IEC 61508
No full textStandardia IEC 61508 käytetään yhä enemmän ohjausjärjestelmien turvallisuuden soittamiseen. Standardi perustuu elinkaarimalliajatteluun ja toisaalta asioiden kvantitatiiviseen tarkasteluun. Siten on tarpeen laskea tuotteille toimintatodennäköisyyksiä ja vikataajuuksia
Method for application of weibull distribution to the reliability calculation of functional safety for industrial machinery
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2014.O desenvolvimento de sistemas elétricos e eletrônicos permitiu a massificação do uso de dispositivos eletrônicos programáveis para comando e controle de operações de sistemas técnicos. Tais dispositivos possibilitaram o desenvolvimento de sistemas técnicos mais complexos, porém, devido a essa elevada complexidade, observou-se um aumento de acidentes causados por falhas inerentes ao controle de tais sistemas. Para se reduzir esses acidentes, foram criadas normas técnicas para sistemas de controle, cuja aplicação seja relevante a segurança, o que deu origem a segurança funcional. Segurança funcional refere-se à segurança que é mantida atráves do correto funcionamento de um sistema técnico. Diferentes segmentos industriais tem aplicado o conceito de segurança funcional, para criar máquinas e sistemas mais seguros. No setor de construção de máquinas, o uso de funções de segurança reduz o número de acidentes de trabalho, ao evitar que operadores, mantenedores e pessoas ao redor fiquem expostas aos perigos inerente das máquinas. As normas técnicos impõe requisitos quantitativos e qualitativos sobre os sistemas de controle de segurança. A norma técnica internacional IEC 61508 definiu um framework para quantificação de segurança funcional. Para cada setor industrial, normas específicas foram baseadas baseadas na IEC 61508. Esse framework é bem adequado para componentes elétricos e eletrônicos. Porém, na área de maquinário industrial, sistemas de controle são realizados não somente com tais componentes, mas também por componentes mecânicos, pneumáticos e hidráulicos, os quais apresentam um comportamento diferente de falha. Tais componentes são considerados pela norma técnica internacional ISO 13849. No entanto, os métodos de quantificação desta norma contém fortes limitações e não são completamente compreendidos pelos usuários. Este trabalho dedica-se ao estudo da norma técnica internacional de segurança funcional no setor de construção de máquinas industriais, a ISO 13849. O foco do estudo é a quantificação de falhas físicas de componentes. Falhas físicas sao quantificadas através de indicadores probabilísticos, sendo objeto de estudo da engenharia de confiabilidade. No primeiro capítulo, desenvolve-se o conceito de segurança funcional. O conceito é explorado como um todo, como uma ferramenta de redução de riscos, e posteriormente como esse conceito é aplicado no setor de construção de máquinas. O apêndice A complementa o capítulo 1 com a estrutura legal no que diz respeito à segurança de máquinas na Europa, definido pela Diretiva Europeia de Máquinas, da qual a norma técnica ISO 13849 faz parte. Ainda no capítulo 1 são identificadas as principais linhas de pesquisa, e o objetivo do trabalho é enunciado. Este trabalho, feito em parceria com a Bosch Rexroth, tem como objetivo o desenvolvimento de um método que possibilite a quatificação de índices de confiabilidade para segurança funcional utilizando distribuição de Weibull. No segundo capítulo, conceitos básicos para a compreensão do trabalho são apresentados. Os primeiros conceitos relacionam-se com conceitos da engenharia de confiabilidade, com o objetivo de esclarecer conceitos como probabilidade, confiabilidade, probabilidade de falha e construir o conceito do índice utilizado pela ISO 13849, a frequência média de falhas perigosas por hora, PFH. O apêndice B complementa esse capítulo, com uma explicação intuitiva do que é medido através do PFH. Neste capítulo também é apresentada a distribuição de Weibull, bem como métodos de cálculo de PFH. Os parâmetros para cálculo do PFH segundo a ISO 13849 são apresentados e explicados. No terceiro capítulo é apresentado como se é calculado o PFH através de simulação a eventos discretos. Um método para cálculo do PFH considerando distribuição de Weibull, para estruturas simples e estruturas redundantes, correspondendo às categorias B, 1, 3 e 4 da norma técnica ISO 13849. O apêndices C desenvolve a equação para determinaão do número mínimo de simulações para se alcançar o resultado desejado, e o apêndice D desenvolve as equações utilizadas pelo método proposto para estruturas redundantes com falha de componentes seguindo a distribuição de Weibull. Os resultados para os casos de comparação com a ISO 13849 são apresentados no apêndice E. No quarto capítulo é apresentado um exemplo de aplicação do método proposto em uma máquina hidráulica simples do Laboratório de Sistemas Hidráulicos e Pneumáticos (LASHIP), da Universidade Federal de Santa Catarina (UFSC). A determinação do PFH e subsequentemente do PL é realizada através do procedimento dado pela norma e pelo método proposto. Utilizando-se o método proposto, foi possível calcular PFH para intervalos de utilização diferente do considerado pela ISO 13849, bem como reconhecer o efeito do desgaste do componente, caracterizado pela distribuição de Weibull. No quinto capítulo é apresentado uma visão geral de como integrar o cálculo de PFH com distribuição de Weibull com o processo de desenvolvimento de uma máquina, baseado em experiência com a Bosch Rexroth. No capítulo de conclusão é analisado o potencial de se realizar análises mais realistas, e as limitações do método proposto, sendo adequado apenas para máquinas o subsistemas produzidos em série, devido ao requerimento de dados de campo para extrair os parâmetros da distribuição de Weibull para cada componente. Analisa-se também como que a pesquisa desenvolvida se encaixa na linha de pesquisa explicitada no primeiro capítulo, e qual a relevância para o cenário brasileiro. Adicionalmente, sugestões para trabalhos futuros são feitas.Abstract : The IEC 61508 standard series defined a framework for quantification of functional safety. For each particular industry sector, specific standards are being developed based on it. This framework is well suited for electrical and electronic components. However, in the field of machinery, control systems are realized not only by such components, but also by mechanical, pneumatic and hydraulic components, which exhibit a different failure behavior. Such components are considered by the ISO 13849 standard. However, quantification methods of this standard are still not quite well understood by the users, and have strong limitations. This work presents a study an alternative method of how to calculate the average frequency of dangerous failures (PFH), required by ISO 13849 in order to achieve a Performance Level (PL). This alternative method includes modeling safety functions as Reliability Block Diagram and evaluation of PFH using the software BlockSim, through Discrete Event Simulation. Modeling hypothesis and limitations are discussed. The proposed method enables calculation of the standard s cases, as well as consideration of different failure distributions, of which Weibull distribution is considered. A study case considering Weibull distributed failures is presented. Applicability of the method is also discussed
Implementation of IEC 61508 in critical systems
No full textA crescente demanda na utilização de componentes eletrônicos em questões de segurança faz com que aumente também a necessidade de se obter garantias sobre quão seguros são os componentes envolvidos. Uma das formas de assegurar a qualidade dos dispositivos utilizados é a verificação de que estes apresentam riscos baixos à segurança, através da obtenção de certificações de segurança. O presente trabalho apresenta um estudo geral da norma internacional IEC 61508, a qual é amplamente empregada na tentativa de obter a comprovação de qualidade dos componentes utilizados em sistemas críticos. São esclarecidos também alguns conceitos inerentes à segurança, visando auxiliar na compreensão de pontos importantes da norma. A parte 61508-3 da norma, a qual apresenta aspectos relacionados diretamente à parte de software, recebe maior enfoque. Nela estão presentes os requisitos de software para dispositivos e sistemas relativos à segurança. Este estudo tem como objetivo principal proporcionar um entendimento sobre a norma e conceitos fundamentais relacionados, além de apresentar críticas sobre a IEC 61508, e também servir como apoio básico na aplicação da norma IEC 61508-3.The growing demand in the use of electronics in safety systems increases also the need to obtain assurances about how safe are the involved components. One way to ensure the quality of the used devices is to verify that they present low safety risks, by obtaining safety certifications. This work presents a general study about international standard IEC 61508, which is widely used in the attempt to obtain quality evidences around components that are used in critical systems. Also, this work intends to clarify some concepts inherent to safety, to assist in understanding some important aspects related to the standard. The part 61508-3 of the standard, which has it main point based on software aspects, receives greater focus. It contains the software requirements for devices and systems related to safety. This study’s main objective is to provide some understanding about IEC 61508 fundamental related concepts, besides presenting criticism of the IEC 61508, and also helps as basic support in implementing the standard IEC 61508-3
SIL rated protection relays meet IEC 61508 safety requirements without lowering process availability
No full textInternational audienceFor systems where safety is critical, it will soon be a requirement that the safety related systems be designed in accordance with the IEC 61508 set of standards. This applies to electrical as well as to electronic equipment - such as protection relays - used in safety related systems, which are subject to the requirements of IEC 61508. The objective of the paper is to demonstrate that the safety requirements defined by IEC 61508 have consequences for the whole engineering process including the design of elementary electronic devices such as protection relays. Applying IEC 61508 to these devices becomes a must for achieving the user's basic requirements - improving the safety and the availability of their industrial complexes. IEC 61508 constitutes is a very powerful tool from organizational and qualitative points of view and systematic failures analysis is an important topic of this standard, and the probabilistic quantification part may be improved
Turvallisuuteen liittyvät dokumentit standardien mukaan - Standardi IEC 61508
No full textTekstissä kerrotaan dokumentointiin liittyvistä vaatimuksista ja ohjeista. Kohteena on pääasiassa koneet ja järjestelmät. Ohjeet ja vaatimukset liittyvät tässä esityksessä konepäätökseen ja siihen liittyviin standardeihin sekä standardiin IEC 61508
Safety Functions in Different Operational Modes and IEC 61508 in the Hydropower Industry
No full textTechnical systems that comprise at least one electrical, electronic, or programmable electronic device and perform safety functions are called safety instrumented systems. Safety instrumented systems are used to reduce the risk related to hazardous events that may result in undesired consequences to humans, the environment, and assets, and the reliability of such systems is therefore important. The international standard IEC 61508 can be used to ensure safe and reliable safety instrumented systems, and it applies to all types of safety instrumented systems. Based on IEC 61508, the process industry and the machinery industry have developed their own versions called IEC 61511 and IEC 62061, respectively. IEC 61508 includes requirements for all activities necessary for achieving reliable safety instrumented systems throughout their whole lifecycle, and the standard introduces concepts and terminology that can be challenging to understand. Some basic concepts and terminology in IEC 61508 are clarified in this master thesis. A safety function, performed by a safety instrumented system, may be demanded from seldom to continuously. IEC 61508 distinguishes between safety functions that are demanded less frequent and more frequent than once per year, and these two modes of operation are called low-demand and high-demand, respectively. Furthermore, the standard requires that different reliability measures are used for demonstrating the reliability of the safety instrumented systems performing low-demand and high-demand safety functions. In two examples, the two reliability measures are used, and the calculated results show that there is an inconsistency with the classification of safety functions in IEC 61508. This inconsistency is, however, not experienced with the classification in IEC 61511, and the approach in IEC 61511 seems better. Other differences between low-demand and high-demand safety functions are not well explained in IEC 61508. Because IEC 61511 considers mainly low-demand safety functions and IEC 62061 considers only high-demand safety functions, specific requirements in these two standards are compared to reveal possible differences between low-demand and high-demand. It is concluded that there are essentially no differences between the compared requirements. Based on the event, loss of control, in an accident scenario, it is proposed a new approach for classifying safety functions. A definition of loss of control is suggested and it distinguishes between safety control functions and safety protection functions. These two functions are further related to two additional events in an accident scenario, and a model that illustrates the proposed classification in relation to the three events in an accident scenario is developed. The proposed classification is neither based on frequency of demands nor does it prescribe use of a specific reliability measure, and the classification is thus different from the classification in IEC 61508. The proposed classification is more similar to the classification in IEC 61511. Safety instrumented systems are used in the hydropower industry, but IEC 61508 is essentially not yet applied. The Machinery Directive requires machine manufacturers to meet the essential health and safety requirements, and some of these requirements can, for safety instrumented systems in machines, be met by complying with IEC 62061. Because IEC 62061 is based on IEC 61508, this is a relationship between IEC 61508 and the hydropower industry. From the perspective of a typical company operating hydropower plants in the Norwegian hydropower industry, some benefits and challenges related to implementation and use of IEC 61508 are discussed. IEC 61508 provides a rigorous, risk-based approach for achieving reliable safety instrumented systems and many of the concepts in the standard could be very useful in the hydropower industry. However, the standard is comprehensive and extensive resources and competence are prerequisites for successful implementation and use. It is concluded that IEC 61508 may not be what the hydropower industry needs, but a joint project for developing a unified approach for ensuring reliable safety instrumented systems may be a better option
Safety Functions in Different Operational Modes and IEC 61508 in the Hydropower Industry
No full textTechnical systems that comprise at least one electrical, electronic, or programmable electronic device and perform safety functions are called safety instrumented systems. Safety instrumented systems are used to reduce the risk related to hazardous events that may result in undesired consequences to humans, the environment, and assets, and the reliability of such systems is therefore important. The international standard IEC 61508 can be used to ensure safe and reliable safety instrumented systems, and it applies to all types of safety instrumented systems. Based on IEC 61508, the process industry and the machinery industry have developed their own versions called IEC 61511 and IEC 62061, respectively. IEC 61508 includes requirements for all activities necessary for achieving reliable safety instrumented systems throughout their whole lifecycle, and the standard introduces concepts and terminology that can be challenging to understand. Some basic concepts and terminology in IEC 61508 are clarified in this master thesis. A safety function, performed by a safety instrumented system, may be demanded from seldom to continuously. IEC 61508 distinguishes between safety functions that are demanded less frequent and more frequent than once per year, and these two modes of operation are called low-demand and high-demand, respectively. Furthermore, the standard requires that different reliability measures are used for demonstrating the reliability of the safety instrumented systems performing low-demand and high-demand safety functions. In two examples, the two reliability measures are used, and the calculated results show that there is an inconsistency with the classification of safety functions in IEC 61508. This inconsistency is, however, not experienced with the classification in IEC 61511, and the approach in IEC 61511 seems better. Other differences between low-demand and high-demand safety functions are not well explained in IEC 61508. Because IEC 61511 considers mainly low-demand safety functions and IEC 62061 considers only high-demand safety functions, specific requirements in these two standards are compared to reveal possible differences between low-demand and high-demand. It is concluded that there are essentially no differences between the compared requirements. Based on the event, loss of control, in an accident scenario, it is proposed a new approach for classifying safety functions. A definition of loss of control is suggested and it distinguishes between safety control functions and safety protection functions. These two functions are further related to two additional events in an accident scenario, and a model that illustrates the proposed classification in relation to the three events in an accident scenario is developed. The proposed classification is neither based on frequency of demands nor does it prescribe use of a specific reliability measure, and the classification is thus different from the classification in IEC 61508. The proposed classification is more similar to the classification in IEC 61511. Safety instrumented systems are used in the hydropower industry, but IEC 61508 is essentially not yet applied. The Machinery Directive requires machine manufacturers to meet the essential health and safety requirements, and some of these requirements can, for safety instrumented systems in machines, be met by complying with IEC 62061. Because IEC 62061 is based on IEC 61508, this is a relationship between IEC 61508 and the hydropower industry. From the perspective of a typical company operating hydropower plants in the Norwegian hydropower industry, some benefits and challenges related to implementation and use of IEC 61508 are discussed. IEC 61508 provides a rigorous, risk-based approach for achieving reliable safety instrumented systems and many of the concepts in the standard could be very useful in the hydropower industry. However, the standard is comprehensive and extensive resources and competence are prerequisites for successful implementation and use. It is concluded that IEC 61508 may not be what the hydropower industry needs, but a joint project for developing a unified approach for ensuring reliable safety instrumented systems may be a better option
Certification of Instrumentation and Control FPGA-based Platform against the Requirements for Functional Safety of Standard IEC 61508
No full textРассмотрены основные положения стандарта МЭК 61508, проанализирован опыт
по реализации процессов жизненного цикла в ходе сертификации информационно-
управляющей платформы RadICS. Соблюдение положений МЭК 61508 является хорошей
практикой, направленной на повышение безопасности ИУС АЭС, которую можно
рекомендовать для внедрения в нормативную практику Украины.Розглянуто основні положення стандарту МЕК 61508, проаналізовано досвід
з реалізації процесів життєвого циклу в ході сертифікації інформаційно-керуючої
платформи RadICS. Дотримання положень МЕК 61508 є хорошою практикою, що
спрямована на підвищення безпеки інформаційних та керуючих систем АЕС і може бути
рекомендована для впровадження в нормативну практику України.The standard IEC 61508 "Functional safety of electrical / electronic / programmable
electronic systems related to safety" is used as the basis of regulatory safety requirements
imposed on the nuclear power plant I&C systems in countries such as Canada, Finland,
Argentina, Korea. In some other countries, the relevant NPP I&C requirements of IEC 61508
have initially high level of confidence in these systems, which significantly reduces the effort for
licensing.
The purpose of this paper is to highlight details of the project for the certification
platform RadICS concerning safe life cycle. Such experience at the moment is unique to Ukraine.
The RadICS platform contains the following components: chassis for modules; input and output
modules for processing and delivery of different types of digital and analog signals; logic
modules to perform control logic; optical communication modules for communication between
the chassis.
The paper describes the main requirements of the standard IEC 61508 as well as the
experience in the implementation of life cycle processes in the certification of instrumentation
and control platform RadICS. Compliance with IEC 61508 is a good practice aimed at
improving the safety of nuclear power plant I&C systems and can be recommended for
implementation in the regulatory practices of Ukraine
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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