Component functional safety

Component Functional Safety (Safety Instrumented System Components)... 

In this step, all functions of the safety requirements specification are allocated to system components, functions or software. Safety integrity requirements will determine the appropriate... 

Column 6 describes how this component failure mode affects the component function of the module (or sub-system). Column 7 lists how this component failure mode affects the next system sub level. In safety evaluations this column is used to indicate safe versus dangerous failures. Depending on the scope of the FMEA, it is possible to consider aU levels of the system (component, module, unit or system). Frequently a FMEA at the component level describes the effect at the module level and perhaps the effect at the unit level. Unless the FMEA is being done for a specific system architecture, another FMEA is done for higher levels. 

If all components functioned with perfection and, in addition, the measures of safety management were perfect plants would be absolutely safe. 

A single failure of a passive component (assuming active components function properly), results in a loss of the capability of the system to perform its safety functions. 

The Zone 1 and Zone 2A ventilation exhaust ducting and HEPA and charcoal filters are passive components. Their safety-related function is performed continuously while the HCF ventilation system is in operation. When the ventilation system is not operating, no isotope processing operations are being conducted, and any residual radioactive materials are in nonvolatile states and are confined within the SCBs and Zone 2A canyon. Thus, the functional requirements applicable to the filters are ... 

When developing new safety related systems, especially in automotive industry, there is the need to verify that the safety of the new system is not worse than the safety of the old system. So, even if the reliability is worse, what has to be expected when new functions are implemented with new components, the safety can be equal or even better. Furthermore, it is possible, to charge the worse reliability against improved safety due to additional functions. But how can systems with nearly the same functions but very different structures, like for example a conventional braking system and a brake-by-wire-sy stem, be compared against each other ... 

The above are all effective methods of eliminating or reducing the hazard effects of a random component failure and lEC 61508/62061 makes reference to using these methods when designing functional safety systems. 

Routine actions which need to be carried out to maintain the functional safety of the SRECS, including routine replacement of components with a pre-defined life. 

This paper will focus on the implication of choosing a certain functional safety standard when designing a complete safety function and thus only those parts of [ISO 13849-1] that are applicable at system level will be considered. The same can not be said for [lEC 62061 ] because this standard only focuses on system level (except for requirements related to electromechanical components). [lEC 62061] requires that the PE-based subsystems shall be developed according to [lEC 61508]. 

A system important to safety, i.e., provided to ensure the safe shutdown of the equipment or otherwise control an operation or to limit the consequences of anticipated operational occurrences and design basis incidents. Safety systems consist of the protection system, the safety actuation systems, and the safety system support features. Components of safety systems may be provided solely to perform safety functions, or may perform safety functions in some plant operational states and non-safety functions in other operational states. Safety system support features are considered the collection of equipment that provides services such as cooling, lubrication, and energy supply required by the protection system and the safety actuation systems. 

Abstract. Component-based architectures are widely used in embedded systems. For managing complexity and improving quality separation of concerns is one of the most important principles. For one component, separation of concerns is realized by defining the overall component functionality by separated protocol behaviors. One of the main challenges of applying separation of concerns is the later automatic composition of the separated, maybe interdependent concerns which is not supported by current component-based approaches. Moreover, the complexity of real-time distributed embedded systems requires to consider safety requirements for the composition of the separated concerns. We present an approach which addresses these problems by a well-defined automatic composition of protocol behaviors with respect to interdependent concerns. The composition is performed by taking a proper refinement relation into accoimt so that the analysis results of the separated concerns are preserved which is essential for safety critical systems. 

Treatment of all shared interfaces and components as safety, unless hardware and software configuration provides functional separation... 

According to ISA, the ability of SIS or other means of risk reduction to carry out the actions necessary to achieve or to maintain a safe state for the process and its associated equipment." Also, functional safety in SIS highly depends on proper functioning of sensors, logic solver, and FCE so that reduced risk level could be achieved. In that sense, it also means proper functioning of these components also (see Clause 8.1 also, for definition as per various standards). 

There is possibility of confusion regarding use of two standards viz ISO 13489. lEC 62061. Normally when medium other than electrical system, ISO 13489 may be more appropriate. Whereas for customer demand for demonstrating safety lEC 62061 may appropriate. Fot safety-related control systems, standard components can be used as it is allowed as pet standard also. However, safety components offer the advantage of reducing workload as the safety-oriented assessment, and analysis of the components used, is carried out by the producer of the safety components. For functional safety, the systematic integrity of components is taken into account, in addition to the use of a suitable category, the implementation of necessary fault detection and the... 

Systematic capability Each element or component carrying safety function and methodology. 

SIL Certification for dfiinctional safety systems regarding lEC 61508 Certifying SIL component safety Bureau Veritas http //www.bureauveritas.com/services+sheet/sil+certification+ for+functional+safety+systems. 

The safety and health function impacts virtually every function within a company or organization, and the safety and health professional does not work solely within a safety and health cocoon. There are safety and health components involved in virtually every aspect of every issue that arises within the operations. Each and every law or regulation has a direct or indirect impact on the safety and health function. Safety and health impact production, quality, environment, human resources, engineering, and virtually every department or function in any operation. The primary reason for this integration by the safety and health function is the interaction with the personnel within and outside of the operations. 

The electrical systems shall be designed to allow the structures, systems and components with safety functions of especially high importance to be fed by either off-site power or emergency on-site power when they need electric power to fulfill their safety functions. (Guide 48.1). 

Structure, systems and components with safety functions shall be so designed that the safety of the nuclear reactor facilities will not be impaired by postulated extenal man-induced events. (Guide 3.1) External postulated man-induced events are said to refer to airplane crashes, collapse of dams, explosions, etc. In Japan, nuclear power plants are not located in the vicinity of dams nor in areas where... 

Safety standards set requirements to achieve the functional safety, while leaving the space for the developers on details on how they should implement those requirements. The same holds for the change management, i.e., the lEC 61508 does not specify which system attributes have to be considered when analysing the impact of changes. More concrete guidelines about this can be found in the avionics domain, concretely in the concept Reusable Software Component (RSC) from the Federal Aviation Administration (FAA) that was developed for the standard... 

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