Component functional safety Association

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). 

The designer now proceeds with a determination of the PFD targets for the components from each safety function. As before, let (ai),Cj (ai) be the costs associated with the components from safety function SF, to which RRF target a PFD(SFf is imposed. 

It is not necessarily the traditional way to use a system development approach for the development of electronic components. In this context, the digital bus cable is seen as electronic connection and the power supply cables and their plugs etc. as electric connections. Since the discussion, whether something is electric or electronic, does not cause any changes in the requirements or benefit the safety, we generally use the term electronics as umbrella term. This should not be mistaken with the distinction of electric safety and functional safety, since also failures of electronic components can lead to hazards, which are associated with electric safety. This applies especially for power electronics in the voltage range of over... 

The complete and assembled component and its parts should meet suitability criteria appropriate for the drug product and the actual use of the component. Safety and functionality are the most common factors to be established for suitability. The length of time that the associated component and the dosage form are in direct contact should also be taken into consideration when assessing the suitability of an associated component. 

Safety instrumented functions are derived from the safety function, have an associated safety integrity ievei (SiL) and are carried out by a specific safety instrumented system (SiS). For exampie, ciose vaive XY123 within 5 s when pressure in vessei ABC456 reaches 100 bar . Note that components of a safety instrumented system may be used by more than one safety instrumented function. 

The SIS logic solver and its associated I/O modules have been assessed by a third party and found to be compliant to the lEC 61508 series. The scope of the lEC 61508 series certification awarded by the third party is for use as a component in SIL 3 safety instrumented functions. 

Figure 13-3 shows a block diagram of the proposed design for the safety instrumented function of the high line pressure. It consists of two separate and independent shutdown functions in two separate and independent systems (ESDI and ESD2). The components associated with the two systems for this function are ... 

Structures, systems, and components (SSCs) that are important to safety and that are identified as Safety SSCs are based on criteria contained in DOE-STD-3009 (p. xix) and the results of safety analyses, which determine the safety contributions of specific SSCs. The degree of consequence mitigation is the basis for identification of Safety SSCs and associated Safety Functions". These Safety Functions are the essential performance requirements that are imposed on Safety SSC s which maintain the consequences of accident scenarios within bounds that are described in the SAR accident analysis. The use of the term Safety Function will be limited to these essential performance requirements in this SAR. While many SSCs provide a material safety benefit and could be considered to perform a safety function, SSCs that are not relied upon to effect an acceptable outcome will not have an associated Safety Function as the term is used in this S/VR. Safety SSCs and associated Safety Functions are based on the results of hazard evaluation and accident analysis described in Chapter 3, and are specifically identified in Section 3.3.2.3. The specific safety functions important to safety are described in Chapter 4, and form the basis of the derivation of Technical Safety Requirements presented in Chapter 5. 

Generic Safety Issue (GSI) 048 in NUREG-0933 (Reference 1), concerns the availability of the Class IE, 120 VAC instrument buses and their associated inverters. The absence of adequate requirements at some operating facilities jeopardizes the availability of the instrument buses and inverters to perform their intended safety function, i.e., to provide reliable power to safety-related systems and components. 

The third objective of the requirements of this clause is to specify acceptance criteria for components and subsystems in terms of associated safety instrumented functions and safety integrity. 

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