Safety requirement specification outcome

The outcome of the hazard and risk assessment and allocation process should be a clear description of the functions to be carried out by the safety systems, including potential safety instrumented systems together with safety integrity level requirements (along with mode of operation, continuous or demand) for any safety instrumented function. This forms the basis for the SIS safety requirements specification. The description of the functions should be clear as to what needs to be done to ensure that safety is maintained. 

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. 

In order to determine the required SIL level, a detailed hazard analysis is performed for the equipment under control (EUC). From the hazard analysis, all safety functions are identified (example—Detect failure of braking). A target safety integrity level is assigned to each of the safety functions (example—detect failure of braking—SIL 3) in order to ensure the residual risk is lower than the acceptable risk (in other words, the risk is sufficiently reduced). The outcome will be an EUC safety function specification detailing the function and target SIL level (between 1 to %) required for each safety function identified in the hazard analysis. 

Therefore, when using the severity and probability techniques simultaneously, hazards can be examined, qualified, addressed, and resolved based upon the hazardous severity of a potential outcome and the likelihood that such an outcome will occur. For example, while an aircraft collision in midair would unarguably be classified as a Category I mishap (catastrophic), the hazard probability would fall into the Level D (remote) classification based upon statistical history of midair collision occurrence. The system safety effort in this case would require specific, but relatively minimal... 

Anomalous behavior is deviation from a general rule or regime it is inconsistent behavior deviating from what is usual, normal, or expected. In systems applications, anomalous behavior is behavior of an item that is not in accordance with the documented requirements or specifications for the item. It is unexpected behavior, and it is generally undesired behavior. System safety is concerned with anomalous behavior because it can typically be the cause of a mishap, or be part of a sequence of events leading to a mishap. Safety HA typically looks for anomalous behavior that is safety-essential or safety-critical in outcome. When performing an HA, potential anomalous behavior should be considered in hardware actions, hardware functions, software functions, and human tasks. For example, inadvertent rudder movement on an aircraft, without a valid command to move, is considered anomalous behavior with safety significance. 

If the pattern does not fit into an immediately identifiable pattern, the process worker may then consciously apply more explicit "if-then" rules to link the various symptoms with likely causes. Three alternative outcomes are possible from this process. If the diagnosis and the required actions are very closely linked (because this situation arises frequently) then a branch to the Execute Actions box will occur. If the required action is less obvious, then the branch to the Select/Formulate Actions box will be likely, where specific action rules of the form "if situation is X then do Y" will be applied. A third possibility is that the operating team are unable or imwilling to respond immediately to the situation because they are uncertain about its implications for safety and/or production. They will then move to the Implications of plant state box. 

Job description and person specification documents that contain safety information can clearly provide the foimdation for the development of a recruitment and selection program which has at least the possibility of a successful outcome. Further, Thompson and Thompson (1982) provide an excellent review of the steps required to help ensure that courts accept job analysis information as the foundation of selection predictor development and or selection decisions. Furthermore, a job description that includes a section on safety can be used in the expectation setting processes as discussed in Chap. 3, Sect. 3.7.2. In contrast, if there has been no systematic attempt to understand what the requirements are to perform a job in a safe manner, it is unlikely that the recruitment and selection system will be delivering the safety benefits that it potentially could. Furthermore, it is likely that employees trust in these processes to deliver a safe new employee may be somewhat misplaced. 

Method validation is a way of ensuring that the analytical method used in a specific test procedure is suitable for that task or fit for purpose. It is required in a variety of different laboratory environments where there is a public interest in the outcome of the analyses (e.g., pharmaceutical laboratories, cosmetics laboratories, forensic laboratories, food safety laboratories). According to Peters, Drummer, and Musshoff (2007), validation is particularly important in a forensic environment—not only to ensure that data are reliable but also to ensure that there are no unjustifiable legal consequences for the defendant in court. Method validation within the forensic arena is usually applied to two types of analytical procedures ... 

The assessment and analysis of the inherent safety performance in the hydrogen system requires sound and appropriate metrics. Several valuable proposals for inherent safety metrics (Cozzani et al. 2007, Tugnoli et al. 2007) as well as the main issues needed for such assessment are well summarized in the literature (Roller ef a/. 2001, Khan eta/. 2003). Recently, a novel consequence-based approach for inherent safety key performance indicators (KPI) assessment was proposed (Tugnoli et al. 2007). The approach bases the calculation of safety indicators on the evaluation of the expected outcomes of the hazard present in the system, by runs of specific physical consequence models. The KPI method was preferred in the current assessment framework, since, unlike other approaches, it allows easily fitting the peculiarities of the analysed systems and does not require subjective judgment. Furthermore, the KPI method was newly reviewed to describe some particular features of the hydrogen chain. In particular the assessment of transport units was added and new index aggregation rules were defined. 

Of conrse, this approach is based on the assumption that safety culture correlates with safety outcomes. Therefore, it is of critical importance to confirm the cnltnre-ontcome link, which is one of the requirements for a safety culture scale, understood as criterion validity - a more comprehensive summary of the required properties can be found in other literature (e.g. Itoh et al. 2012). For this applied purpose of safety culture, this chapter specifically looks at dimensions of safety culture, how to measure safety outcomes, and the safety culture-outcome link through an examination of case studies, primarily drawn from Japanese hospitals. Before stating these issues in detail, we will, in the rest of this section, briefly argue notions of safety culture (and safety climate). 

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