Metrics inherent safety

The approach to developing metrics for process safety is analogous to those that might be used to assess Occupational Exposure risk. One can cite as well several indices that have been developed as metrics for estimating and ranking the safety of a given process or chemical reaction, such as the DOW fire and explosion index,the Stoessel index ° for hazard assessment and classification of chemical reactions, the Inherent Safety Index, the Prototype Index for Inherent Safety, amongst others. ... 

Metrics will become increasingly important as the discipline of process safety continues to evolve and improve. They hold promise to contribute to risk-based process safety, inherent safety, safety culture, and compliance with regulation as well as broader societal interests surrounding sustainability, globalization, and societal risk aversion. 

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. 

From Fig. 11.11 it is possible to verify the improvement in terms of carbon emission from the base case design to the retrofit design proposed (black bars lower than gray bars). Flowever, this retrofit design involved the recovery of water, so metrics related to water impact should be also assessed. The IChemE metrics have been selected to assess the water impact of the new retrofit design [63]. For the social assessment the health and safety issues were considered, through the appHcation of the Inherent Safety Index defined by Fleikldla [60]. The results obtained for the environmental and social assessments are summarized in Table 11.4. 

The mass- and energy-based indicators help to identify process alternatives for which sustainability metrics, environmental impact factors, as well as inherent safety indices can be estimated. The goal here is to optimize the process so that there is improvement in all these metrics with respect to the base case design. The application of the methodology requires a combination of tools ranging from databases to process simulation software (such as Aspen , Hypro , Sim Sci , etc.), to computational routines for various types of indicators and process synthesis/design tools. 

Evaluate the generated alternatives in terms of improvements with respect to resources (mass energy), sustainability metrices, environmental impact factors and inherent safety factors. 

System safety is a specialized engineering discipline for developing safe systems, products, processes, procedures, and operations. Safety itself is a somewhat invisible system quality that is inherent to a system or product. Safety is characterized by a metric called mishap risk, which indicates the danger level (susceptibility to harm) presented by a system hazard. A system is considered... 

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