Inherent safety prototype index

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. ... 

Edwards and Lawrence (1993) have developed a Prototype Index of Inherent Safety (PIIS) for process design. The inherent safety index is intended for analysing the choice of process route i.e. the raw materials used and the sequence of the reaction steps. This method is very reaction oriented and does not consider properly the other parts of the process even they usually represent the majority of equipment. 

Prototype Index of Inherent Safety (PUS) Chemical score inventory, flammability, explosiveness and toxicity Process score temperature, pressure and yield Total score sum of the chemical and process scores... 

Prototype Index of Inherent Safety (Edwards and Lawrence, 1993) ... 

Some initial work on the development of an overall inherent safety index has been done at Loughborough University in the United Kingdom (26). Other, similar work has been done at VTT in Finland (27). Both indices are considered prototypes by the developers, and more work is needed. These proposed inherent safety indices evaluate a number of factors related to inherent safety, including ... 

Several risk indices have been practiced by the chemical and manufacturing industries over the past 50 years (see Table 8.5) (Heikkila, 1999). The important ones among these indices are the Dow Fire and Explosion Index, the Dow Chemical Exposure Index, the HAZAN (Hazard Analysis), and the Prototype Index of Inherent Safety. 

Several methods are available for identifying and assessing hazards (Kletz, 1990). Hazards can be identified through checklists, failure mode effect analysis (FMEA), fault tree analysis, event tree analysis, what-if analysis, and hazard and operability studies (HAZOP). Assessing hazards can be done through hazard analysis (HAZAN), codes of practice, the Dow Explosion Index, and prototype index of inherent safety (PIIS). 

The prototype index of inherent safety (PUS) (developed by Edwards and Lawrence, 1993) is a numerical score based on the nature of chemicals used and the type of process. The PUS was developed to compare processes based on raw materials and the sequence of reaction steps only. This method does not consider the other parts of the process. PUS is calculated as a total score and consists of two parts the chemical score and the process score. The first one is made up of inventory, flammability, explosiveness, and toxicity. The second one is made up of temperature, pressure, and yield. 

---