(40g) Constructing a Process Safety Risk Index Empowered By Aspen Plus Simulation

A safety index, or its counterpart, a risk index, is widely used in the applications regarding the inherent safer designs. Starting from the Dow Fire & Explosion Index first introduced in 1960s, many risk indices have been proposed with various system properties as foci. The quantitative nature of indices makes them advantageous in identifying the potential hazards since a net score that is comparable with the alternatives could help determine inherent safer designs. Unlike the conventional qualitative evaluations, such as Hazard and Operability method (HAZOP), risk indices may not require detailed process information that is retrieved from on-site settings. This characteristic makes risk indices suitable tools for risk assessment during the preliminary design of a process or even a complete industrial complex. In the wake of Industry 4.0 where process simulations become even more prevalent, constructing a risk index that are seamlessly integrated into process simulation results will be highly beneficial.

In this work, we attempt to construct a process safety risk index that is formulated based on the process stream parameters provided by Aspen Plus process simulations. The process properties, such as the mass flow rate, temperature, pressure and the stream enthalpy, are combined with the material properties to calculate the initial index values. With the consideration of adding or removing any desried piece of process equipment in safety instrumented systems, credits and penalties are applied to the initial index values and obtain the final results. The results will then be translated into a straightforward graphic presentation in the form similar to the traffic light to reflect the degree of potential hazard that exists in the design of the process. It is anticipated that potential application of such indices include (i) preliminary process design in the industry and (ii) routine practices of process simulations in the Chemical Engineering design classroom.