Inherent Safety Intervention Framework

Despite being an attractive proposition in terms of safety and cost performance, the
actual implementation of Inherent Safety in design is not widely observed in the
industries. This has been documented in publications which indicated the lack of an
effective Inherent Safety Quantification methodology and the lack of integration
between process design stages with risk and consequence estimation are hurdles to
designing inherently safer process plants.
Initial attempts by other researches to quantify level of inherent safety resulted in the
invention of few indices which are based on reactions involved and have been able to
differentiate the level of inherent safety for various routes producing the same
product. These indices account for temperature, pressure and presences of the
chemicals in the reactions individually. These indices are not able to reflect the
interaction of these process parameters and the actual composition of the process
streams and their impact on level of inherent safety.
This research developed a methodology which is able to differentiate level of inherent
safety for various process routes and subsequently of the various process streams
within a process route. The new indices known as Process Route Index (PRI) and
Process Stream Index (PSI) are based on interactions of various process parameters
and actual composition of process streams. These indices are part of the Inherent
Safety Intervention Framework (ISIF) which is proposed and proven in this research
to allow for proactive identification of consequences of a hazard and subsequently
allow modifications based on Inherent Safety principles. Owing to its integration with
process simulator, the ISIF can quickly reflect the changes of inherent safety levels
when process modifications are simulated iteratively.
In order to represent risk in a format familiar to many, this research proposed the
concept of Inherent Risk Assessment (IRA) which is similar to Quantitative Risk
Assessment (QRA) which is widely used. Similar to QRA, the IRA represent risk by
means of a FN Curve. IRA reflects the inherent risk within the process being designed
without yet considering mechanism and procedures to reduce risk to an ALARP level
as the design stages progresses along. It is proposed that the IRA be used to determine initial acceptance, by government agencies, of a process being designed based on
predetennined set of assumptions.
The case studies presented towards the end of this research clearly demonstrated the
effectiveness of the ISIF to quantify level of inherent safety at process route selection
level using PRJ and using the PSI to prioritize streams for modification purposes.
Based on the PRJ, an inherently safer route can be chosen and modification based on
the principles of inherent safety can be implemented at the streams scoring higher PSI
numbers. The IRA complements the work by representing the level of risk inherent to
the process being considered in comparison to the limits set by local authorities.