Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 62 studies the combination of various methods of designing for reliability, availability, maintainability and safety, as well as the latest techniques in probability and possibility modelling, mathematical algorithmic modelling, evolutionary algorithmic modelling, symbolic logic modelling, artificial intelligence modelling, and object-oriented computer modelling, in a logically structured approach to determining the integrity of engineering design. . | 594 5 Safety and Risk in Engineering Design where RC risk cost Co initial cost constant set to zero for cost comparisons Ci cost constant multiplied with the CER variable of mass C2 cost constant multiplied with the CER variable of material Cs cost variable for ensuring required reliability and safety. The cost of ensuring the required reliability and safety relative to the selected attributes can be formulated as Cs CfR where Cf cost of failure relative to the selected attributes R risk of a failure incident occurring. The risk of a failure incident occurring can be formulated as R p c where p the probability of the event occurring c the consequence of the risk on the estimate. Process Operational Risk Modelling Complex process systems especially complex integrations of systems increasingly have to cope with risk in their operating environment. As a result it is necessary and useful to develop a safety hypothesis expressed as a risk equation which relates system throughput capacity to risk. Such a risk equation has its roots in financial risk management and has been expanded to measure the mean expected loss risk which is more suitable for process systems in general. Such a measure not only quantifies risk but also clarifies system safety principles during conceptual design. Early identification of specific risk costs and safety benefits of different design alternatives enables avoidance or mitigation of hazards that could result in operational losses. a Overview of the Risk Hypothesis and Risk Equation From Eqs. and in Sect. a process system is considered to be a functional unit that converts inputs to outputs and which may be composed of sub-systems connected either in series or in parallel enabling the system to convert a set of process inputs Ip to a set of process outputs Op per unit time so that Op is equivalent to the system throughput Tp where the yield is 100 . Theoretical Overview of Safety and Risk in Engineering
