Inherently Safer Design – Not Only about Reducing Consequences!

Process risk is a function of both the likelihood of occurance of an incident, and of the consequences of the incident. There is a common perception that inherently safer design focuses solely on reducing or eliminating the consequences. However, inherently safer design can also focus on the frequency part of the risk equation. An inherently safer design can make an incident inherently less likely to occur, although the consequences of the incident should it occur would be unchanged. In event tree or Layer of Protection (LOPA) terms, this may be thought of as a design modification which reduces the frequency of the initiating event, rather than improving the reliability or increasing the number of layers of protection. Several examples of inherently safer designs which reduce the likelihood of an incident will be discussed.