3. Conclusion

The LOPA method is well-suited to the implementation of multiple safety barriers. It can be used to describe the chronological sequence of a scenario, and to identify all the technical, human and organizational barriers needed to reduce its criticality. The method is based on the simple principle of defining a scenario by a single initiating event-consequence pair.

Since the emergence of the IEC 61511 standard, this method has become increasingly popular for assessing the SIL required for RIS. On the other hand, this method can be used in a broader sense, i.e. as a semi-quantified risk analysis method. The apparent simplicity of the method, largely based on the use of tabulated values (frequencies of initiating events, barrier failure probabilities, etc.), may be at the root of the method's inconsistency. Indeed, like all risk analysis methods that require the use...