Risk Analysis Methods (Severity)

The Cause-Consequence Diagram is developed from a certain initiating top event, i.e. an event that initiates a specific operational sequence or an event which activates certain safety systems. The Cause-Consequence Diagram consists of two reliability analysis methods previously elaborated, the FTA and ETA methods.

The preliminary hazard analysis (PHA) is a semi-quantitative risk analysis methods that is used to identify potential hazards and the corresponding top events (risks). The PHA sheet identifies as well the required measures and follow-up actions to control the hazard sources. The PHA should consider hazardous components, facilities, safety-related equipment, and environmental constraints.

In a qualitative approach, risks are usually categorized into “high”, “medium” and “low”, and are represented in a risk matrix. This risk matrix represents the possibility and severity in order to integrate the potential accident scenarios that were identified in the threat identification stage. Inside the matrix, the criticality of a risk, through the use of colors, can identified. The results provided by this matrix can be used to compare risks and identify improvement and mitigation measures.

The Failure Mode and Effects Analysis is a cross-industry established method to identify and eliminate potential failures, problems, errors and risks of a system, design or process before adverse consequences reach the internal/external customers. The basic idea of the FMEA is thus the preventive risk identification and error prevention instead of a subsequent correction. 

The Delphi method was developed in order to identify possible targets in the USA during the Cold War. The Delphi method was gradually applied in civilian areas and is now frequently used for political and social questions and issues, for the development of science and technology and in the business environment (e.g. marketing, R&D). The Delphi method is a structured group communication process with the aim of answering questions or finding a consensus on facts about which uncertain and incomplete knowledge naturally exists.