Risk-Based Decision Making for the Management of Change in Process Plants: Benefits of Integrating Probabilistic and Phenomenological Analysis

Management of changes in the work environment is recognized to be a fundamental part of the safety management, in particular for process plants. The approaches for change management usually entail a risk-based decision-making strategy, to verify if the modification of the process, equipment, or procedure can increase the prior level of risk. Usually the risk assessment in process plants is conducted through the quantitative risk assessment traditional techniques, based on consolidated techniques and widely accepted (as hazard and operability analysis, fault trees, etc.). However, they are static, hardly taking into account time-dependent events, and are carried out separately from the consequence analysis. In recent years, some dynamic risk assessment methodologies have been proposed, supported by process simulation. This paper shows an application of the methodology called integrated dynamic decision analysis, highlighting the benefits of integrating the logical-probabilistic modeling and the phenomenological behavior of a system for the risk-based decision making in case of plant modification. The case study refers to a production plant of formaldehyde, where the reactor cooling system, based on melted salts, had to be switched to a water-based system. With the new plant arrangement, the analysis of the risks in terms of extra management costs, showed a reduction in risks of about 83% for dangerous occurrences, against a risk of plant in emergency for low temperatures, affecting the productivity, increased by 16%. But, mostly important, the analysis allowed for the identification of the more critical sequences of events the system could undergo in terms of probabilities, consequences, and risk, returning an integrated model of the revamped system to be used for the process management, the training of operators, and the technological transfer within the organization.