A risk-based methodology to identify fire protection zones

Fire is among the most dangerous accident scenarios that may affect the process and chemical industry. Beside the immediate and direct harms to operators and population, fire may also cause damages to plant structures, that may in turn trigger severe secondary scenarios (domino effect) affecting a greater number of people and/or causing relevant asset damages. As a matter of fact, fire may cause the collapse of structural elements due to the loss of mechanical properties at high temperatures. Fireproofing is usually applied to improve the capacity of support structures to maintain their structural integrity during a fire, and to prevent or at least to delay the collapse of structural elements. However, due to cost issues, fireproofing should be ap-plied only to elements present in areas where an actual risk of severe fire scenarios exist. The available inter-national standards for the application of fireproofing in onshore chemical and process plants do not provide appropriate criteria to identify the areas where the structural elements must be protected. In particular, avail-able methodologies do not consider the effect of jet-fires and are based on a deterministic approach. Account-ing for the effect of both pool fire and jet fire, the present contribution suggests a new risk-based methodol-ogy for the identification of fire protection zones where fireproofing coatings should be applied. The developed methodology is oriented to early design application, allowing the identification of fireproofing zones in the initial phases of lay-out definition. Thus, it is built up on simplified criteria based on radiant heat intensity to identify the extension of fire protection zones. The key point of the methodology is the choice of the fire scenarios to use in the consequence evaluation. These are selected applying a semi-quantitative risk analysis. The characteristics of the initial events are used to evaluate the characteristics of the final outcome scenarios. A risk matrix approach is used to assess the fire risk level of each zone. In order to demonstrate the features and the potentials of the proposed methodology, a case-study was carried out, based on the actual layout of an Oil&Gas facility. The results show that the proposed methodology provides a robust identifica-tion of fire protection zones, giving useful and timely indications for the application of fire protections to structural plant elements.