Risk-Based Approach – Facility Siting Addressing Fires Impacting Process Plant Permanent and Portable Buildings

This manuscript describes a risk-based approach with the aim to identify which occupied buildings in a process facility could be impacted by thermal radiation due to fires. This approach complies with API Recommended Practice 752 and 753 criteria and it consists of the following two steps: (1) risk-based quantitative assessment and (2) exceedance curve development. Additionally, a sensitivity analysis for risk reduction measures is evaluated.

A case study is developed for illustrative purposes and the results confirm the following approach capabilities and characteristics:

• A risk-based approach is considered the foundation for developing exceedance curves,
• Exceedance curves are a good engineering tool for identifying which occupied buildings comply or do not comply with given tolerability risk criteria; and
• Sensitivity analysis of outcomes associated with high risk levels impacting affected buildings is an effective and inexpensive approach for defining and comparing suitable and cost-effective risk reductions measures during the decision-making process.

As part of the sensitivity analysis, it is important to mention that good engineering tools should be provided for decision-making when a building is included in the mitigation plan. Process Safety Office^® SuperChems™ has the capability to provide detailed results and information after HFEC construction. These results allow the user to identify which are the most suitable and cost-effective risk measures to be implemented for risk reduction.

Introduction

The approach described in this manuscript focuses on the impact Loss of Containment scenarios (LOCs) of flammable materials that could lead to fires to portable and permanent buildings. Fire outcomes are based on the source term models which consider released material properties and behavior, conditions of the release and various phenomena that accompany the release of hazardous materials under such conditions (e.g., expansion, choked flow, two-phase flow, aerosolization, rainout, etc.). These models are important because they provide input data to the fire models and the accuracy from the fire models is dependent upon the accuracy in the source term computation. Despite the large number of possible fire events, few categories of industrial fires are relevant for facility siting leading to occupant fatalities located inside a building; i.e., jet fires, pool and tank fires, fireballs and flash fires.