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Project Profile

Detailed Fire Modeling of Jet and Pool Fires

Learn how our Extreme Loads and Structural Risk engineering team uses advanced analysis techniques to model fires and better quantify hazards to personnel.

Project Objectives

Health System Medical Center – Covid 19 Preparedness

Project Overview

Facility Siting addresses explosion, fire, and toxic hazards to occupied buildings. This project profile describes how our Extreme Loads and Structural Risk engineering division addresses prediction of pool and jet fire consequences. 

Evaluating fire, toxic and explosion hazard consequences is required by regulatory agencies to demonstrate worker protection and public exposure.

Detailed Fire Modeling provides the most realistic simulation of jet and pool fire hazards. Applying CFD modeling for fire scenarios also provides better consequence prediction than traditional approaches used in support of Facility Siting studies and has helped many of our clients eliminate expensive remediation options.

ABS Group uses Detailed Fire Modeling to assist with incident investigations and in thermal-structural Finite Element Analysis (FEA) to understand the effects from an extreme loading environment on the behavior of buildings/structures of interest.

Client Needs
  • Assess and predict thermal hazards at facility sites using advanced modeling techniques for better prediction of fire consequences
  • Understand unique risk and practical measures for risk reduction and regulatory compliance
  • Safeguard personnel by maintaining the integrity of critical assets and promoting process safety management through facility siting

 

Detailed Fire Modeling 

The simplest approach to Facility Siting of fire is to use the fire spacing table approach discussed in API RP-752, the Recommend Practice for the Management of Hazards Associated With Location of Process Plant Permanent Buildings. The spacing table approach uses established tables to determine minimum separation distances between equipment and buildings intended for occupancy. This approach does not address specific scenarios and is independent of the quantity released, process conditions (e.g., pressure, temperature, flow rate) and geometry near the release location.

The next level of analysis, and most commonly used, is to apply phenomenological modeling software to address specific scenarios. This approach can address process conditions for the release and provide a relatively quick result showing flame profile and thermal radiation contours. Typically, these models provide a conservative "free-field" flame and radiation profiles that do not address site geometry that can offer flame impingement or shielding.

ABS Group takes fire modeling to a higher level, performing Detailed Fire Modeling. We have the software and expertise to perform Detailed Fire Modeling that can incorporate shielding behind large structures (e.g., tanks, buildings) and flame interaction with objects (e.g., process equipment, berms) between the source and building of interest. This provides the most accurate prediction of fire consequences, allowing for a better assessment of thermal hazards during evacuation.

Our Approach

ABS Group performs Detailed Fire Modeling in two (2) stages.

  • Stage 1 uses approximate representations of pool and jet fire flames in a 3D Computational Fluid Dynamic (CFD) setting to address line-of-site radiation shielding from the source. Pool fires are approximated as wind-tilted cylinders and jet fires are approximated as cones. Worst-case flame directions are assumed for each case (i.e., pointed toward an occupied building), and thermal radiation contours are generated showing heat shielded areas behind large objects (e.g., buildings, large vessels). A dose-based evacuation analysis is performed as described below.
  • Stage 2 uses high-fidelity CFD modeling to predict flame profiles in 3D geometry, flame interaction with objects (e.g., impingement) and radiation shielding. ABS Group utilizes the Fire Dynamic Simulator (FDS) and Kameleon FireEx (KFX), which focus on fire simulations in 3D environments.

Thermal radiation contours from either Stage 1 or 2 are imported using in-house 3D software to perform a dose-based vulnerability analysis and predict hazards along evacuation routes considering the advantages provided by radiation shielding. Thermal dose is calculated based on 1) radiation contour patterns predicted with Detailed Fire Modeling and 2) the evacuation pathway. Exposure time is determined using a variable evacuation speed accounting for obstacles (e.g., fences) along the route. The thermal dose is calculated as the integration of radiant heat exposure over time and is related to vulnerability during the evacuation.

Stage 1: Cone Shaped Jet Fire with Evacuation Around an Obstacle

Stage 1: Cone Shaped Jet Fire with Evacuation Path (Fails)

Stage 2: CFD Jet Fire with Evacuation Path (Passes)

Stage 2: CFD Jet Fire with Shielding from Large Obstacles

 


Our Value: 

ABS Group's Extreme Loads and Structural Risk engineers help clients clearly understand facility siting risks and quantify consequences. Our knowledge and experience with a range of hazard analysis tools, including Detailed Fire Modeling, allows us to select and apply the most appropriate techniques for each situation. Our Facility Siting services cover a wide range of explosion, fire and toxic release hazards that pose a threat to refining, petrochemical and specialty chemical process installations.

Our engineering and risk consulting teams work diligently with clients to develop and implement the practical measures needed for risk reduction and regulatory compliance.

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