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Explosion Exclusion Distances and Escalation Assessment

Explosion Assessment in Unconfined Congested and Confined Regions

Probabilistic Explosion Assessment

BC uses powerful and modern tools for addressing any external and/or internal explosion assessment within complex geometries.

BC capability of explosion modeling accounts for both steady-state and transient simulations both for quantifying primary and secondary events due to accident propagation. Gas, dust, and/or hybrid explosions occurring in Congested but Unconfined geometries, and occurring in Confined Regions are addressed.

Accurate Explosion Exclusion Distances provide precise information to decision-makers when addressing key topics such as human vulnerability, structural damage, implementation of prevention/mitigation measures, and emergency preparedness.

The identification of mechanisms of Escalation triggered by explosions, modeling the behavior of structures exposed, and prevention of accident propagation are studies performed by BC.

The time between the start of the release and the time it ignites is important in Probabilistic assessments:

(1) Time until ignition influences the probability that workers can relocate to a safer area prior ignition;

(2) Size of gas cloud or liquid pool when it ignites influences the consequences.

Depending on the main purpose of the explosion assessment, BC models explosions using different technologies:

  • When the purpose of the explosion assessment allows simplifying the definition of the presence of complex geometries, BC uses simple-correlated methods or one dimensional phenomenological models with the aim to perform screening runs that can be done easily or before detailed design has been completed. The computer time is extremely short, so it is easy to perform many “what if…” runs, testing the effect of design modifications; i.e., sensitivity runs.

  • When detailed explosion modeling results are pursued with the aim to investigate the explosion interaction with complex geometries, BC uses a Computational Fluid Dynamics (CFD)-based tool capable to provide fast and detailed results.

Runaway Reactions - Thermal Risk Assessment / Kinetics Modeling

BC uses powerful and modern tools for Emergency Relief Systems (ERS) design of reactive systems, other applicable Layers Of Protection (LOP), and potential associated consequences.

Not all reactive systems present the same thermal risk level, and accordingly, not all of them require the same level of detail for ERS design. Accordingly, BC approach is based on the following two studies:

1. Initial conservative Thermal Risk Assessment, which is a screening tool intended to optimize the efforts to be performed for ERS design. The results of the screening tool are based on criteria developed in references [1], [2], and [3].

Two variables of the desired and potential secondary reactions are evaluated:

 

(1) Adiabatic Temperature Rise.

(2) Time to Maximum Rate under adiabatic conditions.

The knowledge on these variables allows defining several criticality classes based on temperature levels which contain the thermodynamic and kinetics information required to define a runaway reaction.

Based on these criticality classes, the screening tool is able to technically reveal if more detailed analyses are justified for ERS design.

2. Detailed Kinetics modeling of reactive systems by ensuring the vapor-liquid equilibrium, and kinetic expression of the system under analysis. The input data used for modeling is based on chemical reactivity testing; e.g., Accelerating Rate Calorimeter - ARC, and the kinetic model is validated against it.

The kinetic model development requires to match four graphical results from the calorimetry testing:

 

(1) Temperature history.

(2) Pressure history.

(3) Variation of temperature over the time as a function of temperature.

(4) Pressure versus temperature.

The kinetic modeling is then used for sizing ERS by ensuring criteria from DIERS (Design Institute of ERS); i.e., two-phase flow transient simulations.

 

Additionally, BC ensures capabilities for advanced modeling of confined explosions with reaction.

[1] Gygax , R. “Thermal Process Safety, Data Assessment, Criteria, Measures”, Vol 8 (eds ESCIS), ESCIS , Lucerne, 1993.

[2] Stoessel, F. “Thermal Safety of Chemical Process, Risk Assessment and Process Design”. Wiley-VCN. ISBN: 978-3-527-31712-7, 2008.

[3] Grewer, T. “Thermal Hazards of Chemical Reactions”; Elsevier B.V., 1994.

 

Accurate Calculations, Robust Results, and Elegant Cost-Effective Solutions