This informal CPD article ‘The Significance of Consequence Modelling in Fire and Explosion Risk Assessment’, was provided by Synergen Oil and Gas UK, an independent engineering consultancy specialising in Process Safety, Technical Risk Management and Operational Safety services.
Fire and explosion risks give serious threats to industrial facilities, necessitating comprehensive risk assessments. Consequence modelling plays a pivotal role in Fire and Explosion Risk Assessment (FERA), offering insights into potential hazards and aiding in the development of effective preventive measures.
Consequence Modelling - Concepts and Methods
1. Hazard Identification
The process begins with identifying potential hazards within the facility, examining operations and materials involved. Thorough hazard identification sets the foundation for accurate consequence modelling.
2. Event Tree Analysis
Developing event trees helps visualize the cause-effect relationships of accidents, estimating probabilities of different outcomes. Event trees are essential for assessing potential risks and consequences, considering that not all consequences occur simultaneously.
3. Release Quantification
Quantifying the material released during a loss of containment event, including release rate and duration, is crucial information. This data influences dispersion and fire/explosion modelling, providing insights into potential consequences.
4. Dispersion Modelling
Dispersion models predict the movement of released materials in the environment, considering factors like wind speed and atmospheric conditions. This information aids in estimating the severity of dispersion-sensitive consequences such as flash fires and explosions.
5. Fire and Explosion Modelling
Utilizing empirical models like FDS, FLACS, and PHAST, fire and explosion models predict fire sizes, distance to heat flux levels, and explosion overpressure levels. These models, validated by experimental values, offer valuable insights into the potential consequences of different events.
Commonly Used Modelling Techniques
1. FDS (Fire Dynamics Simulator)
A Computational Fluid Dynamics (CFD) tool, FDS simulates fire behaviour, predicting factors like flame height, temperature, and smoke production. Widely used, it contributes to understanding and mitigating fire risks.
2. FLACS (FLame ACceleration Simulator)
Specializing in predicting gas explosions and dispersion-related phenomena, FLACS is a CFD modelling tool crucial for simulating the propagation of fire and explosions in complex environments.
3. PHAST (Process Hazard Analysis Software Tool)
Globally adopted, PHAST integrates empirical and CFD methods to model discharge, dispersion, fires, explosions, and toxic effects. It plays a key role in comprehensive risk assessments.
Consequence Modelling in Risk Assessment
Consequence modelling is integral to FERA, enabling the prediction of potential equipment failures, injuries, and fatalities based on survivability criteria. It provides a visual representation of potential outcomes, facilitating communication of hazards to stakeholders. The transparency it offers promotes collaboration and understanding among stakeholders.
FERA combines consequence modelling with frequency analysis, forming a subset of Quantitative Risk Assessment (QRA). This holistic approach considers various accident scenarios, including toxic gas releases and occupational accidents, providing a final fatality risk number for comparison with acceptable risk criteria.
Benefits of Consequence Modelling in Risk Assessment
1. Scenario Development
Consequence modelling accommodates the development of numerous credible scenarios, offering flexibility in detailing potential risks. It allows for sensitivity cases, comparing consequences from different design options.
2. Scenario Evaluation
Through event trees, consequence modelling predicts variations in results with and without effective safety systems. It assesses different outcomes, such as fire sizes and durations, with and without isolation, blowdown, or fire and gas detection.
3. Assessment of Sensitive Receivers
Consequence modelling results serve as inputs for studies like Escape Evacuation and Rescue Analysis (EERA) and Emergency Systems Survivability Analysis (ESSA). It assesses the survivability of critical safety equipment and systems.
4. Continuous Improvement
Modelling software refinement occurs through continuous comparisons of predicted consequences against actual experimental results. This ongoing improvement ensures the accuracy and reliability of consequence modelling.
Limitations of Incorporating Consequence Modelling
1. Uncertainties
Consequence modelling involves assumptions and simplifications introducing uncertainties that may impact prediction accuracy and the overall risk assessment process.
2. Data Availability
Reliable data is essential for accurate consequence modelling. Obtaining relevant data, particularly for complex scenarios, can be challenging, affecting the reliability and validity of modelling results.
3. Technical Expertise
Conducting consequence modelling requires specialized technical expertise and resources. Skilled professionals are essential for model complexity, result interpretation, and analysis.
Conclusion
In conclusion, integrating consequence modelling into fire and explosion risk assessment offers substantial benefits, enabling informed decision-making, targeted risk mitigation, compliance with regulations, effective training, regular inspections, and continuous safety protocol improvement. This comprehensive approach aligns with the overarching goal of ensuring personnel safety and protecting assets from the potential consequences of fire and explosion incidents.
We hope this article was helpful. For more information from Synergen Oil and Gas UK, please visit their CPD Member Directory page. Alternatively, you can go to CPD Industry Hubs for more articles, courses and events relevant to your Continuing Professional Development requirements.
