Types of fires

Introduction

Understanding the fundamentals of fire dynamics and the specifics of different fire events is essential for safety engineering, consequence analysis, and risk mitigation. The stages of fire development in solids, liquids, and gases provide a foundational understanding, highlighting the fundamental principles governing combustion. However, fire events can manifest in various forms, each presenting unique challenges for safety engineers and risk analysts. Fires in industrial installations or during the transportation of hazardous substances can be systematically classified based on the state of the fuel involved and the conditions under which combustion occurs.

Exploring fire events

An event tree illustrating the various types of fires resulting from the loss of containment of pressurised liquefied gas is presented in the figure below.

Whilst the combustion of solid materials can lead to significant fires, it is more common for industrial accidents to involve liquids, gases or pressurised liquefied gases as primary fuels. The sequence typically begins with the unintended release of a flammable fluid. In the case of a liquid, this release can form a pool on the ground, contained within a limited area if a dike is present, or on water. A similar outcome can arise when a tank loses its roof due to an explosion. In all these instances, the ignition leads to a Pool Fire, with Tank Fires considered as a particular case of this phenomenon. BLEVE Fireball occurs upon the catastrophic rupture of a vessel containing a pressurised liquefied gas.

When the released material with high momentum immediately ignites it results in a Jet Fire. Gas Fireballs emerge when instantaneously released flammable gases ignite, producing intense flames. A Flash Fire occurs when a dispersion cloud, typically originating from a Jet Release or Pool Evaporation, travels downwind and suffers from delayed ignition. This flammable cloud may travel considerable distances before encountering an ignition source (Bosch, 2005).

Pool and Tank Fires are the most common among the various types of fires, followed by Jet Fires, Flash Fires, and Fireballs. Pool Fires and Jet fires may persist for extended periods, whilst a Fireball typically lasts less than a minute, often only a few seconds. Flash Fires, characterised by their brevity, are short-lived phenomena, lasting only a few tens of seconds. Understanding the nature of these fires is crucial for implementing effective safety measures and response strategies in industrial settings dealing with flammable materials.

X-Suite for understanding flammability and ignition

Gexcon's X-Suite, particularly tools like FLACS and EFFECTS, provide simulation capabilities to model the behaviour of gas, liquid, and pressurised liquefied gas mixtures under varying conditions and the impact of different ignition sources. This aids in comprehensive risk assessment and safety planning.

References

Bosch, C. v. (2005). Methods for the calculation of physical effects 'Yellow book' CPR 14E. The Hague: Ministerie van Verkeer en Waterstaat.