Explosion properties

Introduction

Explosions, characterised by the rapid expansion of combustible gases or suspended particles in the presence of an oxidant, unleash a spectrum of effects ranging from blast waves to intense heat and light. Understanding the nuances of explosion types and their impacts is paramount, especially in high-hazard industries such as oil and gas, chemical manufacturing, and energy sectors. This article explores the mechanics of explosions, their distinct types, and their significance in safety management and risk assessment.

Types of explosions

Explosions can be classified into two main categories based on their origin (Bosch, 2005) (Perry, 1997):

• Mechanical Explosions: These explosions result from the sudden rupture and loss of containment of compressed gases, often occurring in pressurised vessels or equipment. The rapid release of energy per unit of volume generates overpressure or shock waves, contributing to the destructive force of the explosion.

• Chemical Explosions: Chemical explosions arise from rapid combustion or chemical reactions, producing high-temperature combustion products. The intense heat generated during these reactions contributes to the destructive power of the explosion and can trigger secondary effects such as fires.

Impact of explosion

Explosions typically produce thermal and overpressure effects, although in cases involving the sudden release and rupture of non-flammable materials, only overpressure effects may occur. The example below depicts an instantaneous release of pressurised liquefied gas.

Explosions generate intense heat, often reaching temperatures in the thousands of degrees Celsius. This heat generated during combustion or chemical reactions contributes to the destructive force of the event and can initiate secondary impacts such as fires.

Additionally, part of the heat is converted into mechanical energy, which is transmitted into the surrounding atmosphere as a Blast Wave (Bosch, 2005).

The conditions required for an explosion to occur depend on various factors tailored to the particular scenario. These factors encompass elements such as temperature, pressure, gas composition, the presence of an ignition source, turbulence, mixing, and surroundings geometry. Gas explosions can occur in a variety of settings, including inside process equipment, within pipes, buildings, offshore modules, open process areas, and even in unconfined spaces.

Confined vs Unconfined Explosions

Explosions can occur in both confined and unconfined environments, each exhibiting distinct characteristics:

• Confined Explosions: Confined explosions, such as Vapour Cloud Explosions or Dust Explosions, occur within restricted spaces where the geometry of the surroundings, including process equipment, buildings, or vessels, restricts the expansion of the reaction front. The severity of the explosion’s effects is influenced by the degree of confinement, with higher degrees of confinement resulting in more extensive damage.

• Unconfined Explosions: Unconfined explosions occur in open spaces where flammable clouds disperse and mix with air. The concentration of the flammable cloud must fall within the Lower Flammable Limit (LFL) and encounter an ignition source for an explosion to occur. Despite being less common than confined explosions, unconfined explosions pose significant risks due to the presence of large amounts of flammable material over vast areas (Bosch, 2005).

Importance in high-hazard industries

In industries such as oil and gas, chemical manufacturing, and energy sectors, understanding explosion dynamics is crucial for risk assessment, safety planning, and emergency response. Robust safety protocols and risk mitigation strategies are essential to manage the unpredictable and potentially devastating outcomes of explosion events, safeguarding lives and property.

X-Suite for analysing gas explosions

Software tools like FLACS, EFFECTS, and RISKCURVES which are all part of Gexcon’s X-Suite facilitate the modelling of pressure build-up and explosion scenarios. These tools provide invaluable insights for risk assessment, emergency response planning, and even forensic analysis of explosion incidents.

Conclusion

Explosions represent complex phenomena with far-reaching impacts across various domains. Whether confined within structures or occurring in open spaces, their effects can be catastrophic. Understanding explosion dynamics, types, and impacts is imperative for safety management and risk assessment in high-hazard industries. Leveraging advanced software tools for explosion modelling enables organisations to enhance safety measures, mitigate risks, and safeguard lives and property effectively.

References

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

Perry, R. H. (1997). Perry’s Chemical Engineers’ Handbook. McGraw-Hill: New York.