Learn How to make Event Tree of Chemical Release:
Simplified Guide to Consequence Analysis for Chemical Substance Releases
Before performing a consequence analysis of any hazardous event, it's crucial to understand the potential outcomes resulting from the release of chemical substances. Here’s a breakdown of the key points to consider, along with a simplified event tree diagram that outlines possible scenarios for both gas and liquid/liquefied gas releases.
Event Tree for Chemical Releases
Gas Release: When a gas is released, several outcomes can occur depending on the release conditions:
Immediate ignition: May result in a jet fire.
No immediate ignition: Can form a vapor cloud. If ignited later, it could result in a Vapor Cloud Explosion (VCE) or a flash fire.
No ignition at all: A toxic cloud may form, potentially leading to harmful exposure to workers and the environment.
Liquid or Liquefied Gas Release:
Immediate vaporization: Can result in jet fires, similar to gas releases.
Rapid vaporization or slow pooling: If ignited, could result in a pool fire.
No ignition: The liquid may evaporate, creating a toxic exposure risk or potentially contaminating groundwater.
Key Consequences of Chemical Releases
Physical Explosions and BLEVEs:
A physical explosion occurs when a pressure vessel is stressed beyond its design limits, sometimes referred to as an "energy release."
If the chemical substance is flammable, a BLEVE (Boiling Liquid Expanding Vapor Explosion) could occur, leading to a fireball.
Non-Ignited Releases:
In cases where there is no immediate ignition, the chemical substance may spread into the atmosphere.
Depending on the properties of the substance (liquid, gas, or liquefied gas), this could result in vapor clouds or liquid pooling, leading to a potential toxic exposure or environmental contamination.
Types of Fires and Explosions
Jet Fire: Happens when a gas or vapor is released under pressure and ignites, creating a long flame.
Pool Fire: Occurs when a flammable liquid pools on the ground or other surfaces and ignites.
Vapor Cloud Explosion (VCE): A delayed ignition of a vapor cloud, causing an explosion with significant overpressure.
Flash Fire: Similar to a vapor cloud explosion but without the creation of blast waves; only intense flames.
Key Factors Affecting Consequences
Several factors influence the type and severity of consequences from a chemical release:
Release conditions: Pressure, temperature, and the state of the substance (gas, liquid, or liquefied gas) determine how the chemical reacts.
Immediate ignition or delayed ignition: Immediate ignition may cause jet or pool fires, while delayed ignition could lead to vapor cloud explosions.
Physical properties of the released substance: These properties affect how the material disperses and interacts with the environment.
Real-World Examples
BLEVE/Fireball: A flammable liquid spill followed by ignition can result in a fire that consumes the entire tank, leading to a BLEVE or fireball.
Non-Ignited Toxic Cloud: If a chemical release does not ignite, a toxic cloud could spread, putting workers and nearby residents at risk of exposure.
Conclusion
Understanding the behavior of chemical releases and their potential consequences is essential for safety planning in industrial environments. Whether the release results in immediate fires, explosions, or long-term environmental hazards, analyzing the situation beforehand allows for the design of effective mitigation strategies to minimize harm.