Foam for Oil Fire Suppression: Understanding its Role in Fire Protection

Introduction

Foam is one of the most effective fire suppression tools available, especially when dealing with oil or other flammable liquid fires. It works by forming a blanket of bubbles that float on the surface of the burning liquid, smothering the flames and cooling the fuel to prevent reignition. This article delves into the intricacies of foam fire suppression systems, how they work, and their vital role in fire safety for oil fires.

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Quiz on Foam Fire Suppression

Foam Use in Oil Fire Quiz

1. What is the primary function of foam in extinguishing oil fires?

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2. Why is foam not suitable for extinguishing fires involving liquefied petroleum gas (LPG)?

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3. What should be considered when applying foam to unignited flammable liquids?

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4. According to NFPA 11, what must be done to compensate for wind and thermal updrafts during foam application?

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What is Foam Fire Suppression?

Foam fire suppression is a specialized fire-fighting method used to control and extinguish fires involving flammable liquids. Foams used in this process are aggregates of air-filled bubbles created by mixing water, foam concentrate, and air. These bubbles form a cohesive floating layer that covers the surface of the liquid fuel, cutting off oxygen and preventing the release of flammable vapors.

Key Components of Foam Fire Suppression:

Foam Concentrate: This is the liquid used to create the foam. It is mixed with water and air to produce the foam bubbles.
Water: Helps to cool the fuel and assist in generating foam.
Air: Adds volume to the foam, creating a lightweight blanket that can float on liquid fuels.

Foam is especially useful for two-dimensional flammable liquid spill fires or in storage tanks where it forms a vapor-sealing blanket that secures the area even after the fire is extinguished.

How Foam Extinguishes Oil Fires

Foam extinguishes fires through three primary mechanisms:

Smothering: Foam forms a blanket over the liquid fuel, cutting off the oxygen supply necessary for combustion.
Cooling: The water content in the foam cools the fuel below its ignition temperature.
Preventing Vapor Release: By sealing the fuel surface, the foam prevents flammable vapors from escaping and mixing with air to form combustible mixtures.

This combination of effects makes foam an ideal tool for handling oil fires and other flammable liquid incidents.

Types of Foam Used in Oil Fire Suppression

There are several different types of foam used in fire suppression, each with specific advantages depending on the type of fire or fuel involved.

1. Aqueous Film Forming Foam (AFFF):

Usage: Commonly used for flammable liquid fires.
Function: Forms an aqueous film that helps extinguish the fire by sealing vapors.
Advantages: Provides rapid fire knockdown and vapor suppression.

2. Alcohol-Resistant Aqueous Film Forming Foam (AR-AFFF):

Usage: Effective on alcohol-based fuels which are water-soluble.
Function: Resists the breakdown of foam by alcohol, allowing it to form a protective blanket.

3. Protein Foam:

Usage: Used in industrial applications, especially in aviation fire protection.
Function: Composed of natural proteins, it offers high resistance to heat.

4. Fluoroprotein Foam:

Usage: Common in high-risk industries such as oil refineries and chemical plants.
Function: Fluoroprotein foams create a long-lasting barrier against reignition.

NFPA Standards and Application Rates

The National Fire Protection Association (NFPA) sets specific standards for foam fire suppression systems, particularly in industrial settings. NFPA 11 outlines the required application rates for foam in various situations.

Foam Application Rates:

Tank Fires: Continuous foam application is critical to extinguishing fires in storage tanks.
Wind and Thermal Drafts: Foam must be applied at 60% higher rates in situations with wind or strong updrafts to compensate for losses.

The foam must be applied continuously until a cohesive blanket covers the liquid surface, ensuring the fire is fully extinguished and that reignition is prevented.

Foam Application Techniques

Correct foam application is essential for effective fire suppression. Poor application methods can result in foam being blown away or failing to cover the fuel properly, which could result in the fire reigniting.

Methods of Applying Foam:

Manual Application: Using hand lines or monitors to apply foam to the fire. It is important to account for wind and thermal updrafts.
Fixed Systems: Fixed foam chambers installed on tanks deliver foam without generating static electricity, preventing accidental ignitions.
Portable Equipment: When applying foam to unignited flammable liquids, it is crucial to do so gently to avoid generating static electricity, which could ignite the fuel. Using a spray pattern or banking foam off a backboard can help gently guide the foam onto the liquid surface.

Importance of Continuous Foam Application

For fires in oil storage tanks or large spills, it is critical to apply foam continuously until a cohesive foam blanket has formed. Interrupting the foam application can allow the fire to reignite, as the fuel surface remains exposed to air. In some cases, additional cooling water is used to lower the tank temperature, aiding in extinguishment.

Foam Fire Suppression in Industrial Settings

In industrial settings like oil refineries, petrochemical plants, and storage tank facilities, foam is a critical part of the fire protection strategy. The ability to extinguish large-scale oil fires quickly can prevent widespread damage and environmental contamination.

Common Applications:

Oil Storage Tanks: Foam systems are designed to cover the entire surface of a burning tank quickly and efficiently.
Refineries: Industrial foam systems help to prevent spill fires from spreading to critical infrastructure.
Chemical Plants: In chemical processing facilities, foam is used to protect areas where flammable liquids are processed or stored.

Table: Foam Types and Their Applications

Foam Type	Best Used For	Key Advantages
Aqueous Film Forming Foam (AFFF)	Flammable liquid fires	Fast fire knockdown and vapor suppression
Alcohol-Resistant AFFF	Alcohol-based liquid fires	Resists breakdown in water-soluble fuels
Protein Foam	Industrial applications	High heat resistance and long-lasting foam blanket
Fluoroprotein Foam	Refineries and chemical plants	Durable, long-lasting protection for high-risk industries

Foam for Oil Fire Suppression

Foam Safety and Precautions

When using foam to suppress fires, certain precautions must be taken to avoid unintended consequences, such as static discharges that could ignite unburned fuel.

Key Safety Measures:

Avoid Splashing: Apply foam gently to avoid splashing and turbulence, which could generate static electricity.
Use of Cooling Water: Cooling water can help reduce tank temperatures, aiding foam effectiveness in large fires.
Proper Training: Ensure personnel are trained in foam application techniques to maximize efficiency and safety.

Environmental Impact of Fire Suppression Foam

While foam is an effective fire suppression tool, it is essential to consider its environmental impact. Certain foam concentrates contain fluorinated chemicals that can persist in the environment and potentially harm wildlife. Efforts are being made to develop more eco-friendly foam formulations that offer the same fire suppression capabilities without the long-term environmental risks.

Advances in Foam Technology

With ongoing advancements in fire suppression technology, foam concentrates have become more effective and environmentally friendly. New formulations offer:

Enhanced Performance: Improved foam longevity and better vapor-sealing capabilities.
Reduced Environmental Impact: Foams that break down more quickly and pose less risk to the environment.

Conclusion

Foam fire suppression is a highly effective method for controlling oil fires and other flammable liquid incidents. Its ability to smother flames, cool fuel, and prevent the release of flammable vapors makes it indispensable in industrial settings where the risk of large fires is high. By understanding how foam works and using it correctly, facilities can protect against devastating fires, minimize environmental impact, and ensure the safety of personnel.

FAQs

1. What is foam fire suppression?
Foam fire suppression involves using air-filled foam bubbles to smother flammable liquid fires by cutting off oxygen and cooling the fuel.

2. How does foam prevent fires from reigniting?
Foam forms a blanket that seals the surface of the fuel, preventing the release of flammable vapors that could mix with air and reignite the fire.

3. Can foam extinguish fires involving liquefied petroleum gas?
Foam is not effective against fires involving liquefied petroleum gas (LPG) or flammable gases, as these materials require different suppression methods.

4. Why is continuous foam application necessary?
Continuous foam application ensures that the entire surface of the liquid fuel is covered, preventing reignition and allowing the fire to be fully extinguished.

5. What safety precautions should be taken when applying foam?
Foam should be applied gently to avoid generating static electricity, which could ignite unburned fuel. Cooling water may also be used to assist in large fires.