Designing Chemical Energy-Based Fire Suppression Systems for Safety: A Comprehensive Guide

Designing chemical energy-based fire suppression systems for safety involves a deep understanding of the physics, chemistry, and engineering principles behind these systems. This comprehensive guide will provide you with the technical specifications, design considerations, and theoretical explanations necessary to create effective and reliable fire suppression solutions.

Types of Chemical Energy-Based Fire Suppression Systems

Clean Agent Systems

1. Fike Fluoroketones & Hydrofluorocarbons (HFCs):
2. Function: These agents extinguish fires through heat absorption, reducing the temperature of the fire and preventing its spread.
3. Benefit: Clean agent systems are safe for occupied spaces, leaving minimal cleanup and residue behind.
4. Approvals: These systems are approved by FM, UL, ULC, and CE.
5. FM-200™:
6. Function: FM-200™ is a hydrofluorocarbon agent that effectively suppresses fires.
7. Benefit: FM-200™ is the most widely used and globally recognized chemical agent for fire suppression.
8. Approvals: FM, UL, ULC, and CE.
9. ECARO-25®:
10. Function: ECARO-25® is another hydrofluorocarbon agent used for fire suppression.
11. Benefit: ECARO-25® is a cost-effective chemical agent option.
12. Approvals: FM, UL, and ULC.

Dry Chemical Systems

• Function: Dry chemical systems use a dry chemical powder to extinguish fires.
• Agents: The most common dry chemical agents are sodium bicarbonate and mono-ammonium phosphate.
• Cleanup: Dry chemical systems can be time-consuming and expensive to clean up after activation.

Wet Chemical Systems

• Function: Wet chemical systems use a liquid spray to extinguish fires, particularly in commercial kitchens.
• Agents: The chemical agents in wet systems react with fats and oils to produce a foam that smothers the fire.
• Cleanup: Wet chemical systems generally have an easier cleanup process compared to dry chemical systems.

Design Considerations

Automatic Detection

1. Active Detection:
2. Function: Active detection systems require an electrical power supply and are efficient in recognizing fires.
3. Limitation: Active systems are vulnerable to power outages, which can compromise their functionality.
4. Non-Electric Systems:
5. Function: Non-electric systems use heat-activated detection tubes that do not require power, providing automatic suppression.
6. Benefit: These systems are not dependent on electrical power and can operate even during power failures.

System Configuration

1. Direct Release:
2. Function: Direct release systems release the suppression agent directly onto the fire, providing immediate extinguishment.
3. Indirect Release:
4. Function: Indirect release systems flood the protected area through discharge nozzles, effectively suppressing the fire.

Fire Class

1. Class A: Ordinary combustibles (wood, paper, cloth)
2. Class B: Flammable liquids (gasoline, oil)
3. Class C: Electrical fires (electrical equipment, wiring)
4. Class K: Cooking oils and greases

Installation and Maintenance

Certification

• Requirement: Certified fire protection engineers or installers must design and install chemical energy-based fire suppression systems to ensure compliance with NFPA standards.

Regular Maintenance

• Importance: Performing routine checks and maintenance is crucial to ensure the functionality and reliability of the fire suppression system.

Physics and Theoretical Explanation

Heat Absorption

• Principle: Chemical agents in fire suppression systems absorb heat from the fire, reducing the temperature and extinguishing the flames.
• Formula: The heat absorption capacity of a chemical agent can be calculated using the specific heat capacity (c) and the mass (m) of the agent: Q = m × c × ΔT, where Q is the heat absorbed, and ΔT is the change in temperature.

Oxygen Displacement

• Principle: Inert gases used in fire suppression systems displace oxygen, starving the fire of the necessary fuel to continue burning.
• Formula: The oxygen concentration required for combustion can be calculated using the ideal gas law: PV = nRT, where P is the pressure, V is the volume, n is the number of moles of gas, R is the universal gas constant, and T is the absolute temperature.

Chemical Reactions

• Principle: Chemical agents in fire suppression systems react with the fire, producing a cooling effect or suffocating the fire.
• Example: Dry chemical agents, such as sodium bicarbonate, undergo thermal decomposition, releasing carbon dioxide and water vapor, which contribute to fire extinguishment.

Numerical Problems and Examples

Fire Suppression Time

• Requirement: Chemical agent suppression systems must reach the required concentration levels within 10 seconds to effectively extinguish the fire.
• Example: Assuming a protected volume of 1000 m³ and a required agent concentration of 7%, the system must discharge at least 70 m³ of agent within 10 seconds to meet the suppression time requirement.

Fire Extinguishing

• Capability: Clean agent systems can extinguish fires at the molecular level, protecting irreplaceable assets such as electronic equipment and valuable documents.
• Example: A clean agent system using FM-200™ can extinguish a Class B fire (flammable liquids) with a minimum design concentration of 6.25% by volume, effectively suppressing the fire while minimizing collateral damage.

Figures and Data Points

1. Effectiveness: Sprinkler systems are 96% effective in controlling fires, demonstrating the importance of reliable fire suppression systems.
2. System Types: There are five primary types of fire suppression systems: FM200, water mist, foam deluge, chemical foam, and dry chemical, each with its own unique characteristics and applications.

Measurements and Values

1. Agent Concentration: Chemical agents must reach a specific concentration, typically between 4-10% by volume, to effectively extinguish the fire.
2. System Pressure: The pressure of the suppression agent container and the piping network must be carefully designed to ensure the proper discharge and distribution of the agent.
3. Detection Temperature: Heat-activated detection tubes in non-electric systems are designed to burst at a specific temperature, typically ranging from 57°C (135°F) to 93°C (200°F), to trigger the suppression system.

References

1. https://www.statx.com/fire-education/designing-fire-suppression-systems/
2. https://clmfireproofing.com/what-is-a-fire-suppression-system/
3. https://www.firetrace.com/fire-suppression-systems
4. https://www.fike.com/fire-protection/solutions/chemical-agents/
5. https://www.psintegrated.com/blog/ultimate-guide-fire-suppression-systems