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Overview and Working Principle
Unlike stored-pressure extinguishers, cartridge powder types utilize a separate pressurizing cartridge filled with inert gas (typically CO₂ or nitrogen), which is pierced at the time of operation to propel the dry chemical powder onto the fire. This design facilitates quick activation, consistent discharge pressure, and ease of maintenance.
The extinguisher consists of:
- A cylinder containing the dry chemical powder
- An attached cartridge holding the pressurizing gas
- A valve assembly for cartridge piercing and powder discharge
- A discharge hose and nozzle for directing the agent
Design and Construction Specifications
- Cylinder and Materials:
Cylinders are fabricated from high-tensile steel or corrosion-resistant alloys capable of withstanding internal pressures generated during discharge. The interior surface is treated to prevent chemical degradation. - Cartridge and Piercing Mechanism:
The cartridge must be securely mounted to the valve assembly, designed for reliable piercing by a manually operated lever or trigger, ensuring immediate pressurization upon activation. - Powder Agent:
The dry chemical powder, typically monoammonium phosphate or sodium bicarbonate-based, must comply with strict purity and granule size standards to maximize extinguishing efficiency and minimize clogging. - Valve and Discharge Hose:
The valve assembly enables safe storage and controlled discharge, while the flexible discharge hose and nozzle ensure targeted application of the extinguishing agent.
Performance Requirements
- Discharge Time and Range:
The extinguisher must deliver the entire powder charge within a specified time (usually between 8 to 15 seconds), with an effective spray range of 3 to 6 meters depending on nozzle design. - Pressure and Safety:
The discharge pressure, generated by the cartridge, must be sufficient to overcome nozzle resistance while maintaining operator safety and control. - Durability and Reliability:
Components must resist corrosion, mechanical wear, and environmental factors such as temperature variation and humidity to ensure readiness over long service intervals.
Testing and Quality Assurance
- Hydrostatic Testing:
Cylinders are tested to withstand pressures significantly above the maximum working pressure to prevent rupture or leakage. - Discharge Tests:
Performance testing includes verifying powder discharge rate, range, and complete emptying within the specified time. - Leak and Seal Integrity:
Valves, cartridges, and hose connections undergo rigorous leak testing to prevent accidental discharge or agent loss. - Operational Reliability:
The cartridge piercing mechanism is tested for consistent activation without failure or jamming.
Maintenance and Inspection
- Cartridge Replacement:
Cartridges are typically single-use and must be replaced after discharge or as recommended by the manufacturer. - Powder Refilling:
Powder charges should be periodically checked for caking or contamination and refilled as necessary. - Routine Inspection:
Monthly visual checks for corrosion, pressure gauge status (if applicable), and physical damage. - Annual Servicing:
Includes hydrostatic testing, valve function checks, cartridge replacement, and hose inspection.
Conclusion
IS 13385:1992 provides critical specifications for cartridge powder type fire extinguishers, emphasizing safe, rapid deployment and effective fire suppression across various classes. Strict adherence to this standard ensures these extinguishers remain dependable assets in industrial and commercial fire safety systems.
