The 2006 edition of IS 4947 outlines the specifications for gas cartridges used in fire extinguishers, detailing the requirements for materials, design, capacity, and testing procedures. This standard is intended for manufacturers and inspectors to ensure the safety and dependability of gas cartridges, especially those with capacities below 500 ml that are not covered under gas cylinder regulations.
Overview
The 2006 edition of IS 4947 outlines the specifications for gas cartridges used in fire extinguishers, detailing the requirements for materials, design, capacity, and testing procedures. This standard is intended for manufacturers and inspectors to ensure the safety and dependability of gas cartridges, especially those with capacities below 500 ml that are not covered under gas cylinder regulations.
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Steel used in gas cartridges must adhere to the following maximum elemental concentrations: Carbon at 0.3%, Silicon at 0.35%, Sulphur at 0.05%, Phosphorous at 0.05%, and Manganese at 0.8%. Additionally, the material must possess minimum mechanical properties of tensile strength not less than 35 kgf/mm², yield stress at least 25 kgf/mm², and elongation of 20% or more. The steel can be seamless or welded tubing or deep drawn from flat plate, ensuring uniform thickness and smooth surfaces to withstand internal pressures safely.
The hydraulic pressure test involves applying an internal pressure of 250 kgf/cm² on each gas cartridge for a minimum duration of one minute. During this test, the cartridge must exhibit no leakage, bulging, deformation, or permanent elongation beyond 10%. Additionally, an ultimate failure test applies a pressure of 650 kgf/cm² without causing bursting. For leakage verification, cartridges are submerged inverted in water for 30 hours; no bubbles should appear after the initial 6 hours. Sampling sizes are determined by lot size, and the entire lot is accepted only if all samples meet these stringent criteria.
CO2 gas cartridges are filled up to a maximum filling ratio of 0.667, which is the mass of CO2 relative to the mass of water that would fill the cartridge at 27°C. Nominal capacities range from 20 g to 300 g with specific tolerances, such as ±5 g for 20 g cartridges and +10 g/-0 g for larger sizes. The gas must be at least 99% pure and free from moisture in accordance with IS 15222. This ensures the cartridge is filled within safe limits to guarantee reliable performance.
Permissible sealing devices and outlet connections must be fabricated from non-ferrous metals or stainless steel compliant with IS 3224. Sealing typically employs discs positioned 12 ± 0.5 mm from the edge. For frangible seals, the threads are right-handed with major diameters of 20.0 ± 0.1 mm and pitch of 1.8 mm, featuring a 55° thread angle. Other threads follow left-hand orientation per IS 218 (Part II): 1976, with a major diameter of 18.6 ± 0.1 mm and pitch of 1.81 mm. Protective caps, when used, must be screwed onto the outlet threads to safeguard against damage during transport and handling.
Each gas cartridge must bear permanent and legible markings near the neck area, applied by embossing or punching. These markings should include the manufacturer's name or trademark, construction type, sealing device details, capacity, gross charged mass, empty mass, and year of manufacture. The cartridge may also display the BIS Standard Mark under the appropriate licensing terms. Markings must be durable to withstand handling and environmental conditions, facilitating traceability and quality assurance throughout the product's lifecycle.
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