Fire Extinguisher - 135 Litres Capacity Mechanical Foam Type
2001 Edition

The construction materials specified include mild steel sheets for the body (as per IS 1079), leaded tin bronze (Grade LTB 2, IS 318) or mild steel pipes (IS 1239 Part 1) for the neck ring, leaded tin bronze or brass forgings for the cap, and rubber washers resistant to acids and alkalis (IS 538). Safety valves are made of brass or leaded tin bronze, supported by spring steel springs (IS 4454 Part 1). Siphon tubes can be brass, HDPE, copper, or mild steel conforming to respective IS codes. Discharge fittings utilize leaded tin bronze or brass, while foam making pipes may be aluminum alloy, leaded tin bronze, or plastic. The CO2 cylinder must comply with IS 2878, and hoses are fabricated from braided rubber or nylon-braided PVC with a bursting pressure not less than 50 kg/cm². Snifter valves may be brass, stainless steel, leaded tin bronze, or plastic as per relevant standards.

Mechanical foam is produced by mixing foam concentrate with water and expanding it under pressure supplied by a compressed or liquefied gas cylinder, typically CO₂, attached to the extinguisher. When activated, the gas pressure propels the foam solution through a siphon tube into a foam-making branch pipe or nozzle, where it expands and discharges as foam to suppress fires involving non-polar flammable liquids. The foam concentrate adheres to IS 4989 (Part 2) standards, with quantities of 8 litres for 6% concentration or 4 litres for 3% concentration, topped up with water to achieve the full 135-litre foam solution volume.

The extinguisher's internal surfaces must be coated either with an electrolytically or hot-dipped applied lead-tin alloy containing at least 10% tin, with a minimum thickness of 0.012 mm, or alternatively, an epoxy powder coating with a thickness not less than 0.050 mm. External surfaces receive similar treatment with lead-tin alloy, epoxy powder coating, or phosphating per IS 3618. Both internal and external coatings require complete coverage with no uncoated areas visible. Siphon tubes must have equivalent corrosion-resistant coatings on both surfaces. Additionally, corrosion resistance is verified by immersing a test specimen in a solution of 20% sulphuric acid and 5% sodium hydroxide for 10 minutes without any signs of corrosion or damage.

IS 14951 requires a hydraulic pressure test where the extinguisher body and cap (excluding the safety valve) are subjected to an internal pressure of 3.0 MN/m² (30 kgf/cm²) for a duration of 2 minutes, ensuring no leakage or deformation occurs. The adhesion of plastic linings is tested by applying 15 kgf/cm² pressure for approximately 120 hours at 27 ± 5°C; after pressure release, the lining must show no cracking, detachment, or bubbles. Additionally, a hydraulic burst failure test requires the extinguisher body to withstand at least 4.5 MN/m² (45 kgf/cm²) without mechanical failure. These tests ascertain the extinguisher's structural integrity and operational reliability.

The extinguisher must bear black letters 'A' and 'B' each 2.5 cm tall, centrally positioned within a 4 cm square with a cream (lemon yellow, IS 5 shade No. 355) background, indicating suitability for Class A and B fires. It may also display the BIS Standard Mark as authorized. Permanent markings should include manufacturer's identification, clear operating instructions, the phrase 'MECHANICAL FOAM FIRE EXTINGUISHERS,' capacity in litres, and a warning to thoroughly rinse the extinguisher with fresh water after use using at least two water changes. The body must also be marked with a declaration of having undergone pressure testing at 3.0 MN/m² (30 kgf/cm²) and indicate the year of manufacture, ensuring traceability and compliance.