Failure analysis of high-pressure fire extinguisher

•Case of study, failure of a high-pressure fire extinguisher cylinder due to stress corrosion cracking mechanism.•Calculated critical crack size was 0.250 in deep and 10 in long, agrees with preexisting cracks found in the cylinder wall.•The SCC time of growth was estimated as 8.33 × 10−6 s (96.4 days), which corresponds with the time elapsed since the fire extinguisher was refilled and stored, up to the failure.•Crack growth rate of AISI/SAE 4130 steel in moist environments containing CO2.•Effect of water contamination in the development of SCC failure mechanism. The failure analysis of the high-pressure cylinder of a fire extinguisher fabricated by quench and tempered AISI/SAE 4130 steel is presented. The metallographic and mechanical examination indicated that the cylinder’s fabrication material was not properly heat-treated since the microstructure contained an excessive amount of α-ferrite and low hardness. The failure mechanism was identified as Stress Corrosion Cracking induced by the combination of pressure induced and residual stresses, a corrosive environment due to the presence of water and other contaminants in the extinguishing agent, and an incorrectly heat-treated material. A fracture mechanics assessment demonstrated that a critical crack, of 3.35 mm (0.250 in.) deep and 254 mm (10 in.) long, caused the failure at the operation pressure. To prevent similar failures, it is recommended to periodically inspect the high-pressure cylinder by nondestructive testing to prevent internal cracks. Furthermore, the cylinders must be perfectly dry and free of corrosive species.