Cause analysis of inflation of 22mm sub-caliber catridge packing and improvement of shelf life

Mortar ammunition has strong destructive power, making it dangerous and challenging to use for training purposes. Therefore, to achieve realistic training effects within limited resources, training ammunition called "Sub-caliber" has been implemented by removing the explosives and incorporating smoke agents. This ammunition is maintained under vacuum-sealed conditions using protective waterproof barrier bags to prevent moisture and corrosion. On the other hand, an issue arose where barrier bags of several 22mm sub-caliber cartridges for the 4.2-inch mortar stored by the military experienced inflation. Compositional analysis detected hydrogen gas, and the cause of inflation was attributed to a chemical reaction between the magnesium in the smoke agents and moisture. After identifying the factors that can generate moisture, which can induce a chemical reaction with the magnesium in the smoke agents, the internal packaging material was found to be the primary source of moisture. This issue was addressed by controlling the chemical reaction rate through temperature regulation by changing the storage location. Finally, the Arrhenius equation was used to predict and compare the shelf life of an igloo magazine and an above-ground magazine. The Arrhenius equation describes the relationship between the rate of a chemical reaction and temperature. It can be used to predict the stability at different storage temperatures. As a result, the estimated shelf life of an igloo magazine is approximately 21 years (7721 days), representing a 1.5-fold improvement compared to the above-ground magazine. The quality improvement measures presented in the paper are expected to enhance the stability and storage performance of the abovementioned ammunition and all ammunition containing magnesium components.