Qualifying a 40 ft ISO Freight Container as a Type IP-2, IP-3 Package by Performing a Full Scale Drop Test

Abstract

The first successful worldwide free fall drop test with a 40 ft ISO freight container took place in Bremen (Germany) at the dry dock of the former Vulkan shipyard on 25 September 1998. This drop test had to be performed to qualify the ISO Boxcontainer as a Type IP-2, IP-3 package in accordance with the new IAEA Safety Standards Series No ST-1 (1996 Edition). Dynamic impact requirements will become mandatory for freight containers to be qualified as Type IP-2,3 packages in compliance with IAEA ST-1 paragraph §627 ‘Alternative Requirements for IP-2,3 Packages’ (comes into force in January 2001). STM has fulfilled the dynamic impact requirements in performing a full scale drop test. The 40 ft ISO freight container prototype (L × W × H = 12192mm × 2438 mm × 2491 mm) was fully loaded with 28 t of steel plates together with shock absorbing material to simulate the load and load securing system. The total drop test weight was 35.6 t. In accordance with the new IAEA Safety Standards Series No ST-1 requirements, the so-called LONGFORCE® container was dropped onto an unyielding foundation in a position which produced the maximum damage in respect of the package safety features. The package was dropped on its comer, door side down on the roof, with the centre of gravity over the impact area (slap-down drop). The container was lifted 12.6 m high (highest point) and 0.3 m (lowest point) under a drop angle of 70°. The combined mass of the concrete block and the steel plate was more than 100 times that of the container test specimen. The first impact resulted in an acceleration of about loog where the maximum was just before the impact. The second impact, however, turned out to be decisive showing maximum acceleration readings in the range of 250g. The container has been inspected after the drop test and deformations of the container rear comer castings (area of second impact) and a small weld crack in one of the comer casting welds was found. On the container floor one third of transverse profiles showed S-form distortion. The LONGFORCE container was leak tested prior to and after the drop test in compliance with the STM leak test procedure. The leak tests consisted of filling the container with pressurised air up to 5 kPa and recording a possible pressure drop over a determined test period. The container was considered leak tight prior to and after the drop test based on the permissible limits set in the leak lest procedure. The free fall drop test is considered a full success qualifying the 40 ft LONGFORCE container as Type IP-2, Ip-3 package in compliance with the new IAEA Safety Standards Series No ST-1 requirements.