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Drop tests of selected steel drums
This project featured a series of drop tests carried out to evaluate the performance of selected steel drums used for the transport of dangerous goods. A previous study was done by Transport Canada in 1985 (TP 7423E) covering many types of packaging and several types of test. As a result of that study, Transport Canada implemented quality control provisions to address some deficiencies found in 210 L steel drums used in the study. One reason for the current study was to evaluate how well these provisions were working. Secondary objectives were to assess the merits of two different drop orientations, and to evaluate the differences in the two most common types of closures.
Sample sets of 50 drums were purchased from two manufacturers in Canada, two manufacturers in the United States, and one each in the United Kingdom and Germany. Two orientations were tested. In the six o'clock orientation, the drum is dropped diagonally on its top circumferential corner so that the point closest to the large closure strikes the target. The eight o'clock orientation is similar except that the drum is rotated so that the large closure is in the centre of the "crush pattern" that forms when the drum hits the target. Half of the drums tested used the traditional "Reicke" style closure, and the remainder used a newer "Tri-sure" style closure.
Up to 10 of each sample set were used for preliminary testing to determine the starting drop height in the six o'clock and eight o'clock orientations for that particular set. Once the most likely lowest failure height was established, 20 drums were tested in the six o'clock orientation. The average size of the crush pattern was then measured to determine the true angle to be used for the eight o'clock orientation and the remaining 20 were tested in that orientation.
An Up and Down Bruceton Staircase procedure was used to mathematically establish a mean failure height and standard deviation for each set of drums. The drums were filled with water to 98 percent of their maximum capacity and then subjected to the drop test as required for transport of dangerous goods. After each drum was tested it was evaluated to see whether there were leaks (failure). If there were, then the next drum was tested at a 0.2 m lower height. If not, the next was dropped from a 0.2 m higher height. This was continued until all 20 drums had been tested in each orientation, after which the data was analyzed to arrive at an estimate for the mean and standard deviation for each series.
The study found that there was a wide variation in the failure heights between manufacturers, but good consistency between drums from the same manufacturer. Most of the drums tested were more than capable of surviving the drop test required for transport of dangerous goods. One manufacturer had some failures at a height below the required test height, but most of the failures were above that level. Only one set of drums consistently failed at heights well below the required test heights, in fact failing to meet the required test height even once.
Overall, most failures occurred by the unrolling of the chime or rupture of the metal, either at the chime or in the sharpest folds of the "crush pattern". A smaller number of failures occurred at the large closure, mainly during eight o'clock tests and mainly on higher drops.
There is definitely a difference in performance between the two test orientations. The average failure drop height for the eight o'clock orientation was consistently below that of the six o'clock orientation, and the mode of failure was more likely to be by leaking at the closure during the eight o'clock tests.
There was less distinction between the two types of closure. Both types failed a similar number of times and during tests from similar heights. There was not enough difference to justify specifying one closure over another, especially since it was noted that either closure type tended to fail at heights well above the requirements.
Similar studies for other types of package such as plastic drums, 20 L pails and combination packages are recommended. It is also suggested that hydrostatic pressure tests on steel drums be conducted in a similar manner, with the possibility of seeking voluntary participation as a way to reduce costs by eliminating sample acquisition costs.
Ordering information for this report can be found on the Transportation Development Centre web site.
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