加拿大交通部对钢桶跌落试验进行深度研究
文/三哥
加拿大交通部针对钢桶性能评定的项目进行了一系列跌落测试，以评估用于运输危险货物的选定钢桶的性能。之前的一项研究由加拿大运输部于1985年 (TP 7423E)完成，涵盖多种类型的包装和多种类型的测试。作为该研究的结果，加拿大运输部实施了质量控制规定，以解决研究中使用的210L钢桶中发现的一些缺陷。当前研究的一个原因是评估这些规定的运作情况。次要目标是评估两种不同下落方向的优点，并评估两种最常见的封闭器类型的差异。
从加拿大的两家钢桶制造商、美国的两家制造商以及英国和德国各制造商处购买了50个桶的样品组。测试了两个方向。在六点钟方向，桶在其顶部圆周角上对角下落，以便最靠近大封闭器的点击中目标。八点钟方向是相似的，不同之处在于钢桶旋转使得大封闭件位于桶击中目标时形成的“挤压变形”的中心。一半的测试钢桶使用传统的“Reicke”样式封闭器，其余使用更新的“Tri-sure”样式封闭器。
每个样品组中最多 10 个用于初步测试，以确定该特定组在 6 点钟和 8 点钟方向的起始跌落高度。一旦确定了最可能的最低跌落高度，就在六点钟方向测试了 20个桶。然后测量挤压变形的平均尺寸以确定用于八点钟方向的真实角度，其余 20 个在该方向上进行测试。
Up and Down Bruceton Staircase 跌落试验程序用于以数学方式建立每组桶的平均跌落高度和标准偏差。将桶装满水至其最大容量的 98%，然后按照危险货物运输的要求进行跌落测试。在对每个桶进行测试后，对其进行评估以查看是否存在泄漏（损坏）。如果有，则下一个桶在低 0.2 m 的高度进行测试。如果没有，下一个是从 0.2 m 高的高度掉下来的。这一直持续到所有 20 个桶在每个方向都进行了测试，然后分析数据以得出每个系列的平均值和标准偏差的估计值。
研究发现，制造商之间的泄漏（损坏）高度差异很大，但同一制造商的桶之间的一致性良好。大多数测试的桶都能够通过危险货物运输所需的跌落测试。一家制造商在低于所需测试高度的高度出现了一些故障，但大多数故障都高于该水平。只有一组钢桶在远低于所需测试高度的高度上始终不合格，实际上甚至一次都未能达到所需的测试高度。
总体而言，大多数泄漏（损坏）是由于卷边的开缝或金属的破裂而发生的，无论是在卷边处还是在“挤压变形”的最尖锐的折叠处。在大封闭器处发生的泄漏（损坏）数量较少，主要是在 8 点钟测试期间和在较高的跌落下。
两个测试方向之间的性能肯定存在差异。八点钟方向的平均泄漏（损坏）跌落高度始终低于六点钟方向，并且故障模式更有可能是八点钟方向测试期间在卷边处泄漏。
两种类型的封闭器之间的区别较小。两种类型的失败次数相似，并且在相似高度的测试中失败。没有足够的差异来证明指定一个封闭器而不是另一种封闭器是合理的，特别是因为注意到任何一种封闭类型都倾向于在远高于要求的高度上失败。
建议对其他类型的包装（如塑料桶、20 升桶和钢塑复合桶）进行类似研究。还建议以类似的方式对钢桶进行静水压力测试，并有可能寻求自愿参与，作为通过消除样品获取成本来降低成本的一种方式。
Drop tests ofselected steel drums
This project featured a series of droptests carried out to evaluate the performance of selected steel drums used forthe transport of dangerous goods. A previous study was done by Transport Canadain 1985 (TP 7423E) covering many types of packaging and several types of test.As a result of that study, Transport Canada implemented quality controlprovisions to address some deficiencies found in 210 L steel drums used in thestudy. One reason for the current study was to evaluate how well theseprovisions were working. Secondary objectives were to assess the merits of twodifferent drop orientations, and to evaluate the differences in the two mostcommon types of closures.
Sample sets of 50 drums were purchased from two manufacturers inCanada, two manufacturers in the United States, and one each in the UnitedKingdom and Germany. Two orientations were tested. In the six o'clockorientation, the drum is dropped diagonally on its top circumferential cornerso that the point closest to the large closure strikes the target. The eighto'clock orientation is similar except that the drum is rotated so that thelarge closure is in the centre of the "crush pattern" that forms whenthe 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 todetermine the starting drop height in the six o'clock and eight o'clockorientations for that particular set. Once the most likely lowest failureheight 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 trueangle to be used for the eight o'clock orientation and the remaining 20 weretested in that orientation.
An Up and Down Bruceton Staircase procedure was used tomathematically establish a mean failure height and standard deviation for eachset of drums. The drums were filled with water to 98 percent of their maximumcapacity and then subjected to the drop test as required for transport ofdangerous goods. After each drum was tested it was evaluated to see whetherthere were leaks (failure). If there were, then the next drum was tested at a0.2 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 andstandard deviation for each series.
The study found that there was a wide variation in the failureheights between manufacturers, but good consistency between drums from the samemanufacturer. Most of the drums tested were more than capable of surviving thedrop test required for transport of dangerous goods. One manufacturer had somefailures at a height below the required test height, but most of the failureswere above that level. Only one set of drums consistently failed at heightswell below the required test heights, in fact failing to meet the required testheight even once.
Overall, most failures occurred by the unrolling of the chime orrupture of the metal, either at the chime or in the sharpest folds of the"crush pattern". A smaller number of failures occurred at the largeclosure, mainly during eight o'clock tests and mainly on higher drops.
There is definitely a difference in performance between the twotest orientations. The average failure drop height for the eight o'clockorientation was consistently below that of the six o'clock orientation, and themode of failure was more likely to be by leaking at the closure during theeight 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 similarheights. There was not enough difference to justify specifying one closure overanother, especially since it was noted that either closure type tended to failat heights well above the requirements.
Similar studies for other types of package such as plasticdrums, 20 L pails and combination packages are recommended. It is alsosuggested that hydrostatic pressure tests on steel drums be conducted in asimilar manner, with the possibility of seeking voluntary participation as away to reduce costs by eliminating sample acquisition costs.
