Performance tests of selected plastic drums
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This project featured a series of drop tests and internal pressure tests carried out to evaluate the performance of selected plastic drums used for the transport of dangerous goods. A previous study was done by Transport Canada in 1985 (TP 7423E) that covered many types of packaging and several types of tests. As a result of that study, Transport Canada implemented quality control provisions to address some deficiencies found in drums used in the study. In order to evaluate how well these provisions were working, Transport Canada instituted a study of 210 L steel drums. Those results were presented in report TP 14093E, published in April 2003.
The current study continued the work of the 2003 study by performing similar tests on 210 L plastic drums. This study differed from the previous study in that the procedure for drop tests was streamlined slightly, and a series of internal pressure tests was included for the plastic drums.
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, Continental Europe and Asia. Two orientations were tested. In the six o'clock orientation, the drum is dropped diagonally on its top circumferential edge 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. Several different combinations of closure styles were used in the tested drums, and these are noted in the report; however, no particular analysis was done to compare closure styles due to the large variety of styles supplied.
Preliminary testing was done on each set of drums to determine the most severe drop orientation and the starting height. That orientation and starting height were then used in the actual drop tests. This was a significant change from the procedure used in the steel drum study, in which a full series of drop tests were conducted in both orientations. It was also where a difference in the results was found. Whereas in the steel drum study, the lowest mean failure height was always in the 8 o'clock orientation, in this study it was found that plastic drums from different manufacturers behaved differently, with several sets of drums failing earlier in the 6 o'clock 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 drum was dropped from a 0.2 m higher height. This was continued until all 20 drums had been tested in the selected orientation, after which the data was analyzed to arrive at an estimate for the mean and standard deviation for each series.
Five drums from each manufacturer were tested for their ability to withstand internal pressure without leakage. Each drum was pressurized in increments either until they leaked or until a pressure equal to 150% of the drum's rated pressure was reached.
The study found that there was a wide variation in the failure heights between manufacturers, but good consistency between drums from the same manufacturer. All of the drums tested were more than capable of surviving the standard drop test required for transport of dangerous goods. Most of the drums withstood more than their rated internal pressure. Some sets had one or more samples that leaked just below the rated pressure, but this may be attributable to not having the correct torque for securing the closures.
There was a greater variety of failure modes demonstrated by the plastic drums than was the case during the steel drum study. This probably reflects the fact that there is a much greater variation in the design details between different plastic drum manufacturers, whereas steel drums are much more standardized.
Recommendations include requiring at least one drop test in each orientation to ensure the most vulnerable condition has been tested, making the correct torque information readily available to users, and requiring training in the importance of proper torque. Similar studies are recommended for other types of packaging, including 20 L pails and combination packages.
Ordering information for this report can be found on the Transportation Development Centre web site.
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