Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals

Sub-Committee of Experts on the Transport of Dangerous Goods

Forty-first session

Geneva, 25 June – 4 July 2012

Item 2 (a) of the provisional agenda

Explosives and related matters: test series 8

Recommendations for improvement of the Series 8(b) ANE Gap Test and other Gap Tests

Transmitted by the Australian Explosives Industry Safety Group (AEISG)

Introduction

1. In informal document INF.58 (Thirty-ninth session, July 2011), the Working Group on Explosives reported:

Recommendation regarding cold-drawn carbon steel tube.  In informal document INF.6, IME recommended that the wall thickness variation amount specified be changed from 10 to 15% and that the specifications at the end of the paragraph be removed. It was suggested that specifying a minimum inside diameter and minimum wall thickness may be more appropriate than specifying a wall thickness variation.  It was observed that seamless steel tubing was not readily available as “cold drawn”, so the suggestion was made to remove those words from the paragraph. There was no agreement to this suggestion. The group agreed to remove the tensile strength, elongation, and Brinell hardness specifications.

Conclusion.  The working group agreed that specifying a minimum wall thickness and a minimum ID was a way forward and, considering the comments from the working group, IME will prepare a document for consideration in the 41^st Session.

2. Subsequent to the Working Group meeting, IME has submitted document ST/SG/AC.10/C.3/2012/1, which states, in  Paragraph 4 of the Annex:

The controlling elements in the effectiveness of a confining tube are in order (1) its inner diameter, (2) the material’s shock impedance (namely the product of its density and its speed of sound), and (3) the inertia of the wall (controlled by its density and its wall thickness). It is the shock impedance that controls the initial deflection of the interface between the test substance and the wall upon shock arrival; the inertia only begins to have an influence once there has been time for multiple internal shock reverberations between the inner and outer surfaces of the wall. All grades of steel have similar densities and sound velocities (and hence shock impedances and inertias), so only the inner diameter and the wall thickness need to be specified within suitable tolerances to ensure reproducibility of gap test results.

3.  And again in paragraph 11 of the annex:

Price [7] described the results of investigations into the effect of confinement on the results of the NOL LSGT. It was found that confinement had a negligible effect on the results for cast Pentolite, with the length of the critical PMMA gap corresponding to 50% initiation being 67.56 mm for an unconfined test charge and 67.06 mm for a test charge confined in steel – this difference is within experimental scatter for this gap test. The results for cast Composition B did show greater dependence on confinement, with the critical gap increasing from 36.32 mm for an unconfined test charge to 45.47 mm for aluminium confinement and to 51.05 mm for steel confinement. However, increasing the inertia of the confinement further by replacing steel tubing by lead tubing made essentially no further difference, with the critical gap increasing only very slightly to 51.82 mm with the latter. So while the presence of confinement was important for cast Composition B, its specific details were not once a certain level of inertia had been exceeded. It may be inferred that increasing the inertia of the steel confinement by increasing the wall thickness would similarly have made no significant difference to the critical gap.

4. AEISG agrees with the conclusion of the Working Group and the contents of paragraph 4 and 11 of the annex of ST/SG/AC.10/C.3/2012/1. Essentially, as stated in the above extracts, the critical elements of the pipe for the 8 (b) Gap test are the pipe inner diameter and that there is a level of confinement provided by the pipe (wall thickness not particularly critical). 

5. The process of drawing the pipe (hot or cold drawn) is irrelevant for the purposes of the test.

6.  In clause 8 of ST/SG/AC.10/C.3/2012/1, IME proposed:

Amend 18.5.1.2.1(c) of the 8(b) test procedure to read:

(c) Tubing, steel, cold drawn seamless, with an outer diameter of 95.0 ± 7.0 mm, a wall thickness of 9.75 ± 2.75 mm and an inner diameter of 73.0 ± 7.0 mm, and with a length of 280 mm;

7.  AEISG supports the proposal from IME, which has a larger minimum inner diameter than allowed by the existing Manual of Tests, but believes it can be further simplified in line with the decision of the Working Group on explosives to remove any unnecessary or over-specifications.

Proposal

8.  In view of the above, AEISG proposes:

9.  Amend 18.5.1.2.1 (c) of the 8 (b) test procedure to read:

(c) Tubing, steel seamless, with a minimum inner diameter of 66 mm, a minimum wall thickness of 7 mm, and with a length of 280 mm;

联合国危险货物运输专家和全球化学品统一分类和标签制度专家委员会

危险货物运输专家分委员会

第四十一次会议

日内瓦, 2012年6月25日 – 2012年7月4日

议程第2 (a) 项

爆炸物和相关内容：试验系列8

关于改进系列8（b）ANE隔板试验和其他隔板试验的建议

由澳大利亚爆炸品工业安全组提交(AEISG)

介绍

1.  爆炸品工作小组的报告文件—非正式文件INF.58（2011年7月，第39次会议），有如下汇总：

有关无缝冷拉碳素钢管的建议  在非正式文件INF.6中，IME 建议将规定的壁厚变化量从10%改为15%，同时删除章节末尾的规格内容。有专家建议规定最小内径和最小壁厚可能比规定某一壁厚偏差值更可行。也有人表示，无缝冷拉钢管并不容易获取，因此建议删除“冷拉”字样，对此建议工作组并未达成一致意见。工作组同意删除抗拉强度、伸展率及布氏硬度等规格内容。

结论；工作组同意将规定某一最小壁厚和最小内径值作为讨论方向，IME在听取工作组意见后，将在41次会议提交文件以作进一步讨论。

2.  在以上工作组会议之后，IME已经提交了正式文件ST/SG/AC.10/C.3/2012/1，在该文件附件的第4段提到：

封闭钢管中，这些影响因素的有效性排序如下：(1)内直径，(2)物质的冲击阻抗（即密度和声速的乘积），(3)管壁的惰性（与密度和壁厚有关）。冲击阻抗影响冲击到达时试验物质和管壁接触面之间的初始偏差；管壁惰性仅在有足够时间使内外管壁之间产生大量内部反射冲击时起作用。所有等级的钢材都有相似的密度和声速（冲击阻抗和惰性也类似），所以只需将内直径和壁厚规定在一定公差范围内，即可确保隔板试验结果的重复性。

3.  而该附件的第11段再次提到：

Price [7]描述了对封闭条件对NOL LSGT结果影响的调查结果。对于浇铸彭托利特炸药，在无约束试验中50%触发的临界PMMA隔板长度为67.56  mm，而使用钢管约束的试验中其临界值为67.06  mm，这些差异在隔板试验的误差允许范围之内，由此可见，此时约束条件对结果的影响微乎其微。 而约束条件对B炸药的影响要稍微大点，无约束时隔板临界值36.32  mm，铝约束时为45.47  mm，钢约束时为51.05  mm。然而，通过使用铅管代替钢管来增加约束的惰性时，并无大的差别，隔板临界值只是稍微增加至51.82  mm而已。由上可以看出，虽然有无约束对于B炸药而言影响较大，但一旦约束的惰性值超过一定范围，对于具体参数的影响并不大。因此，可以认为通过增加壁厚值来增加钢约束的惰性，对于隔板临界值并无明显影响。

4.  AEISG同意工作组的结论和ST/SG/AC.10/C.3/2012/1附件中第4与第11段的内容。事实上，正如以上摘录所言，8 (b)隔板试验所用管道的关键影响因素为管内径和管道所能提供的密闭程度（而壁厚并非特别关键）。

5.  管道的拉伸过程（热拉或冷拉）与测试目的毫无关系。

6.  ST/SG/AC.10/C.3/2012/1的第8章节，IME提议：

将8（b）试验程序中的18.5.1.2.1(c)节修改如下：

 (c) 冷拔无缝钢管，外直径95.0±7.0mm，壁厚9.75±2.75mm，内直径73.0±7.0mm，长280mm；

7.  IME提案中的最小内径值大于现行试验方法的规定值，AEISG总体上支持该提案，但考虑到爆炸品工作组决定删除试验手册中任何不必要的或多余规定的思路，AEISG认为该提案仍可以进一步简化。

提议

8.  鉴于此，AEISG建议：

9.   将8（b）试验程序中的18.5.1.2.1(c)节修改如下：

(c) 冷拔无缝钢管，最小内径66mm，最小壁厚7mm，长280mm；