{"operation":"document","citation":"PHMSA Guidance, Explanation of Classification of Thermite Mixtures","title":"Explanation of Classification of Thermite Mixtures","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2023-09-22","effective_on":"2023-09-22","summary":"Explanation of Classification of Thermite Mixtures Document PHMSA Thermites Notice.pdf (175.15 KB) Issued Date: Friday, September 22, 2023","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-guidance-explanation-classification-thermite-mixtures-62243085.json","markdown":"https://regulus.evalyn.ai/document/phmsa-guidance-explanation-classification-thermite-mixtures-62243085.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-guidance-explanation-classification-thermite-mixtures-62243085","source_url":"https://www.phmsa.dot.gov/regulatory-compliance/phmsa-guidance/explanation-classification-thermite-mixtures","body":"Explanation of Classification of Thermite Mixtures\n\nDocument\n\n PHMSA Thermites Notice.pdf (175.15 KB)\n\n          Issued Date: Friday, September 22, 2023\n\n<<<PAGE 1>>>\n\nExplanation of Classification of Thermite Mixtures\nSUMMARY: PHMSA is publishing this notice to inform interested parties of the process\nPHMSA has previously used and continues to use in the classification of thermite mixtures.\nFOR FURTHER INFORMATION CONTACT: Steven Andrews, Standards and Rulemaking\nDivision, (202) 366-1655, or Lad Falat, Science and Engineering Division, (202) 366-4545,\nPipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation,\n1200 New Jersey Avenue SE, Washington, DC 20590-0001.\nI. Executive Summary\nThe Pipeline and Hazardous Materials Safety Administration (PHMSA) publishes this\nExplanation of Thermite Formulations Classification (Explanation) to inform the regulated\ncommunity how PHMSA has previously reviewed and classified certain thermite formulations.\nThis Explanation shows how PHMSA has temporarily reclassified certain thermite formulations\nas Division 4.1 flammable solids instead of Class 1 explosives while PHMSA completes its\nongoing research project on thermite formulation classification. This notice also explains how\nPHMSA is instructing its approved test labs to evaluate thermite formulations submitted for\nclassification testing.\nDisclaimer: This notice does not have the force and effect of law and is not meant to bind the\npublic in any way. This notice is intended only to provide information to the public regarding\nexisting requirements under the Hazardous Materials Regulations (HMR).\nII. Background\nPHMSA’s Hazardous Materials Regulations (HMR; 49 CFR parts 171-180) prescribe\nrequirements for the transportation in commerce of explosives. 49 CFR § 173.51 states that,\n“unless otherwise provided in the HMR, no person may offer for transportation or transport an\nexplosive, unless it has been tested and classed and approved by the Associate Administrator\n(173.56).” The HMR further explains in section 173.56 that anyone producing a new explosive\nmust have that explosive first tested by a PHMSA-approved explosives test laboratory, where the\nlab would then provide a classification recommendation for the explosive. PHMSA then\nanalyzes this information, considers the recommendation of the test laboratory, and issues the\nproducer a classification and approval to transport that explosive in commerce.\nIn 2016, PHMSA received several questions from PHMSA-approved explosives testing\nlabs about the proper classification of thermite formulations. Thermite formulations are\npyrotechnic substances containing both a metal powder and a metal oxide, but they may also\ninclude additional ingredients to alter performance. When ignited by heat or chemical reaction,\nthey are capable of undergoing a self-sustaining exothermic chemical reaction through\ndecomposition by oxidation-reduction pathway1, and therefore meet the definition of a Class 1\n(explosive) material under § 173.50. Accordingly, all thermite formulations require examination\nand classification by a PHMSA-approved explosives test lab, as required in 49 CFR § 173.56.\n1 Whereas flammable solids are fuels capable of producing an exothermic reaction (releasing energy in the form of\nheat or light) through an oxidative reduction pathway (gaining or losing electrons), the reaction is not self-sustaining\nbecause an external oxidizer source is necessary. Thermite formulations contain both the fuel and oxidizer, and\ntherefore the exothermic reaction produced is self-sustaining.\n1\n\n<<<PAGE 2>>>\n\nIn response to the questions from PHMSA-approved explosives testing labs, PHMSA\ninitiated a research project to assess the proper classification of thermites. Preliminary results of\nUnited Nations (UN) Manual of Test and Criteria (MTC) Test 6(c) (bonfire testing) indicated\nrisk profiles consistent with classification criteria from Division 1.4 and Division 1.3 for various\nthermite formulations.\n2\nTo ensure thermite formulations are properly evaluated and classed, this notice serves to\nexplain how the testing and classification scheme for explosive substances has been applied to\nthermite formulations. As a means of providing limited regulatory relief from HMR\nrequirements applicable to thermite formulations as Class 1 explosive materials, this notice also\nserves to communicate how PHMSA has, pursuant to 49 CFR § 173.56(i), allowed certain\nthermite formulations to be classified as Division 4.1 (flammable solid) materials.\nIII. PHMSA’s Thermite Research\nPHMSA has been actively researching the proper classification of thermite and thermate\nformulations since 2016, when it received questions related to thermite classification from\nmultiple PHMSA-approved explosives test labs. PHMSA reviewed how thermite formulations\nand articles were previously classified, noting the relatively small number of explosive approval\n(EX) applications received for these materials. The work included consultation with all DOT-\nauthorized explosive testing laboratories, other US Federal agencies, and international explosives\nregulators,3 with the aim of identifying potential safety gaps inherent with thermite formulation\ntransport classifications. PHMSA has previously determined that thermite formulations meet the\ndefinition of an explosive in the HMR, and that further oversight is necessary to properly manage\nthe hazards they pose in transportation.4\nGiven that thermite formulations are used in a wide variety of applications, from metal\nwelding to military munitions, PHMSA sought to mitigate the impact of its determination that\nthermite formulations are properly classified as Class 1 explosives while maintaining safety.\nAccordingly, PHMSA initiated additional research to evaluate the classification of thermite\nformulations and the range of their chemical characteristics.\nFollowing initial inquiries into the formulation of thermites in 2016, PHMSA began the\nresearch phase of investigating the characteristics of thermite formulations in 2018 at Southwest\nResearch Institute. This research indicated that thermite formulations exhibit pyrotechnic\nbehavior that ranges from deflagration to detonation and identified important parameters\nincluding grain size, degree of mixing, morphology, and chemical composition. Additionally,\n2 https://unece.org/fileadmin/DAM/trans/danger/publi/manual/Rev7/Manual_Rev7_E.pdf\n3 PHMSA has consulted with many other Federal agencies to share information about the various research PHSMA\nis conducting into thermite characteristics and potential classifications. Among the Federal and international\nagencies consulted are the US Bureau of Alcohol, Tobacco, Firearms and Explosives, the US Department of\nDefense, the US Department of Homeland Security, as well as transport regulators from Canada, the Netherlands,\nSweden, and the United Kingdom.\n4 49 CFR 173.50(a) states that “For the purposes of this subchapter, an explosive means any substance or article,\nincluding a device, which is designed to function by explosion (i.e., an extremely rapid release of gas and heat) or\nwhich, by chemical reaction within itself, is able to function in a similar manner even if not designed to function by\nexplosion, unless the substance or article is otherwise classed under the provisions of this subchapter. The term\nincludes a pyrotechnic substance or article, unless the substance or article is otherwise classed under the provisions\nof this subchapter.” See Interpretation Response # 18-0141 Onepoint4 Ltd. Clarification of HMR Requirements\nApplicable to Classification of Explosives (Interpretation Response | PHMSA (dot.gov)); and Interpretation\nResponse # 20-0015 Onepoint4 Ltd. Follow Up to 18-0141 Clarification of Requirements for Classification of\nExplosives (Interpretation Response | PHMSA (dot.gov)).\n2\n\n<<<PAGE 3>>>\n\nresearchers identified several potential inadequacies with the UN Classification tests for\nexplosives and flammable solids. In particular, the N.1 Test method for readily combustible\nsolids was not designed to account for mixtures that contain their own oxygen balance to support\na self-sustained exothermic reaction. Specifically, the research noted concerns with the ignition\nsource and dramatic performance changes with increased trough width. With these gaps\nidentified, PHMSA sponsored additional research with Safety Management Services to explore\nclassification testing and further characterization of commercial thermites of various\ncompositions, including detonable and non-detonable formulations. The end goal of this research\nproject is to develop an appropriate testing and classification scheme for these materials.\nIV. Policy on Classification of Thermites as Division 4.1 (UN 3178) Flammable Solids\nIn order to provide clarity on how PHMSA has reviewed thermite formulations while its\ncurrent research project is ongoing, PHMSA has decided to use its authority, in accordance with\n49 CFR § 173.56(i), to issue this Explanation of how PHSMA has reviewed specific thermite\nformulations. PHMSA’s past reviews of these thermite formulations has allowed for\nreclassification of thermite formulations from Class 1 explosives to Division 4.1 flammable\nsolids. PHMSA’s review of thermite formulations indicated that:\n1. Thermite formulations meet the definition of an explosive, in accordance with 49\nCFR § 173.50(a). Articles containing thermite formulations are therefore also\nprovisional Class 1 explosive articles.\n2. Manufacturers of thermite formulations must submit their products for testing at\nPHMSA-approved third party explosive laboratories in accordance with 49 CFR\n173.56 before they are offered for transport.\n3. On an interim basis, and concurrent with ongoing thermite characterization research,\na thermite formulation that meets all UN MTC Test Series 2 criteria is eligible to be\nclassified as a Division 4.1 (flammable solid) material (e.g., “UN3178, Flammable\nsolid, inorganic, n.o.s., 4.1, Packing Group II”), upon the determination of the\nAssociate Administrator for Hazardous Materials Safety at PHMSA.\n4. Articles containing thermite formulations, regardless of whether the thermite\nformulation has a Class 1 or Division 4.1 designation, are not eligible for\nreclassification under this policy.\n5. Articles containing thermite formulations are required to meet Class 1 exclusion\ncriteria incorporated by reference from the UN Model Regulations Section 2.1.3.6 to\nbe classified as not Class 1 explosives.\nThis Explanation is intended to provide the procedures and review that has previously led\nto PHMSA approving the reclassification of certain thermite formulations as Division 4.1\nexplosives until PHMSA has finished the research project it is currently undertaking to\ndetermine the proper testing and criteria required to address the transportation risk of thermite\nformulations more accurately. PHMSA encourages applicants seeking reclassification to\nDivision 4.1 to employ this process if they believe such thermite formulations demonstrate\nsimilar criteria listed above. Lastly, the Explanation of prior reclassification processes described\nabove is limited to thermite formulations. PHMSA emphasizes that articles containing thermite\nformulations require separate evaluation and approval under 49 CFR § 173.56, even if the\nthermite formulations contained within have been classified as “UN3178, Flammable solid,\ninorganic, n.o.s., 4.1, Packing Group II” pursuant to this policy.\n3\n\n<<<PAGE 4>>>\n\nV. Future Actions\nPHMSA continues to conduct research on thermite formulations and their proper\nclassification. Based on the findings of PHMSA’s ongoing research, PHMSA may take action,\nincluding rulemaking, to better classify thermites for transportation.\n4","truncated":false,"body_characters":11773}