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ITA Hopes to Spark Additional Studies On the Dangers of Combustible Metals
By Michael C. Gabriele
Several times during his live Dec. 7th Zoom presentation on the potential hazards of combustible metals, Robert Lee, the chair of the International Titanium Association’s (ITA) Safety Education Committee, made reference a March 2021 U.S. Department of Transportation (DOT) report as a much-need platform to address the topic of combustible metals in the titanium industry and beyond. Lee hoped that this report, which he described as the most comprehensive study to date on the flammability of metals, would generate positive momentum for additional conversations to enhance industrial safety measures.
Lee praised the DOT report, compiled by the Fire and Materials Research Laboratory LLC, Livonia, MI, and issued on March 31, 2021. In essence, he described it as a call to action for ITA members and other trade associations to begin a more thorough, detailed investigation on causes, prevention practices and solutions associated with the dangers of combustible metals. The report is now undergoing a review by the titanium industry and other metals groups.
“The most important point is that this report is the first comprehensive examination of combustible metals,” Lee said. “The ITA helped initiate it with the preliminary investigation, but more work needs to be done. As a group, the titanium industry must decide the best way to push the program forward to provide useful and practical information. It may well be that we should put together a group from industry to undertake a more in-depth evaluation.” As such, several titanium executives who tuned into the Zoom broadcast responded to Lee’s call for volunteers. Some even offered to share data on this topic gathered by their own companies.
Part of the reason to form an ITA committee to study the issue is to be certain that all aspects of the safe handling titanium for all areas are adequately addressed as various members each have different levels of concern and expert knowledge, according to Lee. “What is important for transportation is different than considerations for recycling, disposition, manufacturing and use of titanium, especially now with much wider use of titanium with many different processes. No longer is the primarily use by a few engine and plane manufacturers and few manufacturers of the basic metal.”
Educating Two Audiences
Lee, who also serves as president of Accushape Inc., Albany, OR, offered a candid assessment of his own responsibilities. “When I became the chair of the ITA Safety Education Committee, it was my opinion that I had to emphasize education. And I knew I had two audiences: our members (the ITA) and regulatory agencies.” He said he also understood that the titanium industry needed to do its own homework in order to encourage regulatory agencies to create more accurate, up-to-date regulations.
Elizabeth C. Buc, Ph.D, PE, of the Fire and Materials Research Laboratory, did the independent research to create the DOT report. “When we started this program, I and the ITA board insisted that any study must be funded, managed and conducted by someone independent of ITA to avoid any implication that this was an effort by the titanium industry to carve out and exemption for titanium,” Lee explained. “The Robert Lee, the chair of the International Titanium Association’s Safety Education Committee, and the president investigation must deal with all metals and why they are of Accushape Inc. different than the general term now used ‘flammable solid’. Metals are different than organic solids. After the basic science is created, then it would be logical, and in fact an obligation, of the titanium industry as well as other metals industries to address the issues using the expertise of the each industry.”
Robert Lee, the chair of the International Titanium Association’s Safety Education Committee, and the president of Accushape Inc.
As mentioned above, the ITA funded an initial study to create basic test information to demonstrate concerns for titanium and other metals in particulate form. This study included potential physical hazards such as thermite reactions, pyrophoric reactions with air, fires, flash fires, dust explosions, and the evolution of flammable gases. The Safety Education Committee efforts identified that industry was being subjected by multiple agencies including UN test regulations, the Environmental Protection Agency, the National Fire Protection Association, Qunicy, MA, to many different tests and methods for identification of the hazards creating multiple and sometime conflicting requirements. For example, Lee said the UN test regulations deal only with organic solids, not metals.
The ITA shared its initial study with the DOT, which resulted in the report conducted by Fire and Materials Research Laboratory. Lee noted that the potential implementation of the recommendations in the DOT report is important to ITA members. He said ITA members need to understand how their operations may be affected by these recommendations and what more needs to be investigated. As a result, the Dec. 7 Zoom program outlined these concerns, with additional Zoom broadcasts slated for 2022 to continue the discussion.
Concern Over Static Sparks as an Ignition Source
While staged videotaped flammability tests on various forms of titanium provide some useful data, Lee said those test focus on external sources of ignition. (“Most people don’t walk around with a propane torch,” Lee quipped during the Zoom program.) A study of internal combustion dangers, such as the ignition caused by the spark from a static charge in titanium dust collectors or the storage of titanium powders, would be far more relevant for ITA members. He also raised the issue of safety measures needed for the transport of titanium materials.
These two charts show how different metals are ignited and have different burn rates.
This chart shows how different titanium types and size of titanium ignite and burn.
Another hang-up in the ongoing conversation about titanium safety issues involves possible legal liability penalties for an organization (like the ITA) in publishing “best practices.” As mentioned above, published statements or guidelines from an industry group may have the unintended potential for exposure to lawsuits. Lee stated clearly that the ITA “doesn’t engage in publishing regulator best practices.” He said his answer to this dilemma would be to deal with combustibility issues through testing—relying on scientific knowledge and presenting the statistical results from technical studies, rather than expressing the opinions of an industry group.
Finding safe, effective methods to extinguish industrial titanium fires so far have proven to be elusive, Lee confessed. This is an especially critical issue when it comes to educating municipal fire departments and hazmat teams in the event that they’re forced to confront a titanium blaze. Conventional methods used to control non-metal fires, such as water, sand or flame-retardant chemicals, will have an adverse reaction and only further intensify metal combustion.
— Robert Lee, chair of the ITA’s Safety Education Committee
This chart summarizes how various metals are now classified for transportation purposes and how they might be classified using the new data. The chart illustrates the large differences in burning rates. The information is very useful, but may not be applicable to all manufacturing conditions.
Background Information
Flammability issues are especially important to the titanium industry since titanium in its various forms is more likely to present combustion hazards. The most dangerous forms of a reactive/combustible metal, like titanium, are dust, powders, and “swarf.” Swarf is a term used to describe fine scrap. Swarf and dust and powders represent major fire hazards because they are susceptible to ignition, if discarded in a landfill, swarf, over time, can create explosion hazards.
The principal difference between the definitions of “combustible” and “explosible” involves the size of metal particles. Explosible materials typically have higher surface area or smaller particle size such as fine powders, nanopowders and dust. Fires involving metals are different and often more hazardous than fires involving ordinary combustible fuels. Metal fires typically burn hotter and are difficult, if not impossible, to suppress. However, large titanium components such as castings, forgings and ingots, as well as coarse chips or turnings, generally are not combustible under ordinary conditions.
Because the hazards of combustible metals depend strongly on physical properties including composition (pure versus mixtures), form, moisture content and passivation, characterization is requisite for meaningful results and evaluation of hazard potential. Full characterization of metals and alloys for testing includes composition, description of the material including uniform appearance or heterogeneity (e.g., mixture), particle morphology, particle size distribution, polydispersity of dusts, moisture content and resistivity. Determining whether a particulate metal or alloy is combustible is important for evaluating hazard potential during transportation, use, handling, processing, storage, recycling, emergency response and waste management.
(Editor’s note: The four charts in this article come from the March 2021 U.S. Department of Transportation report compiled by the Fire and Materials Research Laboratory LLC, Livonia, MI. ITA members looking to take part in further conversations on the many challenges associated metal combustion can contact Lee directly via email: accushapeinc@ msn.com)
(The following text comes from excerpts in the March 31, 78-page 2021 DOT report “Improved Reaction-To-Fire Test for Particulate Metals and Method to Evaluate the Efficacy and Limitations of Liquid Suppressant Agents for Metals Fires and Waste Hazard Reduction,” Broad Agency Announcement [BAA] Project No. 78, by Elizabeth C. Buc, Ph.D, PE. As mentioned in the main article, the Fire and Materials Research Laboratory compiled the report. The ITA is distributing a PDF version of the report to association members.)
The DOT project’s scope was to technically review the test method for flammable solids for metals and metal alloys, identify gaps and limitations in the test method, and recommend improvements that consider different forms and compositions including variations in moisture content, admixtures, and contaminants (e.g., cutting fluids). The general test procedure is widely used and easy to execute.
The proposed screening and burn rate tests use a stronger ignition source (propane/oxygen torch flame) to reduce the occurrence of false negatives possible with a weaker ignition source. The burn rate test includes an optional spark ignition source to identify readily ignitable metal and metal alloys; these would likewise ignite upon momentary application of a butane torch flame.
An added screening test for negative, as-received metals after sieving and/or drying also would eliminate false negatives due to contaminants; the faster burning rate metal is classified. The burning duration of 20 minutes or less for the screening test should capture metal and metal alloys that propagate burning away from the ignition source.
The UN’s “Dangerous Goods Tests and Criteria Test N.1: Test Method for Flammable Solids” applies to metal and non-metal substances. Metal and metal alloy fires are different from non-metal fires in that they typically burn at higher temperatures and are difficult to extinguish. Like non-metals, finely divided, high surface area metals can ignite readily, burn rapidly, and have a greater propensity for flash fire and/or explosion if dispersed in air.
Titanium metal can have different alloy compositions and forms, both in large quantities. The raw form of titanium is rutile (TiO2), which is chemically treated and reduced to titanium metal in the form of irregular sponge. Titanium metal is also reclaimed and/or recycled. Reclamation can involve sorting by chemistry and size.
Large and small particulate is subject to washing, drying, and comingling for melting in industrial furnaces then cast into ingots of specific chemistry. Scrap metal can range in size from large sheets after stamping to larger cuttings to fines and turnings. The resulting ingots are further processed by various machining operations into round and other solid stock for traditional manufacturing. Manufacturing methods including powder metallurgy and additive manufacturing will use powder form titanium and titanium alloy starting materials.
