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SEP 2017

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www.rockproducts.com ROCK products • September 2017 • 25 While these used oils can be used in emulsion formulations, emulsion matrix is typically made in a plant setting and would need to be used by explosive companies – not a mine. For this reason, we will center this discussion primarily on ANFO, noting that similar principles would apply to emulsions with proper percentages. Many explosive companies use a used or recycled oil in their emulsions, with some companies using entirely used oil to sensitize their emulsions. Ammonium Nitrate and Fuel Oil (ANFO) typically has around 6 percent oil with an optimal balance of 5.7 percent oil to 94.3 percent ammonium nitrate. Other substances may be present in small quantities to achieve proper prill properties. Two methods exist then for adding used oil to the ANFO. The first method would be to use the entire amount of oil as a used oil. This can work at larger sites that produce enough oil for complete sensitization, but will require more careful monitoring and testing. The second method would be to use a percent of the total oil in the explosive as used oil. This way the used oil is diluted and any impurities are also diluted, leading to more consistently meeting the used oil standards. It is important to note, with proper preventative maintenance schedules most operations will not use oil in the equip- ment long enough to have oil that consistently fails to meet required standards. The major risks associated with used oil in ANFO is in blasting safety and environmental concerns. The first of these risks, blasting safety, will be considered in extreme conditions such as very low ambient temperatures and very high ambient tem- peratures. These safety issues include the ability to change the ANFO to a cap-sensitive state and in the storage of these used oil ANFOs (UOANFO) in contact with different metals. One such study (Ruhe & Bajpayee) observed the properties that different oil mixtures would exhibit in contact with different metals at high ambient temperatures. There tests included 100 percent recycled "used" oil mixtures, mixes of used oil and other petroleum products, synthetic oils, and used oils mixed with graphite. Graphite is sometimes used as a motor oil additive and can cause sensitivity issues. All these mixtures proved to be stable at 140 F (60 C) in steel, stainless steel, and galvanized steel contained. At 176 F (80 C) all samples, besides that containing 1 percent graphite, had limited reactions with galvanized steel. None of these samples proved to be cap sensitize at 75 F (24 C). In addition, small hazards can arise at very low temperatures due to increase in used oil viscosity. Tests have been run (Ruhe & Bajpayee, 1996) with mixes of diesel No. 1 and No. 2 and used oils to quantify these risks at these low temperatures. Blends of No. 2 Diesel and Used Oil in a 50 percent to 50 percent quantity were made down to 0 F (-18 C) and the same blend with No. 1 Diesel was made down to -20 F (-29 C) with minimal changes in detonation velocity, compared to a ANFO made with 100 percent No. 1 Diesel. All tests run at low ambient temperatures, some as low as -40 F (-40 C) have proved that USANFO present minimal risks in blasting safety, as long as proper guidelines are followed for quality of used oil. The oil blends that have a greater percentage used oil than diesel will have slightly lower velocities of detonation. Regulatory Standards The Mine Safety and Health Administration (MSHA) along with the Bureau of Alcohol, Firearms, and Tobacco (ATF) reg- ulate the use of explosives at mines. The ATF has almost no mention of used oil with ammonium nitrate explosives, and when asked for comment responded that "in general, ATF does not regulate the components used to manufacture explosive materials." Therefore, if the proper ATF manufacturing per- mits are held, a USANFO is not viewed differently by the ATF. MSHA does regulate the components to make ANFO and has specific standards (30CFR Part 56.6309) which specifies the minimum flash point of oils in explosives (125 F) and that waste oils shall not be used to prepare ammonium nitrate- fuel oil (ANFO). MSHA has not responded as of this writing to further clarification. However, in response to frequent requests for exemptions from this rule, MSHA released the "MSHA Generic Petition" on Sept. 1, 1994, to provide a simple method for mines to legally begin this process. This standard addresses the use, system and type of used oils allowed for USANFO. Two of the major topics included in the basis of this is that only petroleum-based lubrication oils recycled from equipment can be used and a maximum of 10 percent of 90W oil can be used in USANFO. Additional regulations require testing of the used oil for Arse- nic, Cadmium, Chromium, Lead, Halogens, and Flash Point before mixing with fuel oils. The chemical testing is primarily to ensure environmental compliance (non-hazardous waste requirements) which are derived in 40 CFR 279.11. Flash Point testing must follow either closed-cup ASTM D3941-90 tests or open-cup ASTM D1310-86 tests. MSHA Oils that have then been previously used around the site, particularly in heavy equipment, can be used in explosive products.

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