Safety with explosives

Grenich, A.F., andTolle, F.F., Electrostatic Safety with Explosion Suppressant Foams, Air Force Wright Aeronautical Laboratories Report AFWAL-TR-83-2015, March 1983. 

Wide monographs recently appeared on problems of hazards and safety with explosives (14,15]. 

G.F. Kinney and A.D. Wirath from the US Naval Weapons Research Centre, looking at safety with explosives in 1976, gave us some safety maxims ... 

Annual Proceedings of the Safety Seminars, Dept, of Defense, Explosive Safety Board, Washington, D.C. International symposia on explosives and closely related subjects are excellent sources of information, ie, international symposia on detonation symposia on combustion symposia on chemical problems connected with the stabiUty of explosives international pyrotechnics seminars symposia on compatibiUty of plastics and other materials with explosives, propellants, and pyrotechnics, and processing of explosives, propellants, and ingredients and symposia on explosives and pyrotechnics Mineral Industy Surveys, U.S. Bureau of Mines, Pittsburgh, Pa. Periodic pubhcations dedicated primarily to explosive studies in Propellants and Explosives Journal of Ha yardous Materials, and apparent consumption of industrial explosives and blasting agents in the United States. 

The safety valves of other cars operated, thereby releasing more LPG. At 7 33 a m., the twenty-seventh car ruptured with explosive force. Four fragments were hurled in different directions (Figure 2.21). The east end of the car dug a crater in the track structure, and was then hurled about 180 m (600 ft) eastward. The west end of the car was hurled in a southwesterly direction for a total distance of about 90 m (300 ft). This section struck and collapsed the roof of a gasoline service station. Two other sizable portions of the tank were hurled in a southwesterly direction and came to rest at points 180 m (600 ft) and 230 m (750 ft) from the tank. 

Originally, equipment was made largely from wood or gun-metal and often rubber lined. These materials give the lowest hazards from friction with explosives. Nowadays, improved standards of engineering and of design have made it possible to employ stainless steel and plastics in the construction of explosive machinery with considerable increase in mechanical efficiency. In this way not only can processes be carried out more rapidly, but the quantity of explosive present at any time is reduced, with consequent increase in overall safety. 

Throughout the world explosives manufacturers have amassed many years of experience and have spent many millions of pounds to ensure as far as possible the safety of those working for them with explosives. Even so, accidents still occur with distressing injury and loss of life. Where these companies cannot succeed the amateur would be foolish to try. 

The Explosives Environment. The Army Materiel Command (AMC), which has the primary responsiblity for manufacture and storage of explosives for the Department of Defense, clarified its definition of the type of hazardous location involved with explosives, propellants, and pyrotechnics in its most recently revised safety manual (4). When the only consideration for hazardous environment is the presence of explosive material, it recommends that the environment be classified as Class II, Group G, with the appropriate division based on the probability of the hazardous element being present in the environment. It further states that consideration must be given to vapors which might be present or to the presence of metallic dust. 

The pot temperature should not be allowed to rise above 70° (the submitters used a hot-water bath at 75°), as a fume-off which may proceed with explosive violence is likely to occur. A nitrogen bubbler may be used to eliminate bumping. The distillation should be carried out behind a safety shield. 

Apart from the safety issues normally associated with any chemistry laboratory, there are a number of specific issues associated with explosives and bomb scene examination. An obvious point is the hazards associated with handling and storage of explosives most countries have strict regulations covering this area, and compliance is mandatory. This is not a trivial matter as it is common to receive unknown and unidentified materials, or items that have been subject to physical abuse. 

In specific instances, the application of fogging outstripped the acquisition of prerequisite basic information, not o y in the fleld of biology (entomology) but also in chemistry, physics, and the broad, ill-defined fields which embrace the safety factors—safety to man and animals, safety to vegetation, and safety with respect to fire and explosion hazards. Research in all these fields is under way and is catching up with, or has already caught up with, the practical applications. 

Safety Goggles or Glasses The use of shatterproof safety goggles or spectacles is recommended in order to protect the eyes while working with explosives. Contact lenses are not considered suitable for eye protection. 

Nitroethanol prepared by the formaldehyde-nitromethane method should not be distilled without use of diphenyl ether as a heat-dispersing agent. The residue, consisting of di- and tricondensation products of formaldehyde with nitromethane, when hot and concentrated, and particularly when the vacuum is broken and air is let in on the hot distillation residue, is very likely to undergo a flash detonation, or at least a fume-off which may proceed with explosive violence. Use of diphenyl ether is a wise safety precaution in the distillation of 2-nitroethanol made by other methods as well. 

The increasing use of explosives in mining greatly increased coal output but numerous gas explosions occurred in mines where blackpowder was used. The development of nitroglycerine and more modern explosive compositions did not eliminate this hazard. As thejndustry developed and the demand for coal increased the safety of explosives used in mines become-so urgent and important a problem that in the nineteenth century many countries set up special commissions charged with its detailed analysis. 

For coal work, especially in gassy and dusty mines a safety perchlorate explosive with the composition tabulated below (Table 98) was manufactured in Germany. 

The classical method of firing explosives in a testing gallery with the charge inside the mortar does not present a true picture of the safety of explosives towards coal-dust since the explosives commonly used fail to ignite coal-dust under such conditions. The angle shot mortar (Fig. 138) is therefore sometimes used as an unofficial auxiliary test. 

The greatest advantage of Cardox and Hydrox methods lies in their safety towards methane and coal-dust. They also contribute to the getting of coal in large pieces. In comparison with explosives, however, shotfiring with Cardox and Hydrox devices is more expensive. 

CAUTIONARY NOTE The nitration of phthalic anhydride has been reported to proceed with explosive violence.60 The reaction may be carried out with safety on the scale adopted here provided that strict attention to detail is paid to the rate of addition of the acid and to the control of the temperature. A modified procedure for use in large-scale nitration has been published.606... 

In order to achieve passive safety with reactive material, the radius of the reactor tube is designed to be small to avoid any thermal explosion inside the tube. Using the Frank-Kamenetskii approach (see Chapter 13), the radius remains below the critical radius. Thus, even assuming a purely conductive heat transfer mechanism, corresponding to a worst case, no instable temperature profile can develop inside the reaction mass. The reactor can be shut down and restarted safely. 

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