Explosive classification system

DOT and GHS explosive classification system recognizes that some kinds of explosives are not compatible with others. During transport or storage, placing incompatible explosives together increases their hazard level. In order to address this issue, DOT identifies 35 compatibility groups and charts the combination of the hazard divisions and compatibility groups. 

The pneumatic classification system should be designed to handle ha2ardous dust (28). A ha2ardous dust is one which, when finely divided and suspended in air in the proper concentration, bums, produces violent explosions, or is sufficiently toxic to be injurious to personnel health (see Air pollution control methods Powders, handling). At the least, almost any dust can be irritating to personnel because of inhalation or skin or eye contact. Fully oxidi2ed and hydrated materials are generally considered safe. 

Richard P. Gen on i is a principal engineer with Duratek Federal Services Northwest Operations in Richland, Washington. Genoni maintains the Explosive Classification Tracking System for the Department of Energy s National Transportation Program and reviews all new explosive applications before submittal to the Department of Transportation. He also maintains Department of Energy Interim Hazard Classifications in accordance with the Department of Defense Ammunition and Hazard Classification Procedures, TB 700-2. 

Existing and proposed methods of evaluating transportation hazards of organic peroxides exposed to impact, explosive shock or thermal singe stimuli were reviewed, and a hazard classification system proposed [1]. Commercial 2-butanone peroxide ( MEK peroxide ) as a 40% solution in dimethyl phthalate was previously... 

There are three main categories of hazards namely, fire and explosion hazards, health hazards and environmental hazards. Different evaluation methods exist for each category. Not being experts in every evaluation method, the authors will refer only to the evaluation methods which are generally used. Evaluation methods according to the U.N. classification system, which covers a wide range of hazardous materials, are explained. 

The explosion classification test is usually conducted in a modified Hartmann tube apparatus. The apparatus consists of a 1.2 L vertical tube mounted onto a dust dispersion system. Dust samples of various quantities are dispersed in the tube and attempts are made to ignite the resulting dust cloud by a 10 J electrical arc ignition source. If the material fails to ignite in the modified Hartmann tube apparatus, the testing is continued in the 20 L sphere apparatus. Dust samples of various quantities are dispersed inside the sphere and are exposed to a 10,0001 ignition source. 

The NFPA 43B classification system is used to specify or determine the need for certain requirements that can prevent or mitigate the effects of fire and explosion. These requirements include allowable quantities, automatic sprinkler protection, the need to store certain organic peroxide formulations in a refrigerator or freezer, storage arrangement, and building construction features. 

The NFPA 430 classification system, the fire hazard behavior of liquid and solid oxidizers that can increase the burning rate or cause spontaneous ignition of a combustible material. Also, the reactivity behavior of liquid and solid oxidizers includes those that can undergo a self-sustained decomposition or an explosive reaction. The definitions used to define liquid and solid oxidizer classes can be subject to interpretation. The NFPA 430 classification system is based on the Technical Committee s evaluation of available scientific and technical data, actual experience, and it s considered opinion. A listing of typical liquid and solid oxidizers by class can be found in the Appendix of NFPA 430. The oxidizers listed are assumed to be pure materials unless otherwise specified. 

Many organizations in the U.S. adopted explosive classifications held by the U.S. Department of Transportation for many years prior to using the GHS classifications. The old classification system used three classes Class A, Class B, and Class C. DOT offers a conversion between the old... 

Zone systems are followed in area classification by ATEX and lEC, and even NFPA has included zone systems of classification in their standard. The zone classification system probably has the edge over the class/division system because many consider the zone classification system to be more flexible and safer in hazardous locations. However, zone systems do not take care of the consequence of release. In case the consequences are important, as per the advice of the HSE.UK, it is better to go for a more conservative equipment selection. Although not officially accepted yet, various sources have tried to place time limits on these zones. The most commonly used values are as shown in Table X/3.3.2-l based on probability and duration of explosive atmosphere. 

Classification of Explosives A system of classifiying the hazard level of shipments involving explosive articles. In the United States, the classifcation system changed in January 1991, although it is still referenced in State and local laws. The following may be used to compare old and new hazard class names ... 

The European philosophy on area classification varies from that of the United. States and Canada. Specifically, in Europe and most other inter national areas, the Zone concept is utilized. An area in which an expio sive gas-air mixture is continuously present, or present for long perioiK of time, is referred to as Zone 0. The vapor space of a closed, but vented, process vessel or storage tank is an example. An area in which an explosive gas-air mixture is likely to occur in normal operations is designated Zone 1. An area in which an explosive gas-air mixture is less likely to occur, and if it does occur will exist only for a short time, is designated Zone 2. Zone 0 and Zone 1 correspond to Division 1 in the U.S. and Canada System. Zone 2 is equivalent to Division 2. 

In Division 1 areas, motors and generators must be either explosion-proof or approv ed for the classification by meeting specific requirements for a special ventilation system, inert gas-filled construction, or a special submerged unit. Although explosion-proof motors are expensive, they normally are available. Explosion-proof generators normally are not available. 

Ion mobility spectrometry (IMS) is an instrumental method where sample vapors are ionized and gaseous ions derived from a sample are characterized for speed of movement as a swarm in an electric field [1], The steps for both ion formation and ion characterization occur in most analytical mobility spectrometers at ambient pressure in a purified air atmosphere, and one attraction of this method is the simplicity of instrumentation without vacuum systems as found in mass spectrometers. Another attraction with this method is the chemical information gleaned from an IMS measurement including quantitative information, often with low limits of detection [2 1], and structural information or classification by chemical family [5,6], Much of the value with a mobility spectrometer is the selectivity of response that is associated with gas-phase chemical reactions in air at ambient pressure where substance can be preferentially ionized and detected while matrix interferences can be eliminated or suppressed. In 2004, over 20000 IMS-based analyzers such as those shown in Fig. 1 are placed at airports and other sensitive locations worldwide as commercially available instruments for the determination of explosives at trace concentration [7],... 

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