Explosive zones

Setter,. G Chemical Kinetics of the Cordite Explosion Zone, 10th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA, 1965, pp. 1405-1411. 

Cordite Explosion Zone, Chemical Kinetics of. It was discussed by J.G. Softer in lOthSymp-Combstn(1965), 1405-11... 

Flammable substance Explosion hazard Explosion zone Example... 

Besides other more or less general obligations, i. e. taking necessary, preferred technical measures and providing supervision to protect the safety and health of workers, the employer has to draw up an explosion protection document. This obligation is independent of the number of employees, firstly, it contains information on the risks that have been determined and assessed and what measures have been taken. Secondly, it requires the classification of places having an explosion risk into zones. In annex 1, explosive zones are defined (see Table 6.3). 

European Framework Directive 89/391/EEC 1165 Table 6.3 Explosive zones according to annex I of EU directive 1999/92/EC. 

Suitable pumps for active sampling can be selected from a wide range of commercially available standardized pumps, even pumps that meet the additional requirements for measurements in explosive zones. A hose serves as the connection between the tube holder and the pump. Holders of various sizes are available depending on the size of the tube (see Fig. 6.66a). Most tube types contain 150 or 600 mg of adsorptive material. 

Because of inertia, after the explosion shock waves leave the explosion zone, the earth continues to leave from the explosive places and lasts some time. It induces the negative pressure of explosion zone, and the transportation of sparse waves. 

The shock waves are very weak outside of the crack zone. These shock waves could not induce the deconstruction of rocks and soil, but only the vibration of particles. And the amplitude of vibration are smaller if the particles are further from explosion center, finally it decays into sound waves. For brittle soils, explosion zone is surrounded by compressive zone, crack zone, and vibration/oscillation zone. For cohesive soils, the compressive zone is the closest to explosion zone. The sizes of dilferent zones are related with the properties of explosives, the explosive mass, the packing structure, and the soil properties. 

Descriptive safety. This type of safety is used in situations when it is not possible to provide safety by unconditional or conditional means (i.e., the above two means). Descriptive safety in regard to operation, mounting, replacement, transport, connection, and maintenance may simply be statements such as "Handle with care," "This side up," and "Not for explosive zones."... 

The second indication is a faint smoke-like cloudiness in the zone of the tube which is being heated by the Bunsen this is readily visible as the interior of the tube is normally quite clear and bright. This is a later stage of development of the flash-back than the rise of pressure, already mentioned, and should be counteracted by moving the Bunsen immediately to the point of the combustion tube where heating was commenced. In either case the Bunsen should then be moved slowly forwards as before. A flash-back is attended by the deposition of carbon particles, carried back by the explosion wave, on the cold walls of the tube. Care should be taken that these are completely burnt off as the Bunsen is slowly moved forward again. 

The hazard posed can be limited by maintaining a zone free of people and property around a storage area of explosive material. The minimum radius of the zone depends on the type and quantity of explosive, the extent and type of barrica ding, and the magnitude of loss that would be encountered if an explosive incident occurred. The maximum distance to which hazardous explosive effects propagate depends on the blast overpressure created, which as a first approximation is a function of the cube root of the explosive weight, W. This is termed the quantity distance and is defined as... 

Table 1. Measured Explosion-Cladding Parameters and Bond-Zone Characteristics ...

In commercial practice, powdered explosives on an ammonium nitrate basis are used in most cases. Typical detonation velocities are between 1800 and 3500 m/s depending on the metal system to be bonded. The lower detonation velocity range is preferred for many metal systems in order to minimize the quantity of solidified melt associated with the bond-zone waves (12). In addition, subsonic detonation velocity explosives are required for the parallel cladding technique in order to avoid attached shock waves in the coUision region, which preclude formation of a good bond. 

For Hquid fuels, ignition delay times are of the order 50 ]ls at 700 K and 10 ]ls at 800 K. At low temperatures most of the ignition delay is the result of slow, free-radical reactions, and a distinction between the initiation and explosion periods within the ignition delay time can be made. With increasing ignition temperature for a given mixture, these times become comparable and at temperatures as high as 1500 K, both times may be of the order of lO " s. Consequently, the reaction zone in the flame of a mixture is observed to be one continuous event (12—14). 

Catastrophic Incident An incident involving a major uncontrolled emission, fire or explosion that causes significant damage, injuries and/or fatalities onsite and have an outcome effect zone that extends into the surrounding community. 

This is a location safer than Zone I with a likelihood of concentration of explosive gases, chemical vapour or volatile liquids during processing, storage or handling. This would become a fire hazard only under abnormal conditions, such as a leakage or a burst of joints or pipelines etc. Such a condition may exist only for a short period. A standard motor with additional features, as di.scussed below, may also be safe for such locations. A non-sparking type. Ex. n , or an increased safety motor, type Ex. e , may also be chosen for such locations. 

This test is also applicable to LT capticitor units only. The basic objective is to establish that the failure of a unit is within a safe zone ind is not accompanied by the risk of a violent explosion or fire. 

Dinitrotoluene [121-14-2] M 182.1, m 70.5-71.0 . Crystd from acetone, isopropanol or MeOH. Dried under vacuum over H2SO4. Purified by zone melting. Could be EXPLOSIVE when dry. 

Zone 0 Area in which an explosive gas-air mixture is continuously present, or present for long periods... 

Evaluate air, soil, and water sampling results. Consider the distanees needed to prevent an explosion or fire from aflfeeting personnel outside the exelusion zone. 

Employers, at a minimum, must have an emergency action plan that will facilitate the prompt evacuation of employees when there is an unwanted release of a highly hazardous chemical. This means that the employer s plan will be activated by an alarm system to alert employees when to evacuate, and that employees who are physically impaired will have the necessary support and assistance to get them to a safe zone. The intent of these requirements is to alert and move employees quickly to a safe zone. The use of process control centers or buildings as safe areas is discouraged. Recent catastrophes indicate that lives are lost in these structures because of their location and because they are not necessarily designed to withstand over-pressures from shock waves resulting from explosions in the process area. 

Requirements on parameters that may influence the building and its performance and target levels to be determined for occupational zones and non-occupational zones are the following temperature, humidity, air velocity, contaminant concentration (particles, gases), odors, biocontamination (in air and on surfaces), fire/explosion risk, noise, vibrations, radiation (IR, UV, radioactive, etc.), sunshine, loading on floors, and pressure differences (in,side-outside and between rooms). 

High pressure explosive loading was carried out on both z- and y-cut crystals at pressures between about 25 and 60 GPa ([83S01, 77S01]). The z-cut crystals responded in the plus-x orientation with current pulse wave shapes as predicted by the three-zone model. Nevertheless, limited experiments in the minus-z orientation of lithium niobate do not show the positive currents expected from the three-zone model. 

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. 

The combustion-flow interactions should be central in the computation of combustion-generated flow fields. This interaction is fundamentally multidimensional, and can only be computed by the most sophisticated numerical methods. A simpler approach is only possible if the concept of a gas explosion is drastically simplified. The consequence is that the fundamental mechanism of blast generation, the combustion-flow interaction, cannot be modeled with the simplified approach. In this case flame propagation must be formalized as a heat-addition zone that propagates at some prescribed speed. 

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