Barriers explosive

Given as shock pressure in the barrier at the barrier/expl interface and converted by the writer into shock pressure in the expl at the barrier/explosive interface using the expl Hugoniot data of Refs 32 24 (a)Probably somewhat coarser particles than those in the corresponding LSGT and SSGT data... 

Mechanical barriers Explosion propagation is prevented by some type of physical barrier. Mechanical barriers could include rotary valves that have a sufficient number of blades to form a barrier, screw feeders that are modified to continuously contain a plug of material, and fast acting shutoff valves. 

Sun Jianhua, The porous-leak-pressure barrier explosion of the automatic air-door that is used in the mine, China Mining Magazine, 2011.20(3) 105-106 China Coal Society, 2008, 33(8) 903-907(In Chinese). 

Specially designed impervious suits, eg. Level A suits, are utili2ed by workers handling some rocket fuels and other highly ha2ardous compounds (see Explosives and propellants). Barrier creams are much less effective than gloves for preventing skin contact. 

The mechanical flame barriers, which are used for explosion isolation of flammable gas and solvent vapor explosions, are veiy susceptible to the action of dirt and, with one exception, are thus not suitable for dust-canying pipelines. The exception involves the rotaiy valve (see Fig. 26-45), which is based on the flame-quenching effect through narrow gaps and is mainly used at product charging and discharging points. 

Explosion isolation can also be effected by rapid action barrier valves. At present, they can be arranged only in horizontal pipehnes and are suitable, in general, only for streams with a small amount of dust. Such valves are thus frequently used to protect ventilation lines. As a certain explosion overpressure is necessaiy to close such valves, a distinction is made between self-actuated and externally actuated barrier valves (Fig. 26-46). 

Particularly reasonably priced explosion isolation of systems involves the use of a relief pipe with which the flow direction can be diverted by 180°. It prevents flame jet ignition with precompression in constructionally protected equipment. If suction is present, explosion propagation can occur. To prevent this, the use of an additional extin-gui ing barrier or a rapid-action gate valve is necessary. If a diverter is installed where positive pressure feed is given, then the diverter is, in general, safe against an explosion propagation. 

But probably the most serious barrier has been the paralysis that overtakes the inexperienced mind when it is faced with an explosion. This prevents many from recognizing an explosion as the orderly process it is. Like any orderly process, an explosive shock can be investigated, its effects recorded, understood, and used. The rapidity and violence of an explosion do not vitiate Newton s laws, nor those of thermodynamics, chemistry, or quantum mechanics. They do, however, force matter into new states quite different from those we customarily deal with. These provide stringent tests for some of our favorite assumptions about matter s bulk properties. 

Proper applicadon of a flame arrester can help avoid catastrophic fire and explosion losses by providing a flame barrier between at-risk equipment and anticipated ignition sources. 

The last problem of this series concerns femtosecond laser ablation from gold nanoparticles [87]. In this process, solid material transforms into a volatile phase initiated by rapid deposition of energy. This ablation is nonthermal in nature. Material ejection is induced by the enhancement of the electric field close to the curved nanoparticle surface. This ablation is achievable for laser excitation powers far below the onset of general catastrophic material deterioration, such as plasma formation or laser-induced explosive boiling. Anisotropy in the ablation pattern was observed. It coincides with a reduction of the surface barrier from water vaporization and particle melting. This effect limits any high-power manipulation of nanostructured surfaces such as surface-enhanced Raman measurements or plasmonics with femtosecond pulses. 

The packing of explosives is a matter of importance if they are to reach the user in satisfactory condition. The original wooden boxes have largely been replaced by more efficient fibreboard cases, although certain authorities still insist on the former. In either case, provision of an adequate waterproof barrier is important to prevent moisture causing... 

Commercially, lead azide is usually manufactured by precipitation in the presence of dextrine, which considerably modifies the crystalline nature of the product. The procedure adopted is to add a solution of dextrine to the reaction vessel, often with a proportion of the lead nitrate or lead acetate required in the reaction. The bulk solutions of lead nitrate and of sodium azide are, for safety reasons, usually in vessels on the opposite sides of a blast barrier. They are run into the reaction vessel at a controlled rate, the whole process being conducted remotely under conditions of safety for the operator. When precipitation is complete, the stirring is stopped and the precipitate allowed to settle the mother liquor is then decanted. The precipitate is washed several times with water until pure. The product contains about 95% lead azide and consists of rounded granules composed of small lead azide crystals it is as safe as most initiating explosives and can readily be handled with due care. 

Whenever the operation to be performed involves the potential to cause the initiation of the propellant, explosive or pyrotechnic (PEP) component(s) of a munition item, the APE is either operated by remote control, with the operator behind a protection wall or barrier, or it is enclosed in a protective barricade or operational shield. Barricades or operational shields are designed to protect personnel and assets from the effects of blast overpressures, thermal effects or fireball, and fragments result from the initiation of PEP components, such as the fuze, primer, propelling charge, burster, etc. 

In the Mond Index the plant is divided into individual units on the basis of the feasibility of creating separating barriers. One of the factors taken into account in the index is therefore plant layout. The potential hazard is expressed in terms of the initial value of a set of indices for fire, explosion and toxicity. A hazard factor review is then carried out to see if design changes reduce the hazard, and intermediate values of the indices are determined. Offsetting factors for preventative and protective features are applied and the final values of the indices, or offset indices, are calculated. The elements of the Mond method are listed in Table 1. 

Rotary air lock (active) Extinguishing barrier (active) Explosion protection valve (passive or active)... 

Explosion diverter (passive) Double slide valve (active) Product layer as a barrier (active) Screw conveyer (passive) Extinguishing barrier or explosion protection valve in combination with explosion diverter (active) Flame arresters... 

The pressure detector in the vessel provides the earliest detection of an explosion in the interconnected vessel, whereas the flame detector in the pipeline provides assured detection, even for lazy flames, as they propagate down the pipeline toward the extinguishing barrier. 

Polymerizing, Decomposing, and Rearranging Substances Most of these substances are stable under normal conditions or with an added inhibitor, but can energetically self-react with the input of thermal, mechanical, or other form of energy sufficient to overcome its activation energy barrier (see Sec. 4, Reaction Kinetics, Reactor Design, and Thermodynamics). The rate of self-reaction can vary from imperceptibly slow to violently explosive, and is likely to accelerate if the reaction is exothermic or self-catalytic. 

The first task in applying a spacing table to a facility is to ensure it corresponds to the philosophy of protection adopted by the company. Where limited space is available to provide the required spacing, an examination of the equivalent fire and explosive barriers or active fire suppression system should be confirmed. This analysis should be accepted by the company as part of the design risk analysis. 

In establishing process spacing philosophy or if used, the ratings of fire and explosion barriers (as may be the case offshore), fire suppression effectiveness, a number of principle factors should be considered. These... 

---