Explosion from scale

There have been fires and explosions in compressed air systems. The fuel is a combustible lubricant that has entered the air system from the compressor. Al th 0 ugh m ai nte n an ce of th e ch eck val ves wi 11 m i n i m ize th e h aza rd, th e val ves can stick open from scale or other causes that can affect even recently serviced valves. The explosion potential can be minimized by replacing the combustible lubricants with noncombustible lubricants. 

A problem with this process is the decomposition of ADN as the temperature is raised above the melting point. The problem is that the melting point at 92°C is only 40°C below the temperature of decomposition. At 110°C the decomposition becomes autocatalytic after 15 minutes, at 98°C after a few hours. This is not a problem on the laboratory scale, where the melting period can be reduced to a few minutes. On the industrial scale, where hundreds of kilos of ADN should be melted in a batch, the time is much longer. It is likely that most explosives producers would hesitate and most likely refrain from scaling up this process unless nothing is changed. 

The Army conducted pilot-scale studies of continuous flow column GAC equipment at Badger AAP and Milan AAP. At both sites, GAC treatment was found to be effective for removing every type of explosive from the water and removing 2,4- and 2,6-DNT to below detection levels. 

Case 4 Physical Wear, Some Atmospheres, Liquid Slag or Scale, Leaking Cooling Water These also can be bad for refractories. After installation of castable, rammed, and gunned refractories, a long, slow dryout period is necessary to prevent spalling or explosions from steam formation within the refractories. 

Equation (5) shows that for a given distance and high explosive from Table 3 we can compute the overpressure. This also holds true for the scaled distance. In summary, for the free field case we can express the damage modeling either in terms of radial distances, overpressure, blast impulse values or scaled distances. The expression for the blast impulse uses the scaled impulse [2]... 

This correction is carried out by using the scaled distance, d , based on the similitude principle proposed by Hopkinson in 1915, according to which when two explosive charges of similar geometry and of the same explosive but different sizes, detonate in the same atmosphere, similar pressure waves are generated at the same scaled distance. This principle can also be applied to two different explosives, taking into account the fact that two types of explosion with the same overpressure give rise to the same effects. Because overpressure is a function of the distance and two different explosions do not cause the same overpressure at the same distance from the center of the explosion, the scaled distance is defined as that at which the overpressure has the same value for both explosions. The scaled distance is related to the real distance and to the equivalent TNT mass by the cubic root law. 

Although this approach would have generally been preferred, it seemed impossible to come up with a sound model within the given time and financial limits. Therefore, an experiment-based relationship was finally developed directly from the available data. Simply stated, observed debris mass density stributions from accidents and full-scale tests were taken and correlated with the four main parameters explosives weight, scaled cover depth, chamber loading density, and slope angle of the overburden. 

Manufacture and Economics. Nitrogen tritiuoride can be formed from a wide variety of chemical reactions. Only two processes have been technically and economically feasible for large-scale production the electrolysis of molten ammonium acid fluoride and the direct fluorination of the ammonia in the presence of molten ammonium fluoride. In the electrolytic process, NF is produced at the anode and H2 is produced at the cathode. In a divided cell of 4 kA having nickel anodes, extensive dilution of the gas streams with N2 was used to prevent explosive reactions between NF and H2 (17). 

Economic Aspects. Oxetanes are expensive monomers and are not readily available in commercial quantities. Commercial production of PBCMO has been discontinued its end uses were not able to support its comparatively high selling price. Energetic polymers prepared from appropriately substituted oxetanes have opened a new market for their use to prepare soHd rocket propeUants and explosives. Should this specialty market result in the large-scale production of these oxetanes even at current (1996) high prices and/or in a cheap synthetic route to oxetanes, this economic picture could change. 

On the simplest type of instrument (an explosimeter) only one scale is provided, usually with readings from 0 to 100% LEL. However, the detectable changes produced by combustion are too small to be measured accurately in the presence of the low concentrations of contaminants usually encountered in evaluating potential health hazards. For example, the LEL of even the most explosive gas is of the order of 1 %, or 10,000 ppm, which is well in excess of the toxic limit for any gas. Therefore, explosimeters or combustible gas indicators which have only a 0-to-l(X)% LEL explosive scale are not suitable for environmental health testing in the ppm range. More sensitive instruments, including the type used in sampling for environmental health purposes, have a dual scale, in which the second, more... 

In many cases, it is not readily apparent how the potential impacts from different hazards can be translated into some common scale or measure. For example, how do you compare long term environmental damage and health risks from use of CFG refrigerants to the immediate risk of fatality from the fire, explosion, and toxicity hazards associated with many alternative refrigerants This question does not have a right answer. It is not really a scientific question, but instead it is a question of values. Individuals, companies, and society must determine how to value different kinds of risks relative to each other, and base decisions on this evaluation. 

If 10 tons of propane exploded with an explosive efficiency 0.05, 1,000 ft from you, what would be the peak positive overpressure Referring to equation 9.1-24, W = 0.0.5 ZE4 5E4/4,7E3 = 1E4 lb, where the heats ot combustion are from Table 9.1-4, and 10 tons is 2E4 lb. The scaled range is = 1000/IE4 = 45.6 from which a positive overpressure of 2... 

Experiments on a small scale with stoichiometric methane-air mixtures were carried out by Chan et al. (1980). Comparisons of results of these experiments with those performed by Moen et al. (1982) revealed that simple scaling is not possible for the results of explosions with very high flame speeds, in other words, flame speeds resulting from very intense turbulence. 

Application of the Baker-Strehlow method for evaluating blast effects from a vapor cloud explosion involves defining the energy of the explosion, calculating the scaled distance (/ ), then graphically reading the dimensionless peak pressure (Ps) and dimensionless specific impulse (i ). Equations (4.41) and (4.42) provide the means to calculate incident pressure and impulse based on the dimensionless terms. 

Guirao, C. M., G. G. Bach, and J. H. S. Lee. 1979. On the scaling of blast waves from fuel-air explosives. 6th Symp. on Blast Simulation. Cahors, France. 

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