Pressure maximum explosion

The maximum explosion pressure, denoted and expressed in Pa is the peak value of the time-dependent pressure measured in a closed container upon deflagration of an explosive mixture of defined composition. The maximum explosion pressure is the maximum value of the explosion pressure determined by varying the composition of the mixture. The explosion pressure of gases and vapors is determined in resting mixtures according EN13673-1. 

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The energy required to initiate an explosion and the maximum explosive pressure developed by a number of polyester—epoxy powder coatings has been studied in some detail (89). The variables studied included composition, level and type of pigmentation, particle size, and concentration in air. The lowest MEG for unfilled and unpigmented powders was 33—35 g/m. ... 

Minimum ignition energy (mj) Maximum explosion pressure (psi) " Maximum rate of pressure rise. (psi/s) Maximum oxygen concentration to preyent ignition (% by volume)... 

Tlie maximum explosion pressure is a function of the initial pressure, P. If tlie initial pressure is increased by a factor of 2, tlie maximum explosion pressure and the maximum pressure rise will also increase by a factor of about 2 for both naminable gas and dust mixtures. Wlien tlie initial pressure is less tlian 10 mbar, il is usually no longer possible to Iwve an explosion. 

The maximum explosion pressure is a function of and is directly proportioiuil to die initial pressure. Blast waves are pressure waves of finite amplitude tliat are generated in air by a rapid release in energy and an instantaneous rise in pressure. The most conunon plant explosion types eiicomitered in iiidustiy are chemical, nuclear, expanding vapors, and pressurized gas. 

This is valid for the same degree of gas mixture turbulence and the same ignition source and is illustrated in Figure 7-58. Influence of the vessel shape is shown in Figure 7-56. The behavior of propane is considered representative of most flammable vapors including many solvents [54]. The maximum explosion pressure does not follow the cubic law and is almost independent of the volume of a vessel greater than 1 liter. For propane, town gas, and hydrogen, the volume relationship can be expressed ... 

Figure 7-58 show s the differences in Kg value and maximum explosion pressures for turbulent and non-turbulent systems for the same fuel-air mixtures. 

When systems involving solvent vapor are considered, use the nomogram for propane/air mixtures because most comvian solvent vapors have maximum explosion pressures of 7.1 to 7.6 bar, and the Kg falls between 40 and 75 bar meter/sec (see Ref. [54]). 

Unfortunately, rate of pressure rise and maximum explosion pressure listed in Table 7-31 are subject to uniqueness of the test conditions and are the function of particle size, dust concentration and uniformity, available... 

FPN No. 2) The explosion characteristics of air mixtures of gases or vapors vary with the specific material involved. For Class I locations. Groups A, B, C, and D, the classification involves determinations of maximum explosion pressure and maximum safe clearance between parts of a clamped joint in an enclosure. It is necessary, therefore, that equipment be approved not only for class but also for the specific group of the gas or vapor that will be present. 

Pd = ASME Code design pressure (or maximum allowable working pressure), psi Pdo = pressure on outlet side of rupture disk, psia Pe = exit or back pressure, psia, stamped burst pressure Per = perimeter of a cross section, ft or meters Pn = Initial high pressure, mmHg Pj = maximum initial pressure at which the combustible atmosphere exists, psig P j = initial pressure of system, psia PL = initial low pressure or vacuum, mmHg Pmax =- maximum explosion pressure, bar, or other consistent pressure units... 

Atomised and flake aluminium powders attain maximum explosion pressures of 5.7 and 8.6 bar, respectively, both with maximum rates of pressure rise exceeding 1.36 kbar/s [9],... 

At pressures above 25 Mpa and temperatures above 250°C, vinyl acetate admixture destabilises ethylene and increases the maximum explosion pressure from its decomposition. 

It decomposes explosively at the m.p., 98°C [1], and shows a high rate of pressure increase on exothermic decomposition [2], The heat of decomposition was determined as 1.34 kJ/g by DSC, and Taii24 was determined as 88°C by adiabatic Dewar tests, with an apparent energy of activation of 223 kJ/mol [3], When finely divided, it also shows significant dust explosion hazards, with a maximum explosion pressure of 7.75 bar, and a maximum rate of pressure rise above 680 bar/s [4], Further work on homogeneous decomposition under confinement has been reported [5],... 

The fluoro compound is resistant to nitration and an operating temperature of 90°C is necessary to ensure formation of the 5-nitro derivative. Under these conditions, the atmosphere (containing the fluoro compound, its nitro derivative and nitric acid vapours) in the nitration vessel is explosive and above the flash point. An unknown ignition source led to an explosion and rupture of the 3 cu. m vessel, and a maximum explosion pressure of 50 bar was confirmed experimentally. Such explosive atmospheres are not found in low temperature nitration reactions. 

All aspects of prevention of magnesium (and aluminium) dust explosions in storage, handling or processing operations are covered in two recent US National Fire Codes [1]. Effects of various parameters on ignition of magnesium powders were studied [2], Maximum explosion pressures of 7.9 bar, with maximum rate of rise of 884 bar/s have been recorded [3],... 

The general reactivity of the sulfide depends markedly on the physical form, and differences of a factor of 10 may be involved. It is ignitable by friction, sparks or flames, and ignites in dry air if heated close to the m.p., 275 -280°C. The dust (200 mesh) forms explosive mixtures in air above a concentration of 0.5% w/v [1], and maximum explosion pressures of 4.35 bar, with maximum rate of rise exceeding 680 bar/s have been determined [2], The dust can acquire sufficient static electricity from movement for ignition to occur [3],... 

Flammability limits for vapors are determined experimentally in a specially designed closed vessel apparatus (see Figure 6-14 on page 255). Vapor-air mixtures of known concentration are added and then ignited. The maximum explosion pressure is measured. This test is repeated with different concentrations to establish the range of flammability for the specific gas. Figure 6-5 shows the results for methane. 

Figure 6-16 Pressure rate and maximum explosion pressure as a function of vapor concentra-...

Experimental studies indicate that the maximum explosion pressure is usually not affected by changes in volume, and the maximum pressure and the maximum pressure rate are linearly dependent on the initial pressure. This is shown in Figure 6-20. As the initial pressure is increased, a point is reached where the deflagration turns into a detonation, as shown in Figure 6-21. The spikes in the curves indicate a detonation. 

Figure 6-20 Effect of initial pressure on maximum explosion pressure and rate. Data from W. Bartknecht, Explosions (New York Springer-Verlag, 1981).

An explosion can generally be considered suppressed if the expected maximum explosion pressure Pmax at the optimum concentration of the combustible product (7 to 10 bar)—assuming the explosion suppression system has an activation overpressure P of 0.1 bar—is reduced to a maximum reduced explosion overpressure Pled.ma< < 1 bar. This means that a vessel safeguarded in this way needs to be designed so that it is secured against explosions of up to 1 bar (equivalent to P .d ln, ). The activation overpressure P is that pressure at which an explosion suppression system will be activated. 

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