Explosive vapor

Because chloroprene is a flammable, polymerisable Hquid with significant toxicity, it must be handled with care even in the laboratory. In commercial quantities, precaution must be taken against temperature rise from dimerisation and polymerisation and possible accumulation of explosive vapor concentrations. Storage vessels for inhibited monomer require adequate cooling capacity and vessel pressure rehef faciUties, with care that the latter are free of polymer deposits. When transportation of monomer is required, it is loaded cold (< — 10° C) into sealed, insulated vessels with careful monitoring of loading and arrival temperature and duration of transit. 

For apphcation of Eq. (26-48), x should not exceed 300 m (984 ft). The reason for selec ting 100 percent, instead of the upper flammable limit (UFL), in the equation for Vj is that in an incipient explosion vapor above the UFL may be mixed with additional air and, thereby, contribute to explosion pressure. 

A common cause of a BLE T] in plants of the hydrocarbon-chemical industry is exposure to fire. With an external fire below the liquid level in a vessel, the heat of vaporization provides a heat sink, as with a teakettle evolved vapors exit tnrough the relief valve. But if the flame impinges on the vessel above the liquid level, the metal will weaken and may cause the vessel to rupture suddenly, even with the relief valve open. The explosive energy for a BLE T] comes from superheat. This energy is at a maximum at the superheat hmit temperature. (SLT is the maximum temperature to which a hquid can be heated before homogeneous nucleation occurs with explosive vaporization of the hquid and accompanying overpressure.) The SLT... 

FAST TRACE ANALYSIS OF EXPLOSIVE VAPORS. STATUS AND PROSPECTS... 

After the furnace had been allowed to cool, the operating team, not realizing the extent of the damage, restarted the flow of feed water. They stopped it when they saw water running out of the firebox. It is fortunate they did not start the water flow earlier, or it would have caused explosive vaporization of the water [17]. As stated in Section 9.2.2 (e), equipment that has been taken outside its design or test range should not be used again until it has been examined. 

Figures 6.30 and 6.31 present the same information for saturated hydrocarbons. In Figure 6.30, the saturated liquid state is on the lower part of the curve and in Figure 6.31 it is on the upper part of the curve. Below T y, the line width changes, indicating that the liquid probably does not flash below that level. Note that a line has been drawn only to show the relationship between the points a curve reflecting an actual event would be smooth. Note that a liquid has much more energy per unit of volume than a vapor, especially carbon dioxide. Note It is likely that carbon dioxide can flash explosively at a temperature below the superheat limit temperature. This may result from the fact that carbon dioxide crystallizes at ambient pressure and thus provides the required number of nucleation sites to permit explosive vaporization.

Explosions emergency relief, 450 Explosions, vapor cloud, 520 Explosive limits, 485 External fires, see fires Factors of safety, llow, 56 Fiber bed/pads impingement separator, 254, 255... 

To keep any flammable or explosive vapors from entering the building, it is frequently slightly pressurized. This prevents the possibility of an internal explosion. 

In addition, a linear dependence was found between the concentration of DNB and its fluorescence response profile. All these characteristics demonstrate that this sensor array is suitable for use in detecting explosive vapors. 

Boiling-liquid expanding-vapor explosion (BLEVE) A BLEVE occurs if a vessel that contains a liquid at a temperature above its atmospheric pressure boiling point ruptures. The subsequent BLEVE is the explosive vaporization of a large fraction of the vessel contents possibly followed by combustion or explosion of the vaporized cloud if it is combustible. This type of explosion occurs when an external fire heats the contents of a tank of volatile material. As the tank contents heat, the vapor pressure of the liquid within the tank increases and the tank s structural integrity is reduced because of the heating. If the tank ruptures, the hot liquid volatilizes explosively. 

A confined explosion occurs in a confined space, such as a vessel or a building. The two most common confined explosion scenarios involve explosive vapors and explosive dusts. Empirical studies have shown that the nature of the explosion is a function of several experimentally determined characteristics. These characteristics depend on the explosive material used and include flammability or explosive limits, the rate of pressure rise after the flammable mixture is ignited, and the maximum pressure after ignition. These characteristics are determined using two similar laboratory devices, shown in Figures 6-14 and 6-17. 

A BLEVE occurs when a tank containing a liquid held above its atmospheric pressure boiling point ruptures, resulting in the explosive vaporization of a large fraction of the tank contents. 

Proper ventilation is another method used to prevent fires and explosions. The purpose of ventilation is to dilute the explosive vapors with air to prevent explosion and to confine the hazardous flammable mixtures. 

Daniel A. Crowl, Ph.D. Professor of Chemical Engineering, Michigan Technological University Fellow, American Institute of Chemical Engineers (Section Editor, Process Safety Introduction, Combustion and Flammability Hazards, Gas Explosions, Vapor Cloud Explosions, Boiling-Liquid Expanding-Vapor Explosions)... 

Figure 23-7 is a schematic of a device used to characterize explosive vapors. This vessel is typically 3 to 20 L. It includes a gas handling and mixing system (not shown), an igniter to initiate the combustion, and a high-speed pressure transducer capable of measuring the pressure changes at the millisecond level. 

The failure mode of ESDVs for gas processing areas should always fail in the closed position, since this is the only mechanism to resolve gas fed fires or prevent explosive vapor buildups. The valves should be provided with an automatic fail close device such as an actuator with spring return specification. 

The cost of pretreating contaminated groundwater on site, for discharge to a publicly owned treatment works is often the preferred alternative (provided the facility has the capacity and local regulations allow acceptance). Pretreatment is usually required to prevent explosive vapors in the sewers and disruption of the biological treatment at the plant. The most common pretreatment includes phase separation and reduction of dissolved contaminants to an assured safe concentration. At small sites, it is not unusual to use phase separation, air stripping, and activated charcoal filtration prior to discharge to a sanitary sewer. 

In certain instances, when LNG contacts ambient water, explosive vaporization occurs with concomitant shock waves both in the air and water. While isolated instances of such events were recorded as early as 1956, it was during the 1968-1969 Bureau of Mines tests that the phenomena first attracted wide interest. In these experiments, three explosive... 

These results stimulated a number of studies, both in industry (Conoco, Esso, Shell Pipeline) and in academia (University of Maryland, M.I.T.). The objective was, primarily, to delineate the mechanism that led to these explosive events. The results of many small-scale experiments, primarily conducted by Shell Pipeline Corporation and M.I.T., led to the hypothesis that the apparent explosion was, in fact, a very rapid vaporization of superheated LNG. Contact of LNG, of an appropriate composition, with water led to the heating of a thin film of the LNG well above its expected boiling temperature. If the temperature reached a value where homogeneous nucleation was possible, then prompt, essentially explosive vaporization resulted. This sequence of events has been termed a rapid phase transition (RPT), although in the earlier literature it was often described by the less appropriate title of vapor explosion. 

The first well-publicized incident wherein an LNG spill on water produced an explosive vaporization took place during the 1968-1969 tests carried out by the U.S. Bureau of Mines Safety Research Center in Pittsburgh (Burgess et al., 1970, 1972). Under contract to the U.S. Coast Guard, they were studying the spreading and vaporization rates of LNG on water. 

Liquid propane spills into 341 K water. Explosive vaporization always occurred and the delay between the start of the spill and the event was typically 0.2 sec. Strain-gauge pressure transducers were located 7.6 cm under the water interface and also in the air, 1.38 m from the spill container. The overpressure data are shown in Table I. The highest overpressure measured in the water was 410 kPa (60 psi) and the highest... 

Colorless, mobile, oily, hygroscopic, flammable liquid with a weak ammonia-like odor. Experimentally determined detection and recognition odor threshold concentrations were 40 ng/m (11 ppbv) and 25 pg/m (70 ppbv), respectively (Heilman and Small, 1974). Forms explosive vapors at temperatures >35 °C. 

Figure 20 Schematic diagram of a mass spectrometer for explosive vapor detection [Reproduced from Y. Takada et. al.. Propellants, Explosives, Pyrotechnics, 27 (2002) 224. Copyright 2002, with permission from Wiley-VCH].

The concept of obtaining a sample by wiping an article or object with a cloth strip to collect particulate of explosives, with subsequent heating of the sample in an anvil to desorb explosive vapors, is a general practice and has been described in a... 

M. Tam and H.H. HiU Jr., Secondary electrospray ionization-ion mobility spectrometry for explosive vapor detection. Analytical Chemistry 76(10) (2004) 2741—2747. 

This section includes guidelines for the central control station equipment, emergency alarm stations, supervisory devices, and visual and audible alarm services. These systems can be used for all types of in-house emergencies, such as fires, explosions, vapor releases, liquid spills, and injuries. 

The underwater sensor platform is derived from the Fido explosives vapor sensor, originally developed under the Defense Advanced Research Projects Agency (DARPA) Dog s Nose Program. The vapor sensor, whose operation is discussed in Chapters 7 and 9 and in other publications [7-9], was developed for the task of landmine detection. The underwater adaptation of the sensor is very similar to the vapor sensor. In the underwater implementation of the sensor, thin films of polymers are deposited onto glass or sapphire substrates. The emission intensity of these films is monitored as water (rather than air) flows past the substrate. If the concentration of TNT in the water beings to rise, the polymer will exhibit a measurable reduction in fluorescence intensity. The reduction in emission intensity is proportional to the concentration of target analyte in the water. Because the sensor is small, lightweight, and consumes little power, it proved to be ideal for deployment on autonomous platforms. 

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