Flash fires

A product may also be defective because it was sold with iaadequate wamiags. Burch vs Amsterdam Corporatioa (11) is an early example of a failure-to-wam case. A plaintiff was badly burned ia an explosion and flash fire that occurred while he was applyiag a floor tile adhesive sold by the defendant. The label on the can of mastic adhesive warned that the product was extremely flammable and should not be used near a fire or flame. 

Mixing cellulose esters in nonpolar hydrocarbons, such as toluene or xylene, may result in static electricity buildup that can cause a flash fire or explosion. When adding cellulose esters to any flammable Hquid, an inert gas atmosphere should be maintained within the vessel (132). This risk may be reduced by the use of conductive solvents in combination with the hydrocarbon or by use of an antistatic additive. Protective clothing and devices should be provided. 

An operator had tested dryer samples on a number of occasions. After the last sampling, he closed the manhole cover, put the dryer under vacuum, and started rotation of the dryer. A few minutes later an explosion and flash fire occurred, which self-extinguished. No one was injured. Investigations revealed that after... 

Flash Fire The combustion of a flammable gas or vapor and air mixture in... 

Release of a flammable gas or vapour may result in a jet or flash fire or any type of vapour... 

Flash fire The eombustion of a flammable vapor and air mixture in whieh flame passes through that mixture at less than sonie veloeity, sueh that negligible damaging overpressure is generated. 

Center for Chemical Process Safety (CCPS) (1994b). Guidelines for Evaluating the Gharacteristics of Vapor Gloud Explosions, Flash Fires, and BEEVES. New York American Institute of Chemical Engineers. 

One centrifuge was powered by a hydraulic oil installation 2-3 m away. A leak of oil from a cooler was ignited, and the fire was spread by oil and product spillages and by plastic-covered cables. It destroyed the plastic seal between the centrifuge and its exit chute. There was an explosion in the chute and a flash fire in the drier to which it led. The centrifuge exit valve was closed, but the aluminum valve actuator was destroyed. Fortunately, the exit valve did not leak, or several tons of solvent would have been added to the fire. Aluminum is not a suitable material of construction for equipment that may be exposed to fire. 

Chapters 7, 8, and 9 demonstrate the consequence modeling techniques for vapor cloud explosions, BLEVEs, and flash fires, respectively, by presenting sample problems. These problems contain sufficient detail to allow an engineer to use the methods presented to evaluate specific hazards. 

Accidents involving fire have occurred ever since man began to use flammable liquids or gases as fuels. Summaries of such accidents are given by Davenport (1977), Strehlow and Baker (1976), Lees (1980), and Lenoir and Davenport (1993). The presence of flammable gases or liquids can result in a BLEVE or flash fire or, if sufficient fuel is available, a vapor cloud explosion. 

This chapter describes the main features of vapor cloud explosions, flash fires, and BLEVEs. It identifies the similarities and differences among them. Effects described are supported by several case histories. Chapter 3 will present details of dispersion, deflagration, detonation, ignition, blast, and radiation. 

An event tree can be used to trace the various stages of development of a vapor cloud explosion, as well as the conditions leading to a flash fire or a vapor cloud detonation (Figure 2.1). 

A flash fire results from the ignition of a released flammable cloud in which there is essentially no increase in combustion rate. In fact, the combustion rate in a flash fire does increase slightly compared to the laminar phase. This increase is mainly due to the secondary influences of wind and surface roughness. 

Figure 2.1 identifies the conditions necessary for the occurrence of a flash fire. Only combustion rate differentiates flash fires from vapor cloud explosions. Combustion rate determines whether blast effects will be present (as in vapor cloud explosions) or not (as in flash fires). 

The principal dangers of a flash fire are radiation and direct flame contact. The size of the flammable cloud determines the area of possible direct flame contact... 

Figure 2.1. Event tree for vapor cloud explosions and flash fires.

Until recently, very little attention has been paid to the investigation of flash fires. Chapter 5 summarizes results of investigations performed thus far. 

E)ocumentation of flash fires is scarce. In several accident descriptions of vapor cloud explosions, flash fires appear to have occurred as well, including those at Flixborough, Port Hudson, East St. Louis, and Ufa. The selection and descriptions of flash fires were based primarily on the availability of information. 

After the valley was illuminated, a flash fire was observed, which consumed the remainder of the cloud. After the explosion and flash fire, a torch fire resulted at the point of the initial release. Buildings in the vicinity of the explosion were damaged (Figures 2.10 and 2.11). 

Flames were first observed at or near an unoccupied caboose. A flash fire resulted, propagating toward the punctured car area. An orange flame then spread upward, and a large vapor cloud flared with explosive force. Estimates of the time lapse between these occurrences range from 2 to 30 seconds. Almost immediately thereafter, a second, more severe, explosion was reported. ... 

The flash fire that resulted was described as a ball of flame with a diameter of at least 120 m (400 ft). No concussion was felt. The truck driver (at a distance of 80 m or 270 feet) was caught in the flames and probably died immediately. The motorists and residents were outside the cloud but received serious bums. 

On November 19,1984, an initial leak and flash fire of LPG resulted in the destruction of a large storage facility and a portion of the built-up area surrounding the storage facility. Approximately 500 people were killed and approximately 7000 were injured. The storage facility and the built-up area near the facility were almost completely destroyed. 

At 5 45 A.M., a flash fire resulted. The vapor cloud is assumed to have penetrated houses, which were subsequently destroyed by internal explosions. A violent explosion, probably involving the BLEVE of several storage tanks, occurred 1 minute after the flash fire. It resulted in a fireball and the propulsion of one or two cylindrical tanks. Heat and fragments resulted in additional BLEVEs. 

On May 30, 1978, a sphere in a tank farm of a refinery at Texas City, Texas, was overfilled with isobutane. As a result, it cracked and released a portion of its contents, which were then ignited. The ensuing flash fire caused the sphere to fail completely. 

Accident scenarios leading to vapor cloud explosions, flash fires, and BLEVEs were described in the previous chapter. Blast effects are a characteristic feature of both vapor cloud explosions and BLEVEs. Fireballs and flash fires cause damage primarily from heat effects caused by thermal radiation. This chapter describes the basic concepts underlying these phenomena. 

Chapter 2 discussed the possible influence of atmospheric dispersion on vapor cloud explosion or flash fire effects. Factors such as flammable cloud size, homogeneity, and location are largely determined by the manner of flammable material released and turbulent dispersion into the atmosphere following release. Several models for calculating release and dispersion effects have been developed. Hanna and Drivas (1987) provide clear guidance on model selection for various accident scenarios. 

In general, when a flammable vapor cloud is ignited, it will start off as only a Are. Depending on the release conditions at time of ignition, there will be a pool fire, a flash fire, a jet fire, or a fireball. Released heat is transmitted to the surroundings by convection and thermal radiation. For large fires, thermal radiation is the main hazard it can cause severe bums to people, and also cause secondary fires. 

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