the flammable vapour in the cloud is 90 tonnes (U.S. EPA, b). The threshold is estimated by modeling with Process Hazard Analysis Software The equation for estimating the evaporation rate of a liquid from a pool is . Flammable Gases and Office of Prevention and Toxic Substance (). EPA R KEY WORDS: Acute hazards; environmental equity; GIS; worst-case exposure. 1. Flammable gases and liquids and their hazards (EPA R-. ). Background: Section (r) of the Clean Air Act (CAA) requires facilities that have threshold installation: a hazard assessment, a management program, . Agency (EPA) an RMP that summarizes their Risk Management Program Gases handled as refrigerated liquids at EPA R

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A discussion is also provided that considers mixtures of materials and how these mixtures may be more hazardous than individual material losses. WHAZAN makes certain assumptions regarding atmospheric behavior and accidental release rates of various gases and liquids.

The procedure uses an endpoint adn a vapor cloud explosion as an overpressure of 1 pound per square inch psi. As BLEVEs result from sudden vessel failure, they would always be essentially instantaneous; therefore, it is not clear that any distinction can be made between instantaneous versus prolonged release input in modeling BLEVEs.

Gasoline is not regulated as a special case under any of the regulations or codes mentioned above.

The view factor F is read from tables on pp. Thus, if the site is located in an area with few buildings or other obstructions e. Modeling indicated that BLEVEs may also, in some cases, have the potential for offsite consequences.

Therefore, personnel responding to an hazzrds.epa likely do not know that they are entering a chemical hazard area, and therefore, they are not properly protected. An exemplary list of chemicals that are known to have been involved in vapor cloud explosions is shown in Exhibit 1.


The graph ad released quantity versus distance indicates that distance is proportional to the cube root of quantity, as was the case for vapor cloud explosions. All the figures were developed assuming a wind speed of 1. Now use the calculated heat of combustion for the mixture in Equation 7 to calculate the distance to 1 psi overpressure for vapor cloud explosion. These calculations are presented only as examples; the calculation methods have not been evaluated or compared in detail. The specific substances reported most frequently in the database were gasoline and LPG propaneboth flammables.

Only part of the total combustion energy in the explosive part of the cloud is available for shock wave propagation. For estimating release rates hazards.eap solutions, this procedure uses liquid factors ambient for several common water solutions at several concentrations. The downwind distance is the maximum distance at which the specified concentration is reached; the crosswind distance flammablw.gases the width of the cloud of flammable vapor at that point. Table 1 on p.

Flammable Gases and Liquids and Their Hazards

The five-ton quantity was chosen by API anc a reasonable threshold on the basis of catastrophic potential and probability of explosion. This result is consistent with information presented in the literature. The multi-energy model appears to be more complex than the PC-based models and calculations discussed in the previous sections.

A 30 pound blind flange on a 4 inch nozzle falls. EPA’s evaluation is discussed in Sections 3 and 4. The maximum diameter and time to reach maximum diameter are given by: This fraction is symbolized by the yield factor, n. The facilities most vulnerable to the impact of accidents which should be avoidedsuch as schools, hospitals, and day care centers, are considered.

These methods were applied to the airborne dispersion of vapor clouds of flammable liquids and gases to estimate distances for vapor cloud fires. The models derive their inputs from a data base which contains relevant properties of some hazardous chemicals.


The OSHA Process Safety Management Standard is intended to protect employees by preventing or minimizing the consequences of catastrophic releases of toxic, reactive, flammable, or explosive chemicals.

For an overpressure of 1. The data presented in Exhibit 12 show there is relatively little difference in distance based on varying the hazard criteria levels for the other chemicals analyzed. However, some trucks may be carrying several different materials. The model also estimates the maximum weight of flammable gas that may be airborne at any time. Prepared for Department of Transportation, U. Twenty to 25 minutes later, the cargo tank exploded, burning or otherwise injuring 28 people, one of whom was feet away from the explosion.

Vulnerability of the facilities is calculated as a function of the distance of the facilities from the transportation routes and the population of the vulnerable facility. American Institute of Chemical Engineers.

Brief Records : EPA National Library Catalog

For both of these gases, the other types of accidents modeled gave much greater distances than jet fires. The most conservative assumption would be to assume the entire quantity is in the cloud; such an occurrence seems very unlikely, however. Department of Transportation, U. The two largest spheres, full to theirgallon capacity were saved from BLEVE by water from rail tank cars. WHAZAN results for vapor cloud explosions are presented as distances to four characteristic damage levels; overpressures related to these damage levels are not presented but have been estimated for this report.