Flammable liquids fuels

SwRI 93-01, Testing Requirements for Protected Aboveground Flammable Liquid/Fuel Storage Tanks, includes tests to evaluate the performance of ASTs under fire, hose stream, ballistics, heavy vehicular impact, and different environments. This standard requires pool-fire resistance similar to that of UL 2085. 

It is more difficult to remove the charges from insulating materials. In some cases this may be done by modifying the material to improve its conductivity. For example, flammable liquid fuels can be doped with additive and carbon black can be added to rubber during manufacture to reduce the resistivity of the material. Where this is undesirable, or uneconomic, it may be possible to carry out the process in a humid atmosphere where the water vapour acts as a leakage path to earth. This method is not suitable, however for water-repellent materials. 

In November 1990 a fire occurred at a flammable liquid tank farm supporting Denver s Stapleton international airport. Eight of the farm s twelve storage tanks contained jet fuel, totaling almost 4.2 million gallons. The fire burned for 55 hours, destroying seven tanks. 

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. 

Confined combustion explosions (gaseous or liquid) usually occur when a flammable vapor leaks into an enclosure and mixes witJi air to form a flarmnable mix-ture, whereupon this mix+ure contacts an ignition source tliat was present before the leak occurred. This type of explosion ctm tUso occur in storage taitks or sliips where tlie vapor space above tlie stored flanunable liquid (fuel) is in tlie cxplosivity range. In tliis case, an ignition source accidentally introduced will cause an explosion. 

Liquid Pool Flames. Liquid fuel or flammable spills often lead to fires involving a flame at the surface of the liquid. This type of diffusion flame moves across the surface of the liquid driven by evaporation of the fuel through heat transfer ahead of the flame. If the liquid pool or spill is formed at ambient conditions sufficient to vaporize enough fuel to form a flammable air/fuel mixture, then a flame can propagate through the mixture above the spill as a premixed flame. 

Vibration from a bad pump bearing caused a pump seal to fail in a cumene section of a phenol acetone unit. The released flammable liquids and vapors ignited. An explosion ruptured other process pipes, adding fuel to the original fire. Damage to the plant exceeded 23 million. 

FIG. 23-63 Methods of diking for flammable liquids (a) traditional diking method allows leaks to accumulate around the tank. In case of fire, the tank will be exposed to flames that can be supplied by fuel from the tank and will be hard to control, (b) In the more desirable method, leaks are directed away from the tank. In case of fire, the tank will be shielded from most flames and fire will be easier to fight. (From Englund, in Advances in Chemical Engineering, vol. 15, Academic Press, San Diego, 1990, pp. 73-135, by permission.)... 

The stratified gaseous layer established over the liquid fuel surface varies from a fuel-rich mixture to within the lean flammability limits of the vaporized fuel and air mixture. At some point above the liquid surface, if the fuel temperature is high enough, a condition corresponds to a stoichiometric equivalence ratio. For most volatile fuels this stoichiometric condition develops. Experimental evidence indicates that the propagation rate of the curved flame front that develops is many times faster than the laminar flame speed discussed earlier. There are many less volatile fuels, however, that only progress at very low rates. 

Benzene is a clear, colorless, flammable liquid with a distinct, sweet odor. It burns with a smolcy flame, as do other hydrocarbons with high aromatic concent. (That s why kerosenes with high aromatic content do not make good jet fuel or burning grade kerosene—too much black smoke.) Benzene is only slightly soluble, in water. 

Fires are classified based on the type of fuel involved. Fuels are typically placed into three classes ordinary combustibles (like wood and paper), flammable liquids, and combustible metals. For firefighting, a fourth fire class, electrical fires, is also considered. The four main classifications of fire are shown in Table B-1. 

The release of a flammable gas or the vaporization of a liquefied flammable gas can lead to different types of fire scenarios dependent on the release mechanism and the point of ignition. Figure 5-2 on page 53 illustrates the different outcomes expected from a gas release. If ignition of a gas release does not occur immediately at the origin of the release, then a gas cloud can develop (the same situation can also occur above flammable liquid spills). A delayed ignition of the gas cloud can result in a flash fire in which the premixed (fuel and air) gas cloud burns rapidly, typically in a matter of seconds. 

The disadvantages are that fuel and oxygen must be premixed. The proportions are such that the mixture may be flammable or even explosive, particularly if small variations (e.g. as a result of pumping and vaporizing liquid fuels) are possible. 

UL 2244, Standard for Aboveground Flammable Liquid Tank Systems, covers factory-fabricated, preengineered aboveground atmospheric tank systems intended for dispensing flammable or combustible liquids, sucn as gasoline or diesel fuel, into motor vehicles, generators, or aircraft. 

Underwriters Laboratories of Canada (ULC) publishes a number of standards for aboveground tanks and accessories. All the following pertain to the aboveground storage of flammable liquids and combustible liquids such as gasoline, fuel oil, or similar products with a relative density not greater than 1.0 ... 

Most fuels and oils are classified as Flammable Liquids. Occasionally Gas samples and Flammable Solids are shipped. Further details describing each of the nine hazard classes are provided in TABLE 10-1. 

Class B Fires. These are fires in flammable liquids (oils, gasoline, solvents, etc.), where a blanketing or smothering effect is essential to put the fire out. This effect keeps oxygen away from the fuel, and can be obtained with carbon dioxide, dry chemical (essentially sodium bicarbonate), foam, or a vaporizing-liquid type of extinguishing agent. Water is most effective when used as a fine spray or mist... 

It Ls important to note that a combustible liquid at or above its flash point will behave in the same manner that a flammable liquid would in a similar emergency. As an example No.2 fuel oil when heated to a temperature of 150°F can be expected to act or react in the same way gasoline would at 50°F. In most instances, however, to reach this elevated temperature will require the introduction of an external heat source. Some common examples of combustible petroleum liquids are given in Table 7. 

Most combustible liquids do not present a vapor problem if accidentally released into the atmosphere. The probability of a fire, therefore, is considerably less than it would be if the spill was of a flammable material. If, however, the combustible liquid is at a temperature higher than its flashpoint, then it can be expected to behave in the identical manner a flammable liquid. One major difference between the two in a fire situation is that the potential exists for cooling the combustible liquid below its flash point by the proper application of water (generally applied in the form of water spray). In the event the liquid is burning, and if the fire forces are successful in achieving the required reduction in liquid temperature, then vapor production will cease and the fire will be extinguished because of a lack of vapor fuel. Unless this reduction in liquid temperature can be brought about, the fire will necessitate the same control considerations a low-flash liquid fire would. 

A California statue requiring hazardous materials management was passed in 1985 (24), but guidance for compliance for industries covered by the act was not issued until 1988 (25). A revised standard, which became effective in January of 1994 (26), applies to facilities handling any of 128 toxic materials flammable liquids and gases in quantities of 10,000 lb (4.541) or more, except where used as fuel or in atmospheric pressure, ambient temperature tanks and explosives. 

The regulation lists 137 toxic and reactive substances and a threshold quantity for each. The regulation also applies to flammable liquids and gases in quantities of 10,000 lb or more (>4.5 metric tons), except hydrocarbon fuels and liquids stored in unpressurized, ambient temperature tanks, as well as to the manufacture of any quantities of explosives (see Exlosives and propellants) and pyrotechnics (qv). 

Specific codes or regulations for vehicular storage and dispensing systems for alcohol fuels do not exist. Alcohols are flammable liquids which are covered in NFPA 30, Flammable and Combustible Liquids Code [5.2], Gasoline is included under NFPA 30 as a Class IA flammable liquid, while diesel fuel is included as a combustible liquid. When alcohols are used as fuel for vehicles, they almost always have some gasoline or high vapor pressure hydrocarbons in them which... 

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