Flammability ranges lower explosive limit

Lysergic acid methylpropylamide Lethal dose-50 The dose of a drug that kills half of the test population Like dissolves like Linear dynamic range Lower explosive limit same as LEL, lower flammability range Lower flammability range Ligand field theory Liquid/liquid extraction such as performed in a separatory funnel or Soxh-let extraction unit Limit of detection... 

Flammable or Explosive Limits — the upper and lower vapor eoneentrations at whieh a mixture will bum or explode. The lower explosive limit of p-xylene is 1.1 pereent by volume in air, whereas the upper explosive limit is 7.0 percent in air. A mixture of p-xylene vapor and air having a coneentration of <1.1 pereent in air is too lean in p-xylene vapor to bum. Conversely, a mixture containing more than 7.0 percent is too rieh in p-xylene to bum. By subtraetion (7.0 - 1.1), p-.xylene is said to have a flammable range of 5.9. Materials having low explosive limits and wide flammable ranges are extremely dangerous. 

The volatile solvents recoverable by the activated carbon system or any other system are nearly all organic, and many of them form flammable or explosive mixtures with air. Such mixtures may lie between upper and lower explosive limits. The activated carbon system can avoid the explosive range by staying well below the lowest percentage of vapor which is still explosive it functions well at very low concentrations. The system also recovers solvents efficiently even in the presence of water the recovery efficiency is high (98 percent and 99 percent are not unusual) it may be fully automatic. The annual maintenance charge rarely exceeds 5 percent of the cost of equipment. The recovery expense may be as low as 0.2 cent per pound in some installations it rarely exceeds 1 cent per pound. 

As vent collection systems normally contain vapor/air mixtures, they are inherently unsafe. They normally operate outside the flammable range, and precautions are taken to prevent them from entering it, but it is difficult to think of everything that might go wrong. For example, an explosion occurred in a system that collected flarmnable vapor and air from the vents on a number of tanks and fed the mixture into a furnace. The system was designed to run at 10% of the lower explosion limit, but when the system was isolated in error, the vapor concentration rose. When the flow was restored, a plug of rich gas was fed into the furnace, where it mixed with air and exploded [17]. Reference 34 describes ten other incidents. 

Explosive nature of chemical substances is described with upper and lower explosion limits. The explosiveness of vapour cloud depends especially on the lower explosion limit (LEL). The LEL is the concentration of vapour, at which the vapour cloud is possible to ignite. The wider range between explosion limits means, that it is more probable that the formed vapour cloud is in the flammable region, i.e. the higher tendency for explosion. Edwards and Lawrence (1993) have used explosive limits to determine the explosiveness of chemical substances. 

Flammable (explosive) Range The range of gas or vapor concentration (percentage by volume in air) that will burn or explode if an ignition source is present. Limiting concentrations are commonly called the lower explosive limit and the upper explosive limit. Below the lower explosive limit, the mixture is too lean to burn above the upper explosive limit, the mixture is to rich to burn. 

Flammable vapor burns in air only over a limited range of fuel-to-air concentrations. The flammable range is defined by two parameters the Lower flammable limit (LFL) and the upper flammable limit (UFL). These two terms are also called the lower explosive limit (LEL) and the upper explosive limit (UEL). 

When a combustible substance is mixed with air, the mixture will explode only when it is neither too rich nor too lean. The lower explosion limit (LEL) is the minimum volume percent of the substance in air with flammability, which is separated from the upper explosion limit (UEL) by the explosive concentration range. The tabulations in handbooks are based on experimental data, and sometimes derived from estimation methods based on the elemental composition of the fuel as CmEtxOy. Figure 6.11 shows the LEL for the series of normal paraffins and of 1-alcohols versus the number of carbon atoms. There are two ways to plot the results, which show that, for paraffins, the volume percent shows a steeply declining trend, but the weight percent shows a mildly increasing trend. One may conclude that a smaller volume percent of higher paraffin... 

Steam curtains are best used for diluting heavier-than-air releases of flammable vapors, not toxic materials. For flammable materials the level of dilution with air that has to be obtained is the lower explosive limit toxic materials could require dilution to <100 ppm range. Moreover, while steam curtains can provide the thermal effects that will help disperse flammable material, they hinder the absorption effects needed for toxic materials, especially materials that are water-soluble. 

For a large number of flammable dusts, the lower explosion limit lies between 0.02 and 0.06 kg/m3. The upper explosion limit is in the range of 2-6 kg/m3, but this number is of limited importance. 

National Fire Protection Association. System gives a qualitative rating for health, flammability, and spontaneity. These values range from 0 to 4, with 4 being the most hazardous. These can be used for an initial screen to sensitize engineers to the potential hazard. Quantitative values are published elsewhere for each separate issue health (TLV, STEL, IDLFl) flammability explosivity (upper and lower explosive limits). 

Federal Register (FR) A daily publication of all U.S. government documents required by law. It is the daily supplement to the Code of Federal Regulations (CFR). flammable limits The range of gas or vapor concentrations (percent by volume) in air which will bum or explode if an ignition source is present. The lower explosive limit... 

Flammable gas A gas that at ambient temperature and pressure forms a flammable mixture with air at a concentration of 13% by volume or less or a gas that at ambient temperature and pressure forms a range of flammable mixtures with air greater than 12% by volume, regardless of the lower explosive limit. 

The third component of a fire is the vapour, which can mix with air, over the surface of a flammable liquid. Solvent vapours will only burn in air over a restricted concentration range bounded by the UEL (upper explosive limit) and LEL (lower explosive limit). Table 9.2 sets out for a typical range of flammable solvents their UEL and LEL values and their flash points, which are effectively the temperatures at which the solvent-saturated air attains the LEL. 

The presence of water vapor reduced the flammability in air, whereas NH3 probably lowered the explosion limit [42]. Other explosion limits observed in air at ambient temperature and pressure were 1.6 vol% PH3 [51,52], 1.86 vol% in dry air, and 1.85 vol% in air saturated with humidity [53]. The last two values were constant at total pressures in the range of 150 to 760 Torr. The lower explosion limit of 2.18 vol% PH3 in dry O2 also remained constant in this pressure range at 25 C, whereas for 5 vol% O2 in N2 a lower explosion limit of 1.67 vol% PH3 was measured [53]. 

Combustion can occur only if the mixture of fuel and oxygen lies within a certain range. This is described by the lower and upper explosion limits (LEL and UEL). In older references theses Umits are referred to as the lower and upper limits of flammability (LFL and UFL) (vid. [4]). They represent the volume ratio of fuel vapour in air. Below the lower explosion limit the mixture is too lean, above the upper limit it is too rich for combustion to occur. The explosion Umits are not fixed values. They depend on whether we deal with a mixture with air or with oxygen. Furthermore they are influenced by (vid. [4, 5]) ... 

Dust-air mixtures are flammable only within a certain range of concentrations just like gas-air mixtures. This range is marked by the lower explosion limit (LEL) and the upper explosion limit (UEL). 

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