Upper flammable limit flame propagation

Flammable Limits The minimum and maximum concentration of fuel vapor or gas in a fuel vapor or gas/gaseous oxidant mixture (usually expressed in percent hy volume) defining the concentration range (flammable or explosive range) over which propagation of flame will occur on contact with an ignition source. See also Lower Flammable Limit and Upper Flammable Limit. 

Upper Flammable Limit - The maximum mixture of fuel in air that will support flame propagation. 

Most liquids respond to a temperature rise through a thermodynamic phase change to gas. For ignition to occur, the fuel concentration in air must be in a range that defines a flammable mixture. These bounding limits are commonly referred to as the lower flammability limit (LFL) and upper flammable limit (UFL). These are the lowest and highest fuel concentrations in air (by volume) that will support flame propagation. Fuel concentrations below the LFL or above the UFL are too lean or rich, respectively, and will not support combustion. 

Flammable limits—The minimum (lower flammable limit, FFF) and maximum (upper flammable limit, UFF) concentration of combustible vapor in air that will propagate a flame. 

Let s now turn attention back to the flammability limit itself. When small increments of a combustible gas are successively mixed with air, a concentration is finally attained in which a flame will propagate if a source of ignition is present. This is referred to as the Lower Flammable Limit (or lower explosion limit, LEL or LFL) of the gas in air. As further increments of the gas are added, a higher concentration of flammable gas in air will finally be attained in which a flame will tail to propagate. The concentration of gas and air just as this point is reached is referred to as the Upper Flammable Limit (UFL or upper explosion limit, UEL) of the gas in air. 

UFL Upper Flammability Limit the maximum concentration of a chemical in air at which flame propagation can occur. 

Almost any flammable mixture will, under favorable conditions of confinement, support an explosive flame propagation or even a detonation. When a fuel-oxidant mixture of a composition favorable for high-speed combustion is weakened by dilution with an oxidant, fuel, or an inert substance, it will first lose its capacity to detonate. Further dilution will then cause it to lose its capacity to burn explosively. Eventually, the lower or upper flammability limits will be reached and the mixture will not maintain its combustion temperature and will automatically extinguish itself. These principles apply to the combustible cryogens hydrogen and methane. The flammability and detonability... 

Upper flammability limit. The maximum concentration of vapor or gas in air above which propagation of flame does not occur on contact with a source of ignition. 

The lower and upper flammability limits are the boundary-line equilibrium mixtures of vapor or gas with air, which if ignited will just propagate a flame away from the ignition source. Each of these limits has a temperature at which the flammability limits are reached. The lower flammability limit temperature corresponds approximately to the flash point, but since the flash point is determined with downward flame propagation and nonuniform mixtures and the lower flammability temperature is determined with upward flame propagation and unifrom vapor mixtures, the measured lower flammability temperature is often somewhat lower than the flash point. 

FI. Limits Flammable limits (often called explosive limits), which specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the upper flammable limit, the mixture is too rich. Values refer to ambient temperature and pressure and are dependent on the precise test conditions. A indicates that one of the limits is not known. 

The flammability of a liquid (as vapor) or that of a gas falls between two fairly definite limits of concentrations of the vapor (or gas) in the air. These are the lower explosive limit (LEL) and the upper explosive limit (UEL). These concentration limits in air are also known as the lower and upper flammable limits. The LEL is the minimum concentration of the vapor (or gas) in air below which a flame is not propagated on contact with a source of ignition. There is also a maximum concentration of vapor... 

Flammable Limits—The lower flammable limit is the minimum concentration (percent by volume) of a vapor in air below which a flame is not propagated when an ignition source is present. Below this concentration the mixture is too lean to bum. The upper flammable limit is the maximum concentration (percent by volume) of the vapor in air above which a flame is not propagated. Above this concentration the mixture is too rich to bum. The flammable range comprises all concentrations between these two limits. This range becomes wider with increasing temperature and in oxygen-rich atmospheres. Table 13 lists these properties for a few common laboratory chemicals. 

Two limits of solvent flammability exist. The lower flammability limit is the minimum eon-centration of solvent vapor in oxidizing gas (air) that is capable of propagating a flame through a homogeneous mixture of the oxidizer and the solvent vapor. Below the lower flammability limit the mixture is too lean to bum or explode. The upper flammability limit is the maximum concentration of solvent vapor in an oxidizing gas (air) above which propagation of flame does not occur. Mixtures with solvent vapor concentrations above the upper flammability limit are too rich in solvent or too lean in oxidizer to bum or explode. 

Flammable Limits The mixture of fuel and standard air necessary for combustion of fuel vapors must be within certain limits. The lower flammable limit (LFL) is the minimum concentration of vapor-to-air, below which propagation of a flame will not occur in the presence of an ignition source. The upper flammable limit (UFL) is the maximum vapor-to-air mixture above which propagation will not occur. Mixtures below the lower flammable limit are too lean, with too little fuel. Those above the upper flammable limit are too rich, with too much fuel. The term lower explosive limit is equivalent to LFL. The upper explosive limit is equivalent to UFL. Flammable limits vary somewhat with temperature and pressure. The flammable range is the mixture of fuel and air between LFL and UFL. Table 16-4 includes LFL and UFL values. 

Flammable Limits the minimum and maximum concentrations of a flammable wipor or gas/air mixture that will propagate a flame (flash) when ignited.The currently accepted test method for determining flammability limits is ASTM E 681. Note lower flammable limit (LFL) and upper flammable limit (UFL) are often used interchangeably with lower explosive limit (LEL) and upper explosive limit (UFL)... 

Upper explosion limit (UEL) - the maximum concentration of vapour in air above which the propagation of flame will not occur in the presence of an ignition source. Also referred to as the upper flammable limit or the upper explosive limit. 

UEL - Upper Flammability Limit the maximum concentration of a chemical in air at which flame propagation can occur. WEEL - Workplace Environmental Exposure Limit set by the American Industrial Hygiene Association (AIHA). 

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