flammability and explosion limits

[25362]

Although these expressions are used interchangeably, there is, however, a difference, and the LFL/UFL are preferred over LEL/UEL values for safety reasons, probably because of their wider range. Any comment ?

 

[Guidoo]

25362,

The values for LFL/UFL are identical to the values for LEL/UEL. What makes you think LFL/UFL have a wider range than LEL/UEL?

The Gas Explosion Handbook (

http://www.gexcon.com

) states in section 4.2 that "UEL = UFL and LEL = LFL. We recommend using the term flammability limit instead of explosion limit."


The terms LEL/UEL are somewhat incorrect because of the following:

When a flammable gas/air mixture is within the flammable range and their is an ignition source, this will always result in a flame. Whether this will result in an explosion (defined as a combustion leading to a rapid increase of pressure) depends on other things such as the amount of congestion and the reactivity of the fuel.

 

[25362]

Not all explosions (rapid gas expansions resulting in a rapidly moving pressure or shock wave) are deflagrations or detonations caused by chemical rections such as combustion.

I remember having read articles on hydrogen/methanol fuel cells where the reported explosion limits are in a narrower range than the flammability limits.

Besides, I agree with all Guidoo has said.

 

[Guidoo]

For the record:

NFPA 325, section 1-3.5: "The terms "flammable limits" and "explosive limits" are interchangeable. [...] the "flammable range", also referred to and synonymous with "explosive range"."