Difference between Flammable and Explosive Envelopes

[dogbertcountry2]

I have a system in which there is a mixture of NH3, air, and H2O. After reading a few inter-company reports from the early 70's, I am confused by the way that the report writer and his associates seem to use the term of flammability aand explosive interchangably in regards to an envelope. This is definitely not my area of expertise and I am trying to understand if there is a difference in such a designation.

I found thread798-33615 in this forum from a few years ago, but the questions and comments were not exactly pertaining to this question.

Could someone please explain to me what the difference in terms is, if any?

 

[rbcoulter]

The flammable points are the same as the explosive points (upper, lower, etc.). This is just semantics.

 

[25362]

http://www.galcit.caltech.edu/EDL/public/flammability.html

 

[Guidoo]

LFL/UFL and LEL/UEL can be used interchangeably. If prefer LFL/UFL since for many flammable mixtures to result in an explosion (rapid reaction causing overpressures) it doesn't only need an ignition source but also some form of confinement.

For example, ignition of a flammable methane/air mixture will only result in an explosion if it is confined (e.g. in a building), other wise you will "only" have a flash fire.

 

[Guidoo]

I want to add that I am not familiar with the definition of explosion limits as given in the link from 25362 (

http://www.galcit.caltech.edu/EDL/public/flammability.html)

where they say that explosion limits refer to properties such as AIT (Auto Ignition Temperature). Apart from that it is a useful link.

 

[25362]

As a tutorial I'd recommend reading all the chapters of:

http://www.gexcon.com/index.php?src=handbook/GEXHBchap1.htm

apparently it is free upon registration.

 

[Guidoo]

25362,

You do not even have to register to read the chapters. On the subject they write:

"4.2 Explosion Limits

Same meaning as flammable limits, i.e. UEL = UFL and LEL = LFL. We recommend using the term flammability limit instead of explosion limit."