3 hour flame test for cables

[PierreR]

Hello Everyone,

Does anybody know what sets the time requirement for the 3 hour flame test of certain standards?

For example a MIL-DTL-24643B requires this type of test.

I'm interested what where the reasons of the 3 hours, why not 5hrs or 2hrs or other?

 

[jbartos]

Suggestion: Visit

http://www.kltannehill.com/Technical Documents/Cable Flame Test.htm

etc. for UL 910, UL 1581 and UL 1666 flammability tests, IEEE 383 vertical flame test, ...

 

[PierreR]

jbartos,

Thank you, but this confirms that there is no basis for the duration of the flame test.

The above link mentions tests for 75 seconds, 20 minutes, 30 minutes and again 20 minutes.

Nobody justifies the length of the flame duration. This is what I'm looking for.

In my opinion, although I can't seem to get the right justification in any standard, it should be related to the insulating material and the construction of the cable. Certain materials will burn slower, or take longer to melt. This is what I think is the basis for the duration of the flame test. I'm looking for some kind of guideline or standard that will tell me why a cable, using a particular insulating material, should pass a 3 hour or 1 hour, or 5 hour test.

Thank you but, I'm still looking for help.

 

[jbartos]

Suggestion: 1 hour, 2 hour, 3 hour, etc. fire barriers are coming from Building codes and Fire Protection Departments. The cables are supposed to fit those conditions to some extent. If for example, the electrical room is separated by a 3 hour fire wall, then what is supposed to be cable rating going to some fire pump, valve, etc. outside of the 3 hour fire partition, if that fire pump is supposed to work and have the electrical room designed to supply electricity to it for at least 3 hours? Apparently, the installation to the fire pump is supposed to be 3 hour rated too. For some of these types of electrical engineering, design and installations, it is necessary to use some common sense in addition to the codes and regulations since they do not provide rules for each and every detail.