NEC 501.15(D)(2) Exception

[erickench]

The above NEC section states:

"Multiconductor cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core....."

Question: If it's gas/vaportight then how is it capable of transmitting gases or vapors?

 

[Goroon]

The cable ends need to be sealed.

 

[iwire]

Just like a pipe.

 

[Rockyd]

Kit is like a heat shrink with silicone filled tube to keep gas from being able to travel through the cable(s).

 

[erickench]

I'm questioning the language of the code. It seem's to contradict.

 

[wwhitney]

"Multiconductor cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core....."

Question: If it's gas/vaportight then how is it capable of transmitting gases or vapors?

I take this to mean axial transmission along the cable, from end to end where the sheathing is cut.

Cheers, Wayne

 

[Rockyd]

Check out 500.15 (fpn No. 2) for an explanation.

 

[rbalex]

...
Question: If it's gas/vaportight then how is it capable of transmitting gases or vapors?

"Gas/vaportight" refers to the outer sheath not the cable core.

 

[benaround]

Eric,

It's like explosionproof, it does not mean that it can't explode, it means the apparatus

in that area can contain the explosion, an that keeps the area safe. Thats why your

cable needs to be sealed at terminating points.

 

[erickench]

"Gas/vaportight" refers to the outer sheath not the cable core.

But if the outer sheath is Gas/Vaportight would'nt that also cover the cable core as well?

 

[Rockyd]

Sealing is for EACH conductor. This means that each individual conductor is meant to be addressed wherever it breaks out from the cable sheath and the potential for gas to enter the cable has been raised.

IEEE has commentary if you are a member go here, for a link

Electrical seals
McBride, W.E.
Petroleum and Chemical Industry Conference, 1991, Record of Conference Papers., Industry Applications Society 38th Annual
Volume , Issue , 9-11 Sep 1991 Page(s):215 - 217
Digital Object Identifier 10.1109/PCICON.1991.162950
Summary:The requirements, applications of materials, and problems in making effective electrical conduit and cable seals are discussed. The focus is on sealing process instruments and instrument circuits in Class I hazardous (classified) locations, potentially containing flammable gases or vapors

 

[weressl]

But if the outer sheath is Gas/Vaportight would'nt that also cover the cable core as well?

The gas can travel, in the interstises - the space between the conductors, whether it is air or fillers - of the cable. It is especially true if there is a pressure difference between the two ends of the cable. Ex. a cable connected directly to an in-line mounted instrument where the seal of the instrument fail. (That is one reason for the double seal requirement for inline connections.) At the conenction the jacket is cut and exposes the inner core of conductors and fillers.

 

[markstg]

But if the outer sheath is Gas/Vaportight would'nt that also cover the cable core as well?

No it would not. The cable core could transmit gas/vapor through the interstitial space of the cable, allowing transmission of gas/vapor through cable from one end out the other. Cable seals such as TMCX fittings seal the end of the cable, not allowing the gas/vapor to enter/leave the cable.

 

[markstg]

Or what Lazzlo said, you beat me to it, slow day here.:smile:

 

[LarryFine]

Or what Lazzlo said, you beat me to it, slow day here.:smile:

Yeah, dial-up is like that.