Sealing Fittings for Cables in Class 1 Division 2 Location

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timm333

Senior Member
Location
Minneapolis, MN
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Electrical Design Engineer
I am trying to figure out whether sealing fittings are required for multiconductor cables in class 1 division 2 location. Cables have gas/vapor tight sheaths, but they are still capable of transmitting gases/vapors through the cable core. The enclosure in which these cables will be terminated does not have to be explosion proof, because it does not have any arcing or heat producing device in it.

NEC 501.15(E)(3) states that cables shall not be required to be sealed unless required by 501.15(E)(1). NEC 501.15(E)(1) states that cable seals are required when the enclosure is required to be explosionproof. But it also says that multiconductor cables, whose core can transmit gases/vapors, will require to be sealed.

Maybe there is possibility that if cables are not sealed, then flammable gases/vapors might travel through the cable core and enter into the control room on the other end.

Are cables required to be sealed even if the enclosure does not have to be explosionproof, or can we just install explosionproof glands (suitable for class 1 division 2) on the cables? What do you guys think about it? Thanks.
 
"Maybe there is possibility that if cables are not sealed, then flammable gases/vapors might travel through the cable core and enter into the control room on the other end."

If you are wiring from a non-hazardous control room to a division 2 hazardous space, wouldn't you need a seal regardless?
 
tjdilly said:
"Maybe there is possibility that if cables are not sealed, then flammable gases/vapors might travel through the cable core and enter into the control room on the other end." If you are wiring from a non-hazardous control room to a division 2 hazardous space, wouldn't you need a seal regardless?
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No. Because these cables are in cable tray (not in conduits). So if cables were suitable for class 1 division 2 (like TC/tray cable) then there would be no need to place seals at the boundary where cables transition from non-hazardous to hazardous location. But the issue here is that the cables are not rated for class 1 division 2. The outer sheaths of cables are gas/vapor tight, but gas/vapor can still travel through the core of cables. I think seals would be required; but just thought to see if you guys have some other idea.
 
timm333 said:
No. Because these cables are in cable tray (not in conduits). So if cables were suitable for class 1 division 2 (like TC/tray cable) then there would be no need to place seals at the boundary where cables transition from non-hazardous to hazardous location. But the issue here is that the cables are not rated for class 1 division 2. The outer sheaths of cables are gas/vapor tight, but gas/vapor can still travel through the core of cables. I think seals would be required; but just thought to see if you guys have some other idea.
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MC-HL and teck cable are required to be sealed if going from control room to classified area.

The cable inside may need a gas block kit as well.

Not sure what else you could be using that wouldn’t require a seal of some sort, at least a Roxblox cut out.
 
timm333 said:
I am trying to figure out whether sealing fittings are required for multiconductor cables in class 1 division 2 location. Cables have gas/vapor tight sheaths, but they are still capable of transmitting gases/vapors through the cable core. The enclosure in which these cables will be terminated does not have to be explosion proof, because it does not have any arcing or heat producing device in it.

NEC 501.15(E)(3) states that cables shall not be required to be sealed unless required by 501.15(E)(1). NEC 501.15(E)(1) states that cable seals are required when the enclosure is required to be explosionproof. But it also says that multiconductor cables, whose core can transmit gases/vapors, will require to be sealed.

Maybe there is possibility that if cables are not sealed, then flammable gases/vapors might travel through the cable core and enter into the control room on the other end.

Are cables required to be sealed even if the enclosure does not have to be explosionproof, or can we just install explosionproof glands (suitable for class 1 division 2) on the cables? What do you guys think about it? Thanks.
Click to expand...
Maybe someone else will jump in, but it's not clear to me if "explosionproof enclosures" applies to all of 501.15(E)(1), or just the first two sentences?

If you read the third sentence (starting with "Multiconductor or optical multifiber...") alone and on its own, it seems to say (and I'm paraphrasing here) "yes, specific cables installed in a Div 2 location shall be sealed."
 
steve66 said:
Maybe someone else will jump in, but it's not clear to me if "explosionproof enclosures" applies to all of 501.15(E)(1), or just the first two sentences?

If you read the third sentence (starting with "Multiconductor or optical multifiber...") alone and on its own, it seems to say (and I'm paraphrasing here) "yes, specific cables installed in a Div 2 location shall be sealed."
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To me, it's reading to say (paraphrasing as well): Yes, you need a seal when connecting to an explosionproof enclosure, and if using multiconductor you may also need to seal it differently.


"Where multiconductor cables pass through conduit seals, there are two methods of achieving an effective seal. The method used depends on whether the cable jacket can transmit gases or vapors through the core of the cable. If the cable jacket or sheath allows passage of gases or vapors, the jacket must be removed so the conductors in the cable assembly can be separated when installing the sealing compound. For cables that do not transmit gases or vapors through the sheath to the cable core, the cable can be dammed and sealed without removing the sheath."
 
Fibre optic cable is generally in a large diameter conduit for the 90’s and you might have to use a sweep still or a MC-HL type raceway when installed in industrial areas.

If it was just fibre optic cable in a tray I don’t see how it enters a room or enclosure without some sort of chase or nipple.
 
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