Cable Seals Class 1 Div 2 Area

[amhiner]

Hi,

Im looking for a bit of clarification on perimeter sealing with utilizing a TC or a conduit system. There is some debate internally about the requiremets of perimeter seals for cable systems without conduits. In this instance, the cable system would start in a Class 1 Div 2 area JB and terminate in a safe area location JB utilizing Tray Cable through Roxtec transit blocks. Given that the cable has a gastight/vaportight barrier and is not connected to an explosionproof device in the hazardous area, woudl there be a need for any type of perimeter seal, past the transit blocks given there is no conduit system? We have used primarily flexible conduit systems in the past and have always used perimeter sealing in the conduit. However, given there is no longer a conduit system it has been generating some confusion.

Any clarification given would be most appreciated. I have my opinions but wanted to remain neutral in the debate here currently.

 

[nhee2]

I would say sealing is not required at the transition between non-classified and Cl I Div 2 area, unless the cable is attached to process equipment/devices that could cause pressure to be exerted at cable end, based on 501.15.(E)(4). However the wording in that section is a little confusing - the description in the 2014 handbook, Commentary Table 501.1 is less confusing (to me).

 

[rbalex]

Section 501.15(E) went through a major rewrite in 2014 and the editing created a serious unintended consequence/misunderstanding.

However, since Ohio is still on the 2011 it easier to explain.

The proper Section to apply to Type TC is [2011] 501.15(E)(3):

Cables Capable of Transmitting Gases or Vapors.

Cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall not be required to be sealed except as required in 501.15(E)(1), unless the cable is attached to process equipment or devices that may cause a pressure in excess of 1500 pascals (6 in. of water) to be exerted at a cable end, in which case a seal, barrier, or other means shall be provided to prevent migration of flammables into an unclassified location.

Exception: Cables with an unbroken gas/vaportight continuous sheath shall be permitted to pass through a Class I, Division 2 location without seals.

​

I have emphasized the "not" in the citation, because it was deleted in 2014, but only because the referenced Section 501.14(E)(1) was also revised, supposedly to eliminate the need for it in Section 501.15(E)(3). Although a careful parsing of the two 2014 Sections together will reveal the actual intent hasn't changed, it has caused so much confusion that ISA has a Public Information proposal in for the 2017 NEC to repair it.

So, what is the intent?

• Section 501.15(E)(1) requires ALL cable constructions to be sealed at terminals of enclosures that are required to be explosionproof.
• UL certifies the Type TC has "... a gas/vaportight continuous sheath ..." in the White Book under Category Code QPOR.
• UL does NOT certify any cable construction as "Cables That Do Not Transmit Gases or Vapors" so Section 501.15(E)(2) is essentially useless. NOTE: Technically, Type MI can meet this, but it has several other Sections that cover its installation directly and Section 501.15(E)(2) isn't really necessary.

Therefore, Type TC is only required to be sealed

IF

It terminates in an enclosure that is required to be explosionproof
​

OR

it is "...attached to process equipment or devices that may cause a pressure in excess of 1500 pascals (6 in. of water) to be exerted at a cable end..."​

HOWEVER

It is NEVER required to be sealed at a Class I, Division 2/unclassified boundary.​

 

[amhiner]

Thanks for the responses on this! This is my intrepretation as well. However, I did stumble upon this statement in the Crouse-Hinds catalogue for EYS seals (which I know are more geared towards conduit sytems) I was wondering where the intent of this statement was coming from if the NEC only mentions perimeter sealing for conduit systems:

"In cable systems when the cables either do not have a gas/vaportight continuous sheath or are capable of transmitting gases or vapors through the cable core when those cables leave the Class I, Division 1 or Division 2 hazardous locations."

Thanks

 

[rbalex]

The "proper" NEC term is boundary, rather than perimeter seal and it isn't just limited to conduit systems.

There are certain multiconductor cable constructions, such as unjacketed, interlocked armor MC, where it applies too. See Section 501.15(E)(4) [Cables Without Gas/Vaportight Sheath]. It's tough enough to seal them with exposed cables and next to impossible for such cables in conduit and I strongly recommend avoidance in either case.

Class I, Division2/unclassified boundary seals aren't required to be explosionproof in conduit systems and, in my opinion, aren't necessary at all but for a few cases.

 

[amhiner]

Cable Glands Class I Div II

Cable Glands Class I Div II

Thanks again for the clarification. Based upon the amount of posts on this forum dealing with cable sealing seems to always be a debated topic! I have also read through the updated NEC 2014 edition and can see where the confusion is coming and why. After some extensive searching, it seems near impossible to find a cable gland listed for a Class I Division II area that does not come with a compound seal. Ive looked through the major players such as crouse-hinds, hawke, ect. There are some glands on the market with an AEx marking but many of these stipulate the construction of the bedding be extruded to surround each core which is more typical of a European cable. While the code gives a bit of leeway in the path to approval, my experience as of late has been inspectors are looking for a piece of equipment with the location rating stamped on it.

 

[rbalex]

... This Code is not intended as a design specification or an instruction manual for untrained persons.

I wish it still had its own Section, but it's been relegated to the last sentence in 90.1(A). It used to be 90.1(C) in 2012 and earlier. It still applies to rookies of all shades including inspectors. BTW, if you're going to be, as your profile indicates, an electrical engineer designing Hazardous Location installations, understand that "Class" is identified with Roman numerals ("I", "II" and "III") and "Division" is identified with Arabic numerals ("1" and "2").

? Except for the rare application of Section 501.5, "AEx" means nothing in Article 501.
? Multiconductor conductor cables that are suitable for Classified locations are rarely marked for them. The NEC simply recognizes them as suitable. (If you're going to be " an electrical engineer designing Hazardous Location installations", get familiar with Section 500.8(A). In fact, get very familiar with Section 500.8 altogether.)
? Section 501.10(B)(1)(5) only requires the cables to use listed termination fittings. In this case, it only means they are listed for the cable Type, not necessarily marked for Division 2.


​

Therefore, except as otherwise required by Section 501.15(E)(1), cables listed in Section 501.10(B)(1)(5) only need to be terminated with fittings listed for the cable Type. They do not need additional markings for Division 2.