Sealing intrinsically safe conduits

[Bob5K]

In the 2008 NEC there is a new statement in 504 concerning sealing conduits in I.S. conduit runs. This says that the seal need not be explosion proof or fire proof. My question is I know that the conduit boundry for Class 1 Div 1 still applies, but what sealing material and what kind of seal are they referring to? Any thoughts on this?

 

[hardworkingstiff]

In the 2008 NEC there is a new statement in 504 concerning sealing conduits in I.S. conduit runs. This says that the seal need not be explosion proof or fire proof. My question is I know that the conduit boundry for Class 1 Div 1 still applies, but what sealing material and what kind of seal are they referring to? Any thoughts on this?

I use duct seal and seal where the conduit enters the box.

I normally will pour one traditional sealoff at the building, just because I like it (I wire gas stations). I believe the code will allow for ductseal at all areas needing sealing (for I.S. conductors).

I don't believe the statement that the seals do not need to be explosion proof or fire proof is new to 2008.

 

[rbalex]

What is new 2008 NEC Section 504.70 is the clause ??but shall be identified for the purpose of minimizing passage of gases, vapors, or dusts under normal operating conditions and shall be accessible? that was added to the second sentence.

The change was made to make it consistent with the wording in 501.10(B)(2). Oddly enough, the original Substantiation of the permissions for 501.10(B)(2) was based on the ?logic? of 504.70.

The key word is ?identified.? It does not necessarily mean ?listed? or ?labeled.?

In any case, in my opinion, CMP14 doesn?t know what compound is suitably ?identified? for use in a non-explosionproof seal either. That is left up to an unsuspecting agent for the AHJ.

 

[hardworkingstiff]

In any case, in my opinion, CMP14 doesn?t know what compound is suitably ?identified? for use in a non-explosionproof seal either. That is left up to an unsuspecting agent for the AHJ.

If you were that agent, would you allow the use of ductseal? (I thought I remember in another post that you conceeded ductseal met the requirement, do you still feel this way?)

 

[rbalex]

In most cases, I would probably accept it; but then I'm not an agent for any AHJ. And remember, I don’t believe most boundary seals are necessary between Class I, Division 2 and unclassified locations in the first place.

If you read the history in the ROPs and ROCs, I don't believe CMP14 specifically mentions or even alludes to what should be acceptable.

 

[Bob5K]

Thank you for the replies to my post, I am new here and that was my first post. The wording I was referring to as being new was what someone else noted,
??but shall be identified for the purpose of minimizing passage of gases, vapors, or dusts under normal operating conditions and shall be accessible?
The conduits that I have a question about are I.S. entering a Class 1 Div 1 area from a non-classified area. Sorry for any confusion I may have caused, and thanks again.

 

[rbalex]

You didn?t create the confusion; I think I more-or-less hijacked your thread. I apologize.

Basically, I was saying that there is no product that can be claimed as ?identified? with certainty in either 504.70 or 501.15(B)(2). The historic documentation in the NFPA Code development process simply doesn?t give any substantial direction. The product is not required to be ?listed? or ?labeled? so any seal that ??minimize the amount of gas or vapor within the Division 2 portion of the conduit from being communicated to the conduit beyond the seal ? [and is] ? identified for the purpose of minimizing passage of gases under normal operating conditions and shall be accessible? should be acceptable.

Duct seal would probably work in most cases, but it is a decision that a knowledgeable Authority Having Jurisdiction would need to make.

Identified (as applied to equipment). Recognizable as suitable for the specific purpose, function, use, environment, application, and so forth, where described in a particular Code requirement.

FPN: Some examples of ways to determine suitability of equipment for a specific purpose, environment, or application include investigations by a qualified testing laboratory (listing and labeling), an inspection agency, or other organizations concerned with product evaluation.​

Note "listed/labels" are only examples, not requirements of "identification." You might want to review the definition of equipment too. It is a very general definition when applied to the NEC.