Seal offs for class 1 div2 areas

[ckinney02]

I have a question about NEC 501.15(B)(2). The last sentence reads, "Such seals shall not be required to be explosionproof but shall be identified for the purpose of minimizing gases...". Looking at available seals everything I'm finding is explosionproof (e.g., Crouse-Hinds EYS). Are there non- explosionproof seals available or is there another effective way to accomplish the intent of 501.15(B)(2). For example, I have seen an LB with duct seal being used as a seal-off between a class I, Div II and unclassified location. However, I cannot find any information that duct seal is rated to minimize passage of gases. If non-explosionproof seal-offs are not available, why does this article specify their use? :-?

 

[ckinney02]

Does anyone has a response to this question?

 

[benaround]

I did a search on google and found that Appelton makes ' sealing hubs' , they are not

Ex-proof but are identified for the purpose.

By the way, good question, I have never heard of such a fitting before for a Cl 2 area.

 

[don_resqcapt19]

Here is the ROP for this change.

14-34 Log #2937 NEC-P14
(501-5(B)(2))
Final Action: Accept in Principle
Submitter: Dorothy Kellogg, American Chemistry Council
Recommendation:
At the end of the requirement add a sentence to read:
Sealing fittings shall not be required to be explosion proof.
Substantiation:
Seals in conduits passing from Division 2 locations into unclassified locations are needed to prevent the passage of gases or vapors,
not to contain explosions in the conduit system as is the case with Division 1 conduit systems. This proposal will allow same type seals
as permitted in 504.70 for intrinsic safe installations. The existing text (501.5(B)(2)) eludes to this: "sealing fitting...shall be designed
and installed so as to minimize the amount of gas or vapor within the Division 2 portion of the conduit from being communicated to the
conduit beyond the seal". However, it is now common practice to require explosion proof seals. Explosion proof seals are expensive and
make it difficult to modify wiring once installed. This proposal will make it clear that explosion proof seals are not required as
boundary seals between Division 2 and unclassified locations.
Panel Meeting Action: Accept in Principle
Revise 501.5(B)(2) to read as follows:
"(2) Class I, Division 2 Boundary. In each conduit run passing from a Class I, Division 2 location into an unclassified location, the
sealing fitting shall be permitted on either side of the boundary of such location within 3.05 m (10 ft) of the boundary and shall be
designed and installed so as to minimize the amount of gas or vapor within the Division 2 portion of the conduit from being
communicated to the conduit beyond the seal. Rigid metal conduit or threaded steel intermediate metal conduit shall be used between
the sealing fitting and the point at which the conduit leaves the Division 2 location, and a threaded connection shall be used at the
sealing fitting. Except for listed explosionproof reducers at the conduit seal, there shall be no union, coupling, box, or fitting between
the conduit seal and the point at which the conduit leaves the Division 2 location. Conduits shall be sealed to minimize passage of gases
or vapors within the Division 2 portion of the conduit from being communicated to the conduit beyond the seal. Such seals shall not be
required to be explosionproof."
Panel Statement:
CMP 14 agrees with the submitter but believes that the language used in 504.70 provides greater clarification.
Number Eligible to Vote: 14
Ballot Results: Affirmative: 13 Negative: 1
Explanation of Negative:
COOK: I agree with the first sentence of the submitter's substantiation. I do not agree with the proposed text or the referenced text in
504.70. The text provides no guidance for installers or inspectors as to what is an acceptable seal. Almost anything would have some
affect on gas or vapor passing through a conduit; rags, caulk, silicone, wax, plumbers putty, a four bend saddle in the conduit with water
collected like a plumbing trap, bubble gum, but which ones would "minimize" the passage of the gases? If paper towels are used, do you
need one or two of them to minimize the passage of gas? If caulk or silicone is used, would the installer or inspector know the affect of
the material on conductor insulation? Would conduits that depend on a single compression seal to prevent flammable liquids from
entering the conduit system be safe with bubble gum as a boundary seal (see 501.5(B)(2), Exception No. 4)?
I believe the proposed text will result in inconsistent installations, inconsistent inspections and certainly inconsistent interpretations
of the requirement. Until clear text is proposed, that is enforceable; I will not support this change. I agree that a Division 2 to
unclassified location, boundary seal does not need to be explosionproof, but I am not aware of a seal that is manufactured and listed to
minimize the passage of gas or vapor that is not also explosionproof.
Comment on Affirmative:
WECHSLER: In taking the action that likely will satisfy the proposal, the Panel should also consider making some
other editorial revisions to eliminate the phrase following the subsection title so that a complete sentence exists.
This phrase resulted from the revision that was made during the last code cycle, when this phrase was the lead-in
for the paragraph. The following is offered for consideration:
Revise 501.5(B)(2) additionally to read as follows:
(2) Class I, Division 2 Boundary. So as to minimize the amount of gas or vapor within the Division 2 portion of the
conduit from being communicated to the conduit beyond the seal, a sealing fitting shall be installed in In each conduit
run passing from a Class I, Division 2 location into an unclassified location., the The sealing fitting shall be
permitted on either side of the boundary of such location within 3.05 m (10 ft) of the boundary. and shall be
designed and installed so as to minimize the amount of gas or vapor within the Division 2 portion of the conduit from
being communicated to the conduit beyond the seal. Rigid metal conduit or threaded steel intermediate metal conduit
shall be used between the sealing fitting and the point at which the conduit leaves the Division 2 location, and a
threaded connection shall be used at the sealing fitting. Except for listed explosionproof reducers at the conduit
seal, there shall be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit
leaves the Division 2 location. Conduits shall be sealed to minimize passage of gases or vapors within the Division 2
portion of the conduit from being communicated to the conduit beyond the seal. Such seals shall not be required to be
explosionproof.
1238

 

[don_resqcapt19]

And the ROC for it.

14-43 Log #1932 NEC-P14 Final Action: Accept in Principle in Part( 501.5(B)(2)

Note: It was the action of the Technical Correlating Committee that the panel action be revised to read as follows:
?Such seals shall not be required to be explosionproof, but shall be identified for the purpose of minimizing passage of gases under normal operating conditions and shall be accessible.?

This revision is consistent with Mr. Cookʼs affirmative comment on vote and is consistent with the direction given by the Technical Correlating Committee to all panels that required that the use of the term ?for the purpose? must include what purpose is being identified.

Submitter: Frederic P. Hartwell, Hartwell Electrical Services, Inc.
Comment on Proposal No: 14-34

Recommendation: Accept the proposal in principle. Restate the rule as :?Such seals shall be approved, but they shall not be required to be explosionproof.? In addition to the proposed text, add the following fine print note:
?FPN: Electrical sealing putty is a method of sealing.

?Substantiation: This comment is in response to comments in the voting. There is a long history of the use of compounds to prevent the passage of vapor, as is required in 300.7(A) when there is a temperature/moisture differential. The proposed fine print note occurs in 502.5. I am unaware of any significant field problem with bubble gum or paper towels being used for this purpose. This comment, however, allows the AHJ to review the sealing method.

Panel Meeting Action: Accept in Principle in Part
Revise the text proposed in the comment to read:Such seals shall not be required to be explosionproof but shall be approved identified for the purpose and shall be accessible.
?FPN: Electrical sealing putty is a method of sealing.?Panel Statement: In order to ensure that performance requirements for the seal are quantified, the panel has amended the proposed text to use ?identified? instead of ?approved?. The panel rejected the proposed FPN because there is no assurance that this method will achieve the necessary performance for the seal. The panel has also included an accessibility requirement for these seals because this was necessary based on the action taken on Comment 14-44.
Number Eligible to Vote: 15Ballot Results:
Affirmative: 15
Comment on Affirmative: COOK: I agree with the panel action, but believe the text should read as follows:
?Such seals shall not be required to be explosinproof but shall be identified for the purpose of minimizing the passage of gases and shall be accessible. The added text provides clarification for the purpose of the identification.

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