Moisture Seals

[rbalex]

In another thread I supported use of ?duct seal? as ?acceptable? for certain Classified Location applications. While I stand by that under current 2005 text, I?d like some advice on what the trade commonly uses for ?moisture seals? under 300.5 (G). Part of my Proposal to tighten up the new exception to 501.15(C) is to give a bit more specificity to the material.

 

[macmikeman]

Re: Moisture Seals

Bob, I used to use silicon sealant via a caulking gun to seal up conduits running thru walk in reefer walls. A local senior inspector once rejected this practice on the basis of it not being easy to remove the substance to allow for wire replacement. Refrigeration contractors I work with all swear by expanding foam as the best new way to seal up penetrations including conduits. I have no idea wether this is against any listing use or not.

 

[rbalex]

Re: Moisture Seals

Interestingly enough, the underlying reason for permitting non-explosion proof seals in the new exception is to permit easy removal of the substance to permit wire replacement. The industry has developed several methods to permit easy replacement of equipment at terminations, but boundary seals installed under 501.15(B)(2) virtually guarantee destruction of the raceway system if wires need to be replaced.

 

[hurk27]

Re: Moisture Seals

I would believe that UL would come into place on this as any type of sealant should be listed for direct contact with insulated wires. Some sealants could have adverse affect on the conductor insulation as they have solvent in them which could damage the insulation. 3m makes several reenter-able sealants/encapsulants for water proofing, but for a lift station all I was told to use was the monkey fiber(without the sealent) that's used to keep the sealant from running out of the seal-off?

 

[rbalex]

Re: Moisture Seals

Wayne,

UL may list something, but as of now there is no requirment for listing the compound used in "non-explosionproof" seals referenced in 501.15(C). And quite truthfully, I doubt CMP14 will make it a requirement.

Of course 110.11 could be used as a prohibition against "Deteriorating Agents" but that puts the user in the position of not knowing how to be compliant. To me, good code provides
enough guidance that the user could be confident of compliance without constantly consulting an AHJ first.

Bluntly, in nearly 40 years I've never worked in a refinery that had any routine governmental inspection. And again bluntly most inspectors would be guessing themselves.

 

[hurk27]

Re: Moisture Seals

I H'mm I'm not sure where it came from but somewhere I was told that any compound that makes contact with the insulation of conductor must be listed for the purpose?

I know 300.50(E) requires it to be identified, but not sure if this would apply to above subject?

(E) Raceway Seal. Where a raceway enters from an underground system, the end within the building shall be sealed with an identified compound so as to prevent the entrance of moisture or gases, or it shall be so arranged to prevent moisture from contacting live parts.

 

[jcross]

Re: Moisture Seals

Bob, we here at our site generally accept "duxseal" for moisture or vapor seals such as the one required by 300.5(G), 300.7, 501.15(B)(2)(since the recent change), and 504.70. I have notice in several instances where "duxseal" that was installed several years ago still held it's original form and elasticity. We have never had any problems with any type of deterioration of conductors. In one of your previous posts you mentioned "boundary seals installed under 501.15(B)(2) virtually guarantee destruction of the raceway system if wires need to be replaced". I don't understand where the raceway will be destroyed under the 2005 code for Class 1 Division 2 boundary seals.

 

[rbalex]

Re: Moisture Seals

Originally posted by jcross:
...I don't understand where the raceway will be destroyed under the 2005 code for Class 1 Division 2 boundary seals.

Many boundaries are created at grade. Replacing conductors in an explosionproof seal at a stub-up usually ends up requiring that the seal fitting be removed, as well as the compound material. There is no NEC recognized method of replacing the seal fitting, without re-running a significant part of the aboveground raceway too.

Edit add: Now that I've re-read your post, I realize your reference to the "new" requirements don't require damaging the seal fitting - I agree. My original statement that you refereced was with regard to the "old" sealing compounds. I should have clarified that in that post. The "standard" compounds require destruction of the seal and often the adjacent raceway. This destruction was the reason for the Exception.

[ June 24, 2005, 10:08 AM: Message edited by: rbalex ]

 

[rbalex]

Re: Moisture Seals

Originally posted by jcross:
...I have notice in several instances where "duxseal" that was installed several years ago still held it's original form and elasticity...]

This addresses my question. Now what I want is a way to succinctly describe this mechanical performance such that the user and inspector may reasonably ?identify? it without specifically requiring ?listing.? We don't need to do that here we can wait 'til I post my Proposal for comments.

 

[jcross]

Re: Moisture Seals

Bob, I agree with your intent. The way 501.15(B)(2) was worded, "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." kinda left a lot of people confused. You would think there would have been some kind of new "substance" under manufacture by now that would "comply" with this change but evidently only the code panel knows what is "identified". I heard second handed that one of the panel members that proposed this change had intended on "duxseal" being the preferred method in this case.

 

[rbalex]

Re: Moisture Seals

Originally posted by jcross:
...I heard second handed that one of the panel members that proposed this change had intended on "duxseal" being the preferred method in this case.

 

[H.L.]

Re: Moisture Seals

Re:Moisture seals.
We have been using a product from Raychem for almost 10 years with great success. It is called Rayflate, and it is a mylar bag that has mastic on both faces. It also comes with insert tabs that have mastic. The tabs go between the conductors and the bag wraps around all the conductors as a group. Then the bag is inflated with Co2.

H.L.