Cable Seals in CLass I, Div. 1 & 2 Areas

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Andy Sherrill

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I work in a chemical plant and we are struggling with the NEC Cable Seal requirements. We use a lot of multiconductor cable in conduit. Our electric rooms have supply fans to insure the rooms operate at a slight positive pressure to prevent dust and chemicals from entering the electric rooms. However, this is not verified by pressure switches.
Just to make sure I am understanding the code correctly, I interpret 501.15(D)(1) as requiring teh terminations of the cable to be sealed. I interpret 501.15(D)(2) & (3) as different methods of sealing the cables at the above listed terminations. I interpret 501.15(E) as being similar requirements for Div. 2 areas where the enclosure is required to be explosion proof.
Is my understanding correct?

Our electricians are telling me it is virtually impossible to make sure they get the end of the multiconductor cable stripped back to teh conduit seal for the enclosure and make sure they get the individual conductors separated all in this one seal. I am attempting to use the exception under 501.15(D)(2) and find an "approved" means to seal the end of the multiconductor cable inside the enclosure and treat the cable as a single conductor for the conduit seal.
I understand the "approved" can mean different things. We do not have an outside AHJ. We have our own electrical inspector, so I guess approved means a method our company approves.
Does anyone know of a sealing kit that works well for this type of multiconductor cable?

Also, the actual code and the explaination in the Handbook do not seem to agree completely on the exception under 501.15(D)(1). The code says the shielding does not have to be removed. The Handbook explaination says the outer sheathing does not have to be removed. I have read different posts that discuss the problems with sealing material against the shield. What is the generally accepted practice for this exception?

Sorry for the long post.....very difficult subject to describe adequately!
 
Section 501.15 has been due for a major simplification rewrite for several cycles now. Your electricians are right, properly sealing multiconductor cables in a conduit seal is a bear ? unfortunately, it?s one of the things that a ?major simplification rewrite? just won?t fix; it still needs to be done that way.

That said, except in jurisdictions where approved actually means ?listed or labeled by a third party acceptable to the AHJ,? there are various shrink-on kits, such as Raychem CBK series, with a mastic material that closes up the end of a cable between conductors. Assuming it would be approved, the cable could then be treated as a single conductor.
NOTE: I suspect you actually do have an outside AHJ; State or Federal OSHA is probably a good candidate. They usually only inspect on an exception basis.
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Both the NEC and NECHB are correct with respect to shielded instrument cables. The fact that the outer sheathing does not have to be removed is implied by the clause ??or separate the twisted pair.? The purpose is so that pair shields won?t come in contact with each other inside the seal.
 
Question- Class 1, Zone 2 sealing methods

Question- Class 1, Zone 2 sealing methods

We use Zone methodology over here. Instruments(Class 1, Zone 2 Group II A/B certified) are located in Class 1, zone 2 area are connected to Ex e Junction Box also in Zone 2 , by single Pair cable & eventually to control system in safe area by Multipair cables from junction Box.
Conduit or cable sealing has to be as per NEC 505.16 , (seals where requiredper NEC) . We are providing a Barrier seal type Ex Gland (Pepper or Similar) , A Liquid tight flexible metal conduit (LFMC) , & then RGS (Rigid Steel conduit) till junction box.
The cover of the Junction can be opened, without switching off power as it has only non sparking terminals (or occasionally Hermetically sealed Relays) .
Question - Do we need to provide a Flameproof gland at Junction box and any Sealing when we have transition from Zone 2 to safe area. The multipair cable to control room can be direct buried or on trays but conduits are not generally used. Can we just use RGS conduit with Hub and directly connect to/from the junction box. All cables are unarmored .
Company standard calls for Barrier Seal type Ex Gland at Instrument & flameproof gland at junction box for Armored cables but is silent for unarmored cables.

Sorry for a long one!

Thanks

Jagdish
 
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