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#82276 - 10/30/02 07:28 PM Severe Concern on Sealtight
Admin Offline

Registered: 10/07/00
Posts: 3417
Loc: NY, USA
In the NEC 1999, Art. 351, A, 351-23, B(not-permitted), (3) state that Sealtight length no longer then 6 feet, except by Section 351-23(a)(5).

In our Chemical Plant, ours T-stan used to state that the recommended length was 36" long, minimum 12", maximum 6 foot, anything longer had to have Departmental approval. Our company like most company have started following the NEC and stop using the T-stan, now here where my concern come in.

In NEC 2002, page 70-193 (soft-cover) under Liquid tight Art. 350, 350.12 show Uses Not Permitted, that the length have been taken out. Since ours plant and other are following the NEC, I feel like this can have some serious consequences. I have already seem 20 foot section of flex ran in the feel in Class 1, Div 1 & Div 2 areas. I have talk to ours Electrical Engineers, Electrical people and others, and they say that we need to go by the old standard, but since their is no official documentation, beside the NEC, that technically, contractor or others can run what ever they want. I was just involve in a Explosion last December, I believe this is a risk that isn't worth taking.

Please let me know what you think about my concern and why, so I can share it with ours staff. Thanks.

Jackie R Jennings
2017 / 2014 NEC & Related Books and Study Guides
#82277 - 10/30/02 07:54 PM Re: Severe Concern on Sealtight
edmat Offline
Junior Member
Registered: 10/30/02
Posts: 3
Loc: Hot Springs, AR
The 6ft rule is for grounding purpose. only,if you install a grounding conductor their is no limit to how long it maybe
#82278 - 10/31/02 04:50 AM Re: Severe Concern on Sealtight
Redsy Offline
Registered: 03/28/01
Posts: 2056
Loc: Bucks County PA
'99 351-23(b) refers to non-metallic sealtite, or LFNC. This in now in Art 366.12, and the 6' limitation does remain, with the previous exceptions.
As far as Hazardous Locations, I don't see LFNC permitted in either Div.1 or 2.
Are you sure you're not seeing the installation of MC-HL cable? It looks like sealtite, but is approved for Hazardous Locations.
#82279 - 05/15/03 09:13 AM Re: Severe Concern on Sealtight
Jackie R Jennings Offline
Junior Member
Registered: 05/15/03
Posts: 1
Loc: Longview, TX, USA
I'm sorry I haven't reply, I sent a note to the NEC and was waiting for a reply. Sorry. One of my concern is on longer lenght, we have ended up with water in the flex and are having shorted wiring in long runs. This is extremely dangerous in a Div 1 area, can be bad in a Div 2 area. Our Flex has the metal rib inside, this isn't plastic flex. I would appreciate any reply witha referance so I can share with my folks. Here is the type of flex we used. Thanks.
(100 FT/PKG
#82280 - 05/15/03 10:27 AM Re: Severe Concern on Sealtight
resqcapt19 Offline
Registered: 11/10/00
Posts: 2148
Loc: IL
There never has been a general 6' length restriction on the use of liquidtight flexible metal conduit as long as it is securely fastened every 4.5' and with in 12" of each termination and there is no more than 360° of bend between pull points. Every little up, down or side to side bend in the flex needs to be counted toward the 360° maximum. There is a restriction of using the LFMC as the equipment grounding conductor when the length is over 6', but this restriction does not prevent the use of longer lengths, it just requires you to pull an EGC in the flex.
The rules are different for the classified areas, LFMC is not permitted in Class 1 Division 1 areas. See 501.4(A). It is permitted in Class 1 Div 2 areas by 501.4(B), but only where flexibility is required. Unless the equipment moves 20', I don't see how the use of 20' lengths of LFMC in a 1-2 area is code compliant.
As far as the water in the conduit, it is almost impossible to keep out. The conductors in the conduit should be rated for wet locations and the water should not be causing any problems unless the conductors.

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