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Thread: Sharing Allowed?

  1. #1
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    Sharing Allowed?

    Designing an aircraft engine test facility. Test stands and equipment provided by user. I need to provide a cable tray from one side of building to test stand. Cables are for control and communication between control room and test stands. But they also need to bring the fuel line to the test stand along the same path. Previous similar facilities have run the low voltage cables and the fuel line in the same cable tray. Are they really allowed to share?

    The fuel line is about 1/2 inch in diameter, is flexible enough to route in cable tray, and is very robust (not likely to break or leak). The fuel is JP8, a non-volatile liquid (i.e., no flammable vapors; you could put you cigarette out in a pool of it).
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

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    FWIW, I have been on projects where pneumatic lines have been run in cable tray with line voltage conductors. I don't know of any electrical code issues with other MEP items in a tray with the exception of steam and fire suppression.

    Roger
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    Quote Originally Posted by charlie b View Post
    Designing an aircraft engine test facility. Test stands and equipment provided by user. I need to provide a cable tray from one side of building to test stand. Cables are for control and communication between control room and test stands. But they also need to bring the fuel line to the test stand along the same path. Previous similar facilities have run the low voltage cables and the fuel line in the same cable tray. Are they really allowed to share?

    The fuel line is about 1/2 inch in diameter, is flexible enough to route in cable tray, and is very robust (not likely to break or leak). The fuel is JP8, a non-volatile liquid (i.e., no flammable vapors; you could put you cigarette out in a pool of it).
    The fuel line cannot be in the cable tray. Look at 300.8

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    Quote Originally Posted by packersparky View Post
    The fuel line cannot be in the cable tray. Look at 300.8
    Well that pretty much covers it.


    Roger
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    Quote Originally Posted by roger View Post
    Well that pretty much covers it.


    Roger
    Yep, not much wriggle room there.

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    Quote Originally Posted by packersparky View Post
    The fuel line cannot be in the cable tray. Look at 300.8
    Thanks. Yep, that is clear enough. But I know I have to route the conductors and the fuel line from the same place to the same place, and they have to be high enough for maintenance carts to pass under them. So I know I can simply route two trays side-by-side. But if I wanted to use one tray with a listed barrier, would that fall outside the restriction of 300.8? In other words, would that constitute two trays, in the context of that article?

    Keep in mind that I will have to answer the user's question about why it can't happen here but is already happening at other installations.

    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

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    Probably gonna sound stupid but.. what about pulling it through 3 or 4 inch waste pipe? I mean, it is strong enough to hold shape and wide enough to pull both the fuel line and the LV cables... plus, if it is temp only, the sections can be fitted without glue... you can get long sweeps for it and 45s as well... cuts with a saw... If you need extra strength the 2-1/2 slides into the 3 inch and really makes a strength difference...lol
    or 2 inch into 2-1/2...

    Oh, did I say you dont need to glue it?
    Student of electrical codes. Please Take others advice first.

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    Quote Originally Posted by charlie b View Post
    Thanks. Yep, that is clear enough. But I know I have to route the conductors and the fuel line from the same place to the same place, and they have to be high enough for maintenance carts to pass under them. So I know I can simply route two trays side-by-side. But if I wanted to use one tray with a listed barrier, would that fall outside the restriction of 300.8? In other words, would that constitute two trays, in the context of that article?

    Keep in mind that I will have to answer the user's question about why it can't happen here but is already happening at other installations.

    300.8 first appeared in the 1987 NEC. Maybe the other installations were code compliant at the time they were installed? Or maybe they were never code compliant. I would say that if the cable tray does not contain electrical conductors or cables, 300.8 would not apply.

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    How will you support the tray? Can you support the fuel line off the CT supports, and as suggested use a drain line? In liu of that how about a wire basket tray? Then it could all be installed by electricians. Some of the wire basket trays are 4" wide, Snake Tray is one I see advertised.
    Moderator-Washington State
    Ancora Imparo

  10. #10
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    If the cable tray is being supported by Unistrut, Kindorf, B-Line, etc, I'd suggest mounting an extra run of the strut parallel to the cable tray and dropping the fuel line inside. Way stronger than the cable tray, and I'm sure something can be done for any bends or elevation changes.

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